Fig. 6. Effective mechanical advantages (EMA; ratio of anatomical to GRF moment arms, where GRF is ground reaction force) at the elbow (A), knee (B) and ankle (C) for the phylogenetically constrained sample of primates and the diverse sample of mammals from Biewener (1989). EMA for the elbow and knee increase with body mass (in kg) for both primate and non-primate samples. This indicates that body mass has a similar influence on EMA (and consequently on the muscle force required to resist gravity) in the phylogenetically constrained and diverse samples. In contrast, ankle EMA does not increase with body mass in the primate sample, but does increase significantly in the diverse mammalian sample.