EDITORIAL Nineteen ninety five will be remembered as the year in which South African sport finally emerged from isolation to regain international respect. The victory o f the Springbok team in the Rugby World Cup final on Saturday June 24th restored an uncertain national sporting pride and was, just perhaps, the greatest single achievement in the history o f South African sport. Correctly, much has been made o f the importance o f that victory for the unifi­ cation o f our fledging nation. But for sport and especially the sports sciences and sports medicine, the long-term effects o f that victory hold equivalent potential. Indeed that single victory may yet revolutionize South African sport and help to propel it, at first grudgingly and reluc­ tantly, into the 21st century. Too little has been made o f the significant contribution made by members o f our Association to that historic vic­ tory. In a soon-to-be released book analysing the basis for the South African victory, former Springbok rugby captain and 1995 World Cup manager, Monie du Plessis, pays spe­ cial tribute to the medical team that supported the Springboks - team physician Dr Frans Verster, team phys­ iotherapist Evan Speechley and applied kinesiologist Ron Holder. In the developing tradition o f South African sports medicine teams, this group “ gave unselfishly o f their time and expertise, sparing nothing in the support o f their team” . To their contribution and example must be added those o f the large number o f physiotherapists, bio- kineticians, psychologists, doctors, sports scientists and other colleagues who week after week during an increas­ ingly long winter season, have ministered to the medical, mental, spiritual and psychological well-being and have maintained and improved the physical condition o f all our provincial rugby stars, who are the fountainhead on which the success o f our national rugby team was based. By helping to make that victory a reality', the abiding con­ tribution o f those colleagues will be to hasten the accep­ tance o f sports medicine and the sports sciences as a cru­ cial component o f international sporting success by both the general public and those less innovative sports admin­ istrators. Indeed since the Rugby World Cup victory, the United Cricket board o f South Africa has increased the number o f sports medicine professionals, contracted on either a part- or full-time basis from 2 (physiotherapist and exercise specialist) to 5 (dietician, podiatrist and psy­ chologist). A visiting sports orthopaedic surgeon who works with a number o f professional teams in the Southern United States, remarked recently that sports medicine in this country stands on the brink o f a revolution s i m i l a r to that which launched sports medicine in the United States 25 years ago. And the common ingredient is a compelling national interest in sport and the growth o f professional sport. What South Africa has, in addition, is the desire o f at least three sports (rugby, cricket and to a lesser extent, soccer) to be the leading South African sport and com pet­ itive with the best in the world. Sue]) desire will engender a healthy rivalry between those sports as each pushes the other to be more creative and innovative in the quest to capture the imagination o f the South African public. Such rivalry promises much to those professions and profes- • sionals who can assist in the achievement o f the ultimate goals o f those sports. And few professions have more to offer than sports medicine and the sports sciences. So we stand at the start o f what will prove to be the most exciting period ever in South African sport. We must grab the opportunities that present themselves and so insure the future o f both sport and our profession in the new nation. And, just perhaps, the very7 future o f the nation itself. To make the most o f those opportunities we must continue to increase our professionalism in both our sci­ entific research and in the service that we provide to our athletes. Surprisingly, this Journal will continue to be one crucial measure o f how far we are progressing. It will tell us whether we are achieving world class standards in both those areas. It will also measure the extent to which we have overcome the greatest threats to our future success which are to allay historical divisions and suspicions and to join all those involved in sports medicine and the sports sciences into one unified body with a common goal o f ser­ vice (above self) in the interests o f South African sport and all her athletes. When we can finally harness the abilities o f all our professionals in sports medicine and the sports sciences to that common goal, only then wall we be able to call ourselves and our .Journal, world-class. This issue o f the Journal covers two areas o f importance to our fixture capacity to serve South African sport. Dr John Hawley contributes 2 articles on applied physiol­ ogy'. In “ Powder systems: Implications for high-intensity swim training” , he reviews the contribution o f the differ­ ent metabolic systems to the energy used during exercise o f different durations and dispels som e o f the myths on which current swimming training regimes are based. This information is o f value in the education both o f ourselves but also o f our swim coaches, some o f whom might per­ haps question whether their current training programmes provide the optimal physiological stimuli necessary' to develop superior swimming performance. For example, he makes the point that “ it is difficult to understand how training for such prolonged periods at speeds which are „ markedly slower than planned race pace, prepares the swimmer for supra-maximal competitive efforts” . His second article provides state-of-the-art training guide­ lines for endurance performance. He makes the valuable point that “ ... during the past century, exercise physiolo­ gists can claim to have had only' a very limited impact on the training practices o f successful athletes w'ith the empirical field-based observations precipitating the majority o f breakthroughs in the training patterns o f top sports persons” . South African scientists should respond to this challenge by making their own contributions to this knowledge. Both articles show how' a knowledge o f exercise physiolo­ gy aids in the development o f correct training methods. I f we are to improve the performances o f our athletes in international competition, w'e also need more informa- ( Continued on p a g e 12) SPORTS MEDICINE SEPTEMBER 1995 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. ) U S T W H A T A T H L E T E S W O U L D E X P E C T F R O M A C O M P A N Y C O M M I T T E D T O S P O R T . Smith1* Nephew F O R F U R T H E R Leadership in Worldwide Healthcare I N F O R M A T I O N C O N T A C T T R O Y B I N G H A M O N ( 0 3 1 ) 7 0 1 5 2 4 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. ) m i ; s o i Ti i .u r k a x j o i K Y W. o r SPORTS MEDICINE VOLUME 2 NUMBER 4 NOVEMBER 1995 Editors P rofT D Noakes D r MP Schwellnus Editorial Board Dr M E Moolla Dr P de Jager D r J S k o w n o D r P Schwartz P rof R Stretch D r C de Ridder P r o f B C Andrews Dr E W Derman Mr R H Farman Dr R H Mars D r C A Noble International Advisory B oard Lyle J Micheli A ssociate Clinical Professor o f O rthopaedic Surgery Boston, USA Chester R K yle R esearch Director, Sports Equipment Research Associates California, USA P ro f H C Wildor Hollmann President des Deutschen Sportarztebundes Koln, West Germany Howard J Green Professor, Departm ent o f Kinesiology’ Ontario, Canada George A Brooks Professor, Department o f Physical Education California, USA Neil F Gordon Director, Exercise Physiology Texas, USA Edmund R Burke A ssociate Professor, Biolog)' Department, University o f Colorado Colorado, USA Graham N Smith Physiologist Glasgow, Scotland CONTENTS Editorial TD Noakes 1 Power systems: Implications for high-intensity swim training JA Hawley 4 State-of-the-art training guidelines for endurance performance JA Hawley 7 Instructions for authors 13 The metabolic demand of portage in kayak marathons M Mars 15 Die invloed van oefening op depressie: ’n meta-analise E Pretorius JC Jansen van Rijssen JM van Zyl 20 Product News 24 THE EDITOR THE SOUTH AFRICAN JOURNAL OF SPORTS MEDICINE PO B ox 115, Newlands 7725 PRODUCTION Andrew Thomas PUBLISHING Glenbarr Publishers cc Private Bag X I 4 Parklaiids 2196 Tel: (Oil) 442-9759 Fax: (Oil) 880-7898 ADVERTISING Marika de Waal/Andrew Thomas REPRODUCTION Output Reproduction PRINTING Hortors Cover sponsored by Ciba-Geigy The views expressed in individual articles are the personal views o f the Authors and are not necessarily shared by the Editors, the Advertisers or the Publishers. No articles may be reproduced without the written consent o f the Publishers. i SPORTS MEDICINE NOVEMBER 1995Reprod uc ed b y Sa bi ne t 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. ) Power systems: Implications for high-intensity swim training JA Hawley, PhD, FACSM Introduction Many coaches steadfastly believe that im provem ents in perform ance are directly related to th e volum e o f work p erform ed during training, and that a swim mer can only reach h e r /h is full potential b y undertaking extrem ely lon g and arduous training sessions. C om petitive sw im m ers, for exam ple, often train between two and four hours each day swim ming up to 20,000 m etres, with an energy expenditure exceeding 4 ,50 0 kcal/day. A s the majority o f com petitive swim ­ ming events last less than five minutes, it is difficult to understand how training for such prolonged p eriods at speeds which are m arkedly slower than planned race pace prepares th e swim m er for supra maximal com pet­ itive efforts (Costill et al 1991). A swim mer’s speed and ability to resist fatigue during training and com petition depend on th e m uscles ability to produce m echanical w ork (force) from the break­ down o f stored chem ical energy (mainly carbohydrate and fat). This article d escribes the different m etabolic pow er systems that provide the energy for muscular contraction, examines th e contribution o f these systems to th e energy requirem ents o f maximal exercise, and details the b e st type o f workouts to train those systems. Power systems When describing the physiological entities that pro­ duce the energy required to sustain all cellular p rocess­ es, including muscular contraction, m ost texts o f exer­ cise physiology, and alm ost all coaching manuals, use th e term “ energy system s” . However, as th e primary function o f such systems is to produce powder for exer­ cise, such term inology seem s inappropriate: it would seem conceptually m ore correct to call them pow7er sys­ tem s (Hawley & H opkins, 1995). T he distinction betw een energy and powder systems is not merely semantic: th e output o f a physiological sys­ tem should b e quantified as the pow er that can b e p ro­ duced, and not m erely the amount o f energy potential­ ly available for muscular work. O bese individuals, for example, have vast reserv es o f energy stored in the form o f fat, but are not renowned for their ability to sus­ tain high power outputs! The body has four distinct power systems it can use to supply energy for exercise: two anaerobic (oxygen-inde­ pendent), and two aerobic. The nam es o f the power sys­ tem s represent descriptive summaries o f the com plex Address for Correspondence: Dr JA Hawley MRC/UCT Bioenergetics o f Exercise Research Unit Sports Science Institute o f S/1 Box 115 Newlands 7725 Tel: (021) 686-7330 Fax: (0 2 1 ) 686-7530 Email: JHAWLEY @ SPORTS. UCT. AC.ZA biochem ical pathways each uses to produce e n e r g y for muscular contraction. T hese systems are considered distinct by exercise scientists because (1) they have sub­ stantial!}7 different biochem ical pathways, (2) their rela­ tive contributions to d ie e n e r g y required for exercise depends on the intensity (speed) and duration o f an event, and (3) these contributions can b e m odified by appropriate training and dietary7 interventions. It should b e noted that for m ost Olympic swimming events, tw7o, or at the very m ost three power systems are utilised. THE ATP-CP (PHOSPHAGEN) SYSTEM T h e phosphagen system uses adenosine triphosphate (ATP) and creatine phosphate (CP) stored within the m uscle to provide energy for maximal bouts o f strength and speed that last for up to six secon d s (Gaitanos, et al 1993). ATP and CP are stored at the contractile site o f the m uscle, malting this anaerobic power system the m ost readily available for use during high-intensity ex­ ercise. T h e amount o f ATP and CP stored within skele­ tal m uscle is, how7ever, quite low7 and the phosphagen system can only power bursts o f maximal exercise for very short periods. Indeed, after only a few7 seconds o f exhaustive work, the power p roduced by the ATP-CP system decays, so that after six seconds it provides only h a lf o f th e total energy requirements o f exercise (Figure 1). T h e ATP-CP pow7er system would b e used for the start and the initial seconds o f a 50 m sprint. THE ANAEROBIC (OXYGEN-INDEPENDENT) GLYCOLYTIC SYSTEM This system derives its name from the biochem ical path­ way that produces energy from the breakdown o f carbo­ hydrates without the use o f oxygen. T h is pow7er system is rapidly activated at the onset o f intense work, so that even during a six second maximal sprint, th e contribu­ tion to the total energy requirem ents o f exercise from anaerobic glycolysis reaches alm ost 50% (Figure 1). In a sprint event lasting approximately 30 seconds, the con ­ tribution from anaerobic glycolysis to the total energy requirements o f exercise increases to 60% (M edbo and Tabata 1989) (Figure 1). A s would b e expected, the longer the exercise duration (or the slower th e swim speed ), the sm aller is the contribution to m uscle m eta­ bolism from th e anaerobic glycolytic system. Thus, after a maximal effort lasting one minute, anaerobic energy release has decreased to 50% o f overall metabolism , and after two minutes o f high-intensity work, to around 35% (M edbo and Tabata 1989) (Figure 1). Associated with the anaerobic release o f energy from carbohydrate is the production o f lactic acid by the working muscles. Therefore, wrorkouts that develop the sw im m er’s ability to produce and tolerate high concentrations o f lactate are essential for th e successful sprinter. THE AEROBIC GLYCOLYTIC AND AEROBIC LIPOLYTIC POWER SYSTEMS T h e two aerobic pow er systems are nam ed for th e fact tli at they generate energy for m uscle contraction from the breakdown o f carbohydrate and fats in th e presence 4 SPORTS MEDICINE NOVEMBER 1995 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. ) Figure 1. The contributions o f the different exercise. power systems to the total energy requirements o f maximal Event M ajor pow er duration system s utilised < 6 sec Phosphagen < 30 sec Phosphagen Anaerobic glycolytic Main fuel substrates ATP-CP ATP-CP Muscle glycogen <15 m in A erobic glycolytic >15 m in A erobic glycolytic A erobic lipolytic M uscle glycogen Blood glucose M uscle glycogen Blood glucose Intra & extra-muscular fat u l S ? eX,erC'Se ls,inS longer than two m in­ utes and up to three hours is pow ered predom inantly by the aerobic glycolytic system. For longer, less intense exercise, and all ultra-endurance swim ming events the n S s f o f t h Via aerobic Upolytte system provides m ost of th e energy for m uscle m etabolism. Note that fat Ca”n° i oxidised hi the presence o f oxygen I l ie duration o f maximal exercise for which equal con ­ tributions to energy m etabolism are m ade by the aerobic glycolytic and aerobic lipolytic power systems is probably (IhnvIey & H <>r>k " ^ 1995). During such prolonged endurance events, the use o f fat relative to car- S increases as the intensity ol exercise decreases CBroofe and Mercier, 1994). Although botli carbohydrates and fats are likely to b e used as fuels by th e m uscle dur- m g prolonged endurance training, com petitive swim stored ' n !)0Were< alm° f d elusively by carbohydrate, stored m th e m uscle as glycogen (Costill et al, 1988). IMPLICATIONS f o r t r a in i n g C() TinHi!h'rlinS a year' r.ound '■raini" g programme for d ie r ? W,nlnlei; l he SpeCiBc Physiological demands anrvr S SIX'Cl:dit>’ event(s) should be identified and a -e'Th ' ? in: ng t<:cl,ni(Jues em ployed that will en- P ^-fo™ 5 are critical determinants o f IlllVs i f “ KC| ^ s h o u l d always b e rem em bered that the U he s S n :l; a,Ptati0nS ! ° " 'aining closely related a" d m od e o f Gaining perform ed m g epeated days o f exercise. Since there is little Training objective and B est type o f workouts Development o f explosive pow er Sprint starts Strength training (3 sets o f <4- repetitions @ 95% o f 1RM) Maximal sprints « 2 5 m ) with com plete recovery Lactate tolerance hirt o ” airs PeUU,,nS (<3° S£C) WiUl lon« (3-5 m in) rest Strength training (3 sets o f <8 repetitions @ 85% o f 1RM) D evelopm ent o f aerobic p ow er repetitions (1-5 min) with snort « 6 0 sec) rest intervals D evelopm ent o f aerobic endurance Long repetitions (>5 min) with short « 6 0 sec) rest aeixrtyc ' Continuous shim m ing at b e st steady-state cross-tram m g effect Irom one pow er systems to anoth- 1 ° ne type o f exercise to another, workouts s lould b e structured to develop those power systems required for the swim mers speciality events (Table 1). utilised"?! V u 111116 C0UrSe ° f , he P °wer systems utilised d im n g high-m tensily swim ming events cou­ p led with the need for specificity in lining should assist coaches in assessing w hether their current train­ ing regunens provide the optimal physiological stimuli necessary for superior swimming performance. REFERENCES 1. Brooks G A M Mercier. The balance o f carbohydrate and lipid utilization during exercise: the cross-over’ concept J A v n l Physiol. 7 6 :2 8 5 3 -2 2 6 1 , 1994. ‘ PP '■ d Z s l n i t MG/ CH n, J P Kirwan et aL EJfkcts ° f repeated days oj intensified trainmg on muscle glycogen and swim- , r i‘T t r nT Ce- MecL Sci SP°Hs E x ™ SO; “ 3. Costill DL, Thomas R. Robergs R A et al. Adaptations to m T /t T T GCj ° Williams’ L H -Boobis et al. Human muscle ° " Z t Z 'n l W ° U ° PkiT A e r ° btc ^ c° 1̂ ™ d aerobic lipolytic power system : A new paradigm with implications 2 4 0 ^ 2 5 a W 9 S and llUraendurance evelU*- Sports Med 19: 6. M e d b o J I , Tabata I. Relative importance o f aerobic and anaerobic energy release during short-lasting exhaustinn bicycle exercise. J A pp l Physiol 67 : 1881-1886, 1989. □ 4. SPORTS MEDICINE NOVEMBER 1995 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. ) Accusporl is the first truly p orta ble m eter fo r m easuring lactote levels on the spot ■ affordable convenience at its best! Accusport weighs o mere 12 0 g , it's a cinch to use, and the vital inform ation displayed could result in a PB. By measuring heart rate and lactate levels during exercise you can monitor degrees of exertion, optimise health benefits, maximise endurance and avoid over exertion. . Trainers and sports group leaders know that customized training improves individual performance. . High-performance athletes and health-conscious sports people need to have personol control over their training. ■ Physicians, physiotherapists and biokineticists in rehabilitation can provide greater safety in sport. 0 Heart rale m Time of day with d aily alarm 0 Calendar • Stopwatch with 3 0 lap time memoi y 0 Target lap time 0 Time spent & average HR recordings, within, above & below target zone • Heort rote memory with 256 memory recordings 0 Event markers 0 Kcalaries burnt 0 Water resistant • Bike adapter included TO THESE PRODUCTS, A WIDE RANGE OF HEART RATE MONITORS IS AVAILABLE 0 Heart rate • 12 or 24 haur time o f day • Stopwatch • Heart rate recording with selectable sampling intervals • -Recall recorded heart rate • High & law heart rate lim it alarms • Target zone indication • Water resistant adapter included HEARTSAFE Excludes: Time of day C A R D I 0 5 p * r t / I c c u s r t r r h e a r t r a t e m o n i t o r s O R M ORE INFO RM ATIO N OR THE STO CKIS n e a r e s t y o u , C A L L B I O M A R O L L F R E E : 0 8 0 0 2 2 4 6 8 on the s p a t / 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. ) State of the art training guidelines for endurance performance JA Hawley, PhD, FACSM Introduction and background The purpose o f this article is (1) to identify the physio­ logical factors associated with successful endurance perform ance and (2) provide training guidelines and specific workouts for athletes com peting in strenuous events such as cycling (40 kin time-trial and over), d is­ tance running (5 1cm and longer), the standard-distanee triatldon, and distance-swimming races. Wherever p o s ­ sible scientific studies have been cited to support the physiological rationale underlying specific training principles. In addition the practical experience o f the author as a competitive athlete, coach and exercise physiologist involved in the testing, monitoring and prescription o f training to elite atJdctes in several con­ tinents during the past decade has been drawn on. It shoidd be noted at the outset that despite their best efforts, it has proved extremely difficult for sports scientists to manipulate the training regimens o f elite endurance athletes for the purpose o f scient ific inquiry. Thus, during the past century, exercise physiologists can claim to have had only a very limited impact on the training practices o f sueecsslid athletes, with the em pi­ rical field-based observations o f coa ch es precipitating die majority ofbreakthroughs in the training patterns o f top sportspcisons (Wells and Pate 1988). Nevertheless, many scientific investigations have consistently identi­ fied the physiological variables that are positively relat­ ed to successful endurance performance, 'fh ese variables are defined and briefly discussed, f l i c extent to which these and other factors are “ trainable” as opposed to genetically determ ined is a topic o f considerable debate (Bouchard ct al. 1992). The reader is referred to the excellent reviews o f H olloszy et al. (1977) and Saltin (1969) for more detaded discussions o f the physiologi­ cal adaptations to chronic endurance training. PHYSIOLOGICAL FACTORS RELAFED TO SUCCESSFUL ENDURANCE PERFORMANCE 1. Maximal oxygen uptake Maximal oxygen uptake (VO^. J is the greatest rate at which oxygen can be consiuned by an athlete during exer­ cise and, under steady-state conditions, is a reflection o f an individuals maximum rate o f aerobic energy utilisation (Ast-iund and Rodahl 1977; Costill 1986; Rowell 1986; Sal­ tin and Astrand 1967; Wihnore 1984). Studies performed over (illy years ago established dial oxygen uptake (VOs) increased with running (H erbst 1928; Ldjestrand and Stenstroni 1920b) and swim ming speed (Ldjestrand and Stenstroni 1920a) and that the fastest athletes had die liighcst oxygen uptakes (Herbst 1928; Robinson et al. 1937). ( h e r the next fifty years credibdity was given to the b e lie f that VO*,,,,̂ was a good predictor o f athletic po­ tential in endurance sports (Costill and Winrow 1970a; Costdl et al. 1973; Davies and Thom pson 1979; Leary and Wyndham 1965; Wyndham e ta l. 1969). Judging by the frequency with which the topic is discussed amongst athletes and coaches, it woidd still appear that the vast majority o f runners, cyclists and triathlctes implicitly believe that the V Q .„» is d ie single best predictor o f atldctic potential in all endurance events (Noakes 1988). Although VOi>m„» is a satisfactory' predictor o f endu­ rance performance in a heterogeneous group o f athletes (Costdl et al. 1973; Farred et al. 1979), individuals with similar VO-„„LX values can differ markedly in perfor­ mance velocity (Costdl and Winrow 1970b; Coyle et al. 1988; Daniels 1985; Londeree 1986; Noakes 1988). TABLL 1; Maximttm oxygen uptake values for som e elite endurance runners Athlete VO,.., Best Perform ance Reference (m l/k g /m in ) Said Aouita 83.0 12:58,39 (5 000 m) Zur M egede and Hymans (1991) .Tolui Walker 82.0 3 :49.08 (1 m ile) Agnew (1976) Steve Scott 80.1 3:47.69 (1 m de) Conlev et al (1984) Sebastian Coc 77.0 3:47.33 (1 mile) Zur M egede and Hvinans (1991) Greta Waitz 73.5 2h:24 .54 (marathon) Peronnet and Thibaidt (1989) Peter Snell 72.3 3:54.10 (1 m de) Carter et al (1967) Fraidt Shorter 71.3 2h:10.30 (marathon) Pollock (1977) Willie Mtolo 70.3 2h:08 .15 (marathon) Noakes et al (1990) Derek Clayton 69.7 2h:08 .34 (marathon) Costill et al (1971) Address for Correspondence: Dr JA Hawley MRC/UCT Bioenergetics o f Exercise Research Unit Sports Science Institute o f B ox 115 Newlancls 7725 Tel: (0 2 1 ) 686-7330 Fax: (0 2 1 ) 686-7530 Email: JH AW LEY @ SPORTS. UCT. AC.ZA W hile VO,,.,,* in elite male m iddle and long-distance nuniers typically range from 75 to 85 m l/k g /m in , widi extreme values equal to or exceeding 90 n d /k g /m in (Bergli 1978; Conley et al. 1984; Costill 1986; Daniels 1974; Martin ct al. 1986; Pollock 1977; Saltin and Astrand 1967), such high values are probably not as critical for athletes participating in prolonged endu­ rance events which last 60 lnin or longer (Table 1). 2. Fractional utilisation o f oxygen uptake Fractional utilisation refers to the percentage o f an ath­ letes VO_>„„,, that can be utilised at a specified speed or SPORTS MEDICINE NOVEMBER 1995 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. ) workrate (i.e. race pace). Top marathon runners (i.e. sub 2 hr 20 min) can sustain ~86% o f VOa,,,,,* lor the duration o f a race (Costill 1972), whereas slower run­ ners (i.e. 2 hr 45 min up to 3 hr) can sustain only 75- 76% o f their VOa,„u* for th e sam e distance (Farrell et al. 1979; Wells et al. 1981). In cycling, despite similar VO-, , values (i.e. 69 m l/m in /k g ), elite national class riders are able to sustain 90% o fV O a„ for th e duration o f a 40 km time-trial com pared to 86% for good provin­ cial (state) riders (Coyle et al. 1991). T h is greater frac­ tional utilisation of' VO-,,,,, perm its the elite cyclists to rid e considerably faster over 40 km com pared to the good riders (53 :54 min versus 60:00 min, respectively). Although the physiological basis for th is endurance capability is not clearly understood (Peronnet and Thi- bault 1989), it w ould appear that the fraction o f V Q w that an athlete can sustain for prolonged p eriods is re­ lated to the accumulation o f lactic acid in th e active m uscles (Costill et al. 1973; Farrell et al. 1979; LaFon- taine et al. 1981; Sjodin and Jacobs 1981). In endu­ rance-trained athletes, for example, there is litd e or no increase in b lood (and presum able m uscle) lactate con ­ centration until an exercise intensity that elicits 70-85% o f V Q w (Costill 1986; Costill 1970; Farrell et al. 1979). 3. P e a k s u s ta in e d p o w e r o u tp u t Recently, both sports physiologists (Hawley and Noakes 1992; Hawley et al. 1992; Morgan et al. 1989; Noakes et al. 1990; Scrim geour et al. 1986) and coa ch es (Helle- m ens 1993) have recognised th e im portance o f peak sustained power output as a predictor o f endurance p er­ formance. In runners, fo r example, th e peak treadm ill velocity d ia t an athlete can achieve during a maximal test lias been found to b e as good a predictor o f endurance perform ance as any physiological variable currently measured (Morgan et al. 1989; Noakes e t al. 1990). It has b een p roposed that th e factors which determ ine peak sustained m uscle pow er production in short duration, high-intensity events like running the 800-1,500 m m ight also determ ine perform ance in m ore prolonged endurance events, lik e th e marathon (Noakes 1991). T his would explain th e field-based observations o f coaches like Arthur Lydiard (Lydiard and Gilm our 1978) and Gordon Pirie (Pirie 1961), w ho claim that th ose distance runners who are th e fastest over th e shortest distances will also b e th e fastest over longer distances (Noakes 1991). In cycling, th e peak sustained pow er output mea­ sured during an incremental cycle test to exhaustion has been shown to b e a valid predictor of perform ance during a 20 km time-trial (Hawley and Noakes 1992). In this regard, Coyle et al. (1991) have observed that elite cyclists (m ean tim e o f 53:54 m in tor 40 km ) can sustain average pow er outputs o f 346 Watts (W) for one hr, with d ie b est cyclists (51 m in for 40 km ) able to sus­ tain a power output o f 376 W/hr. 4 . F a tig u e r e s is ta n c e Fatigue resistance is th e ability o f an athlete to resist fatigue (i.e. sustain a high power outp ut/speed ) during prolonged exercise, and is related to the contractile properties o f skeletal m uscle. A major adaptation to chronic endurance training is that th e skeletal m uscles involved in th e activity are m ore fatigue resistant than prior to training (Fitts 1977). Ind eed, a recent study from this laboratory has shown that th e superior p er­ formances o f elite black runners in events from 3,000 m up to the marathon are, in part, due to their superior resistan ce to fatigue com pared to w h ite runners (Coetzer et al. 1993). It may well b e that an important com ponent o f training (and tapering) is to directly alter skeletal m uscle contractility (i.e. m uscle power) as orig­ inally proposed by Noakes (1988). 5. T h e a n a e ro b ic "l a c t a t e ” th resh o ld T h e speed o f m ovem ent at w hich a specific b lood lac- tate concentration (usually 4 m m ol/L ) is observed. Lactate threshold m erely reflects the highest exercise intensity that an athlete can sustain for an extended period without amounts o f lactate accumulating that are limiting for perform ance (Wells and Pate 1988). A lthough there exists m uch debate as to the term inol­ ogy describing th e kinetics o f lactate accumulation dur­ ing steady-state exercise (Brooks 1985; Jacobs 1986), there is, regardless o f how it is m easured and defined, a close relationship betw een lactate threshold and en­ durance perform ance (Coyle et al. 1988, 1991: Sjodin and Svedenhag 1985). In running, for example, endu­ rance training increases the speed at the lactate tum- point and this change correlates closely with actual im ­ provem ents in running perform ance (Tanaka et al. 1984). It is, however, unlikely7 that there is any relation­ ship between the lactate threshold and a heart-rate d e ­ flection point (Kuipers et al. 1988; R ibeiro et ^ 1985), as was originally p roposed b y Conconni et al. (1982). 6. E c o n o m y o f m o tio n Economy o f m otion is th e cost (i.e. oxygen uptake) re­ quired to produce a specific workrate or speed o f move­ ment. T he best endurance athletes are usually th e m ost efficient (Conley and Krahenbuhl 1980; Daniels 1974; Noakes 1988). Better econom y (i.e. a lower oxygen cost) is advantageous during endurance exercise as it is asso­ ciated with a slower rate o f energy utilisation (i.e. m us­ cle glycogen). I f fatigue during prolonged endurance events is associated with th e depletion of b od y fuel stores, then the more efficient athlete will b e able to cover a greater distance on the sam e amount o f fuel (Noakes 1991). Several studies suggest that, for running at least, a major benefit o f the high (i.e. greater than 120 km ) weekly training distances that elite athletes maintain is a p rogressive increase in running efficien cy (Scrim geour et al. 1986; Sjodin and Svendenhag 198o). With prolonged endurance training (i.e. 3-4 years expe­ rience) runners also tend to decrease the length o f their stride at a given velocity, w ith a concom itant increase in stride frequency (Nelson and Gregor 1986). Elite run­ ners also appear to ch ose an optimal stride length at w hich they are m ost efficient (i.e. at which th e oxygen cost is th e least) and when forced to take either longer or shorter strides for the sam e running velocity they require an increased oxygen uptake, thus becom ing less efficient (Cavanagli and Williams 1982). Analogous to the long-slow distance training o f run­ ners top cyclists cover many' m iles, albeit at relatively7 fast speeds, at a high cadence (90-120 revolutions/ min) in a low gear ratio in order to develop a sm ooth efficient leg stroke at speed (i.e. spinning). O f interest here are the results o f a recent study by Coyle et al. (1992) that showed that among a group o f well-trained cyclists, cycling econom y at submaxiinal workrates d if­ fered by as m uch as 15%. Such differences in efficiency were not due to differences in cycling technique but, instead, related to the number o f slow-twitch (type I) m uscle fibres in the quadriceps m uscles o f the cyclists; th ose subjects with a high percentage o f type I m uscle fibres were m ore efficient (i.e. required less oxygen) to work at either 50% o f 70% ofVO»„,„ than subjects with a low7 percentage o f slow-lwitch fibres (Coyle et al. 1992). 8 SPORTS MEDICINE NOVEMBER 1995 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. ) In swimming, tlie distance covered with each stroke has been shown to be an excellent predictor o f p erfor­ m ance for both sprint and distance events (Costill et al. 1985; Hawley et al. 1992). For a given speed, a swim ­ m er who has the greatest stroke-distance is assum ed to have the m ost efficient technique (Costill et al. 1985). Such a technique is assumed to b e a direct con se­ quence o f the enormous distances covered by m ost swim mers during training. 7. Fuel utilisation At high workrates (sp eed s) there is a greater reliance on carbohydrate than lipid substrate (B ock et al. 1928). Highly-trained endurance athletes can m ake greater use o f fat as a fuel for energy provision during high-in- tensity submaximal exercise than less trained individu­ als, thereby conserving m uscle and liver glycogen stores. However, the w hole concept o f training longer and fur­ ther to increase the muscles ability to utilise fat remains contentious. For example, i f an athlete trains m ore than 60 m in /da y there is little additional enhancem ent o f the m uscles ability to utilise fat as a fuel in preference to carbohydrate (Coyle EF, personal com munication). In summary, the principal physiological requirements o f an endurance a th lete wishing to com pete at a high level during prolonged exercise are: (1) a high but not phenomena] Y( ) (2) the ability7 to utilise a high p er­ centage o f VOa„„ for sustained periods, (3) the ability to sustain high pow er outputs and resist muscular fatigue during prolonged exercise, (4) a high pow er output (or speed ) at the lactate threshold, (5) an efficient te ch ­ nique, and (6) the ability to utilise fat as a fuel during sustained exercise at high workrates. Training techni­ ques to prom ote these physiological adaptations will now b e discussed . t r a in i n g t e c h n iq u e s f o r s u c c e s s f u l ENDURANCE PERFORMANCE Since World War II the training practices o f elite endu­ rance athletes have passed through several identifiable and distinct phases. T h ese stages can usually b e asso­ ciated with influential coaches o f the tim e (i.e. Franz Stampfl, Percy Cerruty and Arthur Lydiard in running; Forbes Carlile and Jam es Councilman in swimming; Cyrile Guimard and E ddie Borysewicz in cycling), each o f whom has been credited with the development o f a num­ ber o f leading athletes. A s a result, there currently exists a multitude o f diverse training techniques for d ie perfor­ mance o f prolonged exercise. Elaborate training systems based on multiply macro and m icro cycles with specific attention to the periodisation o f training have been p ro ­ posed. However, such program mes are often theoreti­ cally based, lack scientific validity, and are o f little prac­ tical value for the majority o f coaches and athletes who m ust often train all year round to com pete successfully on an international level (H opkins 1993; Horwill 1992). A com m on trend in many endurance sports has been or coach es and athletes to adopt and im plem ent the prevailing training regimens o f current w7orld-class per- oriners in their discipline. W hile such a practice has obvious drawbacks and typically results in th e downfall ot many a prom ising athlete, this m ethod may, occa ­ sionally, contribute to th e unprecedented success o f an individual. In this regard, it is generally assum ed by many coaches and athletes that improvements in p er­ formance are directly related to the amount o f work Perform ed during training, and that an athlete can only reach his or her full potential by undertaking extrem e - Jy long and Intense training (Costill et al. 1991). A l­ though the volume o f exercise is among th e variables known to determ ine the degree o f adaptation to train­ ing (Davies and Knibbs 1971; Faria 1970; Fox et al 1973, 1975; Shephard 1968), there is now evidence, at least for swim mers, that such extensive training may not necessarily enhance performance (Costill et al. 1991). Intuitively th e perfect training program m e for endu­ rance perform ance should include elem ents o f all the training techniques currently practiced by todays suc­ cessful performers. How7ever, m ost o f the key facets that constitute the generic core o f a year-round training p ro­ gramm e for the endurance athlete can b e divided into ju st three main phases: (1) b ase or foundation training, ) transition training, and (3) speed or power training, incorporating a taper phase before a major com petitive peak. During each phase o f training primary emphasis is given to the development o f one (or more) specific physi­ ological objectives (i.e. the developm ent o f fatigue resis­ tance, or th e im provem ent o f econom y o f motion etc.). 1. Base/foundation training Performed during th e winter or th e non-competitive period o f an athletes m acrocycle, the primary em phasis of this phase o f training is the establishm ent o f a sound aerobic foundation on which to base subsequent (m ore intense) training (LeM ond and G ordis 1990; Lydiard and G ilm ore 1978, 1983; Wells and Pate 1988). T h e physiological benefits ascribed to b a s e / foundation training include enhancem ent o f myocardial function (Clausen 1977) and oxygen transport (Ekblom 1969), an increase in b lood volume (Convertino et al. 1980),' enhancem ent o f m itochondrial and oxidative capacity o f skeletal m uscles (Fink et al. 1977; Kiessling et al. 1971; Saltin 1969) and improved fat m obilisation and utilisation (G ollnick 1985). In the base/foundation phase o f training, the overall training quotient (i.e. duration x intensity x frequency) is kept well below7 that threshold tJiat would over­ extend the athlete and lead to signs o f over-reaching staleness and fatigue (Carlile 1964; Councilman 1968’; Hopkins 1993). Base training is typically perform ed at intensities ranging from 65-70% o f V 0 2n,„ (70-80% o f maximum heart-rate) for a minimum o f 30 min up to several hr duration each day, with a frequency o f b e ­ tween 7-12 session s/w eek, for as long as possible (i.e. 3-4 m onths) depending on the tim e lag after th e ath­ letes last com petitive phase. W hether base training in the high volumes currently undertaken by elite runners (140-160 k m /w eek), cyclists (500-800 k m /w eek ) and swim mers (50-60 k m /w eek ) is essential to elite perfor­ m ance has not been systematically determ ined. In this respect, it is difficult to explain how7 training up to 4 h r/d a y at speeds which are m arkedly slower than planned com petition pace can possibly prepare the elite swim mer for races which typically last less than 15 min. Research is needed to establish whether base training per se results in better endurance perfor­ mances com pared to w7hen the athlete trains at an intensity (or effort) that is m ore specific to th e athletes specialist event from the outset o f a training cycle (H opkins 1993). W hether base/foundation training has any benefit to athletes w hose speciality event has no aerobic com ponent remains speculative. S. Transition training T h e second phase o f training w'hose prim e objective is to expose the various physiological pow er systems to sustained exercise at an intensity (or effort) w hich cor­ responds to the athletes highest current steady-state pace. T h e physiological and perform ance enhancing b e ­ SPORTS MEDICINE NOVEMBER 1995 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. ) nefits ascribed to transition training include enhance­ ment o f lac talc kinetics (MacRae ct al. 1998; Tanaka et al. 1984) and stimulation o f the specific neurological patterns o f muscle fibre recruitment needed during a race (Costill 1986; LeMond and C ord is 1990). Intermittent (or interval) training has been the corner­ stone o f swim training for many decades (Carlile 1964; Daniels and Scardina 1984), although it was not until the 1960’s that the first s p o ils scientists began to study the effects o f different combinations o f work and recovery on physiological system s (Astrand et al. 1960; Christen­ sen et al. 1960). Transition training can be perform ed as continuous steady-state exercise or intermittent work bouts with short rest intervals (Brooks and Fahey 1985; Costill 1986). The intensity o f this phase o f training should correspond to ~85% o f VO<„k« or 90-95% o f the athletes maximal heart-rate, d ie so called aerobic- anaerobic th resh old ” (LeMond and G ordis 1990), or the athletes b est current race-pace for either a 10 km (running) a flat 40 km time-trial (cycling/triathlon) or 1,500 in (swimming). Although exercise prescription based on blood lactate concentrations has becom e pop­ ular with swim mers and more recently cyclists for d e ­ termining the effort o f transition training, there is little scientific evidence to support such practices. An example o f a transition session for a runner or cyclist woidd incor­ porate a thorough 30 min warm-up, followed by 6-8 re­ petitions each o f 5 min duration at the athletes best current race pace for their event, with a maxinumi of 60 sec active recovery (i.e. jogging or low gear spinning). There is no need to measure d ie precise distance covered dur­ ing each work bout; as an athlete gets fitter die)' will merely cover more distance in a given time. Transition training should b e perform ed twice a week for the four weeks im m ediately following the base phase. In a dd i­ tion several time-trials over distances less than die ath­ lete’s planned com petitive event may b e undertaken during this time. The athlete should aim to com plete such trials at a pre-planned pace or effort, at close to projected race pace, but not necessarily all-out. 3. Speed/power tra ining The final phase o f training which is designed to expose the various physiological systems to maximal or supia- maximal exercise at a speed (or efforts) wiiicli are fastei than planned race-pace. S p eed /p ow er training em ploys relatively high intensity work bouts widi long rest periods (Coe and Miller 1981; Moorcroft and Temple 1984). The overall volume o f training is low' during this final phase. An example o f such a session for a runner or eve list would involve an extended warm-up, followed by 6-8 re­ petitions o f up to 90 seconds duration with a com plete (i.e. 5 min) active recover)' (i.e. jogging or low' gear spin­ ning) between repetitions. Heart-rate monitoring is not a valid technique for determ ining the intensity o f s p e e d / I lower workouts; often an athlete will attain a higher heart-rate (and blood lactate concentration) after the exercise bout. S p eed /p ow er training should be per­ form ed up to three tim es/w eek during the final 21 days before a major com petition. In d ie final 7-10 days im­ mediately prior to an important race, the training load is gradually reduced to nearly zero. As has teen previous­ VoUarenssiQQ Diclophenoc s o d iu m 1 0 0 m g M/3.1/63 ly stressed (H opkins 1993), the lower overall workloads in this phase o f training are achieved by reducing the volume and frequency o f training and not the intensity, b id eed , a recent study (S h cp lcy et al. 1992) found that m iddle-distance runners significantly improved their performance times by sharply reducing then' training volume while maintaining or slightly increasing their training intensity' seven days before a race. This method o f taper was superior to b o d i a reduction in training intensity, and total rest (i.e. no running at all) in the w eek prior to com petition (S h cp lcy et al. 1992). Practical research is needed in most endurance sports to determ ine the optimal com binations o f reductions in volume and intensity that will subsequently result in the greatest improvements in performance. When planning a year-round program me for the endurance athlete, the specific physiological dem ands o f the event should be identified and appropriate train­ ing techniques em ployed that will enhance those (ac­ tors that are critical determinants o f performance. It should always be rem em bered that the physiological adaptations to training are closely related to the speed, distance and m ode o f training perform ed d ining repeat­ ed days o f exercise. Since there is litde cross-training effect from one type o f exercise to another (Costill 1986; Wells and Pate 1988), workouts should be structiued to develop only the power system s required for the ath­ letes speciality event (H opkins 1993). Finally, endurance training is not, and will never be, a purely scientific endeavour. Current knowledge ol training practices has evolved mainly through the expe­ riences of many coach es and their charges and not usu­ ally because o f any scientific breakthroughs arising from laboratory-based investigations by sp o ils scien­ tists with top atldetes. Future innovations in training techniques, improvements in atldetic performance, and breakthroughs in applied exercise science will onlj be accom plished as a result o f closer working relation­ ships between athletes, coa ch es and sports scientists who possess a com prehensive and practically based knowledge o f specialised events. REFERENCES 1. Agnew I (1976) Kiwis Can Fly. Markelforce Ltd.. Auckland, pp. 187. 2. Astrand 1. Astrand PO, Christensen EH. Hedman It. (I9 6 0 ) Intermittent muscular work. A d a Physiologica Scandinavia 48: 448-453. 3. Astrand PO. Rodahl K (1977) Textbook of Work Physiology. Second Edition. McOraw Hill. New York. 4. Berqh V. Thornstensson A. Sjodin B. Hullen B. 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European Journal o f Applied Physiology 55 : 202-209. 81. Shephard R (1 9 6 8 ) Intensity, duration and frequency oj exercise as determinants o f the response to a training regi­ men. Internationalle Angew Physiologie 26 : 272-278. 82. Sjodin B, Jacobs I (1 9 8 1 ) Onset o f blood lactate accumula­ tion and marathon running performance. International Journal o f Sports Medicine 2: 23-26. 83. Sjodin B, Svedenhag J (1 9 8 5 ) Applied physiology of marathon running. Sports Medicine 2: 83-99. 84. Shepley B, MacDougall JD, Cipriano N, Sutton JR, Tamopolsky M A, Coates G (1 9 9 2 ) Physiological effects o f tapering in highly trained athletes. Journal o f Applied Physiology 72: 706-711. 85. Tanaka K , Matsuura Y (1 9 8 4 ) Marathon performance, anaerobic threshold, and onset o f blood lactate accumulation. Journal o f Applied Physiology 57: 640-643. 86. Wells CL, Ilecht LH, Krahenbuhl GS (1 9 8 1 ) Physical char­ acteristics and oxygen utilization o f male and female marathon runners. Research Quarterly for Exercise and Sport 52 : 281-285. 87. Wells CL, Pate RR (1 9 8 8 ) Training for performance of pro­ longed exercise. In: Lamb DR, Murray R (E d ito r s), Perspectives in Exercise Science and Sports Medicine Volume 1. Prolonged Exercise, Benchmark Press, Indianapolis, pp. 3 5 7 -3 9 1 .' 88. Wilmore J H (1 9 8 4 ) The assessment of and variation in aer­ obic power in world class athletes as related to specific sports. A merican Journal of Sports Medicine 12: 1 2 0 -1 2 /. 89. Wyndham CII, Strydom NB, Van Rensburg A J , Benade A JS (1 9 6 9 ) Physiological requirements for world-class perfor­ mances in endurance running. S o u t h African Medical Journal 4 3 :9 9 6 -1 0 0 2 . 90. Zur Megede and Hym ans R (1 9 9 1 ) Progression o f World B e st Performances and Official I A A F World Records. International Athletic Foundation, Monaco, pp. 1-705. □ ( Continued from page 1) tion, not only o f human exercise physiology but also the specific requirements o f different sports. Dr Maurice Mars, him self an international athlete and regular com ­ petitor in the ‘Duzi and other canoe marathons, has researched the energy cost o f portaging the canoe on either the preferred or the weaker shoulder. He shows, not unexpectedly, that portaging the canoe substantially increases the energy cost o f running but that the increase is greater when the weaker shoulder is used because there is less control o f the movement o f the canoe. He concludes that canoeists need to train for portaging and provides a simple calculation to assist canoeists in calcu­ lating the running speed they should choose when portaging. His elegant study shows how practical ques­ tion are open to scientific solution to the benefit o f the athletes in that particular sport. To promote physical activity and sport, we must also research the possible health benefits o f regular physical activity. Three colleagues from the University o f the Orange Free State have provided a valuable metanalysis review o f the effects o f exercise on depression. Their analysis suggests that exercise has a significant effect in reducing depression and that this effect is independent o f age and health status. This information is particularly valuable for although we usually prescribe exercise for its physical benefits, it may well b e that the greater value of regular physical activity may b e pn our moods and em o­ tions. I trust that this issue o f the Journal will inspire you fur­ ther in your personal contribution to South African sports medicine and sports science. The 1999 Rugby World Cup is just more than 3 years aw'ay. How' wall each o f us con­ tribute to insure that the William Webb Ellis trophy stays in South Africa in the first decade o f the next millennium? Professor Tim Noakes Professor in the Liberty Life Chair o f Exercise and Sports Science 12 SPORTS MEDICINE NOVEMBER 1995 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. ) South African Journal o f Sports Medicine Instructions for authors Material submitted for publication in the SAJSM is accepted on condition that it has not been published elsewhere. The management reserves the copyright o f the material pub­ lished. All authors must give consent to publication, and the SAJSM does not hold itself responsible for statements made by contributors. Short items are more likely to appeal to our readers, and therefore to be accepted for publication, than very long ones. Original articles of 3 000 words or less, with up to six tables or illustrations, should normally report observations or research o f relevance to Anaesthesiology and Analgesia or related area. 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No. G /1 3 .9/2367[o-j 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 metabolic demand of portage in kayak marathons M Mars Summary Portage forms an integral part o f som e long distance kayak races. The metalmlic demands o f portaging a sin­ gle person racing kayak were investigated in 15 subjects who regularly participated in kayak marathons. Subjects completed 6 minute treadmill runs at 8 km/hr and at ??'/> gradient, both unloaded and carrying a 14.1kg kayak. During the portage run, the kayak was transferred from one shoulder to the other after 3 minutes. Kaycikers are shown to have a preferred shoulder with which they are more efficient at portage. In comparison with running in the unloaded state, portage o f a kayak o f this mass on the preferred shoulder increases mean oxygen uptake by. 4 47 ± 151 ml.min1 and mean heart rate by 15.4 beats/min. On the weaker shoulder, significantly greater increases o f both oxygen uptake 590 ± 139ml.min' (p < 0 .0 1 ) and heart rate 20.5 beats/min (p < 0 .0 5 ) occur. The increase in oxygen uptake on the weaker shoulder is ascribed to lack o f stability o f the kaycik dur­ ing portage and consequent loss o f running efficiency caused by balancing manoeuvres. . 1 .s few kayakers include portage in their training programme, a simple method o f estim ating optimal p orta ge p ace is proposed. Introduction Portage is ail integral part o f long distance canoe and kayak racing. It is defined as, “ the earn ing o f boats or goods between two na\igablc waters” .' While portage is usually undertaken over short distances to avoid a dan­ gerous or non navigable part o f a river, an overland route cutting across an oxbow may be quicker than staying in the water and paddling. Portage therefore becom es part o f race strategy in som e long distance river races. One such race is the Msinduzi canoe marathon. This annual 3 day event from Pietcrm aritzbiug to Durban on approximately 130 km o f the Msinduzi and Mgeni rivers in KwaZulu Natal, South Africa, attracts over a 1 000 com petitors. The tide o f d ie race is misleading as fibreglass racing kayaks and not canoes are used, and because o f various gorges, waterfalls, and oxbows in the river, several sections o f the race are overland, with portages o f up to 10 km being encountered.' The ratio o f paddling to numing is determ ined by the canoeists’ relative skills and the level o f the water. In years o f drought, low water rules allow com petitors to portage alm ost two thirds o f the course. T h e energy dem ands o f portage have not been estab­ lished. It has been shown that the energy requirement o f moving a known mass over a fixed distance is not con­ stant, and is dependent on the method o f c a r r ia g e ."5 Carrying a single person racing kayak on the shoulder Address for correspondence D r M a u rice M ars Department o f Physiology University o f Natal Medical School B ox 17039 Congella 4013 South Africa while on d ie run requires learned skills o f balance, as one arm is removed from the normal numing action and is used to steady the kayak. This may further increase energy e x p e n d i t u r e , hi addition, most canoeists appear to have a dominant shoulder on which they prefer to portage. This preference inav be due to shoulder asym­ metry, and be simply a matter o f com fort, or if may be the result o f a difference in efficiency o f carriage b e ­ tween shoulders. Despite favouring one shoulder for portage, the kayak is usually transferred from shoulder to shoulder every two to three minutes on long portages. While portage potentially forms a major component o f the race, training for portage is largely empirical. A 15 time winner o f the event proposes two training pro­ gram m es lor portage. For the com petitive p ad d lcr/run ­ ner aiming at winning the race, it is suggested that run­ ning with the canoe shoidd be included as part o f the numing training, and should start 3-4 m ondis before the race. T he numing programme outlined for the aver­ age competitor, however, makes no mention o f portage. ' It is estim ated that 95% o f p ad dlcrs follow Uiis sec­ ond option and do not run with a boat on their shoulder in training. A reason for this, is that it is hazardous to run with a 5.2m kavak on one’s shoulder on urban roads. The problem encountered by tliis group is esti­ mation o f the optimal pace at which to jiortage during the race. The aims o f this study were to investigate the energy expenditure o f portage, to determine whcUicr d ie energy requirements o f portage are constant on either shoulder and to propose a sim ple means o f predicting a suitable race portage pace, based on pre-race numing training. Method Fifteen m ales w ho rcgularlv com p ete in kayak marathons, vohuiteercd to take part in this study which was p erform ed 6 w eek s prior to the Msinduzi marathon. All tests were perform ed in d ie morning and no exercise had been undertaken prior to testing. Each subject gave informed consent and com pleted a ques­ tionnaire detailing his kayaking experience ineluding the number o f seasons o f com petitive participation, his Natal Canoe Union grading and the number o f Msinduzi Marathons entered. Their com petitive numing experi­ ence and active participation in o d ie r sports was also recorded. Subjects nominated their preferred shoulder o f portage before testing. The subjects were exercised on a m otorised tread­ mill im der each o f the following four conditions. 1. Running for 6 minutes at 8 k m /h r at a 3% gradient. 2. Running for 6 minutes at 8 k in /h r at a 3% gradient wearing a backpack loaded to 14.1 kg with sand bags. 3. Riuuiing for 6 minutes at 8 k m /h r at a 3% gradient carrying a single person racing kayak weigliing 14.1 kg. The kayak was first carried on die right shoulder and after diree minutes, transferred to die left shoulder. 4. Running to exhaustion on a fixed speed, increasing gradient protocol. Each exercise protocol was followed by a 10 minute recovery period with d ie subject seated oil a chair on SPORTS MEDICINE NOVEMBER 1995 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. ) th e treadmill. A balanced order experimental design was used in w hich 8 subjects wore the backpack first and 8 subjects carried the kayak first. Oxygen consumption (VOa) was record ed throughout th e four exercise protocols and rest periods and was m easured using open circuit com puterised spirometry, (Oxycongamma, Myjnhardt). Calibrations were per­ formed before ea ch 'test. T h e average readings o f the last 30 seconds o f each exercise protocol were used for analysis. H eart rate was recorded using a Beckman electrocardiograph coupled to the Oxycon. All tests were carried out in an ambient temperature o f 22-24°C. T h e treadm ill speed o f 8 k m /h r was ch osen after d is­ cussion with the subjects, following a pre-test familiari­ sation practice run. There was consensus that 8 k m /h r at a slight incline, represented a com fortable portage pace, and that it was probably close to the average pace maintained by the subjects on a long portage. Statistical analysis was by analysis o 1 variance, Duncan’s m ultiple range analysis, and paired t-test, where appropriate, with significance taken at the 9 5 /o probability level. Descriptive statistics are presented as m eans and one standard deviation. Results T h e average age o f the subjects was 31.5 ± 7 . 3 years, range 21-42 years. Canoeing experience ranged from 3 to 15 years averaging 8 ± 3.5 years, with an average o f 6 com pleted Msinduzi Marathons. There were 3 A grade paddles, 9 B grade and 3 C grade paddlers. G rading is based on the ratio o f the com petitors finish­ ing tim e to that o f th e race winner. T h e A grade, co m ­ prises those w ho finish within th e winner’s tim e plus 10%, B grade, is betw een 111% and 125% ol the win­ ner’s time, and C grade, between 126% and 140% o f the winner’s time. All but one o f the subjects was involved in som e form o f regular running training, and only one subject included portage in his training. Twelve subjects indicated that they preferred to portage on their right shoulder. O f these, 10 subjects were right hand dominant. The remaining three sub­ je cts were left hand dom inant and preferred their left shoulder for portage. T h e mean VO,... was 4 218 ± 3 3 3 m l.m in ', range 3 51 3-45 86 m l.m in 1 or 55.7 ± 5.4 m l.k g 1 .m in 1 (45-64 m l.k g'.m in ’), with a mean m aximum heart rate o f 188 ± 11.2 beats per minute. Oxygen consum ption ex­ p ressed in absolute terms and as a percentage o f maxi­ mum, and heart rate under the different exercise con ­ ditions, is shown in table 1. Carriage o f th e additional mass o f 14. l k g resulted in increases in oxygen consum ption of 4 34 ± 154 m l.m in 1 with the backpack and 4 46 ± 150 m l.m in 1 and 590 ± 138 m l.m in 1 with th e kayak on the preferred and weak­ er shoulder respectively. Statistically significant differ­ ences in oxygen consum ption (p < 0.01) and pulse rate (p < 0.05) were noted when comparing shoulders during kayak portage. T he differences in oxygen consumption and pulse rate between carriage ol the backpack and portage on the preferred shoulder were not significant. W hen divided according to their canoe union grading b a se d on race perform ances, A grade subjects had a sig­ nificantly higher VO*,,,,, (62.6 ± 5.0 m l.m in 1.k g ') than those in B (55.0 ± 5.4 m l.m in '.k g ') p < 0.05, and C grade (50.9 ± 10.8 m l.m in 1.k g ') p < 0.05. They p er­ form ed at a significantly lower percentage o f their max­ im um oxygen consumption, than their B and C grade counterparts, in b oth the loaded and unloaded states, p < 0.01 (Table 2). Running unloaded, th e percentage o f VOa,,,,,, utilised d id not differ significantly between B and C grades. U nder load however, C graders used a significantly greater percentage o f their V( ) ■: x than B grade subjects p < 0.05. Comparing shoulders, th e increase in oxygen uptake expressed as a %VOl!,„„x required for portage on the T A B L E 1. O x v q e n c o n s u m p tio n in m l a n d a s a p e r c e n t a g e o f V O s ^ , a n d p u l s e r a te in b e a ts p e r m in ute, w h ile ru n n in g in th e u n lo a d ed s t a t e a n d w ith t h e b a c k p a c k o r k a y a k a r e e x p r e s s e d a s m e a n s a n d o n e s ta n d a r d d e v ia tio n ( n = 1 5 ) . T h e in c r e a s e in b o th o x y g e n c o n s u m p tio n a n d h e a r t r a te w a s s ig n ific a n tly h ia h er w ith v o r ta a e o n th e w e a k e r s h o u ld e r th a n o n th e p r e fe r r e d s h o u ld e r p < O .O o . V 0 2„ „ m l.m in' %VOa.,..« max H eart rate Running unloaded Running with backpack Kayak (preferred shoulder) Kayak (weaker shoulder) 2 537 ± 229 2 9 7 1 ± 185 2 984 ± 201 3 1 2 8 ± 236 60.6 ± 7.4% 70.9 ± 6.5% 71.2 ± 7.7% 74.7 ± 8.5% 137.5 ± 11.2 150.2 ± 11.2 152.9 ± 13.1 158.2 ± 13.1 TABLE 2 . Aqe, V O and oxygen consumption as a percentage o f VOsma,, according to grading o f paddlers based on their performances in races, expressed as mean and one standard deviation. The A grade paddlers have a significantly higher V 'O a„„ than the other grades (p < 0 .0 5 ), and Pê orr^ rat/ Ŝ f CT '^ lower percentage o f their V O ^ in both the loaded and unloaded states (p < 0.01) . Under l° a f ’ ^ e C arade noddies use a siqnificantly greater percentage o f their VU-,™ than B grade paddlers (p < 0.05). A Grade (n = 3) B Grade (n = 9) C Grade (n = 3) All ( 1 1 = 15) A ge (years) VOa,,,̂ (m l.m in 1) VOa,,,,,, (m l.k g '.m in 1) VOa as % o f VOzmm unloaded backpack kayak (preferred) kayak (weak) 25.7 ± 9.3 4 4 22 ± 356 6 2.9 ± 3.5 5 0.3 ± 7.4% 61.4 ± 5.0% 60.8 ± 8.5% 63.2 ± 5,8% 30.6 ± 8.9 4 2 7 1 ± 399 55.0 ± 5.4 62.0 ± 7.4% 7 1.5 ± 5.4% 71.7 ± 4.6% 74.7 ± 6.2% 40.0 ± 3.5 31.5 ± 7.3 3 8 55 ± 5 4 2 4 218 ± 333 51.0 ± 10.8 55.8 ± 5.5 66.4 ± 6.9% 60.6 ± 7.2 78.3 ± 8.1% 70.8 ± 6.6 80.2 ± 15.1% 71.2 ± 7.5 85.9 ± 13.2% 74.6 ± 8.7 16 SPORTS MEDICINE NOVEMBER 1995 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. ) weaker shoulder was significantly greater within the B and C grades p < 0.05 and approached significance in the A grade p = 0.057. Within each grade, there was no d ifference in oxygen consumption when carrying the backpack or portaging on the preferred shoulder. Discussion The changes in oxygen uptake and heart rate w hile run­ ning with the backpack, are shown to b e similar to those observed for portage o f a kayak on th e preferred shoulder which on average required an increase in oxv- gen consumption o f 10% o f VOa™, and a 13-15 beat per minute increase in heart rate. T he similarity in the m eta bolic requirem ents o f b ackpack carriage and portage on th e p referred sh ou ld er suggests that removal o f one arm from the normal running style d oes not on its own significantly influence energy consum p­ tion under these conditions o f loading. T h e dem ands o f portage differed significantly b e ­ tween shoidders, with portage raising heart rate on average 15 beats per minute on the preferred shoulder and 20 beats per minute on the weaker shoulder. The difference may be explained by a description o f the changes in portage technique that occurred in all sub­ jects. On the preferred shoulder the kayak appeared to b e “ lo ck e d ” on th e shoulder. During th e run, the kayak did not bounce, and it’s longitudinal axis remained rel­ atively constant with minimal vertical or horizontal drift. T h e free arm assumed an apparently normal p osi­ tion during d ie run. On the weaker shoulder, the kayak was less firmly positioned on d ie shoulder. Bounce on the shoulder was obvious, being both heard and seen. T h e kayak tended to oscillate from sid e to sid e on it’s long axis, and the free arm was used in a circum duction m otion with the shoidder abducted ± 40°-60°. Stride length and width usually shortened and widened. It w’ould appear that th e increase in m etabolic rate was due to primarily to corrective balancing manoeuvres. T h e percentage increase in oxygen uptake on the weaker shoidder is similar to th e findings o f Legg et al who investigated th e energy requirem ents o f backpack loading and bilateral shoulder carriage. Both heart rate and oxygen uptake were significantly higher for bilater­ al shoulder carriage, which was attributed to the raised position o f the arms causing an extra strain on the car­ diovascular system, increased muscular activity o f (lie shoulders and arms, and use o f th e muscles o f the upper b ody to com pensate for lateral bending o f the trunk during load carriage.3 As m ight be expected in an endurance sport, d ie grading based on race perform ance relates to maximal oxygen uptake, with the different grades each reflecting a 10% difference in relative oxygen consumption during portage at a set pace. The experimental portage pace o f 8 km /hr, although chosen by consensus o f the subjects, resulted in the C graders perform ing at 86% VO-w. One subject required 94% V02„u« for carriage on liis weaker shoulder, a level that exceeded his ventilator}' thresh­ old. How' can d ie data obtained in this study be used to assist those who d o not include portage in their train­ ing, to select an appropriate race portage p a ce? Based on th e information that portage o f an average mass sin­ gle kayak will increase heart rate by approximately 15- 20 beats p er minute, the following sim ple rule o f thum b is proposed. It is suggested that com petitors obtain their heart rate at the end of an 8 to 10 km time trial or hard train- ing run. On a subsequent training run, they should monitor their pulse rates at slower running speeds, until they find the pace which maintains the heart rate &t 15-20 beats per minute below their heart rate obtained at the end o f th e tim e trial. This should rep­ resent the appropriate race portage pace. It is not advo­ cated that subsequent running training be undertaken at portage pace, but rather that the com petitor learns to gauge the difference between training pace and portage pace. An alternative wrould b e to carry7 a w'eighted back­ pack on training runs. For th ose wiio use portage in their training, perfor­ m ance m ight b e improved by improving the stability7 o f the kayak on th e weaker shoulder, thereby reducing unnecessary energy expenditure. Although regular training o f portage is both difficult and hazardous in urban areas it should logically be included in training program mes as a sport specific task, to im prove learned m otor skills and to provide correct m uscle loading at race pace. REFERENCES 1. The Oxford Reference Dictionary. E d J M Hawkins, Clarendon Press Oxford, 1986: p650. 2. Pennefather R. Canoeing in South Africa. Southern, 1991: p i 02. 3. Legg SJ, Ratnsey T, Knowles DJ. The metabolic cost o f back­ pack and shoulder carriage. Ergonomics 19 92 : 3 5 : 1063- 1068. 4. D atta SR and Ramanathan NL. Ergonomics comparison o f seven modes o f carrying load on a horizontal plane. Ergonomics, 19 71 ; 14: 269-278. 5. Kram R. Carrying loads with springy poles. J A ppl Phus 1 9 9 1 ;7 1 :1 1 1 9 -1 1 2 2 . n SPORTS MEDICINE NOVEMBER 1995 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. ) Verw Nr G 2 9 6 3 (Act/We<101.19«!>l6 Celestone' ■ < Soluspan’’ lIC 1 ml Ampoule, Noi Reg. No Celestone* Soluspan* 2 ml Sterile Multip1 Dose Vial S C H E R A G (PTY) LIMITED 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. ) G L E N B A R R PECIALIST PUBLICATION SO U T H A F H IL A X tO U R X A L I lf SPORTS MEDICINE V o lf N o i J u n t M B FREE To Medical Doctors Contact: GLENBARR PUBLISHERS 25 Bompas Road, Dunkeld West, 2196. Tel: (011) 442-9759 Fax: (011) 880-7898R 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. ) Die invloed van oefening op depressie: ’n meta-analise E Pretorius Departement Menslike Bewegingsktmde JC Jansen van Rijssen Universiteit van die Oranje-Vrystaat JM van Zyl Departement Wiskundige Statistiek Universiteit van die Oranje-Vrystaat Abstract A meta-analysis was done on the existing literature regarding the influence o f exercise on depression. The results o f 4 0 studies, with a total o f 3 225 experimental subjects were coded by means o f 12 research questions. The effect sizes were calculated and the statistical signif­ icance o f the results was tested by means o f an A N O V A analysis. A mean o f 94 effect sizes were found with a z- value o f -6,736. This indicates a highly significant (p < 0 ,0 0 1 ) reduction in depression with exercise. I t was also found that neither gender nor the health status nor age play any role in the effect o f exercise on depression. Inleiding D epressie kan vandag m et reg besk ou w ord as ’n wesenlike p robleem in d ie sanielewing en wel om die volgende redes: • D it is ’n geson dh eidsp rob leem vanwee d ie hoe voorkomssyfer daarvan.1 • Dit is ook ’n sosio-ekonom iese probleem vanwee behandelingsm etodes wat hoofsaaklik bestaan uit m edikasie, psigoterapie eii hospitalisasie o f ’n koin- binasie van al drie. Dit bring ’n ekonom iese las m ee en dikwels o ok d ie onttnekking uit d ie gem eenskap en werksom standighede wat verlies aan manure beteken ." D epressie is so algem een dat 15% tot 20% van alle vol- wassenes op enige tydstip sim ptom e van depressie ondervind. By minstens 12% sal d epressie op een o f ander tydstip in hulle lewens so em stig wees dat behandeling nodig sal wees, I erwyl volgens skatting dit vir 75% van h ierd ie groep nodig sal w ees om in psigia- triese hospitale opgeneem te w ord.1 D ie waarde van oefening as m etod e in d ie kliniese evaluering, voorkom ing en rehabilitering van siektetoe- stande, het eers gedurende die sesligerjare vanuit d ie verskillende navorsingsvelde aandag verkry.' D it was egter eers in die laaste twee d ekad es dat navorsers belangstelling begin toon het in d ie psigologiese effek van oefening en veral d ie invloed daarvan op d epressie.' D ie invloed wat oefening op depressie het, w ord al m eer en m eer deur navorsers in verskeie vakdissiplines in die soeklig geplaas. D ie bevindinge wat deur verskil- len d e navorsers in d ie 1 iterat uur opgeteken is, is egter dikwels nie versoenbaar nie. In som inige van d ie studies word aangetoon dat oefenin g w el ’n antid epressiew e invloed h e t.24" 67 H ierdie invloed kan selfs op indirekte wyse m eehelp tot d ie vermindering van depressie. Daar word bew eer dat oefening soos d ra f ook as psigoterapie gebraik sou kon word in d ie behandeling van depressie.6 H ierdie outeur m otiveer sy stelling soos volg: D ra f los n ie die persoon se eksistensiele problem e op nie, maar dit bied wel tydelike verligting wat aan d ie persoon d ie geleent- h eid b ie d om sy problem e op te los (soortgelyk aan ’n aspirien vir d ie verligting van hoofpyn). A nder studies toon geen b eteken isvolle invloed van oefening op depressie aan m e.8'9 H ierdie teenstrydigheid in navors- ingsresultate kan w aarskynlik aan tw ee oorsake toegeskryf word: • Oefening word nie d uidelik gekwalifiseer en gekwan- tifiseer nie. • Heelwat navorsers gebruik d ie tradisionele verhal- ende m etode van navorsing wat som s lei tot subjek- tiewe interpretasies en alleidings. D ie b ree d oel van hierdie studie was om, m et behulp van meta-analise, ’n d eeglik verantwoorde statistiese integrering van resente navorsingsresultate oor die invloed van oefening op depressie te maak. Om verder d ie rol wat sekere geidentifiseerde veranderlikes m et betrekking tot d ie invloed van oefening op depressie speel, na te gaan. META-ANALISE Meta-analise h et ’n kwantitatiewe aanslag op navorsing en maak gebruik van ’n,verskeiflenlieid statistiese teg- n ieke vir die selektering, klassifisering en samevatting van inligting wat verkry is uit verskeie em piriese stud­ ies. Daar bestaan ’n h ele aantal tegnieke wat algemeen aanvaar word en waarmee verskillende tipes statistiese gegewens vanuit verskillende em piriese on dersoeke na een maatstaf, die sogenaam de effekgrootte (effect size), herlei kan word. D ie m etode wat gebruik word in die berekening van d ie effekgrootte, is aflianklik van die tipe statistiek soos gerapporteer in elke studie wat by d ie meta-analise betrek word. Tegniese problem e word som s ondervind in die samevoeging van resultate van eksperim entele studies. D ie red e hiervoor kan moont- lik w ees dat statistiese toetse nie altyd d ie sterkte van d ie verwantskap o f d ie effek van belang aantoon nie en daarom beveel navorsers10'1112 aan dat resultate gekom- bineer m oet word, m et aanduiding van effekgrootte. In hierdie studie is van verskillende out.eurs" se for- m ules gebruik gem aak om d ie effekgrootte te bereken. Beskrywende statistiek word gebruik om d ie navors­ ingsresultate te kondenseer, op te som en vereenvoudig tot ’n enkele resultaat. METODE ’n Literatuursoektog is geloods m et behulp van geiden­ tifiseerde sleutelw oorde (oefening/exercise; fik s h e id / physical fitness; draf/jog; d epressie/depression ; ge- m oed /m ood ; angs/anxiety) wat m et behulp van reke- naarsoektogte op d ie volgende databasisse, T’sychoinfo en M esh gemaak is. Tydens d ie voorondersoek is ’n kodeervorm ontwikkel en verfyn; dit vorm d ie sleutel tot sukses in meta-analise. In die verwerking van die algehele data is d ie z-toets gebruik om vas te stel o f die totale g em id d eld e effekgrootte van depressie beteke- 20 SPORTS MEDICINE NOVEMBER 1995 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. ) nisvol verskil van nul. A s ’n gem id d eld e effekgrootte in hierdie studie betekenisvol verskil van mil, word d ie nulhipotese van geen effek verwerp. ’n Waarskynlik- heidspeil van (p < 0,05) is gebruik om te bepaal o f d ie analise statistics betekenisvol is, al dan nie. D ie veranderlikes word m et behulp van beskry- wende statistiek weergegee in d ie vorm van tabelle vir die versk illen de kategoriee van d ie gean aliseerde veranderlikes en sluit d ie volgende in: d ie aantal efiek- groottes in d ie onderskeie kategoriee, d ie gem id deld en standaardaiwyking van d ie betrokke effekgroottes, asook d ie z-waardes onderskeidelik. D ie Pearson-pro- dukm om entkorrelasie, asook eenrigting ANO\A’s is gebruik in d ie verwerking van gegewens. RESULTATE ’n Totaal van 40 studies is gebruik om 94 effekgroottes van depressie te bereken. D ie totale aantal proefper- sone wat betrek is, is 3 225 (eksperim entele, kontrole en vergelykende groepe). D ie beskrywende statistiek m et betrekking tot d ie invloed van oefening op d epressie word in tabel 1 aangedui. D ie gem id deld van d ie 9 4 effekgrootte oor die invloed van oefening op depressie is -0,5907, m et ’n z- waarde van -6,736, wat h oogs betekenisvol (p < 0,001) is en aandui dat die eksperim entele groep wat oefening gedoen het, betekenisvol van d ie kontrolegroep verskil en ’n laer gem id d eld e depressietelling het. U it d ie resu 1 tate kan dus gekonstateer word dat oefening ’n verlagende invloed op depressie het. H ierdie resultaat korreleer m et d ie van vorige navorsers2131415'61718 dat oefening ’n antidepressiewe effek het. Daar bestaan ook ’n negatiew e k orrelasie (r = -0,6672) tussen depressie en iik sheid wat h oogs betekenisvol is (p < 0,01). ’n Negatiewe korrelasie dui daarop dat namate die proefpersone fikser gew ord het, hulle m inder d ep ressief was. Om te bepaal watter proelpersoon-pop- ulasie die m eeste baat gevind h et b y oefening in die verlaging van depressie, is vier veranderlikes aange- spreek, naam lik ouderdom , geslag, gesondheidstoes- tand en d ie depressie van d ie proelpersone. TABEL 1 BESKRYWENDE STATISTIEK VAN DEPRESSIE TEN OPSIGTE VAN DIE TOTALE GROEP Totale groep Aantal effek­ X Sigma z-waarde groottes Totale data 94 -0,5907 0,8502 -6,736* * p < 0,001 Ouderdom Ouderdom skategoriee is ingesluit om dat b aie van d ie gek od eerd e studies m e d ie gem id d eld e ouderdom van proelpersone aangegee h et nie, maar tog genoegsam e inligting verskaf h et om d ie proelpersone volgens oud- erdom m e in d ie verskillende kategoriee te kon verdeel. Die ouderdom skategoriee wat gebruik is, is kinders (jonger as 18jaar), jon k (tussen 18 and 25 jaar) en mid- deljarig (26 jaar en ouer). Statistiek m et betrekking tot die invloed van oefening op depressie b y d ie verskil­ len d e ou d erd om sk a tegoriee, w ord in ta bel 2 weergegee. D ie m eerderheid van effekgroottes is verkry van d ie jong ouderdom skategorie 18 tot 25 jaar (48,9%) en die iniddeljarige groep wat vir d ie d oel van h ierdie ontled- inS gestrek h et van 26 jaar en ouer (46,7%). D ie eenrigting ANOVA vir d ie vergelyking van d ie gem id d eld e efifekgrootte van oefening op depressie tussen d ie verskillende ouderdom skategoriee, was nie betekenisvol nie (F9,89 = 0,8505; p = 0,4307). Die z-waardes in t’abel 2 toon dat ’n hoogs betekenis- volle verlaging van depressie deur oefening (p < 0,001) by al d ie ouderdom skategoriee gevind is. Daar was egter net vier effekgroottes by kinders (jonger as 18 jaar), wat d it m oeilik maak om d ie verskillende groepe m et mekaar te vergelyk. Daar is ook ’n negatiewe kor­ relasie tussen d ie verskillende ouderdom skategoriee en d ie effekgroottes vir depressie (r = -0,1068) gevind, m aar d it was n ie betek en isvol nie. D ie fe it dat depressie deur m idd el van oefening b y alle ouderdom s- groepe verlaag word, word ondersteun deur d ie studie van M cDonald en H odgdon .19 T A B E L 2 BESKRYWENDE STATISTIEK VAN DEPRESSIE TEN OPSIGTE VAN OUDERDOMSKATEGORIEE Ouderdoms- groep Aantal effek­ groottes X Sigma z-waarde Kinders 4 -0,6510 0,2587 -5,033* Jonk 45 -0,4658 0,6412 -4,873* M iddeljarig 43 -0,7032 1,0632 -4,337* TOTAAL 92 -0,5848 0,8582 -6,536* | * p < 0,001 Geslag Geslag as veranderlike is in berekening gebring om te bepaal o f daar ’n verskil is in d ie invloed van oefening op depressie by mans en dames. Som m ige van d ie gekod eerd e studies het in gebreke gebly om aan te toon wat d ie geslag van d ie proelpersone is en in daardie geval is d ie proelpersone gekodeer as manlik/vroulik. In tabel 3 word d ie resultate verstrek. Allioewel d ie vrouens (z = -5,130; p < 0,001) b eter as d ie mans (z = -1,986; p < 0,05) gerespondeer het, toon d ie eenrigting A N O W dat daar geen betekenisvolle ver­ skil tussen d ie drie groepe is nie (Fg g 1 = 0,3493; p = 0,7061). D it dien verm eld te word d a l slegs 19 effekg­ roottes (20,2% van d ie totaal) vanuit manlike proelper­ sone verkry is, wat m oontlik d ie vergelyking van resul­ tate tussen d ie groepe kan beinvloed. D ie d erd e kate- gorie van m a n lik /vrou lik dui ook op d ie a ntid e­ pressiewe invloed wat oefening op b eid e geslagte het (z-waarde = -5,236; p < 0,001). H ierdie resultate word ondersteun deur verskeie navorsers.2019 T A B E L 3 BESKRYWENDE STATISTIEK VAN DEPRESSIE EN GESLAG Geslag Aantal effek­ groottes X Sigma z-waarde Manlik 19 -0,5999 1,3170 -1,986* Vroulik 39 -0,5091 0,6197 -5,130** M anlik/ vroulik 36 -0,6742 0,7726 -5,236** TOTAAL 94 -0,5907 0,8502 -6,736* * p < 0,05 | ** p < 0,001 SPORTS MEDICINE NOVEMBER 1995 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. ) Gcsondhcidstoestaiul Die gesondheidstoestand van die proefpcrsone is in twee katcgoriee vercleel, naainlik oenskynlik gesondc persone (dit wil sc persone met geen g eiioleeid c psigologiese o f patologicsc Ioeslande ol b cid e nie) en ongesondc persone (dil wil se persone met g cn otccid e en gediagnoseerde ldagtes, pstgologics of patologies van aard). H ierdie resukate word in tabel 4 wcergcgec. Bcide die gesondc en ongesondc proefpcrsone se depressie het bctekciiisvol verlaag (p < 0,001). Die ongesondc groep se z-w aanlc (-4,977; p < 0,001) is die klcinstc, niaar geen bednidende vcrskil tnsscn die twee groepe is met bclnilp van die cciirigUng ANOVA gevind nie (F^ g o = 0,2731; p = 0,6025). Uit (lie b csliid cruig van die gck ond ensecrd c katc- goriec van gesondc versus ongesondc proefpcrsone, blvk (lit dat ook by gesondc persone depressie deur oefening verlaag kan word. Soim nigc studies en oorsi- gartikcls nit die literatuiir bcw cer dat oefening net ’ii invloed liet op persone wat reeds d e p re ss icf i s ." ’'" 1 H ierdie meta-analise dni daarop dat depressie ook by oenskynlik gesondc persone bctekciiisvol deur oefening verlaag kan word. H ierdie aJlciding word ondcrstcun deur Folkins en North. TABEL 4 BESKR\A\TENI)E STATISTIEK VAN DEPRESSIE TEN OPSIGTE VAN OENSKYNLIK GESONDE TEENOOR ONGESOiVDE PROEFPERSONIi Gesondlieids toestand Aantal elTck- groottes Sigma z-waardc G esond 54 -0,5511 0,8783 -4.611* Ongesond 40 -0,6442 0,8186 -4,977* TOTAAL 94 -0,5907 0,8502 -6,736* * [> < 0,001 BESPREKING Daar bestaan verskeie psigologiese teoriec cn bcnader- ings ten o])sigtc van genioedsverstcnrings. Ten einde n verklariiig tc b ied \'ir die antideprcssiewc working van oefening word die verskillende teoriec, wat die oorsake van depressie p robecr vcrklaar, korlliks niteengesit. • N curofisiologicsc faktorc wat predisponcrciid lot depressie optrec, is n nnwe cn intcressan tc navor- singsveld waaruit die biogenc-aniicne-, hormoon- wanbalans- cn clelort. 2 4 ( 4 ) :2 13-217. 9. Perri S & Tempter 1)1. 1985. The effects o f an aerobic exer­ cise program on psychological variables in older adults. International Journal of Aging and Human Development, 2 0 ( 3 ) : 167-173. 10. Cohen P. 1977. Statistical power analysis for the behavioral sciences. (Revised 3rd.) New York: Academic Press. 11. Glass G V, McGrair B & Smith ML. 1981. Meta-analysis in social research. (3rd ed.) Beverly Hills. California: Sage Publications. - 12. Woll FM. 1986. Meta-analysis quantitative methods for research synthesis. Beverly Hills. California: Sage Publications. (Serie: Quantitative Applications in the Social Sciences). 13. lolkins (11 & Sime WE. 1981. Physical fitness training and mental health. American Psychologist. 36(4)-.373-389. 14. Mart insen EW. 1987. The role o f aerobic exercise in the treat­ ment o f depression. Stress Medicine. 3:93-100. 15. Morgan WP 1969. Physical fitness and emotional health: A review. American Correctional Therapy Journal. 23:124-127. 16. Ransford CP. 1982. A role o f amines in the antidepressant effect of exercise: -1 review. Medicine and Science in Sport and Exercise, 14( 1 ):1-10. 17. Sachs ML. 1982. Exercise and running: effects on anxiety, depression, and psychology. Humanistic Education and Development. 21 (2):51-57. 18. Taylor CB, Sallis JF& Needle R. 1985. The relation o f phys­ ical activity and exercise to mental health. Public health Reports, 1 0 0 (2 ): 195-202. 19. McDonald DG & Hodgdon JA. 1991. Psychological effects of aerobic fitness training research and theory. New York: Springer- Verlag. 20. North TC. McCullagh P & Tran Zi : 1990. Effect o f exercise on depression. Exercise and Sports Sciences Reviews. 18■ 379-414. 21. Simons AJ), Epstein LH. McGowan CR. Kupfer DJ & Robertson RJ. 1985. Exercise as a treatment for depression: an update. Clinical Psychology Review. 5:553-568. 22. Folk ins CIT, Lynch S & Gardner MM. 1972, Psychological fitness as a function o f physical fitness. Archives o f Physical Medicine and Rehal>ilitation. 53:503-508. 23. Louw DA & Van Jaarsveld PE. 1990. Psigologiese perspek- tiewe vir algemene praktisyns: gem oedsverstewinqs. Geneesktinde, 3 2 (4):3-9. 24. Schuyler I). 1974. The depressive spectrum. New York: Jason Aronson. 25. Whybrow PC. AkLskal HS & McKinney WT. 1984. Mood dis­ orders: Toward a new psychobiology. New York: Plenum Press. 26. Ebert MH. Past RM & Goodwin FK. 1972. Effects o f physi­ cal activity on urinary MHPG excretion in depressed patients. Ixincet, 2:766. 27. Post RM. Kotin J, Goodwin FK & Gordon EK. 1973. Psychomotor activity cin other com mitm ents. The b est Student Award for the UCT postgraduate Sports M edicine diplom a was introduced som e th re e / four vears ago as an incentive for students. T h is award is in th e form o f a travel grant to th e value o f R 5 000 to enable the winner to attend an international event o f own choice. In addition B oots Healthcare also sponsors the Annual B oots G old Award in conjunction with th e South African Sports M edicine Association. This award, a Kruger Rand, is for th e b e st free paper presented at the annual SASMA Congress and was introduced 8 years ago. The objective being to provide recognition for out­ standing effort in the field o f Sports M edicine. The 1995 B oots G old Award went to Dr. C Jander o f the UCT Student Health Department in Mowbray. BHSA remains com m itted to Continued Medical Education and the developm ent o f H ealthcare Services in South Africa to m eet th e challenges that lay ahead and to ensure the b est p ossible standard o f healthcare for all th e p eople o f South Africa. □ The fight against Athlete’s Foot ing o f non absorbent nylon socks and stockings also aid in prom oting fungal growth o f the feet. In som e instances alkaline soaps alter th e horny layer malting it m ore perm eable for th e fungi. With active participation in sports it has b een found that sportsm en and women are also very prone to fungal infections. Swimming in particular creates favourable conditions, as prolonged and repeated contact with water m odifies the natural skin resistance allowing firngi to enter the layers o f skin. T h ose young men and women w ho are doing military service are highly susceptible to contracting this d is­ ease. T h e wearing o f boots, sharing o f dorm itories and com munal showers, and physical effort all assist in the contraction o f this disease. Treatment o f Athlete’s foot Treatment o f fungi o f th e feet generally depends on the fungal species whether the 5r are local, occasionally gen­ eralised or m ixed in nature. Successful results have been found following short periods o f treatment with Pevaryl. Pevaryl cream is sim ple to use as it is rubbed gently on the affected areas and between the toes - morning and evening. T he cream contains E conazole nitrate w hich kills fungi. To com bat remaining fungi w hich may b e living in the sh oes and which may cause re-infection, it is important to apply Pevaryl powder to the shoes prophylactically. To either prevent or stop A thlete’s foot it is advised that a person wears natural fibre socks, dry's well between the toes and wears open sh oes when possible. Avoid d irect contact with wet floor areas in com m on ablution facilities b y wearing thongs. F o r and behalf o f R oche Products ( P ty) Ltd For more information p lease contact Wayne Vander- wagen at ( O i l ) 442-3815 or 442-9561. A thlete’s foot or (m edically speaking) M ycoses o f the feet is a phenom enon that occurs uniformly throughout th e world, although it has been found that the inci­ dence o f A thletes foot m ay b e higher in the industrial­ ized countries. It is an easily treated com m on infection w hich affects mainly adult m ales and females. (H ow­ ever statistics show a slightly higher incidence in men.) What is Athlete’s foot T h e definition describes it as a d isease that is caused by fungi derm atophytes, yeasts and m oulds wiiich infect th e areas between and under the toes and the soles o f feet. What Athlete’s foot looks like T h e m ost com m on form starts with reddening and scal­ ing betw een the 4th and 5th toes. However, it may appear dry and scaly, m oist, or in th e form o f blisters on the undersurface o f the foot. T h e wet form is characterized by th e eruption o f small pus filled blisters which often m erge to form larg­ er blisters. After 3-4 days they are either scratched open or burst. New blisters form on th e periphery and are extremely inflamed. T h e dry form appears in the form o f isolated blisters below th e skin surface. T h ese blisters dry leaving small bare surfaces wh ich can b ecom e painful crevices. In all cases it is extremely itchy. I f not treated promptly, th e skin may tear and it could b ecom e infect­ ed with bacteria. T h is condition is difficult, to treat and m akes walking a painful exercise. The Factors aiding Athlete’s foot Sweating is th e contributing factor towards prom oting this disease. T h e sweat provokes a break down o f the h om y layer allowing the ftmgi to penetrate into the d eeper layers o f the skin. Summer heat and th e wear- 24 SPORTS MEDICINE NOVEMBER 1995 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. )