Meeting Abstract

P3.55  Saturday, Jan. 5  Primate hand postures across symmetrical and asymmetrical gaits PATEL, B.A.*; UPPAL, K.; POLK, J.D.; Ohio Univ.; Stony Brook Univ.; Univ. Illinois patelb@oucom.ohiou.edu

Understanding how joint postures are influenced by speed and gait provides insight into the mechanical constraints placed on joint function. Speed and gait are relevant variables since increasing locomotor speed will result in higher ground reaction force (GRF) while choice of symmetric vs. asymmetric gaits will determine the number of contact points over which the GRF is distributed. Indeed, high GRFs are often the stimulus for gait transitions with increasing speed in many mammals. Among primates, however, GRFs are higher during asymmetric galloping than during fast symmetric gaits. We investigate how speed and gait affect joint postures in the wrist and hand of two terrestrial monkeys, Erythrocebus patas and Papio anubis, and evaluate if these primates use any elastic energy storage (EES) mechanism in their distal forelimb at higher speeds and across gaits. If primates take advantage of EES mechanisms in their distal forelimb (e.g., tendon stretching) we predict that their hands will become more palmigrade as speed increases across gaits. The 3D wrist joint angle and the angle between the metacarpal segment and the ground, two measures of hand posture, were obtained during forelimb support with motion analysis software. Non-parametric analyses reveal that angles, and therefore hand postures, are not different when subjects use symmetrical or asymmetrical gaits at their gait transition speed. Regressions show that hand postures transition from digitigrade to palmigrade as speed increases during symmetrical gaits, but hand postures are only palmigrade and do not change with increasing speed during gallops. These results suggest that monkeys are not using EES mechanisms during high-speed gallops and imply that their palmigrade postures allow for a more stable ground contact at higher speeds.