Meeting Abstract

P3.56  Jan. 6  Dynamic Gearing in Vertically Jumping Artiodactyls: Packgoats STAKEBAKE, Eric F.*; CARRIER, David R.; University of Utah stakebake@biology.utah.edu

Patterns of variable gearing at limb joints have been suggested to facilitate optimal power production from limb extensor muscles in cases of increasing gearing ratios, or to amplify muscular power output via elastic storage and recovery of strain energy in cases of decreasing gearing ratios. We studied gearing at the limb joints during vertical jumping in goats (Capra hircus) to better understand artiodactyl locomotion. Ground reaction forces were recorded as the goats performed maximal effort, vertical jumps from a force plate. Video images of a lateral view were recorded at 120 Hz. All subjects displayed a pattern of decreasing gear ratios at the elbow, wrist, metacarpophalangeal, hip, ankle and metatarsophalangeal joints. A pattern of increasing gear ratios that is consistent with optimal power production from shortening muscle was observed at two joints, the shoulder and knee. These results are consistent with patterns of dynamic gearing observed in running and jumping dogs. The pattern of decreasing gearing ratios at the distal joints of goats is consistent with an inertial catch mechanism of power amplification as described by Roberts and Marsh (2003).