Gender differences in anaerobic power of the arms and legs--a scaling issue.

PURPOSE: Physiological variables must be scaled for body size differences to permit meaningful comparisons between groups. Using allometric scaling, this study compared the anaerobic performance, using both arms and legs, of men and women. Ten active male and 10 active female subjects performed the leg cycling and arm cranking in a 30-s all-out Wingate test (WAnT). Regional measurements of the legs, gluteal area, arms, and torso taken using dual-energy x-ray absorptiometry (DXA) served as indicators of lower body active musculature (LBAMM) and upper body (UBAMM) active musculature.
RESULTS: Body mass (BM) was the best predictor (i.e., r = 0.93-0.96) for peak power (PP) and mean power (MP) generated from sprint cycling and arm cranking. Sex differences for leg and arm power (i.e., PP and MP) were identified in absolute terms and then expressed in ratio to BM(1.0). When the same data were allometrically scaled to BM and expressed as power function ratios (Power;BM(b)), the sex differences in PP and MP for sprint cycling were nullified (female:male ratio x 100: 100-103%), but remained for arm cranking (female:male power ratio x 100: 69-84%).
CONCLUSIONS: These results confirmed that anaerobic power of the upper body and lower body were best normalized to BM and, when statistically appropriate methods were used to take into account differences in BM, PP, and MP generated from sprint cycling were similar for both men and women. In contrast, after allometric scaling for BM, men remained more powerful than women for the supramaximal arm cranking task. Qualitative differences in the upper body musculature between men and women are speculated to account for the more powerful performance of men, but confirmatory evidence using noninvasive techniques is warranted.