Meeting Abstract

P3.52  Tuesday, Jan. 6  Ankle flexion and foot clearance during flexed hip and knee walking WILSON, M.P.*; SIMS, E.L.; SCHMITT, D.; DUKE UNIVERSITY; DUKE UNIVERSITY; DUKE UNIVERSITY megan.pruette@duke.edu

Modern humans walk with a relatively stiff gait that minimizes the muscular work done to move the lower limbs and the center of mass. Nonhuman primates, and perhaps our earliest ancestors, use a form of bipedalism in which the hip and knee are held in a deeply flexed position and the center of mass undergoes very little vertical oscillation. This study follows up on other studies examining loading and energetic costs during these compliant walking gaits by examining the effects of increased hip and knee flexion on the dorsiflexion of the ankle and the toe clearance in adult humans. During a flexed hip and flexed knee gait, our subjects demonstrated an average increase in dorsiflexion of 16 degrees during stance phase and 13 degrees during swing phase, as well as reduced toe clearance compared to a normal walking style. Increased dorsiflexion requires more muscular effort to stabilize the ankle during both stance and swing phase, and may explain differences in distal tibia orientation and muscle markings on bones between apes, early humans, and modern humans. The decreased foot clearance during flexed hip and knee gait suggests that the changes at the hip, knee, and ankle were still not enough to bring about the same foot clearance as normal walking. This, in combination with the fact that our ancestors had unusually long feet and particularly long toes, suggests that they would have had to use other mechanisms such as toe flexion to clear the substrate. These data provide novel insight into the nature and costs of locomotion in bipedal primates and the earliest human ancestors.