Background: Anytime a trend or correlation is observed between fitness scores and the size of the participating individuals, it is possible that body weight (BW) is confounding the performance. A common method employed to correct this bias is ratio scaling (i.e., dividing the score by BW). However, another method, allometric scaling, may be more accurate in partitioning out BW effects from performance scores. The purpose of this study was two-fold. First, to compare the results of ratio scaling and allometric scaling in removing the effects of BW from maximal strength scores. Second, to validate the scaled strength scores by examining their differences across groups of varying BW. Methods: A cross-sectional convenience sample of N = 80 traditional male college students ages 18 to 24 years was used in the analysis. Four different maximal strength tests were administered including hand grip strength (GS), 1RM bench press (BP), 1RM leg press (LP), and vertical jump (VJ). Body measures of height, BW, BMI, and WC were collected using standardized procedures. Scaling was performed using the following general calculation: MS/BW^b, where MS is the maximum strength score and b the scaling exponent for BW. An exponent of 1.0 was used for ratio scaling. The fit BW coefficients from log-log regression models supplied the exponents for allometric scaling. Pearson correlations were utilized to examine the relationships between body measures and scaled strength scores. ANOVA was used to examine differences in scaled strength scores across BW tertile groups. Results: Mean age of the sample was 20.5 ± 1.6 yr with mean BMI, GS, BP, LP, and VJ of 27.5 ± 4.7 kg/m², 54.2 ± 8.6 kg, 230.3 ± 63.8 lb, 582.4 ± 159.5 lb, and 23.7 ± 4.3 in, respectively. BW, BMI, and WC were significantly related to BP, LP, and VJ. Body measures were not related to GS. Ratio scaling increased the dependence between the body measures and maximal strength scores. Allometric scaling removed the effects of all body measures from maximal strength scores except for a weak association between height and LP. ANOVA models indicated no significant differences across BW tertile groups for the four allometric scaled maximum strength scores. Conclusion: Results from this study indicate that ratio scaling is a poor method for removing BW from maximal strength scores in traditional college-aged males. Allometric scaling for BW however adequately removed the effects of BW, BMI, and WC from maximal strength scores. Finally, GS does not appear to be dependent on body measures in this population.

allometry, scaling, measurement, evaluation, muscular strength