The mechanics of acceleration and deceleration in primate quadrupeds:implications for primate locomotor evolution.

Abstract

The ability to accelerate and decelerate is critical for animal survival and may be a selective priority determining body form in mammals. Studies of quadrupedal mammals have shown that pitching moments around an animal's center of mass (COM) limit maximum acceleration and deceleration and that the ability to resist such moments is influenced by limb length, COM position, and the ability to shift weight to the fore‐ or hindquarters. Primates have relatively long, gracile forelimbs and have higher vertical ground reaction forces on their hindlimbs than forelimbs, unlike most mammals. Primates should then differ from other mammals in that they will be effective in producing acceleration but limited in producing deceleration. This hypothesis was tested with lateral video and single limb forces recorded during accelerating and decelerating steps for two strepsirhine primate species: Eulemur fulvus and Lemur catta. Results show that primates are limited in maximum acceleration and deceleration by their limb length and that they adopt specific mechanical solutions including loading the trailing limb relatively more, initiating decelerations with the hindlimbs rather than the forelimbs, and increasing contact time to limit instantaneous vertical force increases. These solutions are consistent with other unusual primate gait characters associated with adaptations to arboreal locomotion.