Meeting Abstract

P3.57  Saturday, Jan. 5  Peak pressures and cheiridial postures in baboons (Papio anubis) WUNDERLICH, R.E.*; PATEL, B.A.; Dept. of Biology, James Madison University; Department of Biomedical Sciences, College of Osteopathic Medicine, Ohio University wunderre@jmu.edu

Digitigrade postures are common among cursorial quadrupeds who benefit from the increased effective leg length and speed advantage afforded by these postures. Terrestrial monkeys, however, use digitigrade hand postures at low speeds and increasingly palmigrade postures at higher speeds. These palmigrade postures may moderate peak loads on the forelimb by distributing loads over a larger contact area, or they may serve to moderate wrist joint moments by redirecting ground reaction forces. We collected dynamic palmar and plantar pressure data on two adult baboons walking and galloping quadrupedally (velocity 0.46-4.0m/s) across a pressure mat. Contact area and peak pressure were quantified in two regions of the hand (phalanges and palm/metacarpals) and two regions of the foot (phalanges and midfoot/metatarsals) throughout the speed range. Direction and length of center of pressure movement were tracked throughout stance. Baboons use digitigrade hand postures at slower speeds and become increasingly palmigrade at higher speeds, resulting in absolutely greater palmar contact area and lower pressure across the hand. Center of pressure translates proximally from the metacarpal heads towards the carpus, and this translation is larger at faster speeds. Foot postures, however, become increasingly digitigrade at higher speeds, peak pressures increase, and plantar contact area decreases. Quadrupedal primates appear to respond to speed changes differently in the hands and feet. Whereas the hindlimb may function more like that of nonprimate mammals, increasing stride length but also peak loads using digitigrade postures, the forelimb exhibits more palmigrade postures at slower speeds to reduce peak pressures on the forelimb.