VOLUME 8 • NUMBER 1 • MARCH 2001 The South African Journal of Sports Medicine The official publication of the South African Sports Medicine Association R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) Editorial Exercise Science and Sports Medicine Resource Centre ■ The contents o f the first edi­ tion o f the S outh A frica n Jo u rn a l o f Sports Medicine for 2 0 0 1 reflect the m ulti-dis­ c ip lin a ry nature o f sports m e dicine. The stu d y by Nurok and colleagues on the a th le tic a b ility o f young Kenyan athletes reaches the conclusion that the superior running a b ility o f the K enyans can perhaps be explained by specific inheri­ ted characteristics. However, it is a difficult theory to prove and it is going to take m any more studies in disciplines rang­ ing from sociology to m olecular biology and genetics before we can conclude with confidence th a t factors governing suc­ cess in athletics are inherited. The study by W eston and her colleagues on heart rate as a m arker o f exercise intensity during m ini-tram poline exer­ cise contributes to the knowledge in the field o f applied exer­ cise physiology. T his study show s th a t the oxygen consum ption/heart rate relationship during m ini-tram poline exercise is not always linear. Clearly, under these conditions heart rate is not an accurate m arker o f exercise intensity and therefore should be used with caution in prescribing exer­ cise. This study once again exposes the predicam ent that we have in the fields of sports m edicine and exercise physiolo­ gy. For exam ple, on the one hand we have devices fo r m ea­ suring heart rate which are highly sophisticated and can m easure heart rate under free living conditions with a high degree o f accuracy. Furthermore, the heart rate data can be stored for several days before being transferred to a com ­ puter fo r analysis. On the other hand we have an emerging understanding of how heart rate changes during exercise under various conditions. We know that factors such as environm ental tem perature, state o f hydration, mode of exer­ cise, duration o f exercise and com petition all have a signifi­ cant effect on the heart rate/exercise intensity relationship. More recently it was shown that as physical fitness increases, maxim um heart rate decreases (Zavorsky G S. Evidence and possible m echanism s o f a ltered heart rate w ith endurance training and tapering. Sports Med 2000; 2 9 : 13 - 26.) This finding has important im plications in the health industry w here exercise participants are encouraged to monitor their training intensity according to their heart rate expressed as a percentage of maxim um heart rate. Clearly if the decrease in m aximum heart rate with increasing fitness is not taken into account, then the relative intensity o f the training sessions will becom e harder and harder as fitness improves. In sum ­ mary, the study by W eston and her colleagues is important in that it contributes to narrowing the large gap between the technical capabilities of heart rate m onitors and the under­ standing of how heart rate responds to exercise. This gap has to be narrowed even further before heart rate monitors can be used to their full potential. The study by Marino and Booth addresses the question of w hether precooling before endurance exercise in moderate and high environm ental tem peratures has any ergogenic effect. Research into this area is fascinating fo r two reasons. Firstly, the underlying physiological mechanism s o f the 'pre­ cooling’ effect are not fully understood. Secondly, the applied spin-offs of this research may result in m arathon race organ­ isers moving their jacuzzis to the start of the race rather than the end! The article on the popliteal vascular entrapm ent syn­ drome describes a possible cause of leg pain in young ath­ letes. This article points out that the syndrom e is more prevalent than previously believed and that a late diagnosis can have serious consequences for the patient. In contrast, an early diagnosis and surgical correction result in prompt and lasting relief of the symptoms. This article will surely contribute significantly to more clinicians making the correct diagnosis of the condition thus sparing their patients much discomfort, frustration and expense. Identifying the com petitive edge in sport is always a pop­ ular topic. Therefore the article on creatine supplem entation will be interesting fo r a wide range of readers. Although the study in this journal focussed prim arily on the perform ance- related effects, the side-effects that a large proportion o f the subjects experienced in this study should not go unnoticed. In summary, this edition of the Journal should have something of interest to cater for the needs of all the health professionals and scientists who belong to a m ulti-discipli­ nary sports medicine association. This Journal is a vehicle for new ideas in sports m edicine. You are encouraged to read it, enjoy it and hopefully learn som ething which can be used to improve perform ance and reduce the risk o f injury! Mike Lam bert E ditor-in-C hief SPORTS MEDICINE MARCH 2001 1 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) THE SOUTH AFRICAN JOURNAL OF SPORTS MEDICINE Volume 8 • Number 1 • March 2001 EDITO R-IN -C HIEF P rof M Lam bert U niversity of C ape Town SENIO R ASSOCIATE EDITOR Prof M Mars U niversity o f Natal EDITO RIAL BOARD Prof V Coopoo University o f Durban W estville Dr K M yburgh University of Stellenbosch P ro fT D Noakes U niversity o f C ape Town Prof G Rogers U niversity o f W itw atersrand P rof K Vaughan U niversity o f C ape Town PRO DU CTIO N EDITOR Julia Casciola SA Medical Association PRO JECTS MA NA GER W ayne Press SA Medical Association PRO DU CTIO N MANAGER Anne Collins SA Medical Association PUB LISHING S A M edical Association Health and M edical Publishing Group 14 C entral Square, Pinelands 7405 Private Bag X1, Pinelands 7430 Tel (021) 531-3081, fax (021) 531-4126 REPRO & PRINTING Ince (Pty) Ltd CONTENTS Editorial M Lambert Original research articles Cardiovascular responses to self-paced running in warm humid conditions following whole-body precooling................ 3 F E Marino, J Booth Does heart rate adequately reflect exercise intensity during mini-trampoline exercise?...................................................... 9 A R Weston, A Khan, M Mars Clustering of athletic ability in male Kalenjin scholars......... 14 M Nurok, A G Morris, C O’Connell, T D Noakes Popliteal vascular entrapment syndrome — a cause of leg pain to be considered in young athletes....................... 18 L J Levien Creatine supplementation and exercise performance in rugby players........................................................................ 26 R M N Kohler Letters to the Editor Drug-free sport..................................................................... 31 D Bradbury, SA Institute for Drug-Free Sport Early postural correction.......................................................32 A Wenham Instructions to Contributors............................................ 33 The Editor The S o u th A fric a n J o u r n a l o f S p o rts M e d ic in e P O B ox 115 N e w la n d s 7725 Tel: 021 - 6 50 4561 Fax: 021 - 6 8 6 7530 The views expressed in individual articles are the personal views of the authors and are not necessarily shared by the editors, the advertisers or the publishers. No articles may be reproduced w ithout the written consent o f the publishers. 2 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) Cardiovascular responses to self-paced running in warm humid conditions following whole-body precooling ORIGINAL RESEARCH ARTICLE Frank E M arino1 (PhD) John Booth2 (PhD) 'Human Movement Studies Unit and Human Performance Laboratory, Charles Sturt University, Bathurst, Australia d e p a rtm e n t o f Biomedical Sciences, University o f Wollongong, Wollongong, Australia Abstract O bjective. This study exam ined the extent to w hich an ' attenuated cardiovascular strain during prolonged exer­ cise follow ing precooling m ight be attributed to changes in either plasma or blood volum e. Design. Seven subjects perform ed a 30-m inute self- paced treadm ill run in w arm (32°C) humid (60% rela- . tive hum idity) conditions following w hole-body precooling (PC) or no precooling (control (CON)) in a , counterbalanced fashion. All subjects w ere m oderately , trained and had a mean peak pulm onary uptake ; ( V 0 2peak) o f 60.3 ± 2.4 m l/kg/m in/. Blood sam ples w ere ; collected pre and post-exercise fo r the determ ination o f j haem oglobin (Hb) and hem atocrit (Hct). Heart rate (HR), rectal tem perature (Tre) and m ean skin tem pera­ ture (Tsk) w ere monitored continuously during exercise. Total body sweating (l/h) w as calculated from changes in nude body mass and corrected for fluid ingestion. Results. The distance covered at the end o f CON was 6 912 ± 345 m and increased following precooling to 7 263 + 389 m (P < 0.01). On com pletion o f the run CON Tre increased to 39.4 ± 0.4°C, w hile PC Tre increased to 38.8 ± 0.4°C (P < 0.03). The end o f exer­ cise Tsk w as 34.5 ± 0.6°C and 35.6 ± 0.5°C (P < 0.01) for PC and CON, respectively. The HR response w as low er (P < 0.05) for PC a t 5 m inutes of exercise but not 1 fo r the rem ainder o f the run. The changes in Hb and Hct resulted in percentage changes in plasma volum e CORRESPONDENCE: Frank E Marino Human Perform ance Laboratory Human M ovem ent Studies Unit Charles S turt University Bathurst NSW, 2795 Australia Tel: 61 2 63 384268 Fax: 61 2 63 384065 E-mail: fm arino@ csu.edu.au . (% APV) o f -6 .9 ± 3.6 fo r CON and - 3 . 0 ± 5.4 fo r PC, and percentage changes in blood volume (% ABV) of -3 .4 ± 1.2 fo r CON and -1 .8 ± 4.1 for PC; these ; changes w ere not significantly different between condi­ tions. Conclusions. Although the subjects significantly increased their perform ance in warm humid conditions following precooling w ith an attenuated cardiovascular 1 strain, it is unlikely that changes in either plasma or I blood volum e contributed to the attenuated cardiovas­ cular strain. Introduction W hen exercise is performed in a hot environm ent a severe strain on the cardiovascular system is observed . 1 This strain is usually reflected by the changes in heart rate (HR), stroke volum e (SV) and cardiac output (Q ) . 1 753 These cardiovascu­ lar dynam ics change in order that a finite Q satisfies the m etabolic dem ands o f the w orking muscle and that the skin is highly perfused in order fo r the body to deal with the accu­ mulating body heat. Moreover, during exercise in the heat cardiovascular drift is exacerbated due to a substantially reduced cardiac filling and SV which require a higher HR in order to m aintain Q. Progressive dehydration as a consequence o f exercise, particularly in the heat, can have a significant effect on the cardiovascular system resulting in haemoconcentration and a reduction in blood volum e (BV ) . 8 A reduced BV has been shown to com prom ise the cutaneous circulation ,5 w hich dim inishes convective heat transfer from the body core to the skin. H aem oconcentration resulting from running exercise is w idely reported .10 However, variable responses have been- shown w here some subjects displayed transient haem ocon­ centration w h ile others displayed tra n sie n t haem odilu- tio n .3,1720 N evertheless, Fortney e f a/.6 have shown that during 30 minutes o f exercise at 60% o f m aximum aerobic power, a 10% reduction in BV resulted in significantly greater heat storage and core tem perature (Tc) w ith substantially reduced SV and Q and an elevated HR compared with indi­ viduals w ith a m aintained BV. Moreover, it is generally accepted that a greater loss o f plasma volum e (PV) is asso­ SPORTS MEDICINE MARCH 2001 3 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) mailto:fmarino@csu.edu.au ciated with greater increases in Tc, tachycardia and hypoten­ sion during exercise heat stress .14 This is particularly im por­ tant as a reduced PV has been shown to limit exercise in concert with decreased plasma osmolality, skin blood flow and sweating ra te .1924 In addition, SV is low er and HR higher in the early stages of exercise when PV is reduced following hypohydration .2227 Therefore, m inim ising the therm al strain during exercise in the heat is extrem ely important for attenuating a d e crem ent in exercise perform ance and increasing the safety of exercise under more extrem e condi­ tions. Several studies 12 1526 have shown the precooling strategy to be beneficial in enhancing endurance perform ance during moderate and high environm ental tem peratures. Generally, these studies show cardiovascular and therm oregulatory strain to be reduced substantially during exercise following precooling. However, it is still unclear w hether precooling reduces cardiovascular strain during exercise heat stress as a consequence o f an attenuated reduction in either PV or BV. Therefore, this study examined to w hat extent prolonged exercise perform ance m ight be im proved-following precool­ ing and w hether that im provem ent m ight be in part due to an attenuated cardiovascular strain. Materials and methods •The therm oregulatory and perform ance aspects o f this study have been published in a com panion paper.2 Subjects and experim ental design Seven subjects (five men and tw o w om en) volunteered for the study. All w ere com petitive runners and apparently in good health as reported by a health history questionnaire and an exercise stress test. None of the subjects reported heat exposure within the preceding 2 months of the study. The mean (± SD) fo r age, mass, height, body surface area, peak pulm onary uptake ( V 0 2peak) and m axim um HR w ere 25 ± 4.5 years, 66.2 ± 9.5 kg, 171.0 + 8 . 8 cm, 1.76 ± 0.15 m2, 63.5 + 2.6 ml/kg/min, and 188 ± 7 beats/min, respectively. The experim ent w as approved by the Ethics in Human Research Com m ittee of Charles Sturt U niversity and all subjects gave w ritten inform ed consent. All participants refrained from vigorous exercise, caffeine and alcohol ingestion for at least 24 hours before reporting to the laboratory. During the initial visit the subjects w ere fam il­ iarised with treadm ill running, anthropom etric m easurem ents w ere recorded and a maximal incremental treadm ill test to exhaustion w as undertaken. V 0 2peak w as defined as the highest V 0 2 (m l/kg/m in) attained over a 1-m inute period.' The first subject w as random ly assigned to either a run in the heat (control (CON)) or a run in the heat following w hole-body precooling (PC). All subsequent subjects were assigned in a counterbalanced fashion. The am bient tem ­ perature (Ta) and relative hum idity (RH) w ere set at 32°C and 60% , respectively. Testing was scheduled a t least 3 - 7 days apart but at the sam e tim e of day so th a t circadian variation could be minimised. On the day of testing participants reported to the laboratory and rested quietly for approxi­ m ately 2 0 minutes, after which a pre-exercise blood sample w as drawn and nude body mass measured. A rectal probe w as inserted and HR transm itter and skin therm istors secured. Subjects then either com m enced their perfor­ mance run or were immersed in a w ater bath for w hole-body precooling as previously described .16 During the run sub­ je cts ingested a controlled volum e of distilled w ater in an attem pt to control for a progressive dehydration effect. Once the run w as com pleted a post-exercise blood sam ple was drawn, subjects w ere tow elled dry and nude body mass was re-measured. Precooling manouvre The method of w hole-body cooling has been previously described . 16 Briefly, however, subjects reclined in a water bath to the level of the neck. The initial w ater tem perature was set at 28 - 29°C. A fter an accom m odation period water was siphoned and replaced with cold w ater (approxim ately 13°C) until w ater tem perature reached 23 - 24°C. The immersion protocol lasted fo r 60 minutes or until continuous shivering w as observed. O nce subjects left the w ater bath they were towelled dry, prepared for exercise, and com ­ menced running within 3 minutes. Perform ance run The subjects ran on a motorised treadm ill. The speed was set by the experim enter to the nearest 0.5 km/h and increased or decreased on dem and through previously rehearsed signals. The aim of the test was for subjects to run as great a distance as possible w ithin the allotted 30 m in­ utes. On com pletion of the run the total distance travelled was recorded. During and following the run participants were not given any feedback regarding their performance other than the self-selection of running speed. Therm oregulatory m easurem ents and calculations Rectal tem perature ( T J was monitored and measured with a 12-gauge rectal th e rm is to r (M on-a-therm , M a llin ckro d t Medical Inc., St. Louis, MO) inserted 10 cm beyond the anal sphincter. Skin tem perature (Tsk) w as measured at four sites (chest, arm, thigh and calf) with therm istors (427 series, Yellow Springs Instrument, OH) secured with transpore tape. All therm istors were connected to an eight-channel telether­ m om eter (Zentem p 5000, Zencor, Australia). Temperatures w ere monitored continuously and recorded pre-exercise and at the end o f exercise. Mean skin tem perature (Tsk) w as cal­ culated using the area weighted form ula25: Tsk = 0.3 ( T ^ + Tarm) + 0.2 (T,high + Tleg). Heat storage (S) w as calculated from Tsk and Tre using the formula15: S = 0.97 . m . A TB. A ^ , where TB = (Tre .,0.65) + (Tsk . 0.35), 0.97 is specific heat of body tis­ sue (W/kg), m is body mass (kg) and Ao"1 is surface area (m2). Body mass, fluid intake and total body sweating C hange in nude body mass was measured to the nearest 10 g on an electronic precision balance (HW - 100KAI, GEC, Avery Ltd., Australia). Before com m encing the performance run a drink bottle w as filled w ith a known quantity of distilled 4 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) w ater (range 500 - 600 m l) so that subjects could drink ad libitum. In the subsequent trial subjects w ere only perm itted to drink a sim ilar volum e of w ater to that consum ed during the initial trial. A t the end of the trial the rem aining w ater vol­ ume w as subtracted from the initial w ater volum e and recorded. This value was also used to adjust the nude body m ass measurem ent. W ater volum e w as m easured to the nearest 1 ml using a graduated 1 0 0 ml cylinder. Heart rate HR w as m onitored continuously and recorded pre-exercise, at 5-m inute intervals during exercise and a t the end of exer­ cise using a Sports Tester (Polar Electro, Oy, Finland). Blood sampling, analysis and calculations Pre and post-exercise blood sam ples w ere drawn from a superficial vein on the dorsal aspect o f the hand using a 2 1 - gauge needle. The pre-exercise blood draw was obtained w hile subjects w ere seated. The post-exercise blood sam ­ ple was obtained within 2 m inutes of com pletion of exercise. In all cases the blood sam ples w ere collected while the sub­ je c t rem ained seated. Blood w as collected in vacutainers containing EDTA for determ ination of haem oglobin (Hb) and haem atocrit (Hct). H aem atological variables w ere quantified using the C oulter principle with a C oulter STER analyser. The percentage changes in blood volum e (% ABV) and plas­ ma volum e (%APV) w ere calculated using the following equations4: %ABV = (H b,/H b 2 - 1 ) x 100 (equation 1); and % APV = (((Hb,)x (1 - Hct2)/ (Hb2) x (1 - Hct,)) - 1 ) x 100 (equation 2); w here Hb, and Hct, are pre-exercise values and Hb2 and Hct2 are post-exercise values. 1 i Statistics Statistical analyses w ere perform ed using an SPSS for W indows (release 7.5.1) softw are package (SPSS Inc., 1996). Descriptive statistics were generated fo r all variables. S tudent’s paired f-tests w ere used to com pare pre and post­ exercise m easurem ents for w ithin treatm ents and between conditions. Continuous m easurem ents such as HR w ere analysed using analysis of variance (ANOVA) for repeated m easures on time. W hen significant main effects w ere detected Tukey's HSD (honestly significant difference) post- hoc procedure was employed to locate the source of signifi­ cance. Statistical significance was set at P < 0.05. Values are reported as mean + standard deviation (± SD). Results Running performance The distance covered at the end o f CON w as 6 912 ± 345 m. This result was significantly im proved following precooling to 7 263 ± 389 m (P < 0.01). The running speeds at each 5- minute interval are shown in Fig. 1. The running speeds w ere only different at 30 m inutes w hen subjects w ere able to accelerate from 14.6 km/h in CON to 16.8 km/h (P < 0.03) in PC. Although the running speeds w ere only different at 30 minutes, participants w ere able to maintain a higher average 19 11 T fm e (m /n ) Fig. 1. Mean heart rate response and running speeds at pre- exercise (0 minutes), 5-minute intervals and end-exercise (30 minutes) for control and precool conditions. *P < 0.05 com­ pared with precool. running speed throughout PC at 15.1 + 1.5 km/h compared with 14.3 ± 1.5 km/h (P < 0.01) for CON. Therm oregulatory responses W hile the pre-exercise Tre fo r CON was 37.4 + 0.1 °C, w hole- body precooling reduced pre-exercise Tra from 37.3 ± 0.1 °C to 36.6 ± 0.6°C (P < 0.0001) so th a t precooled subjects start­ ed the exercise bout with a significantly reduced T,e. On com pletion o f the run CON Tre increased to 39.4 ± 0.4°C, while during PC Tre increased to 38.8 ± 0.4°C (P < 0.03, Fig. 2). Precooling reduced the pre-exercise Tsk from 34.1 ± 0.20°C to 28.8 ± 1.6°C (P < 0.0001), w hile the pre-exercise Tsk for CON was 34.4 + 0.28°C. The end of exercise Tsk was 34.5 ± 0,6°C and 35.6 + 0.5°C (P < 0.01) for PC and CON, respectively (Fig. 2). The end o f exercise heat storage increased from 62.8 ± 12 W /m 2 fo r CON to 124 ± 23 W /m 2 for PC (P < 0.05). Body mass and total body sweating responses The pre-exercise values fo r nude body m ass w ere 63.8 + 3,1 kg and 63.9 ± 3 .1 kg (P = 0.34) for CON and PC, respec­ tively. The end o f exercise body mass was adjusted for w ater ingestion and was 63.0 ± 3.0 kg fo r CON and 63.1 ± 2.9 kg (P = 0.76) for PC. The change in body m ass for both trials w as 0 . 8 kg am ounting to an equal and total body sweating of 1 . 6 l/h. SPORTS MEDICINE MARCH 2001 5 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) 40 35 Measurement time Fig. 2. Mean changes in rectal and mean skin temperatures at pre-exercise and end-exercise.*P < 0.01 compared with precool condition. Pre- versus end-exercise values are all significantly different. Heart rate response The HRs at 5-m inute intervals are shown in Fig. 1. Resting HR following w hole-body precooling was reduced from 75 ± 3 beats/min to 62 ± 4 beats/m in (P < 0.05). The HR at 5 m in­ utes was significantly (P < 0.05) lower a t 158 ± 10 for PC com pared with 166 ± 10 beats/m in for CON, after which it w as not different fo r the rem ainder o f the run between con­ ditions. The end-exercise HRs w ere sim ilar for CON (189 ± 4 beats/min) and PC (190 ± 4 beats/min). Haem atological responses The Hb and Hct values are given in Table I. Pre-exercise Hb values w ere sim ilar fo r both CON and PC. On com pletion o f the run, Hb concentrations w ere not significantly altered. The pre-exercise H ct values w ere also sim ilar for both trials. However, the end-exercise CON Hct increased significantly from 45 + 0.03% to 47 ± 0.03% (P = 0.006) com pared with 46 + 0.04% for PC. The percentage changes in BV and PV are given in Table II. The changes in Hb concentration and Hct did not significantly alter the % APV or % ABV for either experim ental condition. TAB LE 1. Mean (± SD) haem oglobin and haem atocrit values fo r pre and post-exercise (N = 7) CON PC Pre- P ost­ Pre- P o st­ exerc ise exercise exercise exercise Hb (g/dl) 15.3 ± 1 .2 15.8 ±1 .2 15.3 ± 1.5 15.6 ± 1.4 Hct (%) 45 ± 0.03 4 7 ± 0.03* 46 ± 0.04 47 ± 0,04 ' P = 0 .0 0 6 com pared with C O N value. C O N = control trial, P C - precooling trial. * TABLE H. Percentage changes fo r blood (BV) and plasm a volum e (PV) %ABV (CON) %ABV (PC) %APV (CON) %APV (PC) Mean - 3 . 4 -1 .8 - 6 . 9 - 3 .0 ±S D 1.2 4.1 3,6 - 5.4 C O N = control trial; P C = precool trial, % A = percentage change. Discussion Previous precooling studies have shown th a t endurance exercise either at a fixed % VOZmax or during either self-paced running or cycling im proves exercise perform ance in m oder­ ate and warm , humid conditions .2 12,526 Although traditional­ ly e n durance pe rfo rm a n ce has been evaluated using protocols at a fixed w orkload to exhaustion, it is now appar­ ent th a t the reliability of such protocols is questionable .18 In addition, it is now thought that self-paced or stochastic pro­ tocols are able to give a better representation of perfor­ m ance e n h a n ce m e n t b e cause o f p o te n tia lly hig h er reliability." Therefore, in the present study a self-paced pro­ tocol was used in order to evaluate better the m agnitude of im provem ent in running perform ance, thereby evaluating the practical application of precooling. Previous precooling studies21215 indicate th a t therm oregu­ latory and cardiovascular strain are attenuated as a result of the precooling manouvre. However, none of these studies report or exam ine to w hat extent the attenuated cardiovas­ cular strain following precooling is influenced by changes in BV or PV. The effects o f sm all alterations in BV and PV on circulatory dynam ics during exercise in a hot environm ent can be critical to perform ance. The dem ands placed on the circulatory system during exercise in the heat are partly due to an increased blood flow to the skin to facilitate the dissi­ pation o f heat. Additionally, fluid is lost from the vascular com partm ent, w hich further com prom ises cardiac fillin g .21 In the present study, exercise endurance was enhanced following w hole-body precooling. This im provem ent was accom panied by a reduced therm oregulatory and cardiovas­ cular strain. The attenuated therm oregulatory strain result­ ing from precooling has been previously dealt w ith .1,12 Briefly, however, it is clear th a t precooling enhances the capacity to store heat m ainly as a result o f the large reduction in skin tem perature .12 A larger capacity to store heat, coupled with the capacity for higher exercise intensity, would enable sub­ je cts to com plete more work. In fact, the subjects maintained a higher average running speed throughout the run following PC, and it was evident that the m ajority of gains in perfor­ 6 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) mance w ere a result o f increasing running velocity toward the end o f the trial (25 - 30 m inutes). During the early stages o f exercise (0 - 5 minutes) HR w as significantly lower, after which it was not different. However, the observation that HR was not different between conditions for the rem ainder of the run ( 1 0 - 3 0 min) indicates that subjects w ere able to run at a higher intensity with a sim ilar HR, as evidenced by the higher average running speed and significantly greater dis­ tance achieved by the precooled subjects in the allotted 30 minutes. However, the end o f exercise HR was sim ilar for both conditions. It rem ains unclear w hy HR would be similar at the end o f exercise given the reduced therm oregulatory strain, increased capacity for heat storage and higher work output fo r subjects following precooling. This result indicates that subjects perform ed to their m axim um physiological capacity. It is also possible that subjects adopted a pacing strategy that was consistent with reduced cardiovascular and therm oregulatory demands. For instance, it has been suggested that during self-paced exercise, subjects are able to take advantage o f pacing rather than perform ing to an im posed o r fixed external w orkload which would allow the individual to com plete the activity with an attenuated physio­ lo g ica l stra in and reduce the likelihood o f prem ature fatigue . 13 During prolonged exercise in the heat, haem oconcentra­ tion can result as a consequence o f progressive dehydration9 and can ultim ately lead to a reduced BV com prom ising skin blood flow and reducing the am ount of convective heat trans­ fer from body core to skin. In the present study the % ABV was -3 .4 % for CON compared w ith - 1 . 8 % for PC, although these values w ere not significantly different. The non-signif- icant APV of -6 .9 % for CON com pared with -3 .0 % for PC, indicates that precooling had very little effect on PV. As can be seen from Table I, the percentage changes in PV are mainly a result o f the discrete change in Hct, particularly for CON w here the post-exercise Hct was significantly elevated com pared with PC. This sm all change in Hct was unable to augm ent significantly the %APV for CON. Fortney et al.6 have shown that a 10% reduction in BV can substantially increase the heat storage and Tc during 30 m in­ utes o f cycling exercise at 60% V 0 2max in Tfl of 35°C. Our results show that BV was relatively unaffected as a result of exercise in the heat either with or w ithout w hole-body pre­ cooling. Hence, it is difficult to attribute the attenuated car­ diovascular strain to either changes in BV or PV. There are several reasons why we do not find a significant attenuation in reductions o f either BV or PV. For instance, during both CON and PC trials subjects ingested sim ilar volum es o f w ater w hich may have prevented a large, and gradual dehy­ dration. Also, w hile adjusting the change in post-exercise body m ass for fluid intake, it was apparent that total body sw eating was sim ilar for both trials. However, what is not readily apparent is the greater absolute w ork rate of the sub­ je cts during PC compared with CON. Hence, although w ater ingestion was similar, the sw eat rate during PC was relative to the increased intensity of exercise. This indicates that car­ diovascular strain during exercise w as attenuated m ainly as a result o f a significantly reduced Tsk possibly alleviating the need to increase cutaneous circulation for increased con­ vective heat transfer. O ther possible reasons for a reduced cardiovascular strain and increased perform ance following precooling m ight be an increased ru nning econom y. Although not measured in the present study, oxygen con­ sum ption was m easured in tw o other sim ilar studies.212 In both these studies oxygen consumption, w as sim ilar for con­ trol and precooled subjects, and given the increased exer­ cise intensity either by higher running speeds2 or cycling speeds12 for a sim ilar m etabolic cost, it is quite possible that econom y of running in the present study w as increased fol­ lowing precooling. Another difficulty relating to studies quantifying BV and PV changes during exercise is the possible effect of posture. It has long been recognised that posture has a confounding effect on BV.5 For instance, pre-exercise blood samples taken while seated may indeed result in different BV calcula­ tions if a subsequent sam ple is taken w hile standing.4 For this reason the blood sam ples w ere taken while subjects w ere seated during both pre and post-exercise. Conclusion In conclusion, the results o f this study indicate that whole- body precooling does not induce haem atological changes that could account in a significant w ay for an attenuated car­ diovascular strain during prolonged running exercise in warm, humid conditions. A lthough the benefits of precooling can in part be attributed to attenuated therm oregulatory and cardiovascular strain, it seems that the attenuated cardio­ vascular strain is prim arily a result of a reduced Tc and Tsk reducing the need for increased cutaneous circulation. R e f e r e n c e s 1. Adams WC, Fox RH, Fry J, MacDonald IC. Thermoregulation during marathon running in cool, moderate, and hot environments. J A ppl Physiol 1975; 38: 1030-7. 2. Booth J, Marino F, Ward JJ. Improved running performance in hot humid conditions following precooling. M ed S ci Sports Exerc 1997; 2 9 : 943-9. 3. Diaz FJ, Brandsford DR, Kobayashi K, Horvath SM, McMurray RG. Plasma volume changes during rest and exercise in different postures in a hot humid environment. J A ppl Physiol 1979; 4 7 : 798-803. 4. Dill DB, Costill DL. Calculation of percentage changes in volumes of blood, plasma, and red cells in dehydration. J Appl Physiol 1974; 37: 247-8. 5. Fawcett JK, Wynn V. Effects of posture on plasma volume and some blood constituents. J Clin Pathol 1960; 13: 304-10. 6. Fortney SM, Nadel ER, Wenger CB, Bove JR. Effect of acute alterations of blood volume on circulatory performance in humans. J Appl Physiol 1981; 50: 292-8. 7. Galloway SDR, Maughan RJ. Effects of ambient temperature on the capacity to perform prolonged cycle exercise in man. Med Sci Sports Exerc 1997; 29: 1240-9. 8. Gonzalez-Alonso J, Mora-Rodr(guez R, Below PR, Coyle EF. Dehydration markedly impairs cardiovascular function in hyperthermic endurance ath­ letes during exercise. J A ppl Physiol 1997; 82: 1229-36. 9. Harrison MH, Edwards RJ, Leitch DR. Effect of exercise and thermal stress on plasma volume. J Appl Physiol 1975; 39: 925-31. 10. Harrison M. Effects of thermal stress and exercise on blood volume in humans. Physiol Rev 1986; 65:149-209. 11. Jeukendrup A, Saris HM, Brauns F, Kester ADM. A new validated endurance performance test. Med Sci Sports Exerc 1996; 28: 266-70 12. Kay D, Taaffe DR, Marino FE. The effect of whole-body precooling and heat storage during self-paced cycling performance in warm humid condi­ tions. J Sports Sci 1999; 18: 937-44. 13. Kay D, Marino FE, Cannon J, St Clair-Gibson A, Lambert Ml, Noakes TD. Evidence for neuromuscular fatigue during high intensity cycling in warm humid conditions. E ur J A ppl Physiol (in press). 14. Kenney WL, Johnson JM. Control of skin blood flow during exercise. Med Sci Sports Exerc 1992; 24: 303-12. 15. Lee DT, Haymes EM. Exercise duration and thermoregulatory responses after whole-body precooling. J A ppl Physiol 1995; 79 : 1971-6. SPORTS MEDICINE MARCH 2001 7 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) 16. Marino F, Booth J. Whole-body cooling by immersion in water at moderate temperatures. J S ci M ed Sport 1998; 1(2): 12-21. 17. Maron MB, Horvath SM, Wilkerson JE. Acute blood chemical alterations in response to marathon running. E u r J A ppl Physiol 1975; 34: 173-181. 18. McLellan TM, Cheung SS, Jacobs I. Variability of time to exhaustion dur­ ing submaximal exercise. Can J A ppl Physiol 1995; 20: 39-51. 19. Montain SJ, Coyle EF. Fluid ingestion during exercise increases skin blood flow independent of increases in blood volume. J Appl Physiol 1992; 73: 903-10. 20. Myhre LG, Hartung GH, Tucker DM. Plasma volume and blood metabo­ lites in middle-aged runners during a warm weather marathon. E ur J Appl Physiol 1982; 48: 237-40. 21. Nadel ER, Cafarelli E, Roberts MF, Wenger CB. Circulatory regulation dur­ ing exercise in different ambient temperatures. J Appl Physiol 1979; 46: 430-7. 22. Nadel ER, Fortney SM, Wenger CB. Effect of hydration state on circula­ tory and thermal regulation. J Appl Physiol 1980; 4fj: 715-21. 23. Nielsen B, Hales JRS, Strange S, Christensen NJ, Warberg J, Saltin B. Human circulatory and thermoregulatory adaptations with heat acclama­ tion and exercise in a hot, dry environment. J Physiol 1993; 460: 467-85. 24. Nose H, Mack GW, Shi X, Morimoto K, Nadel ER. Effect of saline infusion during exercise on thermal and circulatory regulations. J Appl Physiol 1990; 69: 609-16. 25. Ramanathan LN. A new weighting system for mean surface temperature of the human body. J Appl Physiol 1964; 19: 531-3. 26. Schmidt V, Briick K. Effect of a precooling maneuver on body temperature and exercise performance. J Appl Physiol 1981; 50 : 772-8. 27. Senay LC jun. Temperature regulation and hypohydration: a singular view. J A ppl Physiol 1979; 47 : 1-7. Now more important than ever! Can you take it? Do you know? DrugSportFolio 2000 for Sport in South Africa 2/e Compiled and edited by Marlize Smuts, M Pharm Published by iNFOSOURCE CC Foreword by Sam Ramsamy, President of NOCSA An essential working reference of up-to-date inform ation on prohibited and permitted substances for sportsm en in South Africa. “I found it to be complete, easily accessible and user friendly and it quickly provides the answers to the questions asked of me.’’ Prof. Wayne Derman, President of the SA Sports Medicine Association What does this publication contain? Explanatory notes; Anti-doping information, The International Olympic Committee anti-doping code, 1 January 2000; Accredited laboratories; Doping - General Information; 13 steps in drug testing; Listing of prohibited, restricted and permitted drugs; Pharmacological classification of prohibited and permitted substances; Pharmaceutical and health companies. Who should have this reference work? All medical practitioners, pharmacists, sports administration institutions, coaches, relevant libraries and research institutions. ORDER INFORMATION [ ] CD-ROM, June 2000, ISBN 1-919770-19-4 Price R185.00 (incl. VAT) Carriage R17.50 for 1st copy, R3.00 for each additional copy. [ ] PAPER, July 2000, ISBN 1-919770-20-8 Price R215.00 (incl. VAT) Carriage R22.00 for 1st book, R5.00 for each additional copy. [ ] COMBO: CD-ROM + Paper, Price R277.50 (incl. VAT) Carriage R25.00 for 1st book & CD-ROM, R5.00 for each additional set. Orders: South African Medical Association, Private Bag X1, Pinelands 7430. Tel (021) 531-3081, Fax: (021) 531-4126 E-mail: jstrydom@samedical.org Prepayment by cheque or Visa/Mastercard required. Local stock. 8 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) mailto:jstrydom@samedical.org ORIGINAL RESEARCH ARTICLE Does heart rate adequately reflect exercise intensity during mini-trampoline exercise? Adele R W eston (PhD) Anw ar Khan (MMedSc) Maurice Mars (MB ChB) Department of Physiology, Nelson R Mandela Medical School, University of Natal, Durban Abstract Objectives. Quantification o f exercise intensity for exer­ cise prescription on the m ini-tram poline is difficult, as the relationship between heart rate (HR) and oxygen con­ sum ption ( V 0 2) during m ini-tram poline exercise is not clear. The aim s o f this study w ere to elucidate the rela­ tionship between HR and V 0 2 during mini-tram poline exercise, and to com pare this with the equivalent rela­ tionship obtained during treadm ill running over a com ­ parable range of HRs. r Design. Fifteen male subjects aged 1 7 - 2 4 years jogged on a m ini-tram poline at cadences o f 1 0 0 , 1 2 0 , 160 and 2 0 0 steps/min w ith a 15 cm leg lift, and at a fu r­ th e r w orkload o f 120 steps/m in w ith 90° hip flexion. A fter a 90-m inute rest period, five subm axim a] treadm ill w ork­ loads w ere selected fo r each subject to give a sim ilar range o f HRs to those achieved on the mini-tram poline. Following the fifth w orkload on the treadm ill, subjects continued to exhaustion fo r determ ination o f peak V 0 2. Main outcom e measures. V 0 2, HR, minute ventilation, tidal volume, and breathing frequency before and during exercise. Results. V 0 2 relative to HR w as significantly lower dur­ ing exercise on the m ini-tram poline (P < 0.001). HRs obtained during m ini-tram poline exercise overestim ated V 0 2 by up to 450 ml/min when com pared with treadm ill exercise at the sam e HR. The relationship between V 0 2 (m l/m in) and HR (beats/min) on the treadm ill w as linear: V 0 2 = 19.99 x HR - 1 046 (r2 = 0.97), while the relation- CORRESPON DENCE: P rofessor M Mars D epartm ent o f Physiology Nelson R M andela Medical School U niversity o f Natal Private Bag 7 Congella, 4013 KwaZulu-Natal Tel: 031 - 260 4364 Fax: 031 - 260 4455 E-mail: m ars@ m ed.und.ac.za ship between V 0 2 and HR fo r tram poline exercise . showed a pronounced elevation in HR before any ele- j , vation in V 0 2. The mean V 0 2 w hile stepping at 120 steps/min with a leg lift o f 90° hip flexion w as signifi- f cantly higher than w ith a leg lift o f 15 cm (2.10 l/min v. : 1.97 l/min, P < 0.001), ; Conclusions. These results suggest that the use o f HR , as a sim ple m onitor o f exercise intensity and the use o f j step frequency as the method o f changing exercise J ! in te n sity durin g m in i-tra m p o lin e jo g g in g should be } , viewed w ith caution'. . Introduction Running or bouncing pn a m ini-tram poline or ‘rebounder’ has been advocated as a sim ple m eans o f achieving aerobic fit­ ness and w eight lo ss . '2 The m ini-tram poline is relatively inexpensive, small, portable, and offers the benefit o f a low- im pact w orkout in a confined space. It is therefore suitable fo r home exercise. Despite the m ini-tram poline having been developed in 1938 and patented in 1975, the physiological response to rebounding rem ains unclear and very little has been published to support the claim s o f improved cardiovas­ cular fitness and w eight loss.9 Exercise prescription fo r im provem ent o f cardiovascular fitness requires quantification of the intensity o f the exercise performed. Exercise energy costs on the m ini-tram poline reported in five studies2'46910 show a variation o f 279% . This indicates that a range o f exercise intensities can be obtained on the m ini-tram poline .9 M ethods o f changing the intensity of m ini-tram poline running or bouncing include changing the fo o t strike frequency ,59 the height o f leg lift12 and the addition o f sim ultaneous ‘pum ping’ o f hand-held w eights. 10 Heart rate (HR) has been proposed as a m eans of quantifying exercise intensity on the rebounder, 12 and has been used in training studies .34 Target HRs of 70 - 85% o f age-predicted maximal HR (H R max) are said to be required to achieve aerobic train­ ing using the m ini-tram poline . 12 W hile the oxygen consum ption (V 0 2) to HR relationship (V 0 2/HR) fo r treadm ill running is w ell established, it is not well defined fo r exercise on the mini-tram poline. It is con­ ceivable that exercise involving spring-assisted vertical movem ent may alter venous return and stroke volum e and thereby affect the V 0 2/H R relationship. Bhattacharya e t a!.' reported a linear V 0 2/H R relationship w ith tw o-footed bounc­ SPORTS MEDICINE MARCH 2001 9 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) mailto:mars@med.und.ac.za ing on a ‘regular size ’ trampoline at foot-lift heights o f 18 - 1 0 0 cm, with no difference between tram poline and tread­ m ill-derived V 0 2/H R relationships.1 At any given HR, the average V 0 2 on the tram poline was, however, not signifi­ cantly low er than the treadmill-derived V 0 2. Gerberich e f a/ . 5 measured the relationship between V 0 2 and HR during m ini-tram poline and treadm ill jogging in a group of occupationally sedentary women. A 17% increase in HR with a 14% increase in V 0 2 was reported over a range o f stepping frequencies from 105 ste p s/m in to .2 0 5 steps/min on the mini-tram poline. At rebound jogging cadences o f 105 - 165 steps/min, V 0 2 (ml/min) was unchanged, w hile HR rose from 156 to 170 beats/min. This unusual observation was not elaborated upon. In addition, at any given HR the average V 0 2 obtained on the trampoline w as also low er than that obtained on the treadmill. These findings have not been confirm ed, nor have the ventilatory responses to different stepping frequencies been reported. Data on energy expenditure during m ini-tram poline use, w hich would be useful for optimising exercise prescription for w eight loss, are also limited. Reported V 0 2 varies from 1 7 - 4 0 m l/kg/m in .2610 This broad range is probably a reflec­ tion o f the variation in m ini-tram poline technique, particularly with regard to stepping frequency and leg-lift height. A limited num ber o f training studies using rebounding exercise have been completed investigating cardiovascular improvem ents and w eight loss. Some report a significant im provem ent in V 0 2max,411-13 while one showed no significant im provem ent.3 D escriptions o f m ini-tram poline protocols used in these studies are scanty and certainly not standard­ ised between studies with regard to step frequency and step height. Step frequency has varied considerably and leg-lift h eight is fre q u e n tly unspecified. Som e studies have involved ‘rebound aerobics’ rather than jo g g in g .11 The aims of this study w ere to investigate the V 0 2/H R relationship over a sim ilar range of HRs on both the m ini­ tram poline and the treadm ill and to investigate concurrently the effect of step frequency and leg-lift height on HR, V 0 2 and ventilatory param eters while exercising on the m ini­ tram poline. Methods Subjects Eighteen m ale subjects aged 17 - 24 years w ere recruited for this study. All w ere healthy and active, with a considerable range in the level of daily activity within the group. One sub­ je c t experienced cram p of the hip flexors during the trial and was unable to com plete the testing protocol. HR data were incom plete fo r tw o subjects and their results w ere excluded, leaving 15 subjects for analysis. Informed written consent' was obtained from all subjects and the study was conducted with the approval o f the Ethics and Research Com m ittee of the Faculty o f Medicine, University o f Natal. Procedures All subjects w ere fam iliarised with both m ini-tram poline and treadm ill jogging before testing. Prior to the com m encem ent o f testing, the subjects’ height and w eight w ere measured, and a medical history obtained. A multi-gtage submaximal exercise protocol was then com pleted on the mini-tram po- line. This was followed by a m ulti-stage subm axim al exercise protocol on the treadmill, w hich was then extended to elicit a maximal response. It w as not possible to random ise the order o f the two tests as the treadm ill w orkloads for each subject were assigned according to the range o f HRs achieved during the m ini-tram poline protocol and because of the maximal nature of the treadm ill protocol. The subjects performed a five-stage subm axim al protocol on the m ini-tram poline at stepping frequencies from 1 0 0 to 200 steps/m in (Table I). The duration o f the first workload was 5 minutes, with subsequent w orkloads lasting 3 min­ utes. There was a 1-minute rest interval between each o f the first four w orkloads and a 5-m inute rest interval before the final workload. Step frequency was tim ed to a metronome. A step height o f 15 cm w as used for the first four stages and w as closely monitored by a designated observer using mea­ sured vertical markers. Leg lift fo r the fifth stage required subjects to flex their hips to 90° during each stride. The step frequency o f 1 2 0 steps/min chosen fo r com parison o f leg-lift heights w as based on Katch e f a/.’s6 observation that a step frequency o f approxim ately 1 2 0 steps/m in w as the most com m on naturally selected frequency when m ini-tram poline jogging. TAB LE I. Five stage m ini-tram poline protocol S tep pin g freq uen cy (step s/m in)* S tep h e igh t (cm ) Duration (m in) 100 15 5 120 15 3 160 15 3 200 15 3 120 90° to vertical 3 * E ac h foot strike equals one step, t T h e subject's hip is flexed to 90°. Subjects then rested fo r 90 minutes before undertaking the treadm ill protocol (Pow erjog EG10). During this tim e sub­ je cts were allowed to drink water. Mean resting HR after 90 minutes o f rest w as no different to that before the m ini-tram - poline protocol. W orkloads w ere of the same duration and w ith the sam e rest intervals as during the m ini-tram poline exercise. W orkloads w ere individually assigned according to the range of HRs achieved by each subject during the m ini­ tram poline exercise protocol, with knowledge o f their tread­ mill HR response from the fam iliarisation session. The first tw o w orkloads w ere at w alking speeds, with the remaining three at running pace with increases in speed and slope between w orkloads. A fter the fifth workload, slope and speed were increased every minute until the subject could no longer continue. In all instances, the HR at the point of exhaustion was more than 90% o f the predicted HRmax for age and in all but two cases, the respiratory exchange ratio (RER) was greater than 1.05. The gas exchange analysis was performed using open circuit spirom etry (Oxycon Gamma, M ijnardt) calibrated for gas concentrations and volum e before every testing session. 10 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) Throughout both mini-tram poline and treadmill exercise, m inute ventilation (VE), V 0 2 and RER w ere measured con­ tinuously. HR w as measured every 5 seconds throughout exercise using telem etry (Polar Sport Tester HR monitor). All values reported are those averaged over the last 30 seconds o f the workload. Energy expenditure, based on the thermal equivalent o f oxygen adjusted for the RER, was calculated at each w o rklo a d .7 A dditional investigations in five subjects confirmed that subm axim al m ini-tram poline exercise followed by 90 minutes o f rest did not influence V 0 2 or HR response during the treadm ill protocol. Statistical analysis Data are presented as mean and one standard deviation (SD). The effect of w orkload and mode o f exercise (mini­ tram poline v. treadm ill) on V 0 2 with regard to HR was deter­ mined by tw o-w ay analysis o f variance with repeated m easures. The effect o f m ini-tram poline stepping cadence on respiratory responses was determ ined using a one-way analysis o f variance (ANOVA). Comparison o f leg-lift height w as carried out using the S tu d e n t's paired f-test. Correlations between variables utilised Pearson’s correlation coefficient. Significance was set at P < 0.05. Results The subjects’ age, mass, height and V 0 2max are shown in Table II. M ean HR and V 0 2 for each subm axim al workload during m ini-tram poline and treadm ill exercise and the maximal data from the treadm ill exercise test to exhaustion are presented in Table III. There w as an increase in both V 0 2 and HR with increased stepping frequency ( 1 0 0 - 2 0 0 steps/min) on the mini-trampoline and with increased workload on the treadmill. TABLE II. Subjects’ characteristics ( N = 15) C h a rac teristic . M ean Range Age (yrs) 20.9 (1.8) 1 7 - 2 4 Mass (kg) 63.6 (4.7) 58.2 - 73.8 Height (cm) 170.9 (3.7) 1 6 2 .5 - 176.7 V 0 2ma, (ml/kg/min) 52.3 (5.9) 40.9 - 59.6 V 0 2ma, (l/min) 3.32 (0.42) 2.55 - 3.83 In order to compare V 0 2 relative to HR during the two modes o f exercise, the oxygen pulse (V 0 2 per heart beat) was examined. For ease of comparison, treadm ill V 0 2 values were modelled for the exact HRs obtained during mini-tram- poline exercise, using the treadmill V 0 2/H R relationship derived from the treadmill linear regression equation in Fig. 1 . The differences in VOa and oxygen pulse between trampoline and treadmill exercise at any given HR are shown in Table IV. H R (b e a t s / m in ) Fig. 1. Relationship between HR and oxygen consumption on treadmill and on the mini-trampoline at stepping frequencies o f 100, 120, 160 and 200 steps/min and 200 steps/min with 90° hip flexion. The regression equation for treadmill data is V 0 2 (ml/min) = 19.99 x H R - 1 046. Two-way ANOVA indicated a significant effect of mode of exercise on the oxygen pulse, with a low er result during trampoline exercise (P < 0.001). Thus at any given HR, V 0 2 was higher on the treadmill than on the mini-trampoline. The magnitude of the difference is shown in Table IV. Although there was no significant interaction effect of mode o f exercise and increasing exercise workload on oxygen pulse (P = 0.08), the data displayed in Fig. 1 reflect the trend toward a different slope of the V Q 2 v. HR relation­ ship. During treadm ill exercise, HR and V 0 2 both increased from workload 1 through to m aximum workload, resulting in a linear relationship (V 0 2 (ml/min) = 19.99 x HR (beats/min) - 1 046, r2 = 0.97). During m ini-tram poline exercise, HR was increased with each increase in stepping frequency, while V 0 2 only increased significantly when the step frequency was raised to 200 steps/min (P < 0.01). This was an unex­ TABLE III. Heart rate and oxygen consumption during mini-trampoline and treadmill exercise, expressed as mean and 1 SD M in i-tram po line Treadm ill Heart rate < O Heart rate < O Steps/min . ( beats/minutes) (l/min) Stage (beats/min) (l/min) 100 134 (19), 1 .5 7 (0 .3 6 ) 1 143 (14) 1.81 (0.16) 120 147 (17) 1.53 (0.32) 2 153 (16) 1.9 7 (0 .1 8 ) 160 153(19) 1.56 (0.25) 3 160 (17) 2.17 (0.23) 200 166 (-19) 2.00 (0.29) 4 169(17) 2.41 (0.19) 120/90° 1 7 3 (1 5 ) ' 2.14 (0.27) 5 180 (15) 2.50 (0.18) Max 201 (6) 3.32 (0.42) SPORTS MEDICINE MARCH 2001 11 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) TA B LE IV. Com parison o f mean oxygen consum ption and oxygen pulse at HRs obtained during tram poline exercise. The m ean treadm ill oxygen consum ption is calculated from the regression equation derived in Fig. 1 , and th e mean treadm ill oxygen pulse is calculated from the m odelled treadm ill oxygen consum ption HR tram p o lin e (b eats/m in) V O z tram p o lin e (ml/m in) v o 2 tread m ill (m l/m in) D ifference (m l/m in) . 0 2 pulse tram po line (m l/b eat) 0 2 pulse tread m il (m l/b eat) D ifference (m l/b eat) 134 1 5 7 0 1 6 3 4 64 11.72 1 2 .1 9 • 0 .4 8 1 4 7 1 5 3 0 1 8 9 4 3 6 4 10.41 1 2 .8 8 2 .4 7 1 5 3 1 5 6 0 2 0 1 4 4 5 4 1 0 .2 0 1 3 .1 6 2 .9 7 1 66 2 0 00 2 2 7 4 2 7 4 1 2 .0 5 1 3 .7 0 1 .6 5 1 7 3 2 140 2 4 1 4 2 7 4 1 2 .3 7 1 3 :9 5 1 ,5 8 pected finding and more interm ediate stepping frequencies are required in order to describe the curve with precision. The mean HR and V 0 2 obtained at a step frequency of 120 steps/min with the hips flexed to 90° on the m ini-tram - poline was significantly greater than with a fo o t lift of 15 cm (P < 0.001) (Table III). The mean energy expenditures a t the different step frequencies are shown in Fig. 2. .? 12 1 Ik 120 140 160 200 120/90 S teps/m in Fig. 2. Energy expenditure a t the different stepping frequencies expressed as mean and one standard deviation. The ventilatory changes during m ini-tram poline jogging are shown in Table V. W ith increasing step frequency on the m ini-tram poline, V E and respiratory rate increased signifi­ cantly (P < 0.001), in a fashion best described by a third- order polynom ial, although m ore points are required to describe this relationship with precision. In contrast, tidal volum e w as not significantly increased over the range of step frequencies used in this study despite the increase in V E, w hich m ust therefore be accounted fo r primarily by the increases in breathing frequency (P < 0.001). A t 120 steps/m in with higher leg lift, the respiratory rate w as less than at 200 steps/min, despite the 120 steps/min with 90° hip flexion workload provoking a higher V E and V 0 2. The relationship between % H R max and % V 0 2max differs between the tw o exercise m odalities. W hen exercising on the tram poline, a higher percentage o f H R ^ i s required to achieve a % V 0 2max com parable with that achieved on the treadm ill. For example, 75% H R max represents 60% V 0 2max during treadm ill exercise, w hile during m ini-tram poline exer­ cise, 75% H R max equates to only 47% V 0 2max(Fig. 3). The percentage of HRmax utilised by individuals when exercising on the m ini-tram poline at step frequencies of 1 2 0 steps/min and 160 steps/min show s a w eak relationship with individu­ a ls ’ V O 2m0X (Table VI). % HRmax Fig. 3. The relationship between %HRmax and % V 0 2m3X on tread­ mill and on the mini-trampoline. TABLE V. Ventilatory results during m ini-tram poline exercise expressed as m ean and 1 SO S tep s/m in V E (l/m in) VT(I) f (b reath s/m in) S tep s/b reath v6/v02 1 00 3 2 .6 (9 .3 ) 0 .9 7 (0 .3 0 ) ' 33.1 (1 0 .4 ) 3 .0 2 0 .8 1 20 3 8 .4 (1 1 .1 ) 0 .9 9 (0 .2 7 ) 3 8 .0 (1 2 .7 ) 3 .2 25.1 160 4 0 .0 (8 .6 ) 1 .0 0 (0 .2 7 ) 4 0 .0 (1 2 .4 ) 4 .0 2 5 .6 2 0 0 5 2 .7 (1 2 .7 ) 1 .1 7 ( 0 . 3 3 ) 4 5 .6 (1 6 .8 ) 4 ,4 2 6 .4 1 2 0 /9 0 ° 5 4 .4 (9 .4 ) 1 .3 2 ( 0 . 3 0 ) 4 2 .1 (1 3 .2 ) 2 .9 2 5 .2 V6 = minute ventilatory volume; VT = tidsi volume; f = respiratory rate; VE/V 0 2 = oxygen equiavalent. 12 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) TABLE VI. Correlation o f the percentage o f HRmax with the perecntage V 0 2max achieved on the mini-trampoline %HRmax at 100 steps/min r = - 0.42, NS %HRmax at 120 steps/min r = - 0.58, P < 0.05 %HRmax at 160 steps/min r = - 0.55, P < 0.05 %HRmax at 200 steps/min r = - 0.31, NS %HRmax at 120/90° steps/min r = - 0.10, NS N S = not significant. Discussion In a review o f rebounding exercise and cardiorespiratory fit­ ness, Sm ith and Bishop m ade the following assertion, ‘O bviously the rate at w hich a subject jogs on a rebounder will influence the energy cost’ .9 In the present study, at a foot lift o f 15 cm, an increase in the jogging rate did not, however, provoke an increase in V 0 2 or energy expenditure except at the highest step frequency o f 2 0 0 steps/min. As the m ini-tram poline is a popular exercise m odality in the home, w here the sim plest objective m easure o f exercise intensity is HR, a knowledge o f the V 0 2/H R relationship is important. V 0 2 w as consistently low er during exercise on the m ini-tram poline when com pared with treadm ill exercise at a com parable HR. In addition, the V 0 2/H R relationship observed while jogging on the m ini-tram poline w as non­ linear, w ith the HR relative to the m easured V 0 2 being dis­ proportionately high at stepping frequencies of 1 0 0 , 1 2 0 and 160 steps/m in. As no m easurem ents w ere taken between 160 and 2 0 0 steps/min, it is not possible to clarify the point or nature of the inflection in the V 0 2/H R curve. This finding partially supports the findings o f G erberich et al.’s study5 o f untrained w om en, w hich did not illustrate a significant increase in V 0 2 even at the higher workloads. The cause o f the increasing HR w ith an unchanging V 0 2 is unclear. If the constant V 0 2 reflects a constant cardiac out­ put, then the increase in HR may be explained by a reduc­ tion in stroke volume secondary to possible changes in venous return. Venous return may be altered by vertical m ovem ent and reduced calf muscle pump activity or breath­ ing pattern relative to vertical m ovem ent. This response requires further investigation. The V 0 2 and associated energy expenditure observed in the current study fell within the range o f values reported in previous studies .610 A t the low er three stepping frequencies, V 0 2 w as below that recom m ended fo r im provem ent in car­ diovascular fitness .8 Even at a stepping frequency as high as 160 steps/m in, the mean V 0 2 o f 1.56 l/min (24.5 m l/kg/min), represented 47% of V 0 2max with a range o f 27% V 0 2max - 6 8 % V 0 2max. This exercise intensity is unlikely to result in signifi­ cant im provem ents in cardiovascular fitness, nor is it likely to be associated with substantial w eight loss. Use o f HR target zones fo r training has become popular, and 70% HRmax is often quoted as the threshold level above w hich aerobic training effects will occur. Extrapolation o f data from the m ini-tram poline and treadm ill % HRmax/% V 0 2max curves indicate that a level o f V 0 2 com parable with that achieved at 70% HRmax on the treadm ill is achieved at approxim ately 80% HRmax on the mini-tram poline. HRs in excess o f 80% HRmax w ere only achieved at a step frequen­ cy of 200 steps/min with a 15 cm lift, and at 120 steps/min with 90° hip flexion. The height o f leg lift significantly affects V 0 2, and at 120 steps/min an increase in the leg lift from 15 cm fo o t lift to 90° o f hip flexion resulted in an increase in the V 0 2 o f 41 % (P < 0.001). This is in contrast to an increase in V 0 2 o f only 3% when stepping frequency w as increased from 120 to 160 steps/min. A significant 31% increase in V 0 2 was obtained when stepping frequency was increased to 200 steps/min (P < 0.001), but this stepping frequency requires consider­ able co-ordination and motivation from the subjects. Studies investigating the use o f hand-held w eights while mini-tram- polining have reported an increase in energy expenditure of a sim ilar degree, dependent upon the w eight and the ‘pump­ ing’ height. Increasing the height of leg lift m ay be a suitable and sim pler alternative to the addition o f hand-held w eights.'0 Energy utilisation at HR zones com m only associated with training and aerobic weight reduction programmes is low er in tram poline jogging than in treadm ill running and may be insufficient to achieve the desired effect. The use o f HR as a sim ple m onitor of exercise intensity and the use of step frequency as the method o f changing exercise intensity during m in i-tram poline jo g g in g should be view ed with caution. Further studies o f w ays to increase exercise intensity and V 0 2 using the m ini-tram poline are required, and the cause o f the reduction in V 0 2 relative to HR in tram poline jogging w arrants further investigation. Traditional target HR zones need to be reassessed fo r use with m ini-tram poline jogging. R e f e r e n c e s 1. Bhattacharya A, Shvartz E, McCuthcheon EP, Greenleaf JE. Body accel­ eration distribution and 0 2 uptake in humans during running and jumping. J Appi Physiol 1980; 49: 881-7. 2. Cooter GR, Tinklepaugh P. Physiological response to exercise on a ‘rebounder’. Southern C hapter o f the American College o f Sports Medicine Selected Research Abstracts 1983: 38. 3. Evans BW, Clairborne JM, Thomas S. Changes in aerobic capacity and body composition subsequent to an eight week rebounding running pro­ gram. Med Sci Sports Exerc 1984; 16: 104. 4. Gerberich SG, Bishop PA, Leon AS. The effects of rebound exercise upon physical fitness, body composition, and blood lipids. Med Sci Sports Exerc 1983; 15: 90. 5. Gerberich SG, Leon AS, McNally C, Serfas R, Edin J. Analysis of the acute physiologic effects of minitrampoline rebounding exercise. Journal o f Cardiovascular Rehabilitation 1990; 10: 395-400. 6. Katch VL, Villanacci JF, Sady SP. Energy cost of rebound running. Res Q Exerc Sport 1981; 52: 269-72. 7. McArdle WD, Katch FI, Katch VL. Measurement of human energy expen­ diture. In: Exercise Physiology. 3rd ed. Philadelphia: Lea and Febiger, 1991: 145-57. 8. Shephard RJ. Aerobic Fitness and Health. Champaign: Human Kinetics, Champaine 1994; 208. 9. Smith JF, Bishop PA. Rebounding exercise. Are the training effects suffi­ cient for cardiorespiratory fitness. Sports Med 1988; 5: 6-10. 10. Smith JF, Bishop PA, Ellis L, Conerly MD, Mansfield ER. Exercise intensi­ ty increased by addition of handheld weights to rebounding exercise. J Cardiopulm Rehabii 1995; 15: 34-8. 11. Tomassoni TL, Blanchard MA, Goldfarb AH. Effects of rebound exercise training program on aerobic capacity and body composition. The Physician in Sportsmedicine 1985; 11: 111-15. 12. Walker M. Jumping fo r Health: A Guide to Rebounding Aerobics. New York: Avery Publication Group, 1989: 10-28. 13. W hite JR. Changes following ten weeks of exercise using a minitrampo­ line in overweight women. Med Sci Sports Exerc 1980; 2: 103. SPORTS MEDICINE MARCH 2001 13 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) ORIGINAL RESEARCH ARTICLE Clustering of athletic ability in male Kalenjin scholars M Nurok (MB ChB) A G Morris2 (PhD) C O ’Connell3 (BA) T D Noakes1 (MB ChB, MD, FACSM) . 'MRC/UCT Research Unit for Exercise Science and Sports Medicine, University of Cape Town and Sports Science Institute of South Africa, Newlands, Cape Town de p a rtm e n t of Anatomy and Cell Biology, University of Cape Town 3Former Headmaster, St Patrick’s School,. Iten, Kenya I Abstract ! Aim . The present study aim ed to establish any biologi- ( cal or socio-cultural differences between a group o f run- j ners and non-runners attending high school in the heart j o f Kenya’s Kalenjin-speaking region, f M ethods. A case-controlled dem ographic and anthropo- J m etric study w as perform ed on schoolchildren at St I Patricks School, Kenya. Two sam ple groups w ere used. ! The first group consisted o f pupils w ho participated in athletics, and the second group consisted o f pupils who did not. Results. Eighteen o f the runners had a t least one first- J degree relative involved in com petitive running, while of | the non-runners, tw o had a first-degree relative running competitively. Runners tended to be heavier and taller I than non-runners and jum ped significantly further in the ! standing long jum p test. I Conclusions. These data could support the hypothesis ; that among the Kalenjin Kenyan tribe, there exists on a , hereditary basis specific lineages with superior running { ability. Alternatively, the social-cultural hypothesis that a J proven fam ily history of running ability encourages | potential adolescent runners to follow the fam ilial exam- ; pie may also be supported by these findings. Introduction There is substantial speculation th a t specific biologically defined populations have genotypes th a t enable them to succeed in given athletic events at a rate disproportional to those w ithout the speculated genotype .4 Areas o f focus CORRESPONDENCE: T D Noakes Sports Science Institute o f South Africa PO Box 115, Newlands, 7725 Tel: 021 - 650 4557 Fax: 021 - 6 8 6 7530 E-mail: TD N O AKES@ SPO R TS.UC T.AC.ZA include the com petitive successes o f W est African sprinters and East African long distance runners,2,811 and elite black male South African long distance runners .313-14 A previous study3 showed that elite black male South African long dis­ tance runners dem onstrated ‘superior fatigue resistance' to their non-black counterparts. This finding could explain why 90% o f the top positions in South African road races from 5 to 56 km are filled by black athletes,3 w ho com prom ise less than 20% o f the South African running population. As early as 1944, the South African scientist Ernst Jokl5 speculated that: ‘Serious consideration should be given to the hypothe­ sis that the Negro muscle — in contrast to the muscles o f whites — is a superior m achine, producing from a given am ount of fuel more energy and less heat'. In recent years Kenyan runners have dom inated long and middle distance running events .6912 Kenya’s more than 40 indigenous languages, which correspond closely with ethnic groups or tribes, are commonly classified as Bantu, Nilotic or Cushitic. Approximately three-quarters of Kenya’s international runners come from a Nilotic group known as the Kalenjin, who comprise about 11% o f the Kenyan population.715 Manners6 has suggested th a t the conventional explana­ tions for the extraordinary com petitive success o f Kenyan runners — living at 2 0 0 0 m altitudes, enjoying the ideal cli­ mate o f the Kenyan highlands, subsisting on a high carbo­ hydrate diet, using walking o r running as a principal mode o f tra n sp o rta tio n and stro n g ly m otivated by the m aterial rew ards available to successful runners — do not adequate­ ly explain the concentration of running success am ong the Kalenjin. He invokes the possibility of genetic predisposition to running ability based on a collection o f case studies and the hypothesis that custom s peculiar to the Kalenjin people may have acted as selective pressures tow ards such genet­ ic ability. These include cattle raiding, w hich called fo r long treks w here speed and endurance w ere essential, and which was rewarded by increased ability to pay fo r brides. If this hypothesis is correct and the relevant custom s have been practised fo r m any centuries, one w ould expect running abil­ ity to be distributed throughout the Kalenjin population, as indeed M anners6 and his inform ants believe. However, based on the high degree o f biological relations among inter­ nationally successful Kalenjin runners, there is also the sug­ gestion that even within the Kalenjin and perhaps other Kenyan populations, specific lineages with superior running ability may exist. 14 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) mailto:TDNOAKES@SPORTS.UCT.AC.ZA Eldoret is the second largest town in the Rift Valley province. N ear Eldoret lies Iten, hom e o f St P atrick’s school, w hich has, over the years, produced a disproportionate num­ ber o f elite Kenyan runners.12 St P atrick’s has developed a lim ited policy o f preferentially adm itting athletically talented pupils w hose academ ic standard may otherwise have pre­ cluded their entrance into the school. The present study aimed to establish w hether there w ere any biological or socio-cultural differences between a group o f runners and non-runners, all o f w hom attend St Patrick's school in the heart o f Kenya’s R ift Valley province. Material and methods The case-control study w as conducted at St P atrick’s School, Iten, Kenya. The form er headm aster and running coach at the school and coach to a num ber o f other elite Kenyan athletes (C O ’C), adm inistered a standard question­ naire to 50 male students at the school between the ages o f 15 and 21 years. Two sample groups w ere used. The first (N = 25) w as com posed o f pupils w ho participated voluntar­ ily in athletics as an extra-curricular activity. The second sam ple (N = 25) consisted o f pupils w ho did not participate in athletics. All these boys w ere born and grew up in Kenya's Rift Valley. The questionnaire detailed: (/) dem o­ graphy, including questions regarding parents’ highest level o f education; (ii) w hether there w ere any first-degree rela­ tives who participated in com petitive running and at w hat level; (iii) tribal background dating back to m aternal and paternal grandparents; and (iv) w hat students planned to do after leaving school. A standing long jum p test was also adm inistered to all participants. The test required both feet to be flat on the ground, shoulder width apart, toes ju st behind the line, knees at 120°, and arms to the sides. A counter m ovem ent o f the arm s was allow ed im m ediately before the jum p. The jum p was measured to w here the heels landed. Three opportunities were given, and the best result was recorded. Additionally, pupils w ere weighed to the nearest kilogram , and height was m easured to the nearest centim etre. This inform ation was used to calculate the body mass index (BMI) (kg/m 2). A standard chi-square analysis w as perform ed to assess the significance o f differences betw een variables in the two groups for each o f the following: related running relatives, tribal background, level o f parental education, and intention to pursue fu rth e r'e d u ca tio n . A Student’s (-test w as per­ form ed to assess the significance o f differences between BMIs of runners and non-runners, long jum p differences, height and w eight differences, age differences, and differ­ ences between centim etres jum ped per kilogram o f body weight. Results O f the 25 runners, 23 could confidently trace their origins to Kalenjin o r one o f the Kalenjin sub-tribes, bilaterally for two generations. Twenty-one o f the non-runners could do like­ wise. There was no significant difference between the tribal background o f runners and non-runners. O f the runners, 16 had at least one parent with post-prim ary school education, w hile 19 o f the non-runners had a t least one parent with post-prim ary school education. This difference w as not significant (Table I). Eighteen o f the runners had a t least one first-degree relative involved in com petitive running. These 18 included 4 international, 4 national, 2 provincial, 5 district and 1 zonal runner(s). O f the non-runners, 2 had at least one first- degree relative running competitively, 1 at provincial level and 1 at district level. This difference w as significant (P < 0.001, Table I). Ten runners intended to seek post-secondary school edu­ cation, while 24 non-runners had a sim ilar intention. This dif­ ference w as significant (P < 0.001, Table I). O f the 15 runners who did not intend to seek such education, 6 hoped to become professional athletes, and 9 hoped to seek em ploym ent. W hen the 6 intending to becom e professional athletes w ere rem oved from the group, leaving 10 o f 19 run­ ners intending to pursue post-secondary education, the num ber w as still significantly (P < 0.001, Table I) less than the 24 of 25 non-runners intending to pursue such education. W hen the runner sam ple w as broken down into runners com peting at provincial level and above and those com pet­ ing below this level, 4 o f the 11 runners com peting at the higher level intended to pursue a career in athletics com ­ pared with 2 o f the 1 2 runners competing at the lower level. This difference was not significant. TABLE I. Socio-cultural com parison between runners and non-runners attending St Patrick’s School, Iten, Kenya C ate g o ry value) R un ners (N) N on -runn ers (N) S ig n ifica n ce (P- Exclusively Kalenjin background over 23125 21/25 NS two generations One or more first-degree relatives 18/25 2/25 < 0.001 running competitively One or more parents with post-primary 16/25 19/25 NS school education Intention to seek post-secondary education 10/25 24/25 < 0.001 Intention to seek post-secondary 10/19 24/25 < 0.001 education, excluding subjects intending to become professional athletes SPORTS MEDICINE MARCH 2001 15 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) TABLE II. Anthropometrical data (mean (SD)) for runners and non-runners M easu rem en t R unners N on -runn ers S ig n ificance (P-value) Age (years) 17.6 (1.114) 16.8(1.218) < 0.05 Height (m) 1.74 (0.06) 1.65 (0.08) < 0.001 Weight (kg) 57.9 (5.29) 52.5 (8.27) < 0.05 Body mass index (kg/m2) 19.06 (1.28) 19.09 (2.21) NS Best standing long jump (m) 2.29 (0.21) 1.90 (0.21) < 0.001 Long jump/weight (cm/kg) 3.97 (0.39) 3.71 (0.78) NS Table II lists the anthropom etrical data of runners and non-runners and their standing long jum p perform ance. The tw o groups w ere not ideally m atched as runners w ere signif­ icantly older, heavier and taller, but BMIs w ere not different between the tw o groups. Runners also dem onstrated less variation in body mass than the non-runners. Runners jum ped significantly further in the standing long jum p, but this difference disappeared when results w ere corrected for differences in body mass. Discussion The finding that the tribal backgrounds of runners and non­ runners w ere not significantly different suggests that both sam ples w ere indeed from one population. Accordingly, the most notable finding of this study was that the schoolboy run­ ners had an overw helm ing preponderance of first-degree rel­ atives also involved in com petitive running. In contrast, only 2 (8 %) o f the schoolboy non-runners had a close relative participating in com petitive running. St P atrick’s longstanding reputation for producing out­ standing runners, m any o f whom have achieved internation­ al success, has made it the institution of choice in the Rift Valley province for boys who have serious running am bi­ tions. In view of this, the marked difference in the figures for relatives involved in com petitive running suggests one o f two possible interpretations. It can be argued6 that the difference results from fam ily differences in role m odels and encour­ agem ent — boys encouraged to run by other runners in the im m ediate fam ily are more likely to seek education at St P atrick’s and to participate in athletics after joining the school. Or, alternatively, perhaps instead of or in addition to these social effects, the data offer strong support fo r the initial hypothesis that among the Kalenjin there exists on an hereditary basis specific lineages with superior running abil­ ity. It should be noted that athletics at St P atrick’s is open to all scholars, and the rewards earned by successful runners, nam ely opportunities to travel and possible scholarships to Am erican Colleges or professional running careers, are fam iliar to every boy in the school. Yet the school’s runners com e predom inantly from fam ilies whose mem bers include other com petitive athletes. However, there are important lim itations to this study that need to be recognised. First, neither of the tw o sam ple populations w as ran­ dom ised, nor w ere the tw o sam ples well m atched for age. Second, the reliability of the measuring instrum ents is not known. Finally, we failed to establish w hat percentage o f the runner sam ple w as attending the school as a result of St Patrick’s preferential adm issions policy. In view of these considerations, these results should be considered provisional pending a sim ilar study conducted by researchers using larger random ised age-m atched samples and certified measuring equipm ent, taking into account the num ber o f preferentially adm itted athletes. If the present results are confirm ed, a further study would be needed to test the hypothesis that lineages with superior running abili­ ty exist on a biological basis. This study would need to per­ form physiological tests on the younger siblings of fam ilies with and w ithout histories o f athletic excellence before the siblings had started running, and therefore before they had experienced a training effect. Surprisingly, the BMIs o f the tw o groups w ere essentially identical. As the teenage years are the m ost m etabolically expensive of an individual's life, and as running would add a further m etabolic stress, one w ould expect the runners to have lower BMIs. This is especially true for Kenyans in Iten who m ust subsist, for econom ic reasons, on a high-bulk, low- caloric rural d ie t.12 It may be that the runners sim ply ate more than the non-runners, as food at St P atrick’s is not strictly rationed and the kilojoule intake of the populations was not m onitored. Alternatively, the runners’ m etabolic rates may have adapted to higher energy dem ands and a relative caloric deficiency. R unners w ere taller and heavier than non-runners. This could be because runners w ere older, although growth velocity generally declines in the late te e n s .10 Alternatively, runners m ight com prise a separate population within the Kalenjin-speaking people or they may indeed have enjoyed better than average nutritional circum stances. The significantly better perform ance of the runners in the long jum p may be explained by their greater height and pre­ sumed greater stride length. An alternate explanation would be th a t the runners w ere more powerful, again either on a genetic basis or as a result of their training. The finding that a disproportionate num ber of athletes com peting at provincial level and above intended to pursue a career in athletics suggests that running perform ance may influence career choice. The know ledge that close relatives pursued a running career w ould probably act as the spur to start running. However, new runners must also be aware of the large num ber o f Kalenjin runners w ho do not achieve international success or for whom international success does not guarantee long-term financial security.1612 This explanation, however, does not tell us w hy runners not planning to pursue a career in athletics do not intend to pursue post-secondary school education. This is especially surprising since the educational levels of the parents of the runners and non-runners w ere similar, and the non-runners 1 6 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) overw helm ingly intended to pursue such education. This finding m ay be an artefact o f St Patrick’s preferential adm is­ sions policy, in that a disproportionate num ber o f the running subjects m ay have demonstrated low er academ ic capacity from the start. Alternatively, running perform ance could be a better predictor o f career choice in Iten than the level o f parental education. In summary, if the localisation o f athletic talent in circum ­ scribed areas o f the Rift Valley o f Kenya1 is due to the bio­ logical pressure o f a high altitude rural lifestyle, then one w ould expect running ability to be distributed throughout the population resident in that area. But this study seems to identify a group o f runners from the sam e population as their non-running counterparts with sim ilar opportunity to partici­ pate in running at school, but with a marked difference in the num ber o f biological first-degree relatives who are com peti­ tive athletes, with sim ilar BMIs despite presum ed increased energy expenditure from participating in running, and with sim ilar role m odels in term s o f level o f parental education, yet dissim ilar goals in term s o f education. The argum ent for a biological basis for this finding is sug­ gested by the strong fam ilial links, presum ed more efficient m etabolism , superior relative absolute long jum p ability, and sim ilar parental role models in a population that is otherwise identical. Alternatively, an equally convincing socio-cultural expla­ nation can be made by arguing that a proven fam ily history o f running ability encourages potential adolescent runners to follow the fam ilial example, especially as the prospect o f financial success for children born in a poor rural com m unity will be a profound motivator. Further, it is possible that lin­ eages w ith superior running ability, if they do indeed exist, may have been formed through a culture o f running. Until very recently, social pressures governing mate selection cannot have related directly to com petitive running which has assum ed social significance in Kenya in the last 50 years. But success in the possibly related enterprise o f cattle raiding has long been a significant factor in mate selection6 and could have resulted in the observed concen­ trations o f ability. This study was funded by the Medical Research Council and the Harry Crossley Staff Research Fund of the University of Cape Town. The authors thank the participants and members of staff at St Patrick’s School in Iten who made this study possible. Informed interpretation of the findings would not have been pos­ sible without liberal access to Mr John Manners’s encyclopaedic knowledge and intimate understanding of Kenya, her people and her runners. His gracious assistance with the preparation and refinement o f the final manuscript is gratefully acknowl­ edged. R e f e r e n c e s 1. Bale J, Sang J. Kenyan Running. London: Frank Cass, 1996. 2. BurfootA . White men can’t run. Runners World 1992, Aug: 89-97. 3. Coetzer P, Noakes TD, Sanders B, et al. Superior fatigue resistance of elite black South African distance runners. J Appl Physiol 1993; 75: 1822-7. 4. Himes JH. Racial variation in physique and body composition. Canadian Journal o f Sports Science 1988; 13: 117-26. 5. Jokl E. Physiological data showing that standards of physical efficiency and of heat resistance of African natives are high. Clinical Proceedings 1944; 4 : 355-76. 6. Manners J. Kenya’s running tribe. The Sports Historian 1997; 19(2): 14- 27. Also available at htto://www.umist.ac.uk/UMIST Sport/2 art2/htm, 1997. 7. National census data. Daily Nation (Nairobi). 12 March 1994: 3. 8. Noakes TD. Why do Africans run so swiftly? A research challenge for African scientists. South African Journal o f Science 1998; 9 4 : 531-5 9. Noakes TD. Lore o f Running. 3rd ed. Cape Town: Oxford University, Press, 1992. 10. Rudolph MR. Rudolph's Pediatrics. 20th ed. Engelwood Cliffs, Calif.: Prentice Hall International, 1996. 11. Saltin B, Kim CK, Terrados N, Larsen H, Svedenhag J, Rolf CJ. Morphology, enzyme activities and buffer capacity in leg muscles of Kenyan and Scandinavian runners. Scand J Med Sci Sports 1995; 5: 222- 30 12. Tanser T. Train Hard, Win Easy. The Kenyan Way. Mountain View, California: Tafnews Press, 1997. 13. Weston AR, Karamizrak O, Smith A, Noakes TD, Myburgh KH. African runners exhibit a greater fatigue resistance, lower lactate accumulation, and higher oxidative enzyme activity. J Appl Physiol 1999; 86: 915-23 14. Weston AR, Mbambo Z, Myburgh KH. Running economy of African and Caucasian distance runners. Med Sci Sports Exerc 2000; 32: 1130-4 15. Winkler EM, Sokal RR. A phenetic classification of Kenyan tribes and subtribes. Hum Biol 1987; 59(1): 121;45. SPORTS MEDICINE MARCH 2001 17 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) http://www.umist.ac.uk/UMIST ORIGINAL RESEARCH ARTICLE Popliteal vascular entrapment syndrome — a cause of leg pain to be considered in young athletes Lewis J Levien (MB BCh, FCS(SA), PhD, FACS) Milpark Hospital, Parktown, Johannesburg Abstract Objective. To provide an explanation for the sym ptom s e xp erienced by, and clinical approach to patients presenting with fo o t and calf pain or paraesthesiae brought on by exercise when such sym ptom s are due to popliteal vascular entrapm ent. Design. In this study the clinical features of 93 instances o f popliteal vascular entrapm ent occurring in 51 patients over an 11-year period are presented. In addition, the em bryology of the popliteal artery is reviewed and its rel­ evance to the developm ent o f popliteal entrapm ent explained. Setting. The study w as conducted in a single m ajor vascular surgical centre in the Johannesburg area, and the cases w ere drawn from all the vascular surgeons practising at that centre. Interventions. In patients suspected o f suffering from popliteal vascular entrapm ent, the diagnosis w as confirmed angiographically. Patients were subjected to release of the entrapment mechanism if the underlying artery had not yet undergone occlusion, or to replacement o f the popliteal artery if the artery w as occluded. M ain outcom e m easu res. The d ia g no sis was confirm ed by the operative findings, and the adequacy o f treatm ent w as determ ined by the e xtent of relief of sym ptom s and return to sporting activities postopera- tively. Results. Bilateral popliteal entrapm ent w as found in 42 o f 51 patients. The m ean age at the time o f presentation w as 34.9 years (SD 11.6 years). C laudication was the m ost frequent presenting sym ptom (75 of 8 8 limbs). Types I, II, III and IV popliteal entrapm ent w ere found in 61 limbs (15 arteries occluded), w hile 32 limbs (3 occlu­ sions) presented w ith a ‘functional' popliteal artery entrapm ent (apparent absence o f a developm ental anatom ical abnorm ality). O f 18 lim bs w ith severe ischaem ia and associated occlusion of the popliteal artery, 15 underwent, bypass grafting with reversed saphenous vein grafts. All replacem ent vein grafts rem ained patent during follow-up (m edian 4.2 years, range 1 - 1 1 years). One patient was treated with vein patch angioplasty w hich re-occluded w ithin 6 months and required vein graft replacement. C onclusions. The popliteal entrapm ent syndrom e is much more prevalent than has form erly been appreciat­ ed. Failure to appreciate the diagnosis w hen the patient presents with early sym ptom s usually results in progres­ sion o f the pathology o f the entrapm ent to the point w here degenerative changes in the entrapped vessel culm inate in occlusion and throm bosis. Correct diag­ nosis and surgical intervention before the developm ent o f throm bosis at the site o f the entrapm ent results in prom pt and lasting relief o f sym ptom s, and has the additional m ajor benefit o f preventing further degenera­ tion of the involved artery. On the basis o f observations made in this series and in the surgical literature, surgical correction is advised in all cases of types I, II, III, and IV entrapm ent at time o f diagnosis to avoid occlusion as a result o f continued arterial w all degeneration. On the other hand, in those patients presenting with sym ptom atic ‘functional’ entrap­ ment, surgery is only advised if the sym ptom s are typi­ cal and severe, since up to 50% o f the normal population dem onstrate transient popliteal artery compression with extrem es o f plantar- or dorsiflexion. . On the basis o f the severe histological changes found in those popliteal arteries th a t have undergone occlusion at the tim e o f presentation, it is advised that the popliteal artery should be com pletely replaced, ideally by a vein graft, w hen significant degeneration or occlusion of the popliteal artery is noted at the tim e o f operation. CORRESPONDENCE: D r Lewis J Levien PO Box 2738 Houghton 2041 Tel: 011-726 6789 Fax: 011-726 7775 E-mail: ljlevien@ iafrica.com Introduction The young athletic individual who presents with sym ptom s of leg and foot pain on exercise presents a problem in diag­ nosis and m anagem ent for the clinician. Full and correct evaluation and investigation o f these patients usually per­ mits an accurate diagnosis to be m ade, ' 5 resulting in correct m anagem ent and consequent alleviation o f symptoms. In the young athlete presenting with typical claudication-like sym ptom s o f the calf and foot, popliteal vascular entrapm ent 18 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) mailto:ljlevien@iafrica.com is an im portant and reversible cause o f leg pain and paraes- thesiae, and m ay be the u n d e rlyin g cause o f the claudication sym ptom s in up to 60% o f cases5160 in som e series. Unlike most other com m on causes o f leg pain, popliteal vascular entrapm ent, if not correctly diagnosed and m anaged, m ay well result in occlusion of the popliteal artery w ith the developm ent o f an ischaem ic threat to the lim b .5164 It is therefore im portant fo r all health professionals who deal with patients presenting with leg pain on exercise, to have a good appreciation o f the m anifestations and natural history o f the popliteal vascular entrapm ent syndrom e. Failure to make the diagnosis when the condition is the cause o f the presenting sym ptom s may result in the condition progressing to popliteal artery occlusion and even to the developm ent of critical ischaem ia o f the leg. On the other hand, correctly diagnosed and treated, the long-term prognosis is good, with the m ajority o f individuals returning to their norm al sporting activities .51 First described by a m edical student73 in 1879 following dissection o f an am putated leg, popliteal artery entrapm ent syndrom e was considered by early authors to be a rare phe­ nomenon. A fter Hamming41 described the first clinical case in 1958, v a rio u s isolated case re p o rts w e re p u b ­ lis h e d .1'3'12-13'20'26'28'33'35'42'44̂ ^^^ In the m id-1960s the term ‘popliteal artery entrapm ent syndrom e’ w as introduced811 to describe the condition. Servello71 first drew attention to the reduction in palpable distal pulses frequently observed when patients with this condition perform ed forced plantar- o r dor- siflexion. Biem ans and Van B ockel,7 in an extensive review of the literature in 1977, focused attention on the clinical syn­ drom e o f popliteal vascular entrapm ent. Early authors believed the popliteal artery entrapm ent syndrom e to be rare ,71217192236374752647274 but it has becom e apparent that the condition is considerably m ore comm on than previously appreciated .8 17-192229-31,35,,5,',7'ss's1's2s;,,ss W hile the incidence of the condition in the general population is not known, Bouhoutsos and D askalakis ,8 in the first large series o f cases described, reported an incidence o f 0.165% in young m ales entering the G reek military service. In a post­ m ortem study Gibson e t a / .37 found a prevalence o f 3.5%. Unfortunately, a substantial proportion o f normal individuals will com press or occlude their popliteal artery with forced plantarflexion or dorsiflexion and will have no sym ptom s, a phenom enon that has precluded the use o f non-invasive tests or duplex D oppler being used as a potential screening tool fo r accurately evaluating the true occurrence o f popliteal artery entrapm ent syndrom e in the asym ptom atic general population .2J4'2127'65r7 The entrapm ent m echanism s has been docum ented to in vo lve the p o p litea l vein in up to o n e -th ird o f cases .7 1936374Z-6375 The bilateral occurrence o f the condition was at first assum ed to be rare, but recent literature indicates a high prevalence o f bilateral d isease .12 17 22 28 3764 Popliteal artery entrapm ent syndrom e has been reported to occur in m ore than one individual in a fam ily .72 Classification and embryology E arly attem pts to classify the various types of popliteal artery entrapm ent syndrom e w ere based on the anatom y observed at operation .847 Better appreciation o f the em bryology o f the leg arterial supply, and how the developm ent m ay vary resulting in different types o f vascular entrapm ent, led to a more rational classification based on the developm ental anatomy, with five types of popliteal artery entrapm ent syn­ drom e 6164 currently described. Embryology During developm ent in the human, with limb bud rotation m edially and extension of the knee, the medial head o f the gastrocnem ius muscle migrates from its original lateral posi­ tion616 and moves across the popliteal fossa. W ith further developm ent the definitive attachm ent o f the medial head of the gastrocnem ius muscle is to the posterior surface o f the medial fem oral condyle. The embryological popliteal artery in the developing limb bud is the continuation o f the primitive axial or ischiadic artery.6970 The proxim al portion o f the adult popliteal artery develops from the fem oral artery’ 6 by fusion of the develop­ ing fem oral arterial plexus and the axial popliteal artery. The mid-portion of the definitive popliteal artery is directly derived from the rem nant of the axial artery. The prim itive distal popliteal axial artery, lying deep to the form ing popliteus muscle, disappears at about the 2 0 - 2 2 mm stage o f the embryo, while the definitive distal popliteal artery forms superficial to the popliteus muscle by the fusion o f two new vessels (the new ly anterior and posterior tibial vessels) after the medial head o f the gastronem ius has migrated m edially across the popliteal fossa. During the developm ent of the popliteal fossa, the medial head o f the gastrocnem ius there­ fore m igrates through the popliteal fossa a t about the same time as this rearrangem ent o f the arterial structures.16 Classification of popliteal vascular entrap­ ment syndrome If the definitive distal popliteal artery form s before the m igra­ tion o f the medial head, the newly form ed popliteal artery may be sw ept m edially w ith the definitive artery now lying medial to the norm ally placed medial head o f the gastroc­ nemius muscle. This results in the type I popliteal entrap­ ment with a marked medial deviation o f the popliteal artery in the popliteal fossa, both anatom ically and on angiography, as depicted in Fig. 1 (type I). C om pression o f the artery then results from pressure by the gastrocnem ius tendon. A lternatively, a p re m a tu re ly form ed d e fin itive distal popliteal artery m ay arrest the medial migration o f the m edi­ al head, resulting in a type II entrapm ent with the medial head of the gastrocnem ius now more laterally placed than normal. In the type II entrapm ent, the popliteal artery is m edi­ ally displaced to a lesser degree, and lies deep and medial to the m edial head o f the gastrocnem ius muscle, which attaches more laterally on the medial fem oral condyle or intercondylar area. The artery therefore lies on the medial aspect of, and is entrapped by, the abnormally placed medial head o f the gastrocnemius as demonstrated in Fig. 1 (type II). Should m esoderm al rem nants of the migrating medial head persist posterior to the popliteal artery, or should the SPORTS MEDICINE MARCH 2001 19 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) Type I Type II Clinical picture Popliteal artery Medial head o f Gastrocnemius muscle A ccessary slip o f Gastrocnem ius muscle Medial head o f Gastrocnemius muscle’ Compressed P o p liteal Artery Popliteus Muscle Type III Type IV Fig. 1. Classification o f types o f popliteal artery entrapment syndrome. artery develop w ithin the migrating muscle mass, a type III popliteal entrapm ent m ay result. Here the entrapm ent m ech­ anism is form ed either by fibrous and tendinous bands derived from the rem nants o f the migrating medial head, or more com m only by an abnorm al slip of mature skeletal mus­ cle. These abnorm al additional slips o f muscle tissue may arise from either the medial or lateral fem oral condyles (Fig. 1 (type III)). The definitive popliteal artery may even pass between a double origin o f the medial head o f the gas­ trocnem ius. If the axial artery persists as the definitive distal popliteal artery, it will lie in the prim itive position, deep to the popliteus muscle or fibrous bands ,'10 resulting in a type IV entrapm ent (Fig. 1 (type IV)). W hen any type o f entrapm ent m echanism includes or sur­ rounds the popliteal vein as well as the artery, Rich ef a /.63 64 have termed this a type V entrapm ent.7,3642 50 A ny of the types of entrapm ent (with the possible exception of type I), may include the tibial nerves resulting in neurological paraesthe- siae in addition to claudication as the presenting sym ptom . 15 A type of popliteal artery entrapm ent occurs in the appar­ ent absence of an anatom ical abnormality, termed ‘function­ a l’ entrapm ent.27,65 77 The exact nature of the entrapm ent mechanism rem ains uncertain, but it has been postulated th a t a hypertrophic medial head o f the gastrocnem ius im pinges on the medial and posterior aspect o f the popliteal artery.’ 4,65 Up to half o f apparently norm al asym ptom atic indi­ viduals m ay display the phenom enon o f reduced o r abol­ ished p o p litea l a rte ry blood flo w w ith e xtre m e s o f plantarflexion or dorsiflexion against resistance .214 6577 Such com pression o f the popliteal artery in the absence of sym p­ tom s should not be regarded as pathological, but when clas­ sica l sym p to m s are a sso cia te d w ith the clinical dem onstration o f functional popliteal vascular entrapm ent syndrom e, the condition probably requires treatm ent. It has been proposed that this ‘functional’ type of popliteal entrap­ m ent be term ed type V I.51 O ccasionally popliteal artery entrapm ent syndrom e may be acquired following vascular surgical reconstruction for fem oropopliteal arterial disease .611 The clinical diagnosis of popliteal artery entrapm ent relies on recognition o f the clinical picture o f calf or foot claudication occurring w ith exercise in the young and often athletic indi­ vidual, som etim es accom panied by paraesthesiae of the fo o t.25,12’5,1863 The syndrom e was previously thought to be more com m on in males. Often the initial sym ptom s are precipitated by an episode o f intense physical activity o f the low er limbs, e.g. running a m arathon. S ym ptom s may include cram ping in the calf and foot, coldness, blanching, paraesthesiae and num bness. Som e patients m ay present with an aneurysm o f the popliteal artery. Any popliteal artery aneurysm in a young patient w ithout a history o f risk factors should suggest the presence o f popliteal vascular entrap­ m ent syndrom e. The ankle pulses are norm al at rest if occlusion has not taken place. Untreated, the com pression m echanism fre­ quently results in deterioration of the popliteal artery with the passage o f time resulting in eventual occlusion 13,23 and the absence o f normal ankle pulses. Sudden onset o f severe disabling claudication and absent ankle pulses, usually in the absence of risk factors predisposing the individual to ather­ oma, characterise those patients in whom occlusion o f the popliteal artery has taken place due to popliteal entrapm ent. These patients may present with rest pain or ischaem ic ulcers, although the developm ent o f critical ischaem ia with occlusion o f the popliteal artery is rare .51 Distal em boli19303768 m ay result consequent on focal throm bus form ation 2 33 a t the site o f entrapm ent or from popliteal aneurysm fo rm a ­ tion 61939,5164 secondary to the entrapment. In pa tie n ts w h o p re se n t w ith classical sym ptom s as described above, the presence of normal pulses at rest w hich dim inish or disappear with forced plantarflexion or dorsiflexion, is diagnostic. A bsent pulses in a young athletic individual w ho presents with claudication should always be considered to be due to popliteal vascular entrapm ent syndrom e unless other pathology is demonstrated. Diagnostic modalities The diagnosis o f popliteal artery entrapm ent syndrom e may be confirm ed by D oppler ankle pressures ,8,22,43,5864 pulse volum e recordings, 18 duplex D oppler,24 222354 com puterised axial s c a n n in g ,5966 79 m a g n e tic re sonance (M R) im ag- jng M,32,57,77 anC| angiography. All of these m odalities rely on the dem onstration o f popliteal artery com pression with reduced or abolished popliteal artery blood flow occurring w ith forced active plantarflexion or dosiflexion of the foot against resistance. However, the m ost w idely used diagnos­ tic modality continues to be contrast angiography (Fig. 2a-d), particularly in order to plan surgery when degeneration, aneurysm or occlusion o f the popliteal artery is suspect- ecj 31,38.61 clinical evaluation, non-invasive tests, and angiography all require forced active plantarflexion o r dorsi­ flexion o f the foot against resistance, with the knee fully extended, in order to dem onstrate the abnorm ality if the artery has not yet undergone degenerative changes .27,77 20 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) Patients and methods This study presents 51 patients (93 limbs) treated for popliteal artery entrapm ent syndrom e from January 1988 to D ecem ber 1998. All these patients presented with claudica­ tion-like sym ptom s o f the legs causing severe and debilitat­ ing sym ptom s. All patients w ere subjected to clinical evaluation follow ed by D oppler ankle/brachial pressure index m easurem ent and duplex D oppler o f the popliteal artery at rest. Patients w ith norm al distal pulses were screened using both popliteal artery duplex D oppler and ankle D oppler recording during active plantar- and dorsiflexion against resistance. W here these tests were found to be positive, with reduced or abolished popliteal o r distal flow w ith this m anoeuvre, and in all patients w ith absent ankle pulses or abnorm al D oppler findings at rest, the patients w ere sub­ jected to conventional contrast arteriography, both in the resting and in the forced plantarflexion and dorsiflexion posi­ tions, fo r confirm ation o f the diagnosis. O nly patients with unequivocal evidence o f popliteal artery entrapm ent, either on angiography or at operation, were included in this study. Patients w ere not included if their sym ptom s w ere not typical o f popliteal artery entrapm ent syndrom e, and no patient was included in the study on the basis o f positive non-invasive tests alone in the absence o f severe sym ptom s th a t interfered with norm al sporting activi­ ties. Results N inety-three instances o f popliteal vascular entrapm ent in 51 individual patients w ere included in this study over an 11- ye a r period dating from January 1988 to D ecem ber 1998. The type o f entrapm ent, presenting features and treatm ent are sum m arised in Tables I - IV. In 42 patients the sym ptom s and entrapm ent w ere pre­ sent bilaterally, and in 9 patients the condition w as either totally asym ptom atic or not present in the contralateral leg. The mean age o f all the patients w as 34.9 (range 16 - 55) years. There w ere 58 affected lim bs in male patients (mean age 36.4, range 1 6 - 5 5 years), and 35 affected lim bs in fem ales (mean age 32.0, range 16 - 52 years). In 75 lim bs angiographical exam ination confirm ed the presence o f popliteal artery entrapm ent syndrom e and dem onstrated a healthy and patent popliteal artery. In all 75 limbs, the entrapm ent mechanism was released at opera­ tion, usually by m yotom y o f the medial head o f the gastro­ cnem ius m uscle o r abnorm al muscle slips or tendinous bands responsible for the entrapm ent m echanism , and a healthy popliteal artery was confirm ed on exam ination at surgery. All patients treated in this m anner have retained healthy and patent popliteal arteries on follow-up (m edian follow-up 4.7 years, range 1 - 1 1 years). Alm ost without exception, those patients who had previously been com ­ pelled to stop their sporting activities because o f the sym p­ tom s o f popliteal artery entrapm ent, w ere able to resume normal sporting activities following their postoperative recov­ ery. In 2 patients angiography suggested m oderate 'func­ tional' popliteal artery entrapm ent syndrom e bilaterally with a long, diffuse narrowing o f the popliteal artery on plantarflex­ ion, but an otherw ise angiograhically norm al artery at rest. Both patients experienced resolution o f their sym ptom s w hen they elected to discontinue their extrem e physical activity, and they rem ain well and asym ptom atic with normal popliteal arteries on duplex D oppler scan after 2 and 3 years’ follow-up respectively. Eighteen limbs dem onstrated occlusion o f the popliteal artery o r distal embolisation due to aneurysm al change at the entrapm ent site (13 in males, mean age 33.9 years, SD 11.6 years; and 5 in fem ales, mean age 35.4 years, SD 14.5 TABLE I. Presenting features o f 93 lim bs with popliteal artery entrapm ent syndrom e Type I II III IV Fu nction al o r ty p e VI Total Total in series 5 12 36 8 32 93 O cclusion with seve re ischaem ia 4 5 3 3 3 18 E ntrapm ent cau sin g typical claudication sym ptom s 1 7 33 5 29 75 Venous entrap m ent 1 3 6 0 0 10 TABLE II. A nalysis o f treatm ent o f different types of popliteal entrapm ent syndrom e Type 1 II III IV Fu nction al o r ty p e VI Total Total 5 12 36 8 32 93 O cclusion 4 5 3 3 3 18 M yo tom y and vein graft 3 4 3 3 3 16 M yotom y only 1 7 33 5 25 71 N o op eration 1 1 0 0 4 6 SPORTS MEDICINE MARCH 2001 21 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) TABLE III. Demographics of 51 patients (93 limbs) presenting with popliteal artery entrapment syndrome 9 5 lim bs in 51 patients M ean age o f 51 patients 34.89 yrs (SD 11.62) 9 unilateral 42 bilateral Males Females Total lim bs 58 35 A ge (yrs) 36.46 32.03 S tandard devia tion (yrs) 11.32 11.46 R ange (yrs) 1 6 - 5 5 16 - 52 years). Fifteen limbs w ere treated by replacem ent of the occluded segm ent o f the popliteal artery with reversed saphenous vein grafts. E ight instances o f aneurysm s change w ere noted in this group of patients, all associated with type I - IV entrapm ents. All 15 remain well and patent on follow -up (median follow-up 4.8 years, range 1 - 11 years), with 14 o f the 15 returning to norm al sporting activities. One patient required am putation for advanced ischaem ic change at the time o f original presentation, and 1 patient was treat­ ed conservatively because of extensive distal throm bosis of the infragenicular vessels. Both o f these patients were found to have hypercoaguable states. No other patients in this series w ho u n d e rw e n t o cclusion developed critical ischaemia. Discussion With a greater awareness of popliteal artery entrapm ent syn­ drome we are observing an increase in the frequency of this diagnosis in young adults presenting to the sports medicine specialist.9'0'25,1655 Better evaluation of the problem of the ath­ lete with calf p ain'5'485376 by sports m edicine specialists, and improved investigation and screening o f these cases has improved the diagnostic yield in the young patient with unex­ plained calf pain. More than half the patients under the age of 50 years presenting with claudication sym ptom s o f the low er limbs in this and other series were subsequently dem onstrated to have popliteal artery entrapm ent syndrom e as a cause of their sym ptom s.4251 Most early reports o f popliteal artery entrapm ent syn­ drom e described patients who had progressed to total occlu­ sion of the artery. The natural history o f the popliteal artery with unrelieved com pression was docum ented to be an aggressive one, and on this basis surgery was advised in all patients with a confirm ed diagnosis.31 The description of pro­ gressive fibrosis of the entrapped vessel wall leading to aneurysm form ation and throm bosis1 15 19 24 64 supports this recom m endation. As the pathology progresses with time, progressive fibrosis and destruction o f the arterial wall occurs,51 first in the arterial adventitia (stage I), then in the media (stage II), and finally in the intima (stage III). The im plication is that the degree o f arterial degeneration observed when throm bosis has occurred is so severe that the arterial wall cannot be salvaged. This explains the poor m edium -term patency results obtained after popliteal artery occlusion treated with a lesser procedure such as throm bol­ ysis, angioplasty or throm bectom y with patching. On the other hand, excellent long-term patency is reported after aneurysm repair or occlusion treated by saphenous vein graft. This argues strongly in favour of com plete replacem ent of the popliteal artery, preferably by saphenous vein, when significant degeneration o f the artery or aneurysm formation is noted either on pre-operative angiography, or at the time of operation. Although the data in this study dem onstrate no significant difference between the age of those patients presenting with popliteal artery occlusion and those in whom a myotomy only was required, the youngest patients in the series were in most cases athletes with type I or II entrapm ents, or with tight localised tendinous bands of the type III and IV entrap­ ments who had undergone popliteal artery occlusion. The patients presenting with occlusion at an older age invariably had m uscular entrapm ent m echanism s of type III or type VI. This finding suggests that the rate of arterial wall degenera­ tion in popliteal artery entrapm ent syndrom e may depend on the degree of com pression and the m agnitude o f the forces exerted on the popliteal artery by the com pression m echa­ nism. TAB LE IV. L im b s w ith se ve re is c h a e m ic s y m p to m s d ue to p o p lite a l a rte ry o c c lu s io n c a u se d b y p o p lite a l a rte ry e n tra p m e n t s y n d ro m e Presenting with severe ischaemia Male Female N um b er of lim bs 13 5 A ge of patients (yrs) 33.87 35.40 S tandard deviation (yrs) 11.60 14.49 Most cases of type I and II entrapm ent are easy to diag­ nose on angiography and other imaging modalities. In addi­ tion, the more localised types o f entrapm ent seen with type III and IV, are in our experience frequently distinguishable from the more diffuse narrowing of the artery found at angiography with the ‘functional’ or type VI entrapment. On the basis o f these observations, it is strongly advised that surgical correction be offered in all cases of type I - IV at the time of diagnosis,31 w ithout waiting until arterial degeneration has resulted. The demonstration that the popliteal artery will undergo some transitory com pression or even tem porary occlusion with extrem es of plantarflexion or dorsiflexion in up to half of the normal population, cannot be ignored. The simple dem onstration o f popliteal artery com pression in such stress positions cannot justify operation in patients with otherwise normal anatom y and m inor or no sym ptom s.14-2778 On the other hand, we have in the present series docum ented three popliteal arteries that have undergone occlusion in two patients with a ‘functional’ or type VI sym ptom atic entrap- 22 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) ment, and apparently normal anatomy. The dem onstration that a functional popliteal artery entrapm ent syndrom e may progress to occlusion with the histological picture o f chronic com pression,51 with the degeneration not due to antheroma, justifies a more aggressive surgical approach to sym pto­ matic patients who are dem onstrated to have a functional or type VI entrapm ent. Until further research elucidates the clin­ ical significance and natural history o f degeneration of the popliteal artery in the functional type o f entrapm ent in both the asym ptom atic and sym ptom atic patient, the correct m an­ agem ent of this condition must remain controversial. The various m anifestations and types o f popliteal artery entrapm ent syndrom e are much more prevalent than origi­ nally appreciated. This diagnosis should be considered in any patient under the age o f 50 years presenting with typical calf and foot claudication sym ptom s on exercise, particularly if the sym ptom s occur in an athletic individual and partic­ ularly if the normal risk factors for atherom a are absent. The finding o f an isolated popliteal artery aneurysm or isolated popliteal artery occlusion in the young physically active indi­ vidual w ithout evidence o f system ic disease should be con­ sidered to be due to popliteal artery entrapm ent syndrom e unless proven otherwise. The evidence suggests that all patients in whom the type I - IV entrapm ent is diagnosed before occlusion o f the artery should receive surgical release o f the entrapm ent m echanism prior to deterioration o f the popliteal artery by repetitive com pression. On the other hand, only patients with a significant and typical history of 2b. A lo c a lis e d e n tra pm e nt o f the arte ry w ith p la n ta rfle x io n due to a lo c a lis e d m u s c u la r ba nd ca u sin g a type III entrapm ent. Fig. 2. Some exam ples o f a n g io g ra p h y o f the p o p lite a l artery e n tra pm e nt syndrom e. 2a. A m ed ia l de via tio n o f the arte ry at re s t du e to a type III a d d itio n a l m u s c u la r head ca u sin g the entrapm ent. 2c. L o ca lise d p o p lite a l arte ry aneurysm fo rm a tio n due to p o p lite a l arte ry e n tra pm e nt syndrom e. SPORTS MEDICINE MARCH 2001 23 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) 2d. The lo n g e r sm o o th e n tra pm e nt often seen w ith the ‘fu n c ­ tio n a l’ o r type VI entrapm ent. sym ptom s should be offered surgical treatm ent for the func­ tional or type VI popliteal artery entrapm ent. Once the popliteal artery has undergone occlusion, the evidence sug­ gests that the artery is beyond repair, and it is recom m end­ ed that the artery be replaced, preferably by saphenous vein graft, to ensure optimum long-term popliteal artery patency in these often young and physically active individuals. R e f e r e n c e s 1. Abbott WM, Darling RC. Axillary artery aneurysm secondary to crutch trauma. Am J Surg 1973; 125: 515-20. 2. Akkersdijk WL, de Ruyter JW, Lapham R, Mali W, Eikelboom BC. Colour duplex ultrasonograhic and provocation of popliteal artery compression. Eur J Vase Endovasc Surg 1995; 10: 342-5. 3. Albertazzi VJ, Elliot TE, Kennedy JA. Popliteal artery entrapment. Angiology 1969; 20: 119-28. 4. Allen MJ, Bames MR, Bell PR, Bolia A, Hartshome TC. Popliteal artery entrapment syndrome. Eur J Vase Surg 1993; 7: 342-5. 5. Baker WH, Stoney RJ. Acquired popliteal entrapment syndrome. Arch Surg 1972; 105: 780-2. 6. Bardeen CR. Development and variation of the nerves and the muscula­ ture of the inferior extremity and of the neighbouring regions of the trunk in man. American Journal o f Anatomy 1907; 6: 259-390. 7. Biemans RGH, Van Bockel JH Popliteal artery entrapment syndrome. Surgery, Gynecology and Obstetrics 1977; 144: 604-9. 8. Bouhoutsos J, Daskalakis E. Muscular abnormalities affecting the popliteal vessels. Br J Surg 1981; 68: 501-6. 9. Bouhoutsos J, Goulios A. Popliteal artery entrapment: report of a case. J Cardiovasc Surg 1977; 18: 481-4. 10. Cairols MA, Blanes I, Gimenez A, Miralles M, Sieyro F, Latorre E. An exceptional case of popliteal entrapment syndrome. Eur J Vase Surg 1994; 8: 754-6. 11 Carpenter JP, Lieberman MD, Shlansky-Goldberg K, et at. Infrageniculate bypass entrapment. J Vase Surg 1993; 18: 81-9. 12. Carter AE, Eban RA. A case of bilateral development abnormality of the popliteal arteries and gastrocnemius muscles. B rJ Surg 1964; 51: 518-22. 13. Chavatzas D, Barabas A, Martin P. Popliteal artery entrapment. Lancet 1973; 2: 181-2. 14. Chernoff DM. Walker AT, Khorasani R, ef al. Asymptomatic functional popliteal entrapment: demonstration at MR imgagmg. Radiology 1995; 195: 176-80. 15. Clanton TO, Solcher BW Chronic leg pain in the athlete Clinics in Sports Medicine 1994; 13: 743-59. 16. Colborn GL, Lumsden AB, Taylor BS, Skandalakis JE. The surgical anato­ my of the popliteal artery. Am Surg 1994; 60: 238-46. 17. Collins PS, McDonald PT, Lim PC. Popliteal artery entrapment: An evolv­ ing syndrome. J Vase Surg 1989; 10: 484-90. 18. Cummings RJ, Webb HW. Lovell WW, Kay D. The popliteal artery entrap­ ment syndrome in children. J Pediatr Orthop 1992; 12: 539-41. 19. Darling RC, Buckley CJ, Abbot WM, Raines JK. Intermittent claudication in young athletes: popliteal artery entrapment syndrome. J Trauma 1974; 14: 543-52 20. Delaney TA, Gonzalez LL. Occlusion of the popliteal artery due to muscu­ lar entrapment Surgery 1971; 69: 97-101. 21. Di Cesare E. Marsili L, Marino E. et a l Stress MR imgaging for evaluation of popliteal artery entrapment. J Magn Reson Imaging 1994; 4: 617-22. 22. di Marzo L, Cavallaro A, Sciacca V, et al. Surgical treatment of popliteal artery entrapment syndrome: a ten year experience. E ur J Vase Surg 19 91 ;5 :5 9 -6 4 . 23. Di Marzo L, Cavallaro A, Sciacca V, et al. Diagnosis of popliteal artery entrapment syndrome: the role of duplex scanning. J Vase Surg 1991; 13: 434-8. 24. di Marzo L, Cavallaro A, Sciacca V, Mingoli A, Stipa S. Natural history of entrapment of the popliteal artery. J Am Coll Surg 1994; 178: 553-6. 25. Duwelius PJ. Kelbel JM, Jardon OM, et al. Popliteal artery entrapment in a high school athlete: a case report Am J Sports Med 1987. 15: 371-3. 26. Edmondson HT, Crowe JA. Popliteal artery and venous entrapment. Am Surg 1972; 38: 657. 27. Erdoes LS, Devine JJ, Berhard BM. Baker MR, Berman SS, Hunter GC. Popliteal vascular compression in a normal population. J Vase Surg 1994; 20: 978-86. 28 Ezzet F, Yettiz M Bilateral popliteal artery entrapment: case report and observations. Cardiovasc Surg 1971; 12: 71-4. 29. Ferro R, Barile C, Bretto P, Buzzachino A, Ponsio F. Popliteal artery entrapment syndrome: report on seven cases. J Cardiovasc Surg 1980; 21: 45-52. 30. Fong H, Downs AR. Popliteal artery entrapment syndrome with digital embolisation — a report of two cases. J Cardiovasc Surg 1989; 30: 85-8. 31. Fowl RJ, Kempczinski RF, Whelan TJ. Popliteal artery entrapment. In: Rutherford RB, ed. Vascular Surgery 4th ed. Philadelphia: WB Saunders, 1995: 889-94. 32. Fujiwara H, Sugano T, Fujii N. Popliteal artery entrapment syndrome: accurate morphological diagnosis utilizing MRI. J Cardiovasc Surg 1992; 33: 160-2. 33. Gallagher EG, Hudson TL. Popliteal artery entrapment. Am J Surg 1974; 128: 88. 34. Gaylis H, Rosenberg B. The popliteal artery entrapment syndrome — a bilateral case. South African Journal o f Surgery 1973; 11: 51-4. 35. Gedge SW, Spittel JA jun., Ivins JC. Aneurysm of the distal popliteal artery in its relationship to the accurate popliteal ligament. Circulation 1961; 24: 270-3. 36. Gherkin TM, Beebe HG, Williams DM, Bloom JR, Wakefield TW. Popliteal vein entrapment presenting as deep venous thrombosis and chronic venous insufficiency. J Vas Surg 1993; 18: 760-6. 37. Gibson MHL. Mills JG, Johnson GE, Downs AR. Popliteal entrapment syn­ drome. Ann Surg 1977; 185: 341-8. 38. Greenwood LH, Yrizanny JM, Hallett JW. Popliteal artery entrapment: importance of the stress runoff for diagnosis. Journal o f Vascular Interventional Radiology 1986; 9: 93-9. 39. Haddad M, Barral X, et al The embolic type of popliteal entrapment syn­ drome Vasa 1990; 19: 1. 40. Haimovici H, Sprayregen S, Johnson F. Popliteal artery entrapment by fibrous band. Surgery 1972; 72: 789-92. 41. Hamming JJ. Intermittent claudication at an early age, due to an anom­ 24 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) alous course of the popliteal artery. Angiology 1959; 10: 369-70. 42 Hamming JJ, Vink U. Obstruction of the popliteal artery at an early age. J Cardiovasc Surg 1965; 6: 516-24. 43. Harris JD, Jepson RP. Entrapment of the popliteal artery. Surgery 1971; 69: 246-50. 44. Husni EA, Ryu CK. Entrapment of the popliteal artery and its manage­ ment. Angiology 1971; 22: 380-6. 45. Ikeda M, Iwase T, Ashida K, Tarkawa H. Popliteal artery entrapment syn­ drome — report of a case and study of 18 cases in Japan. Am J Surg 1981; 141: 726-30. 46. Inada K, Kirose M, Iwashima V, el al. Popliteal artery entrapment syn­ drome: a case report. Br J Surg 1978; 65: 613-5. 47. Insua JA, Houng JR, Humphries AW. Popliteal artery entrapment syn­ drome. Arch Surg 1970; 101: 771-5. 48. Iwai T, Konno S. Soga K, Hatano R, Yamada T, Menjo M. Diagnostic and pathological considerations in the popliteal artery entrapment syndrome. J Cardiovasc Surg 1983; 24: 243-9. 49. Jeffery PG, Immelmenn EJ, Harries-Jones P. Popliteal artery entry syn­ drome: a report of two cases. S A fr Med J 1985; 67: 692-4. 50. Leon M, Volteas N, Labropoulas N, el ai. Popliteal vein entrapment in the normal population. E u rJ Vase Surg 1992; 6: 623-7. 51. Levien LJ. Popliteal artery thrombosis caused by popliteal entrapment syndrome. In: Greenhalgh RM, Powell JT. eds. Inflammatory and Thrombotic Problems in Vascular Surgery. London: WB Saunders, 1997: 159-68. 52. Love JW, Whelan TJ. Popliteal artery entrapment syndrome. Am J Surg 1965; 109: 620-4. 53. Lysens RJ, Rensen LM, Ostyn MS, el al. Intermittent claudication in young athletes: Popliteal artery entrapment syndrome. Am J Sports Med 1983; 11: 177-9. 54. MacSweeny STR, Cumming R, Greenhalgh RM. Colour doppler ultra­ sonographic imaging in the diagnosis of popliteal artery entrapment syndrome. Br J Surg 1994; 81: 822-3. 55. Mark LK, Kiselow Me, Wagner M, Goodman JJ. Popliteal artery entrap­ ment syndrome. JAMA 1978; 240: 465-6. 56. McDonald PT, Easterbrook JA, Rich NM, et al. Popliteal artery entrapment syndrome. Clinical, noninvasive and angiographic diagnosis. A m J Surg 1980; 139: 318-25. 57. McGuinnes G, Durham JD, Rutherford RB, Thickham D, Kumpe DA. Popliteal artery entrapment: findings at MR imaging. Journal o f Vascular interventional Radiology 1991; 2: 241-5. 58. Miles S, Roediger W, Cooke P, Mieny CJ. Doppler ultrasound in the diag­ nosis of the popliteal artery entrapment syndrome. Br J Surg 1977; 64: 883-4. 59. Muller J, Morris DC, Nichols DM. Popliteal artery entrapment demonstrat­ ed by CT. Radiology 1984; 151: 157-8. 60. Murray A, Halliday M, Croft RJ. Popliteal artery entrapment syndrome. Br J Surg 1991; 78: 1414-9. 61. Persky JM, Kempczinski RF, Fowl RJ. Entrapment of the popliteal artery. Surgery, Gynecology and Obstetrics 1991; 173: 84. 62. Rich NM. Popliteal entrapment and adventitial cystic diseases. Surg Clin North Am 1982, 6: 449-65. 63. Rich NM, Hughes CW. Popliteal arlery and vein entrapment. Am J Surg 1967; 113: 696-8. 64. Rich NM, Collins GJ, McDonald PT, Kozloff L, Clagett GP, Collins JT. Popliteal vascular entrapment — its increasing interest. Arch Surg 1979; 114: 1377-84. 65. Rignault DP, Pailler JL, Lunel F. The functional' popliteal artery entrap­ ment syndrome. Int Angiol 1985; 4: 341-3. 66. Rizzo RJ, Flinn WR, Yao JST, McCarthy WJ, Vogelzang RL, Pearce WH. Computed tomography for evaluation of arterial disease in the popliteal fossa. J Vase Surg 1990; 11: 112-9. 67. Rudo WD, Noble HB, Conn JJ, et al. Popliteal artery entrapment syn­ drome in athletes. Physician Sports Medicine 1982; 10: 105-14. 68. Schuurman G, Mattfeldt T. The popliteal arlery entrapment syndrome. Eur J Vase Surg 1990; 4: 223-31. 69. Senior HD. The development of the arteries of the human lower extremi­ ties. American Journal o f Anatomy 1919; 25: 55-95. 70. Senior HD. The development of the human femoral artery, a correction. American Journal o f Anatomy 1920; 17: 271-9. 71. Servello M. Clinical syndrome of anomalous position of the popliteal artery. Circulation 1962; 26: 885-90. 72. Soyka P, Dunart JH. Popliteal artery entrapment syndrome: familial occur­ rence. Vasa 1993; 22: 178-81. 73. Stuart TP. Note on a variation in the course of the popliteal artery. Journal of Anatomy and Physiology 1879; 13: 162. 74. Turner EH, Grove JA. Popliteal arterial and venous entrapment. Am Surg 1972; 38: 657-9. 75. Turner GR, Gosney WG, Ellingson W, et al. Popliteal artery entrapment syndrome. JAMA 1964; 208: 692-3. 76. Turnipseed W, Detmer DE, Gridley F. Chronic compartment syndrome. Am J Surg 1989; 210: 557-63. 77. Turnipseed WD, Pozniak M. Popliteal entrapment as a result of neurovas­ cular compression by the soleus and plantaris muscles. J i/asc Surg 1992; 15: 285-94. 78. Verhoeven ELG, Lucarotti ME, Campbell WB. Vanishing popliteal entrap­ ment. E ur J Vase Endovasc Surg 1995; 9: 944-6. 79. Williams LR, Flinn WR, McCarthy WJ, ef al. Popliteal artery entrapment: diagnosis by computed tomography. J Vase Surg 1986; 3: 360-3. SPORTS MEDICINE MARCH 2001 25 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) ORIGINAL RESEARCH ARTICLE Creatine supplementation and exercise performance in rugby players R M N Kohler (MB ChB) South African Sports Science Institute, Cape Town Abstract Objective. To determ ine w hether creatine supplem enta­ tion im proves exercise perform ance in rugby players. . Setting. Buffalo Park, East London. Subjects. Twenty-five club rugby players, after com ple­ tion o f pre-season training. Design. Field study. Seventeen rugby players volun­ teered for the creatine group and 8 rugby players volun­ teered for the control group. The creatine group ingested a creatine m onohydrate supplem ent. The players inges­ ted 20 g of creatine per day for 5 days as a loading dose, followed by a m aintenance dose o f 5 g of creatine per day fo r 79 days. The control group ingested no supple­ ments. Subjects had baseline m easurem ents taken before starting creatine supplem entation. Players' body mass in kg, 50 m isolated sprint time, and the num ber of sit-ups and push-ups each in 30 seconds, w ere m ea­ sured. The final m easurem ents w ere taken 84 days after starting creatine supplem entation. Only players who com pleted the study were analysed. Results. Fourteen rugby players from the creatine group and 7 rugby players from the control group com ­ pleted the study. The age o f the players in the creatine and control groups was 25.2 ± 3.9 versus 21.3 ± 3.3 years respectively. Body mass did not change signifi­ cantly in either group. The body mass changed from 88.8 ± 16.0 to 86.6 ± 14.0 kg in the creatine group and from 87.8 ± 9.9 kg to 87.0 ± 9.7 kg in the control group. Isolated sprint perform ance improved significantly in the creatine group from 8.3 ± 0.6 s to 7.9 ± 0.5 s (P < 0.05) Sprint perform ance did not change significantly in the control group: 8.4 ± 0.4 s to 8.5 ± 1 . 1 s. The num ber of CORRESPONDENCE: Dr Ryan Kohler 1 Rhodesview Sawkins Road Rondebosch C ape Town 7700 Tel: 082 - 784 5737 (cell) Fax: 021 - 683 5434 E-mail: ryank@ yebo.co.za push-ups and sit-ups in 30 s increased significantly in the creatine group from 34.7 ± 8.6 to 45.2 ± 6.3 (P < 0.05). and from 30.0 ± 5.9 to 35.0 ± 4.7 (P < 0.05) respectively. In the control group, the num ber of push­ ups did not change significantly: 33.1 ± 9.9 to 33.4 ± 8.5. The num ber of sit-ups increased from 27.3 ± 3.2 to 29.2 ± 2.5. Forty-tw o per cent o f the players in the creatine group experienced side-effects when ingesting creatine, compared with the control group w hich had no side- effects. Conclusion. A fter 84 days o f creatine supplem entation, body mass did not change significantly, but isolated sprint perform ance and the num ber o f push-ups and sit- ups performed by the rugby players in the creatine group increased significantly. A large proportion of the rugby players experienced side-effects w hen ingesting crea­ tine monohydrate. Introduction Creatine supplem ents are being ingested by athletes at all levels of sporting com petition. The use o f creatine is further popularised when anecdotal inform ation of O lym pic athletes reportedly using creatine as a supplem ent are reported in the press.2 Athletes perceive that creatine may enhance their specific sports performance. It is estim ated that adenosine triphosphate (ATP) and phosphocreatine (Per) can sustain very high-intensity exer­ cise for approxim ately 10 seconds.3 Theoretically, creatine supplem entation could increase intram uscular Per concen­ tration and subsequent ATP form ation, prolonging the dura­ tion o f high-intensity physical activity and pow er output.818 Overall, creatine supplem entation could be o f benefit to the athlete. O f the many studies published on creatine, many, but far from all, show an im provem ent in perform ance.911 The most convincing evidence for an ergogenic effect is seen in activ­ ities requiring isotonic strength and those that involve repet­ itive bouts of high-intensity. exercise interspersed with short rest periods.34 Most of these studies w ere performed under laboratory conditions. There are few studies on the effects of creatine supplem entation on perform ance in the field and during com petitive events. One o f the purported effects of creatine supplem entation is an increase in body mass, particularly muscle m ass.31'33 This may occur in a num ber o f w ays. C reatine, being osmot- ically active, could cause an intracellular fluid shift, thereby 26 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) mailto:ryank@yebo.co.za increasing intracellular w ater and body mass. It has been suggested that increased cellular hydration and/or increased Per may also stim ulate protein synthesis and decrease pro­ tein degradation.2231'33 This effect, however, may not be directly due to increased intracellar PCr or hydration, but due to som e other factor that creatine is affecting. O f the approx­ im ately 20 studies on the effect o f long-term creatine sup­ plem entation on body mass, about 80% show body mass gains.34 The best gains w ere seen in those athletes under­ going resistance training.34 According to available literature, isolated sprint running perform ance in athletes after creatine supplem entation is either im proved26,30 or unaffected.232527'28Therefore, the ability o f creatine to improve isolated sprint running performance rem ains controversial. Creatine supplem entation may improve high-intensity, short-duration (< 30 s) exercise tasks, as demonstrated in another field study6 where a continuous jum p test fo r 45 s show ed that subjects supplem enting with creatine showed an increase in w ork output during the first 30 s o f the task. Accordingly, the aim o f this study w as to determine, in a. field design, w hether creatine supplem entation over 84 days, increased body mass, im proved isolated 50 m sprint perform ance and im proved short-duration high-intensity exercise, as measured by the num ber o f push-ups and sit-ups performed in 30 s each. Methods Research methods T w e n ty-five rugby players v o lu n te e re d fo r the study. Seventeen rugby players volunteered fo r exercise testing w ith creatine supplem entation and form ed the creatine group. These players w ere given 500 g o f creatine m onohy­ drate o f the sam e brand. Eight players volunteered fo r exer­ cise testing only and form ed the control group. All players gave inform ed verbal consent to participate in the study and agreed to adhere to the conditions thereof. None of the play­ ers in the creatine group had ingested a creatine m onohy­ drate supplem ent in the previous 3 months. This would be sufficient tim e fo r creatine levels to return to baseline should any player have previously ingested creatine m onohy­ drate. 17,21 None of the players w as vegetarian. This is rele­ vant as vegetarians have virtually no dietary intake of creatine and rely on creatine synthesis in the liver, pancreas and kidneys.11 Vegetarians have been shown to have lower plasma creatine levels.10 This does not necessarily mean decreased tissue creatine content.19 Theoretically, muscle Per levels could be low er in vegetarians. It has been shown that individuals with a 'lo w e r muscle Per can have a greater increase in muscle Per with creatine supplem entation;14,19 raising the question of greater perform ance benefit.12 All 25 rugby players had com pleted the sam e organised pre-season training and w ere match fit and ready to play their first match. The training schedule fo r the duration o f the study (and fo r the season) fo r all the players w as as follows: practice sessions took place on Tuesdays and Thursdays, circuit training on M ondays in the gym, and matches on Saturdays. Exercise at practices involved running and skills training, and in the gym exercise involved using light w eights fo r 15 - 20 repetitions. Baseline testing was performed on all players directly before creatine supplem entation. Exercise testing was con­ ducted again after 84 days of creatine supplem entation. Param eters to be tested were: body mass in kg, 50 m sprint time, the num ber o f push-ups in 30s and the num ber o f sit- ups in 30 s (as a m easure o f short-duration high-intensity exercise). Body fat percentage was not measured. Environm ental testing conditions w ere consistent. Data collection took place in the early evening before rugby prac­ tice. Dry, w indless conditions prevailed and the sam e strip of dry grass was used on each occasion. The players were tested barefoot in order to standardise footwear. W hen per­ forming push-ups, the tester placed a fist on the ground to ensure a full range of movem ent. Touching the te ste r’s fist with the chest yielded a count. The p la ye r’s feet w ere anchored during the sit-up test and a full range o f m ovem ent w as achieved by the player’s back touching the te ste r’s fist on the ground behind him. Three minutes elapsed between the push-up and the sit-up test. Creatine and control subjects w ere tested in the evening on the same day. The creatine used in the study w as creatine m onohydrate w ith a percentage purity o f 99.6% gravim etric. The dosing regimen fo r the creatine subjects consisted o f a loading dose o f 20 g/day divided into four daily doses and consum ed over 5 days. This w as followed by a m aintenance dose o f 5 g/day fo r the 79 days. Research has shown that creatine uptake into skeletal muscle is enhanced during creatine supplem en­ tation if the creatine is consum ed together with a carbohy­ drate.1620 Players w ere instructed to consum e the prescribed creatine am ount mixed with 250 ml o f grape juice, which am ounts to 30 g o f carbohydrate, to optim ise creatine uptake into skeletal muscle.313,16,20 Players w ere given 500 g o f crea­ tine fo r the study period accom panied by written instructions concerning dose and frequency o f cre a tin e ingestion. Creatine consum ption started imm ediately after baseline testing and continued fo r an 84-day period. Players in the creatine group consum ed no other nutritional supplem ents. At the end o f the study period o f 84 days, 14 rugby play­ ers in the creatine group, and 7 rugby players in the placebo group had all their m easurem ents taken and successfully completed the study. Two players in the creatine group w ith­ drew because o f w ork com m itm ents, w hile 1 player from each group w ithdrew because of injury. The 14 rugby play­ ers in the creatine group answered a questionnaire that eval­ uated the subjective effects o f creatine supplem entation. Statistical methods Only the data fo r those players w ho com pleted the study w ere analysed. The analysis o f each group w as done as fo l­ lows: m easurem ents recorded before starting creatine sup­ plementation w ere considered as ‘pre’ creatine effect, and the m easurem ents recorded after 84 days of creatine sup­ plementation as ‘post’ creatine effect. This design allowed for the use o f the dependent f-test or its non-param etric equivalent, the W ilcoxon m atched pairs test, to analyse the relationship between the pre- and post-creatine results in each group separately. As none o f the variables o r the dif­ SPORTS MEDICINE MARCH 2001 27 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) ference o f the relevant variables w ere norm ally distributed, the W ilcoxon m atched pairs procedure w as used. Due to the non-norm ality of the data, the Mann-W hitney U-test was used to exam ine any relationship and com pare the creatine and control groups. Results are expressed as the mean ± standard deviation (SD). The statistical significance was accepted when P < 0.05. Results Body mass and physical performance In the creatine group, the average body mass decreased from 88.8 ± 16.0 kg to 86.6 ±14. 1 kg and w as not significant. The 50 m isolated sprint speed decreased from 8.3 ± 0.6 s to 7.9 ± 0.5 s (P < 0.05). The num ber o f push-ups per 30 s increased from 34.7 ± 8.6 to 45.2 ± 6.3 (P < 0.05) and the num ber of sit-ups increased from 30.0 ± 5.9 to 35.0 ± 4.7 (P < 0.05) (Table I). Comparison of the creatine and control groups The 14 rugby players in the creatine group w ere significantly older than the 7 players in the control group (25.2 ± 3.9 v. 21.3 ± 3.3 years, P < 0.05). The players in the creatine group com pleted more push-ups per 30 s at the final test compared with the players in the control group (45.2 ± 6.3 v. 33.4 ± 8.5, P < 0.05). The players in the creatine group com pleted more sit-ups per 30 s at the final test com pared with the players in the control group (35.0 ± 4.7 v. 29.2 ± 2.5, P < 0.05). There w ere no other significant differences between the creatine and control groups. Results of the questionnaire O f the 14 rugby players supplem enting with creatine, 42% reported side-effects while ingesting creatine (Table II). There w ere no reported sym ptom s in the control group. These reported side-effects involved the gastro-intestinal tract (4 players), the m usculoskeletal system (1 player) and the cardiovascular system (1 player). These side-effects occurred in different players. The reported gastro-intestinal side-effects w ere experienced during the 5-day loading phase o f creatine supplem entation. The side-effects were diarrhoea, with 1 player reporting colic. One player reported cram ping o f the m uscles in his thighs. One player described increased thirst, a dry mouth and having to pass urine less frequently, indicating possible dehydration. This effect was reported sporadically during the creatine supplem entation period. All 14 rugby players reported that they felt they had an increase in strength, stam ina, recovery tim e and perfor­ mance, with about half o f the subjects experiencing these effects as early as 14 days after starting creatine supple­ mentation. ■ All 14 rugby players considered creatine to be a safe product and would purchase it as an ergogenic aid. The players who decided not to supplement with creatine did so because they believed that it would not improve their performance. Discussion Isolated sprint perform ance over 50 m showed a significant im provem ent in the creatine group o f rugby players. The increased Per stores in the creatine group means that there w ould be more PCr to break down before fatigue starts to set in.815 More ATP could be available to enhance muscle con­ traction, and possibly account for the im provem ent in isol­ ated sprint perform ance in the creatine group. These findings are consistent with studies in the literature that used sim ilar sprint distances to test the athletes.2630 The im prove­ ments in perform ance w ere significant in these studies and ranged from 1 to 2%. Sprint distances in the studies that did not show an im provem ent in isolated sprint perform ance TABLE I. Com parison o f the pre- and post-test values (mean ± SD) in the creatine and control groups C reatin e (N = 14) C on trol (N = 7) M easu rem en ts Pre Post Pre Post Body mass (kg) 88.8 ± 16 86.6 ± 14.1 87.8 ± 9.9 87.0 ± 9.7 50 m sprint(s) 8.3 ±0 .6 7.9 ± 0.5 8.4 ± 0.4 8.5 ±1.1 Push-ups in 30s 34.7 ± 8.6 45.2 ±6.3 33.1 ± 9.9 33.4 ± 8.5 Sit-ups in 30s 30.0 ± 5.9 35.0 ±4.7 27.3 ± 3.2 29.2 ±2.5 TABLE II. S ide-effects am ong rugby players (N = 14) ingesting creatine System S ide-effects N um ber P ercen tag e Gastro-intestinal Diarrhoea 3 21 Colic 1 7 Musculoskeletal Cramping 1 7 Cardiovascular Dehydration 1 7 6 42 28 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) w ere longer and ranged from 60 m to 150 m.2830 The m ajor finding in this study w as a significant im prove­ m ent in the num ber o f sit-ups and push-ups among players in the creatine group compared w ith the control group. Supplem enting with creatine assum edly increased muscle Per stores in m ost subjects in the creatine group.815 In this study, players in the creatine group w ere able to increase their pow er output during the 30 s duration o f the push-up and sit-up test and delay the onset o f fatigue. However, the study w as non-blinded, and the possibility of the placebo effect does exist in order to account for these significant find­ ings. Most studies show that total body mass increases with creatine supplem entation.4,5,7'13'24 This occurs within 5 days during the loading phase and continues during the m ainte­ nance phase.24 Initially this is due to w ater retention, and later, with continued creatine supplem entation, possibly to increased m y o fib rilla r protein syn th e s is .21 T his study revealed that the body mass o f players did not change significantly w ith creatine supplem entation. This is not consistent with the data from the questionnaire, which revealed that 65% o f players supplem enting with creatine felt that their body mass had increased and that there w as a change in their physical profile. There may have been a change in their ratio o f fat-free mass to .body mass. Dietary factors and calorie intake could also have affected the body mass m easurem ent. One o f the ‘expected’ outcom es o f this study w as that creatine supplem entation would increase body mass. However, this did not happen and the reasons fo r this ergogenic effect w ithout an increase in body mass need to be examined in further studies. The only docum ented side-effect from clinical research studies is that o f w eight gain.31'33 U ndocum ented side-effects o f creatine supplem entation have appeared in lay publica­ tions and in the m edia.1 These include gastro-intestinal dis­ tress, muscle cram ping/m uscle injury and dehydration. The speculated m echanism of stom ach upset is that the m axim um absorption rate o f creatine in the intestine may be exceeded. Creatine in the intestine draws w ater into the intestine and could cause loose stools and diarrhoea.34 One could hypothesise that supplem enting w ith large doses of creatine (> 35 g/day) may cause gastro-intestinal symptoms. In this study, it was interesting that players in the creatine group who developed stom ach upset did so during the 5-day loading phase. The most com m only reported anecdotal side-effect is that o f muscle cram ping.129 Only 1 player out of 14 reported this effect in this study. It is thought that this muscle dysfunction may be related to electrolyte imbalances in the muscle cell.29 These anecdotal side-effects have been refuted in certain scientific studies.24 Despite the reports on side-effects, all subjects supple­ menting with creatine felt that creatine w as a safe product and would purchase creatine as an ergogenic aid. In summary, this study showed that creatine supplem en­ tation significantly im proved isolated sprint perform ance and the num ber of sit-ups and push-ups rugby players could per­ form. C ontrary to results from other studies, body mass did not change significantly. A large proportion o f the players reported experiencing side-effects when ingesting creatine. However, the rugby players did not interpret this as a cause fo r concern and would purchase creatine m onohydrate as an ergogenic aid. Thanks to Mr J Baxter, Department of Statistics, Rhodes University, Grahamstown, for statistical analysis of the data. R e f e r e n c e s 1. Armour S. Creatine: No scare just yet. USA Today, 24 April 1998. 2. Associated Press. Creatine naturally boosts performance. 9 May 1993. In: Williams MH, Kreider RB, Branch JD. Creatine the Power Supplement. Human Kinetics Books, 1999. 3. Balsom P, Soderlund K, Ekblom B. Creatine in humans with special refer­ ence to creatine supplementation. Sports Med 1994; 18: 268-80. 4. Balsom P, Soderlund K, Sjodin B, Ekblom B. Skeletal muscle metabolism during short duration high-intensity exercise: Influence of creatine supple­ mentation. Acta Physiol Scand 1995; 154: 303-10. 5. Barnett C, Hinds M, Jenkins DG. Effects of creatine supplementation on multiple sprint cycle performance. Australian Journal o f Science and Medicine in Sports 1996; 28: 35-9. 6. Bosco C, Tihanyi J, Pucsk J. Effect of oral creatine supplementation on jumping and running performance. In tJ Sports Med 1997; 18: 369-72. 7. Burke L . The Complete South African Guide to Sports Nutrition. Cape Town: Oxford University Press, 1998: 138-140, 236. 8. Casey A, Constantin-Teodosiu D, Howell S, Hultman E, Greenhaff PL. Creatine ingestion favourably affects performance and muscle metabolism during maximal exercise in humans. Am J Physiol 1996; 271: E31-7. 9. Clark JF. Creatine and phosphocreatine: A review of their use in exercise and sport. Journal o f Athletic Training 1997; 32: 45-50. 10. Delanghe J, De Slypere JP, De Buyzere M, Robbrecht J, Wieme R, Vermeulen A. Normal reference values for creatine, creatinine and carni­ tine are lower in vegetarians. Clin Chem 1989; 35: 1802-3. 11. Derman W, Schwellnus M. Creatine supplementation in sport. Modern Medicine 1998; 23: 42-4. 12. Ekblom B. Effects of creatine supplementation on performance. Am J Sports Med 1996; 24 : S38-9. 13. Engelhardt M, Neumann G, Berbalk A, Reuter I. Creatine supplementation in endurance sports. Med Sci Sports Exerc 1998; 30 : 1123-9. 14. Gonzalez de Suso JM, Prat JA. Dietary supplementation using orally- taken creatine monohydrate in humans. CAR News 1994; 6: 4-9. 15. Gordon A, Hultman E, Kaijser L. Creatine supplementation in chronic heart failure increases skeletal muscle creatine phosphate and muscle performance. Cardiovasc Res 1995; 30 : 413-38. 16. Green AL, Hultman E, MacDonald IA, Sewell DA, G reenhaff PL. Carbohydrate feeding augments skeletal muscle creatine accumulation during creatine supplementation in. humans. Am J Physiol 1996; 271: E821-6. 17. Greenhaff PL. Creatine supplementation and implications for exercise per­ formance and guidelines for creatine supplementation. Advances in Training and Nutrition for Endurance Sports 1997; 30: 8-11. 18. Greenhaff PL, Bodin K, Soderlund K, Hultman E. Effect of oral creatine supplementation on muscle phosphocreatine resynthesis. Am J Physiol 1994; 266: E725-30. 19. Harris RC, Soderlund K, Hultman E. Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation. Clin Sci 1992; 83: 367-74. 20. Haughland RB, Chang DT. Insulin effects on creatine transport in skeletal muscle. Proc Soc Exp Biol Med 1975; 148: 1-4. 21. Hultman E, Soderlund K, Timmons JA, Cederblad G, Greenhaff PL. Muscle creatine loading in men. J Appl Physiol 1996; 81 : 232-7. 22. Ingwall JS. Creatine and the control of muscle-specific protein synthesis in cardiac and skeletal muscle. Circ Res 1976; 38: 115-23. 23. Javierre C, Lizarraga MA, Ventura JL, Garrido E, Segura R. Creatine sup­ plementation does not improve physical performance in a 150 m race. Revista Espanola de Fisiologia 1997; 53: 343-8. 24. Kreider R, Ferreira M, Wilson M, et al. Effects of creatine supplementation on body consumption, strength and sprint performance. Med Sci Sports Exerc 1998; 30: 73-82. 25. Lefavi RG, McMillan JL, Kahn PJ, Crosby JF, Digioacchino RF, Streater JA. Effects of creatine monohydrate on performance of collegiate baseball and basketball players (Abstract). Journal o f Strength and Conditioning Research 1998; 12: 275. SPORTS MEDICINE MARCH 2001 29 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) 26. Noonan D, Berg K, Latin RW, Wagner JC, Reimers K. Effects of varying dosages of oral creatine relative to fat free body mass on strength and body composition. Journal o f Strength and Conditioning Research 1998; 12: 104-8. 27. Peyrebrune MC, Nevill ME, Donaldson FJ, Cosford DJ. The effects o f oral creatine supplementation on performance in single and repeated sprint swimming. J Sports Sci 1998; 16: 271-9. 28. Redondo DR, Dowling EA, Graham BL, Almada AL, Williams MH. The effects of oral creatine monohydrate supplementation on running velocity. Int J Sport N utr 1996; 6: 213-21. 29. Strauss G, Mihoces G. Jury still out on creatine use (News). USA Today. 4 June 1998. 30. Stout JR, Echerson J, Noonan D, Moore G, Cullen D. Effects of creatine supplementation on exercise performance and fat-free weight in football players during training. Nutritional Research 1999; 19: 217-25. 31. Volek JS, Boetes M, Bush JA, Putukian M, Sebastionelli WJ, Kaemer WJ! Response of testosterone and cortisol concentrations to high-intensity resistance exercise following creatine supplementation. Journal o f Strength and Conditioning Research 1997a; 11: 182-7. 32. Volek JS, Kraemer WJ. Creatine supplementation: Its effect on human muscular performance and body composition. Journal o f Strength and Conditioning Research 1996; 10: 200-10. 33. Volek JS, Kraemer WJ, Bush JA, et al. Creatine supplementation enhances muscular performance during high-intensity resistance exer­ cise. J Am Diet Assoc 1997b; 97: 765-70. 34. Williams MH, Kreider RB, Branch JD. Creatine the Power Supplement. Human Kinetics Books, 1999. Sports Medicine in Primary Care Rob Johnson Sports Medicine in Primary Care provides an easy-to-read refer­ ence for the primary care physician who treats common musculo­ skeletal and sports medicine problems. Written by expert clinicians that practice both primary care and sports medicine, this resource contains invaluable information for the non-sports medicine trained physician. Features ■ Includes only those topics that are most commonly encoun­ tered in the primary care office. ■ The format for musculoskeletal and medical problems is the same from chapter to chapter, helping readers to easily find a specific topic or answer a specific question. ■ Summary sites, illustrations, and decision protocols make criti­ cal information easy-to-find. ■ Excellent chapter on preparticipation evaluation is included. ■ Presents return to activity guidelines. Contents: 1. The Essential Points of the Musculoskeletal Exam: The Focused Injury History, the Focused Musculoskeletal Exam 2. Preparticipation Evaluation, Youth and Adolescent: History, Youth and Adolescent: Physical Exam, Adult, 3. The Exercise Prescrip­ tion: Youth and Adolescent, Adult, 4. Principles of Training 5. Ad­ vising the Athlete on Nutrition, 6. Office Based Rehabilitation, 7. Return to Play, 8. The Use of Nonsteroidal Anti-inflammatory Drugs and Analgesics, 9. Office Evaluation of Minimal Brain Injury, 10. Neck and Cervical Spine Injury, 11. The Upper Extremity, 12. Sports Injuries to the Lower Extremity, 13. Back Injuries in Athletes, 14. Chest Injury, 15. Gastrointestinal Problems and Abdominal Trauma in Sports, 16. Genitourinary Problems, 17. Special Issues of the Young and Adolescent Athlete 18. Special Issues of the Woman Athlete, 19. The Mature Athlete'20. Risk of Exercise, 21. The Ath­ lete with Medical Problems, The Hypersensitive Athlete, The Asth­ matic/Allergic Athlete, Caring for the Diabetic Athlete, The Athlete with Heart Disease, The Athlete with Chronic Obstructive Pulmo­ nary Disease, Seizure Disorders and Athletes, The Role of Exer­ cise and Athletes in Anxiety and Depression, The Athlete with Infectious Disease, 22. Injection Techniques. Sept 2000, hardback, 384 pp, 108 ilius., WBS, R550 Clinical Decision Making in Sports Medicine Dinesh Kumbhare and John Basmajian As more therapies and technologies have developed in the area of sports medicine, the need has grown for scientific evidence and critical appraisal of the effectiveness of specific treatment meth­ ods. This informative text fills this gap by offering discussions on evidence-based sports rehabilitation through a comprehensive and contemporary examination of the subject. It is divided into the fol­ lowing sections: Basic Considerations which includes cardiovascular considera­ tions, nutritional strategies, dehydration, inflammation, and psy­ chological, sociological and physiological factors in sport Therapeutics which covers physiotherapy, chiropractic and al­ ternative treatment approaches Special Considerations which covers pregnancy, the mature ath­ lete and the paediatric athlete Neuromuscular Considerations which includes epilepsy, concus­ sion, neuropsychology and neuromuscular conditions Regional Considerations which covers the shoulder, hand and wrist, lower back, hip and knee, and the ankle. Features ■ The focus on evidence-based practice gives practitioners a firm basis for decision making. ■ Comprehensively examines clinical decision making in all fac­ ets of sports medicine ■ Covers special topics such as Neurological Issues, Arthritis, Pregnancy and Paediatrics, which are not typically addressed by sports medicine texts ■ The chapter on the aging athlete reflects the current trend toward athletic activity throughout the lifespan ■ Applies many of the authors’ principles on decision making in rehabilitation to sports medicine. July 2000, hardback, 432 pp, 55 illus., CL, R499 ORDERS The South African Medical Association, Private Bag X1, Pinelands 7430. Tel (021) 531-3081, Fax (021) 531-4126. E-mail: jstrydom@samedical.org Prepayment required but not actioned until order despatched. Please allow 6-8 weeks for delivery. 30 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) mailto:jstrydom@samedical.org LETTER TO THE EDITOR Drug-free sport To the Editor: The South African Institute for Drug-Free S port has noted with surprise and concern the conclusions o f the research article in the N ovem ber edition o f the South African Journal o f Sports M edicine entitled ‘Substance abuse and knowledge thereof am ong elite South African athletes’.1 The use o f drugs to enhance athletic perform ance is against the rules laid down by the governing bodies o f most recognised sports w orldw ide, and elite athletes, particularly those com peting at international level, have an obligation to fam iliarise them selves and com ply with the policies and reg­ ulations o f their governing bodies regarding drugs and sport. Relevant inform ation on prohibited and permitted drugs in sport is available from a variety o f sources. Most sports fed­ erations are updated annually with the IOC list o f permitted and banned substances in sport, N OCSA produces an excellent booklet which it distributes free o f charge com pris­ ing an alphabetical and therapeutical list o f prohibited, restricted and perm itted drugs in sport, and inform ation can be accessed from the Internet, the SA Institute fo r Drug- Free S port Hotline (021 - 448 3888, 9.00 a.m. - 1.00 p.m. weekdays) and the Institute’s website, www.drugfreesport.org.za Ignorance of the issues surrounding doping can also no longer be used as an excuse by doctors and pharm acists. It is im portant that they equip them selves with salient inform a­ tion in order to avoid the possibility o f recom m ending or pre­ scribing the use o f prohibited substances to patients involved in com petitive sport. Doping substances and m ethods are prohibited in sport fo r various reasons, most notably: (i) their perform ance- enhancing effects which contravene the ethics of sport and underm ine the principles o f fair participation; (ii) the harm which they may cause to a com petitor’s health; and (Hi) the legal im plications o f using certain substances, such as ana­ bolic androgenic steroids, a Schedule V drug. The Institute conducts a com prehensive national drug te stin g p rogram m e in a cco rd a n ce w ith International Standards fo r Doping Control (last year 1 600 sportsm en and w om en from 41 sporting disciplines w ere tested both in and out o f competition, and this will be increased to 1 700 tests across 49 sporting disciplines during the current year). The Institute has over 50 independent Doping Control Officers nationally, w ho undergo strin g e n t annual training and refresher courses, and in line with international practice, out o f com petition testing will be increased substantially in future. Education and the provision o f inform ation are also key elem ents in any national anti-doping strategy. Athletes and coaches need to be inform ed o f their obligations under the drug-testing policy o f their sport. School program m es are needed to raise awareness of the issues surrounding doping and drugs in sport and to influence attitudes tow ards health­ ier behaviour. The medical and pharm aceutical professions must be kept inform ed and updated on prohibited and per­ mitted substances and the risks associated with the use of those substances both on and off the playing field. The Institute tries to reach all these target markets through a variety o f education and aw areness cam paigns, sem inars, lectures, w orkshops and the distribution o f prom o­ tional and educational material. This year the education pro­ gram m e has been extended to target schoolchildren, as research has produced some disturbing statistics regarding steroid abuse. South Africa enjoys considerable status internationally in the field of anti-doping, and is at the forefront o f the latest anti- doping strategies and testing m ethods. The Institute is am ong a handful o f international anti-doping agencies preparing fo r ISO 9002 accreditation this year, and South Africa has one of only 27 IO C-accredited laboratories w orld­ wide. The Institute is represented at m eetings o f the Monitoring Group on Anti Doping at the Council o f Europe; Minister N Balfour, the M inister o f Sport, serves on the Executive Board of the World Anti Doping Agency (WADA); and the C hairm an o f the Board o f SAIDS, Dr Ismail Jakoet, was selected as a W ADA anti-doping m onitor at the Sydney Olympics. S port is an im portant part of the South African w ay o f life, and our sporting achievements are a source o f great national pride. Doping violates the integrity of sport, carries serious health risks fo r individuals, and prom otes the notion that dis­ honesty can be rewarded. As custodian o f South A frica’s anti-doping programme, the South African Institute for D rug-Free Sport, created by an A ct o f Parliam ent in 1977 as an initiative of S port and Recreation South Africa, is com m itted to prom oting drug-free sport and ethical sporting practices in this country. Enquiries: Tel. 021 - 683 7129 / Fax 021 - 683 7274 / Email: drugfree@ iafrica.com Daphne Bradbury General M anager South A frican Institute fo r D rug-Free Sport 1. Coopoo Y, Jakoet J. Substance abuse and knowledge thereof among elite South African athletes. South African Journal o f Sports Medicine 2000; 7: 10-13. SPORTS MEDICINE MARCH 2001 31 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) http://www.drugfreesport.org.za mailto:drugfree@iafrica.com LETTER TO THE EDITOR Early postural correction To the Editor: May I draw your attention to the opinion of renowned doctors in the field of sports m edicine, namely that the aetiology o f the m ajority o f sports injuries concerns w idespread postural faults in w eight-bearing joints. W hat is little known, however, is the discovery by Neumann-Neurode at the turn of the last century that babies like to practise effective rem edial exercises in adult hands, with better and quicker results than are obtained with older children o f any age. Since postural faults are frequently inherited, it is not sur­ prising that they are usually noticeable in infancy. The m ed­ ical value of early rem edial exercise is backed up by the positive research results o f P rofessor J Trueta1 at the Nuffield Centre o f Orthopaedic Surgery in Oxford. He proved that infantile partially ossified bones respond more strongly to the stim ulus of exercise and becom e thicker, longer and stronger in less tim e than older ossified bones. That infants have greater capacity for growth, regenera­ tion and adaptation is already com m on medical knowledge and points to the advantage and need to recognise and cor­ rect postural faults in babyhood (club feet and dislocated hips are w ell-know n examples). Such corrections are one im portant form o f preventing com m on postural injuries in later years. At present it is im possible to m easure a baby’s postural changes accurately enough fo r research. A t the sam e time the need fo r tim ely correction is so great and the technique o f baby exercise is w ell-enough docum ented that the subject o f o rth o p a e d ia tric m u sculoskeletal correction has now becom e a postgraduate physiotherapy subject in ongoing university courses. I am not alone in thinking th a t early pos­ tural correction will become generally accepted as one means o f preventing comm on sports injuries. For more inform ation contact: Agnes W enham (MCSP), tel: (011) 788-5028; or Colleen Westgate (BSc Physio), tel: (011) 787-7293. A gnes W enham Parktow n North Johannesburg 1. Trueta J. R ehabilitation — past and future. British Journal o f Physiotherapy 1963; Nov: 348-50. Exercise Testing and Interpretation A Practical Approach Christopher Cooper and Thomas Storer This book provides a practical and systematic approach to the acquisition, interpretation, and reporting of physiologic responses to exercise. Pulmonologists, cardiologists, and sports physicians, as well as respiratory therapists and other allied health profes­ sionals will find this book an indispensable resource when learn­ ing to select proper instruments, identify the most appropriate test protocols, and integrate and interpret physiologic response vari­ ables. The final chapter presents clinical cases to illuminate useful strategies for exercise testing and interpretation. Useful appendi­ ces offer laboratory forms, algorithms and calculations, as well as answers to FAQs. A glossary of terms, symbols, and definitions is also included. Exercise Testing and Interpretation: A Practical Ap­ proach offers clearly defined responses (both normal and abnor­ mal) to over thirty performance variables including aerobic, car­ diovascular, ventilatory, and gas-exchange variables. Practical, portable, and easy-to-read, this essential guidebook can be used as a complement to more detailed books on the topic, or stand on its own. May 2001, Cambridge University Press, 246 x 189 mm, 310 pp, 92 line diagrams, 7 half-tones, 67 tables, R450 Benefits and Hazards of Exercise Edited by Domhnall MacAuley This internationally contributed book addresses the important issues relating to the long-term benefits and hazards of exercise in the healthy and those with specific chronic condi­ tions. Backed up by useful summary boxes and MCQs which add a CME element, this is a comprehensive discussion of an important and current topic in sports medicine. Contents: the optimal type of physical activity to enhance health; systematic reviews of physical activity promotion; exercise and psychological well being; exercise and hyperten­ sion; exercise and diabetes; viral illness and sport; sudden death and cardiovascular disease in young athletes; exercise and the older woman; the effect of exercise on reproductive function in male endurance athletes. 1999, BMJ, 216 x 138 mm, 284 pp, paperback, R490 ORDERS South A frican Medical A ssociation Private Bag X1, Pinelands 7430. Tel (021) 531-3081, Fax: (021) 531-4126 E-mail: jstrydom @ sam edical.org Prepaym ent by cheque or Visa/M astercard required. Please allow 6-8 w eeks fo r delivery. 32 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) mailto:jstrydom@samedical.org INSTRUCTIONS TO CONTRIBUTORS South African Journal of Sports Medicine Scope. The South African Journal o f Sports Medicine is an international, refereed journal published for professionals with a primary interest in sports medicine and exercise science prac­ tice. The journal publishes original research and reviews cover­ ing diagnostics, therapeutics and rehabilitation in healthy and physically challenged individuals of all ages and levels of sport and exercise participation. Original manuscripts, i.e. those that have not been published elsewhere except in abstract form, will be accepted from all countries and subject to peer review by the Editors and Editorial Board. The South African Journal o f Sports Medicine invites articles for submission from the areas of: (1) diagnosis, treatment, and, rehabilitation of sport- and exercise- related injuries, (2) medical illnesses induced by or exacerbated by exercise, (3) the relationship between exercise and health, including exercise physiology, (4) the medical care of physically active individuals, (5) sports psychology, (6) sports nutrition, and (7) biomechanics related to sport. Articles are invited from with­ in the following categories: ORIGINAL RESEARCH: Clinical research and basic science articles that are clinically relevant. BRIEF REPORTS: Clinical studies that are limited in depth or scope but with important findings to report. CASE REPORTS: Reports of clinical observations that have been carefully documented are particularly instructive. Additional manuscripts may be submitted, after consulting with the Editor-in-Chief, in the following categories: LETTERS TO THE EDITOR: LEAD EDITORIALS: These are short syntheses of data and current thought on topical issues in the field of sports medicine. REVIEW ARTICLES: These should be concise, in-depth, and well referenced; they should use the principles of critical appraisal (evidence-based medicine). POSITION STATEMENTS: These succinct but comprehensive documents are typically prepared by a recognised society for the purpose of providing clinical guidelines in important areas of sports medicine. Form of manuscript. Send manuscripts to Professor Mike Lambert, Sports Science Institute of South Africa, P O Box 115, Newlands, Cape Town, 8000, Tel: (021) 650 4558, Fax (021) 686 7530. Three copies of each manuscript must be submitted, in English in triple-spaced, typewritten form with a 5 cm (2 inch) left margin. Pages should be numbered from the title page. The text of the manuscript should be in the following sequence: Structured abstract (including key words), Introduction, Methods, Results, Discussion, Conclusions, Acknowledge­ ments, References, tables, and figure legends. For clarity, sub­ headings are recommended wherever appropriate. In the case of research articles, a short section in the Discussion or Conclusion should summarise the clinical relevance of the research. The author should retain a copy for reference, as manuscripts are not routinely returned. The title page of each manuscript should include only the article title, the author’s full names (first name, middle initial, last name), academic degrees and affiliations, the name, address, telephone and E-mail numbers of the person to whom proofs and reprint requests should be addressed, necessary footnotes to these items, and a running title not exceeding 45 letters and spaces. Indicate specific institutional affiliations of each author. Please list degrees or their equivalents. Information concerning sources of financial support should be placed in the Acknowledgement section. The page following the title page should include a structured abstract prepared according to the detailed instructions listed below. Up to six key words should be included at the end of the structured abstract. In the case of research studies, a single statement summarising the clinical relevance should be included. Case report. Case reports considered for publication must meet the following criteria. They must: 1) report a new syndrome, injury, or medical condition, 2) report a new test or diagnostic technique or method, or 3) draw attention to important clinical complications or problems associated with a common condition. The format of a case report is different from other submitted manuscripts. The differences are as follows; 1) The case must have at least one and a maximum of two figures. 2) The report will be published without an abstract. 3) A maximum of 10 references will be accepted. 4) The subheadings to be used are: Introduction, one or two sentences Case Report(s) Discussion 5) The total length of the manuscript must not exceed two type­ set pages (or approximately six typed, double-spaced manu­ script pages) and the Editor(s) reserve the right to shorten a manuscript to fit the space requirements. Generally speaking, two figures plus references will limit the maximum text to approx­ imately 1 000 words. Instructions for structured abstracts. Articles containing orig­ inal data concerning the course (prognosis), cause (aetiology), diagnosis, treatment, prevention, or economic analysis of a clin­ ical disorder or an intervention to improve the quality of health care must include a structured abstract of no longer than 250 words using the following headings and information; OBJECTIVE. State the main question or objective of the study and the major hypothesis tested, if any. DESIGN. Describe the design of the study indicating, as appro­ priate, use of randomisation, blinding, criterion standards for diagnostic tests, temporal direction (retrospective or prospec­ tive), and so on. SETTING. Indicate the study setting, including the level of clin­ ical care (for example, primary or tertiary; private practice or institutional). INTERVENTIONS. Describe essential features of any interven­ tions, including their method and duration of administration. MAIN OUTCOME MEASURE(S). The primary study outcome measures should be indicated as planned before data collection began. If the hypothesis being reported was formulated during or after data collection, this fact should be clearly stated. RESULTS. Describe measurements that are not evident from the nature of the main results and indicate any blinding. If pos­ sible, the results should be accompanied by confidence intervals (most often 95% interval) and the exact level of statistical signif­ icance. For comparative studies confidence intervals should relate to the differences between groups. Absolute values should be indicated when risk changes or effect sizes are given. CONCLUSIONS. State only those conclusions of the study that are directly supported by data, along with their clinical applica­ tion (avoiding over-generalisation) or whether additional study is required before the information should be used in usual clinical settings. Equal emphasis must be given to positive and negative findings of equal scientific merit. ABSTRACTS for review articles should have the following head­ ings and information: OBJECTIVES. State the primary objective of the review article. DATA SOURCES. Describe the data sources that were searched, including dates, terms, and constraints. STUDY SELECTION. Identify the number of studies reviewed and the criteria used for their selection. DATA EXTRACTION. Summarise guidelines used for abstract­ ing data and how they were applied. SPORTS MEDICINE MARCH 2001 33 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) DATA SYNTHESIS. State the main results of the review and the methods used to obtain these results. CONCLUSIONS. State primary conclusions and their clinical applications, avoiding over-generalisation. Suggest areas for additional research if needed. For more detailed information and examples of structured abstracts, please contact the Editor-in-Chief directly. Three copies of original tables, illustrations, and photos must accompany the manuscripts. TABLES should be typed neatly, each on a separate sheet, with title above and any notes below. Explain all abbreviations. Do not give the same information in tables and figures. Each table should be accompanied by an explicit, detailed legend. ILLUSTRATIONS should be submitted unmounted, identified on the back with the author’s name and figure number, and the top plainly marked. If any tables or illustrations submitted have been published elsewhere, written consent to republication should be obtained by the author from the copyright holder and the author(s). GRAPHS AND DRAWINGS should be 12 x 18” (approximately) glossy prints and should be of professional quality. X-RAYS OR CLINICAL PHOTOGRAPHS. Remove all markings from X-rays before photographing (such as patient’s initials, dates, degree markings). Any arrows or lettering must be applied with a professional product. These identifying marks should be large enough to be seen when the photo is reduced. Sequences of radiographs should be of the same magnification. The subject should be centred in clinical photographs. Crop out extraneous material and background. Each figure should have a separate, detailed, fully explicit legend; all sections of the fig­ ure and all abbreviations and symbols used should be clearly defined. Colour illustrations will be charged to the authors. Details of style. DRUG NAMES: Use generic names only on referring to drugs, followed in parentheses after first mention by a commonly used variant generic. ABBREVIATIONS. Follow the CBE Style Manual (available from the Council of Biology Editors, 9650 Rockville Pike, Bethesda, Maryland 20814, USA) or other standard sources. For abbreviations of journal names, refer to List o f Journals Indexed in Index Medicus (available from the Superintendent of Documents, US Government Printing Office, Washington, DC 20402, USA, DHEW Publication No. (NIH) 83- 267; ISSN 0093-3821). References. References are to be numbered alphabetically and cited in text by number. The reference section should be typed double-spaced at the end of the text, following the sample formats given below. Journal titles should be abbreviated according to the abbre­ viations approved by Index Medicus. All single word journal titles should be spelled out. Complete information should be given for each reference, including titles of journal articles, names of all authors and editors, and inclusive pagination. It is the author’s responsibility to verify references from the original sources. Journal article 1. Stratford PW, Miserfi D, Ogilvie R, Binkley J, Wuori J. Assessing the responsiveness of Five KT1000 knee arthrom- eter measures used to evaluate anterior laxity at the knee joint. Clin J Sport Med 1991; 1L: 225-8. Book 2. Antonaccio MJ. Cardiovascular Pharmacology. New York: Raven Press, 1990. Chapter in a book 3. McGinty JB. Ligament, bone, and nerve complications. In: Sprague NF, III, ed. Complications in Arthroscopy. New ' York: Raven Press, 1989: 87-106. Proofs and reprints. Proofs must be returned within 3 days of receipt; late return may cause a delay in publication of an article. Please check text, tables, legends, and references carefully. To expedite publication, page proofs rather than galleys will be sent to the author, and it may therefore be necessary to charge for alterations other than correction of printing errors. Copyright. Copyright on all published articles will be held by the publisher. In view of the present copyright law, it is neces­ sary that each co-author of a submitted manuscript sign a state­ ment expressly transferring copyright in the event the paper is published in the journal. A copyright transfer form will be sent to the corresponding author by the office of the Editor-in-Chief when receipt of a manuscript is acknowledged. Instructions for electronic manuscript submission. Once the paper has been accepted for publication you will be required to submit an electronic version which matches the accepted paper version. The preferred storage medium is a 31/2 inch disk in an MS-DOS compatible format. Files should be submitted in one of the following standard word processing formats: Microsoft Word (preferred), WordPerfect, WordStar, or XY-Write. Each submitted disk must be clearly labelled with the name of the author, item title, journal title, type of equipment used to generate the disk, word processing program (including version number), and file names used. The file submitted on disk must be the final corrected version of the manuscript and must agree with the final accepted version of the submitted paper manu­ script. The disk submitted should contain only the final version of the manuscript. Please follow the general instructions on style/arrangement and, in particular, the reference style as given in ‘Instructions to Authors’. Note, however, that while the paper version of the manuscript must be presented in the traditional triple spaced format, the electronic version must be typeset and should not contain any extraneous formatting instructions. For example: Use hard car­ riage returns only at the end of paragraphs and display lines (e.g. titles, subheadings). Please observe the following conventions concerning dashes: Use a single hyphen with a space before it for a minus sign, use a double hyphen (with space before and after) to indi­ cate a ‘long dash’ in text, and a triple hyphen (with no extra space) to indicate a range of numbers (e.g. ‘23— 45’). Illustrations and tables will be handled conventionally. However, figure and table legends should be included at the end of the electronic file. Non-standard characters (Greek letters, mathematical sym­ bols, etc.) should be coded consistently throughout the text. Please make a list of such characters and provide a listing of the codes used. 34 SPORTS MEDICINE MARCH 2001 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2. ) SASMA’S 9TH BIENNIAL CONGRESS, 6 - 8 SEPTEMBER 2001 9th Biennial Congress of the South African Sports Medicine Association URGENT C ALL FOR PAPERS Please don'ltorget that W you would like to pre«nl a paper aim® Conference. Ihe»e ne§d to be wttti us by Ihe and of May 3001 Form* tor paper* wGI be tent to you wMi ttw regulation totmi wttfch wll be wim you dwrtty. TTnmb muii be lerrt to Dr Chrttfa Janie van Rensburg on tax number (012) 386 9901 or u ro ile d to i a*rwCton*<.co.ia SASMA immbsfs R1,135.00* Non-m«mbere R 1,400.00 * Remember mat It only c o iij R220 per annum to |o