Meeting Abstract
Quadrupeds, like most bipeds, tend to walk with an even left/right footfall timing. However, the phasing between hind and forelimbs shows considerable variation. Here, we account for this variation by modeling and explaining the influence of hind-fore limb phasing on mechanical work requirements. These mechanics account for the different strategies used by: 1) slow animals (a group including crocodile, tortoise, hippopotamus and some babies); 2) normal medium to large mammals; and 3) (with an appropriate minus sign) sloths undertaking suspended locomotion across a range of speeds. Phases predicted to be particularly costly are not observed in nature. While the unusual hind-fore phasing of primates does not match global work minimizing predictions, it does approach an only slightly more costly local minimum. Further, modeled instants of the ‘toppling’ motion in the gait cycle with normal walking phases occurs just prior to forefoot placement, an observation consistent with footfall phasing in grazing livestock. In contrast, primate phases result in these toppling instants instead occurring just prior to hindfoot placement, with potential advantage in terms of controlled forefoot placement on narrow or unpredictable substrates.
