R e s e a r c h A r t i c l e T h e R e l ia b il i t y o f B e r g e r ’s T a b l e in E s t im a t in g 1 - R M a n d 1 0 - R M o f t h e E l b o w F l e x o r M u s c l e s in N o r m a l Y o u n g A d u l t s A B S T R A C T : I s o to n ic s tr e n g th tr a in in g r e m a in s o n e o f th e m e th o d s o f s tr e n g th e n in g m u sc le s, a s it re q u ire s in e x p e n s iv e m a te r ia ls . T h e m e th o d re q u ire s th e d e te r m in a tio n o f m a x im a l is o to n ic s tr e n g th o r o n e r e p e titio n m a x im u m [ 1 -R M ] a n d /o r s u b -m a x im a l is o to n ic s tr e n g th (2 - R M - 1 0 -R M ) o f a m u s c le g r o u p in o r d e r to k n o w th e a p p r o p r ia te re sis ta n c e to s u b je c t th e m u s c le g r o u p to, a n d to m o n ito r s tr e n g th g a in s b y th e m u s c le g ro u p . B e r g e r ’s ta b le c o n ta in s p e r c e n ta g e s f o r p r e d ic tin g 1 -R M - 1 0 -R M , a n d it is in te n d e d to im p r o v e th e e ffic ie n c y o f d e te r m in in g is o to n ic m u s c le stre n g th . T h e a im o f th is s tu d y w a s to in v e s tig a te th e re lia b ility o f B e r g e r ’s ta b le in p r e d ic tin g 1 -R M a n d 1 0 -R M o f th e r ig h t e lb o w f l e x o r m u sc le s. 1 -R M a n d 1 0 -R M w e re e s tim a te d u sin g B e r g e r ’s ta b le in 1 0 0 y o u n g a d u lts fo llo w in g th e d e te r m in a tio n o f th e n u m b e r o f re p e titio n s th a t c o u ld b e c a r r ie d o u t a g a in s t r a n d o m ly s e le c te d w e ig h ts. W eig h t a d ju s tm e n ts w e r e m a d e to o b ta in th e a c tu a l 1 -R M a n d 1 0 -R M . D a ta w e re s u b je c te d to r e g r e s s io n a n a ly sis. A s ig n ific a n t lin e a r r e la tio n s h ip e x is ts b e tw e e n th e e s tim a te d a n d a c tu a l v a lu e s o f 1 -R M a n d 1 0 -R M . R e s u lts a ls o s h o w e d th a t B e r g e r ’s ta b le e x p la in s 9 3 % o f 1 -R M a n d 9 8 % o f 10-R M . I t w a s c o n c lu d e d th a t B e r g e r ’s ta b le is re lia b le in d e te r m in in g 1 -R M a n d 1 0 -R M o f th e e lb o w f l e x o r s in y o u n g h e a lth y a d u lts. R e g r e s s io n e q u a tio n s th a t m a y im p ro v e th e a c c u r a c y o f e s tim a tio n w e re d e riv e d . K E Y W O R D S : B E R G E R ’S TA B L E , S T R E N G T H , IS O T O N IC , R E S IS T A N C E , M A X IM U M . AKINPELU AO, PhD’, IYANIWURA JO, PhD2, AJAGBE BO, BSc' 1 Department of Physiotherapy, College of Medicine, University of Ibad Department of Stc Ibadan, Nigeria. University of Ibadan, Ibadan, Nigeria. Department of Statistics, University o f Ibadan, INTRODUCTION M any m ethods have been developed for increasing the strength o f skeletal m uscles. They include the isotonic, iso­ metric and isokinetic training m ethods [Kisner and Colby, 1990]. The isotonic and isom etric m ethods require simple and inexpensive materials like metal weights and springs to resist muscular contractions, whereas isokinetic exercises require an electrom echanical device. This device keeps the jo int motion at a constant predeterm ined speed thereby varying the resistance through the range of motion. The isokinetic m ethod has been shown to be more efficient in strength training than other training methods [Moffroid et al, 1969, Smith and M elton, 1981]. However, in spite of this advantage, the use o f isotonic and isom etric training m ethods still prevails in a great majority o f physiotherapy clinics, especially in the developing countries because o f the high cost of isokinetic m achines. A lso, isotonic strength training is still used in research [Housh et al, 1996; Taaffe et al, 1999; Trappe et al, 2000].- Strength m easurem ent is an integral part o f m uscular training. In the isotonic strength training, m uscular strength is often recorded in terms o f repetition m axim um [RM]. D eLorm e [1954] intro­ duced this concept o f isotonic strength m easurem ent along with that o f heavy resistance-low repetition exercises. One rep etitio n m axim um [1-RM ] is the m axim al load that can be lifted through a com plete range o f m ovem ent once by voluntary contraction o f a m uscle group. Ten repetition m axim um [10-RM] is the m axim um load that can be lifted through a com plete range o f movem ent by volun­ tary contraction o f a group o f muscles 10 consecutive times only [Kisner and Colby, 1990], M axim al isotonic strength is usually recorded as 1-RM and, isotonic exercise program m es are often based on sub-m axim al isotonic strength, 2-RM to 10-RM, or a percentage o f 1-RM [Housh et al, 1996; Taaffe et al, 1999; Trappe et al, 2000], Values of repetition m axim um are generally determined by the trial and error method [Berger, 1961; Belanger et al, 1984]. This m ethod is time consum ing and prone to error due to m uscle fatigue. The need to alleviate these problem s has long been recognized. M any studies have been carried out in this respect Clark and Herm an, 1955; Berger, 1961; Klein and Johnson, 1961; Walsworth et al, 1996]. In one such study, B erger [1961] cam e up with a table o f percentages for estim ating any value between 1-RM and 10-RM, when only a value or weight situated between l-R M and 10-RM is known [Table 1], Berger [1961] collected his data using the bench press-lift, which involves the pectoralis, triceps anterior deltoid and serratus anterior m uscle groups. He how ever hypothesized that the same proportional result should be obtained with any other m uscle group. In 1984, B elanger et al investigated the usefulness o f B erg er’s table for deter- CO RRESPO N D EN C E TO: Dr. (M rs.) Aderonke O. Akinpelu, D epartm ent o f Physiotherapy, College o f M edicine, U niversity College Hospital, Ibadan, N igeria SA J o u r n a l o f P h y s io th e ra p y 2001 V o l 57 No 2 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 3. ) TABLE 1. Berger's table, an adapted version by Belanger et a| [1984] Repetition Maximum [RM] Percentages [%] 1 100.0 2 97.4 3 94.9 4 92.4 5 89.8 6 87.6 7 85.5 8 83.3 9 81.1 10 78.9 Example of the use of the table: If a subject lifts a weight of 36kg 5 times, then 36kg = 5 RM. 5RM = 89.8% of 1 -RM 1 -RM = 1 0 0 /8 9 .8 x 3 6 = 40kg. 10-RM = 78.9% of 1-RM 10-RM = 7 8 .9 /1 0 0 x 40 = 3 1 kg TABLE 2. Means and standard deviations of 1-RM and 10-RM Variables Subjects Males (n = 50) Females (n = 50) Total (n = 100) Estimated Mean 12.23 6.98* 9.61 1-RM (kg) SD ± 1.85 ± 1.08 ± 3.04 Actual 1 -RM Mean 13.24 7.68* 10.46 (kg) SD ± 1.56 ± 0 .9 7 ± 3.08 Estimated 10- Mean 9.64 5.46* 7.55 RM (kg) SD ± 1.43 ± 0 .8 0 ± 2.40 Actual 10-RM Mean 9.74 5.57 7.65 (kg) SD ± 1.44 ± 0 .8 7 ± 2.41 Legends SD = Standard Deviation * = Differs significantly (P <0.05) from male value. FIGURE l.Test Procedure Legends A = Starting position B = Completion of range 12 SA J o u r n a l o f P h y s i o t h e r a p y 2 001 V o l 5 7 N o 2 m ining 1-RM and 10-RM o f the knee extensor m uscles in normal subjects, and reported high correlation coefficients betw een the actual values o f 1 -RM and 10-RM , using B e rg e r’s table. They therefore concluded that B erger’s table was efficient in determ ining 1-RM and 10-RM o f the knee extensor muscles. The present study was carried out to investigate the reliability o f B erg er’s table in estim ating values o f 1-RM and 10-RM o f another group o f m uscles, the elbow flexor muscles. MATERIALS AND METHODS O ne hundred volunteers [50 males and 50 females] from the student community o f the U niversity C ollege H ospital, Ibadan, Nigeria participated in the study. T he volu n teers w ere health y young adults who were not involved in com ­ petitive or regular leisure-tim e sports (such as w eight lifting, squash, law n/ table tennis, soccer, hand/basket ball). They had no history or obvious evidence o f m uscular weakness, physical defor­ mities or disabilities. Subjects were right handed and their ages ranged between 20 and 29 years. The num ber o f times [repetitions] a random ly selected w eight could be lifted by active contraction o f the right elbow flexor m uscles was determined. T he instructions were read out to each subject and the test p ro ced u re was dem onstrated. The subject was made to sit on a chair w ithout armrests. The upper trunk was strapped to the backrest o f the chair with a sling, and the shoul­ ders were stabilized by one researcher who stood behind the subject in order to prevent trick m ovements. The left arm hung loosely by the side. Two horizontal projections from a w ooden fram e were adjusted to the ends o f range o f elbow movem ents w hile the subject lifted an unloaded barbell. A second observer w ho sat some distance in front o f the subject was able to observe the range o f motion. The barbell was then loaded, and subject was instructed to carry out as many lifts as possible [Figure 1 A & B]. A w eight was considered too heavy when it could not be lifted and too light when the num ber o f lifts exceeded 10. W hen the load was too heavy, it was decreased; and when it was too light, it 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 3. ) TABLE 3. Regression Coefficients of Actual 1-RM and 10-RM on Estimated 1-RM and 10-RM Subjects Variable Coefficients a b S.E (b) R2 T value P value Male (n=50) 1-RM 10-RM 4.21 0.55 0.74 1.01 0.06 0.04 0.77 0.92 12.70 23.54 <0.0001 <0.0001 Female (n=50) 1-RM 10-RM 2.37 0.06 0.76 1.01 0.08 0.05 0.62 0.88 8.87 18.59 <0.0001 <0.0001 Total (n=l 00) 1-RM 10-RM 1.03 0.15 0.98 0.99 0.03 0.02 0.93 0.98 36.99 65.88 <0.0001 <0.0001 Legends a = constant or intercept b = regression coefficient S.E. (b) = standard error of b R2 = the coefficient of determination Regression equations (y = a + bx) for the total sample (n = 100) Actual 1 -RM = 1.03 + 0.98 estimated 1 -RM Actual 10-RM = 0.15 +0.99 estimated 10-RM. TABLE 4. Multiple Regression Coefficients O f Actual 1 -RM and 10-RM On Sex and Estimated 1-RM and 10-RM Variable Coefficients R2 S.E. T value P value Constant 2.65 0.33 8.07 <0.0001 (S) Sex 1.68 0.27 6.18 <0.0001 (S) Est. 1-RM 0.73 0.95 0.55 16.17 <0.0001 (S) Constant 0.23 0.18 1.28 0.213 (NS) Sex 0.09 0.15 0.60 0.551 (NS) Est. 10-RM 0.98 0.98 0.03 31.08 <0.0001 (S) Legend R2 = Coefficient of determination S.E. = Standard error of estimate S = Significant NS = Not significant Est. = estimated Regression equation for 1 -RM (y = a + b l si + b2s2) = Actual 1 -RM = 2.65 +1.68 +0.73 estimated 1 -RM. (Where y = actual 1-RM, a = the constant, b l = the regression coefficient for sex, si = the dummy value for sex, which is 0 for female and 1 for male, b2 = coefficient of standard error, and s2 = estimated 1 -RM). was increased. The test was then repeated after a 10-minute rest. W henever the need arose to adjust the w eight more than tw ice, the su bject was given another appointm ent and the test was repeated one or two days after the first visit. W hen the num ber o f lifts carried out against the w eight was between 1 and 10, the w eight in kilogram s and the num ber o f repetitions were used to cal­ culate 1-RM and 10-RM, using B erg er’s table [Table 1], The actual 1 -RM o f the m uscle group was determ ined during another visit, 1 to 2 days after the last one. The calcu­ lated or estim ated 1-RM was used as the baseline weight. The w eight was adjusted until the actual 1-RM was obtained. D uring another visit, also 1 to 2 days after the last visit, the actual 10-RM was similarly determined. Statistical Analysis: The means and standard deviations o f 1-RM and 10-RM [estimated and actual] were calculated for the total sam ple and according to gender. P earson’s correla­ tion coefficient was calculated to deter­ m ine the relationship between estimated and actual values o f 1-RM and 10-RM respectively. Scatter graphs were also plotted. In addition, regression methods were used to analyze the relationship between estim ated and actual values of 1 -RM and 10-RM respectively. A predic­ tion model with an intercept was used in the analysis. In order to determ ine w hether it was necessary to include gender as a predictor variable, data for males and fem ales were analysed sepa­ rately, and appropriate equations for predicting actual values for estim ated values were derived. Regression ana­ lysis was done using the E P I 6 statistical package. RESULTS The mean age o f the subjects was 22.8 [SD = 2.0] years. Their mean w eight was 59.5 [SD = 8.9] Kg.; and their mean height was 169.0 [SD = 8.6] cm. The male subjects were aged 23.4 [SD = 2.3] years and the fem ales were aged 22.1 [SD = 1.5] years. The mean weight (64.0 [SD = 7.3] kg) and height {175.1 [SD = 6.1] cm.} o f the male subjects w ere sig n ific a n tly h ig h e r th an the respective values o f 55.0 [SD =8.2] kg and 162.9 [SD = 8.6] cm for the female subjects [p< 0.05]. The mean value o f the estimated 1 -RM o f the right elbow flexor o f the total study sample was 9.61 kg, w hile for the actual 1-RM, it was 10.46 kg. The estim ated and actual 10-RM values were 7.55 kg and 7.65 kg respectively [Table 2]. The mean 1-RM and 10-RM (estim ated and actual) o f the m ale subjects were significantly higher than those o f fem ale subjects [<0.05] as r shown in Table 2. The correlation coefficient between estim ated and actual values o f 1-RM was 0.97, and that betw een estimated and actual values o f 10-RM was 0.99. SA J o u r n a l o f P h y s io th e ra p y 2001 V o l 57 No 2 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 3. ) FIGURE 2. Scatter graph for 1 -RM FIGURE 3. Scatter graph for 10-RM 6 8 10 12 14 Estimated 1 - Rm (kg.) Legends ■ = Male • = Female Legends ■ = Male • = Female Figures 2 and 3 show a linear relation­ ship betw een the estim ated and actual values of 1-RM and 10-RM o f subjects’ elbow flexor m uscles. The intercept [a] o f the regression line for 1 - RM (total n) was 1.03 and the regression coefficient [b] was 0.98. The coefficient o f determ i­ nation [R2] was 0.93. The intercept and regression coefficient o f 10-RM (regres­ sion line) were 0.15 and 0.99 respectively, and R2 was 0.98. Regression analysis in d ic a te d a s ig n ific a n t re la tio n s h ip betw een estim ated and actual values of each variable [p<0.0001] as show n in Table 3. Table 3 also shows the regres­ sion coefficients o f actual 1-RM and 10-RM on estim ated 1-RM and 10-RM o f the elbow flexor m uscles for each sex. These coefficients were significant in all instances [p <0.0001]. Table 4 shows multiple regression analysis o f actual 1-RM and 10-RM on sex and estim ated 1-RM and 10-RM. Results indicated that for 1-RM, there was sig­ nificant difference between the regres­ sion coefficients o f the two sexes, hence the need to include sex as a predictor variable. F o r 10-RM, the regression analysis for male and fem ale subjects was not significantly different. T here­ fore, as shown in Table 4, the appro­ priate equation for predicting actual 1-RM from estim ated 1-RM is: A ctual 1-RM= 2.65 + 1.68 sex +0.73 estim ated 1-RM. (W here the dum m y values for sex is 0 for fem ales and 1 for males). Similarly, the appropriate equation for predicting actual 10-RM from estim ated 10-RM is: Actual 10-RM = 0.15 + 0.99 estimated 10-RM. DISCUSSION The results o f this study indicate that a sig n ifican t lin ear relatio n sh ip exists betw een the actual and estim ated 1-RM and 10-RM using the B erger’s table. Based on the coefficients o f determ ina­ tion [R2] obtained in this study, B erger’s table appears reliab le in estim atin g values o f 1-RM and 10-RM o f the elbow flexor m uscles in norm al young adults. The findings o f the present study agreed with those by B elanger et al [1984] who also found B erg er’s table efficient in estim ating values o f 1-RM and 10-RM o f the knee extensor muscles. The study by B elanger et al [1984] and the present study found B erger’s table reliable in estim ating values o f repetition maximum o f two different m uscle groups and would appear to support the notion that such data could be obtained for other m uscle groups. T he m ale subjects in this study reco rd ed sign ifican tly h igher values of both 1-RM and 10-RM o f the elbow flexor m uscles than the fem ale subjects. This is in agreem ent w ith the well- know n fact that men generally have more m uscular strength than women, and was also corroborated by the signi­ ficant difference in the mean w eight o f 64.0 kg for the male subjects com pared with 55.0 kg for the females. M ultiple regression results indicate gender as the predictor variable in the equation for predicting the actual 1-RM from esti­ m ated 1-RM, but not in the equation for predicting the actual 10-RM from esti­ m ated 10-RM. This suggests that the strength difference between males and fem ales is h igher at m axim al effort than at sub-m axim al effort. The regres­ sion equations derived from this study could further im prove the accuracy o f estim ating repetition maxim um values. Further studies would need to focus on the clinical application o f our results in various neurom uscular disorders. CONCLUSION O ur results confirm that B erger’s table is reliable in estim ating 1-RM and 10-RM o f the elbow flexor muscles in normal young adults. The accuracy o f estim a­ tion may be further im proved by using the regression equations: 1) Actual 1-RM = 2.65 + 1.68 sex +0.73 estim ated 1-RM (W here the dum m y value o f sex equals 1 for male and 0 for females). 2) Actual 10-RM = 0.15 + 0.99 estimated 10-RM. ACKNOWLEDGEMENT We acknow ledge the contributions o f Prof. E. A. B am g b o y e and Mr. D. K angave during the p rep aratio n o f the m anuscript. M rs. Funlola Ashebu assisted with translating the paper by Belanger and associates from French to English. 14 SA J o u r n a l o f P h y s io th e ra p y 2001 V o l 57 No 2 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 3. ) REFERENCES B e la n g er A .Y N oel G, B ilodean 1, B o uton A, G ingras C , G u ille m en t S, 1984 L’utilisation de la table B erg er pour d e te rm in e r le 1-RM et le 10-RM des m uscles ex ten so rs du genou. P h y sio th e rap y C a n ad a 35:11-15. B erger R A 1961 D eterm in atio n o f resistance loan fo r 1-RM and 10-RM. Journal o f the A sso c ia tio n o f Physical a nd M ental re h ab ili­ tation 51:100-110,117. C lark D H, H erm an E L 1961 O bjective d e te rm in a tio n o f resistance load fo r ten re p eti­ tion m axim um fo r qu a d ric ep s developm ent. R esearch Q u a rterly 26:385-390. D eL orm e T F 1954 R e storation o f m uscle p o w e r by heavy resistance exercises. Journal o f B one a nd Jo in t S urgery 27:645-649. H oush T J, H oush D J, W eir J P, W eir L L 1996 E ffects o f unilateral c o n ce n tric ally d y nam ic c o n stan t ex te rn al re sistan c e training. In ter­ national Journal o f Sports M e dicine 17 (5): 338 - 343. K is n e r C , C o lb y L A 1990 T h e ra p e u tic E x e rc is e - F o u n d a tio n s a n d T e c h n iq u e s 2n d ed, F A D avis, P h iladelphia: 88-92. K lein K K Jo h n so n E 1961 A m ethod o f d e te r­ m ining the m axim um load for ten re p etitions in p ro g ressiv e re sistan c e ex erc ise fo r q u a d ri­ cep s d e velopm ent. Journal o f the A ssociation o f P hysical and M e ntal R e h ab ilitatio n 7:4 M offroid M , W h ipple R, H ofkosh J, T h istle H 1969 A study o f isokinetic ex ercise. P hysical T h era p y 49: 735-737. S m ith M J, M e lton P 1981 Isokinetic vs. iso ­ tonic v ariab le-resistan ce training. A m erican Journal o f Sports M e d icin e 9: 275 - 279. T aaffe D R , D uret C , W h ee le r S, M aru s R 1999 O nce w eekly resistance exercise im proves strength and n e u ro m u sc u la r p e rfo rm a n ce in o ld er adults. Jo u rn a l o f A m e ric an G eriatrics S ociety 4 7(10): 1 2 0 8 - 1214. T rappe S, W illiam D, G ordon M , P orte D, R o w e ten G , C o stil D 2 0 0 0 E ffec t o f re sis­ tan c e training on sin g le m uscle fib re c o n tra c ­ tile fu nction in o ld e r m en. Journal o f A p plied P h y siology 89 (1): 1 4 3 - 152. W alsw orth M , S c h n e id e r R , S ch u ltz J, D ahl C, A lliso n S, U n d e rw o o d F, F re u n d J 1998 P re d ic tio n o f 10 re p e titio n m ax im u m fo r sh o rt-arc q u a d ric ep s ex erc ise from hand-held d y n a m o m e te r and an th ro p o m etric m ea su re ­ m ents. Journal o f O rth o p a ed ic and S ports Physical T h era p y 28(2): 97 - 104. Physio's do you want to work in the UK? 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