Allometric Scaling Hip Joint Moments Optimally Reduces Anthropometric Differences in Males and Females.

Running biomechanics are scaled to reduce the effects of anthropometric differences between participants. Ratio scaling has limitations, and allometric scaling has not been applied to hip joint moments. The aim was to compare raw, ratio and allometrically scaled hip joint moments. Sagittal and frontal plane moments of 84 males and 47 females were calculated while running at 4.0 m/s. Raw data were ratio scaled by body mass (BM), height (HT), leg length (LL) and BM multiplied by HT (BM*HT) and LL (BM*LL). Log-linear (for BM, HT and LL individually) or log-multilinear regression (BM*HT and BM*LL) exponents were calculated. Correlations and r² values assessed the effectiveness of each scaling method. Eighty-five per cent of raw moments were positively correlated to the anthropometrics with r² values of 10-19%. In ratio scaling, 26-43% were significantly correlated to the moments and a majority were negative, indicating overcorrections. The most effective scaling procedure was the allometric BM*HT, as the mean shared variance between the hip moment and anthropometrics was 0.1-0.2% across all sexes and moments and none had significant correlations. Allometric scaling of hip joint moments during running are advised if the goal is to remove the underlying effects of anthropometrics across male and female participants.