Meeting Abstract

8.5  Jan. 4  External joint work modulation in goats during climbing jumps YOO*, E. H.*; LEE, D. V.; BIEWENER, A. A.; Harvard University, Concord Field Station edwinyoo@eecs.harvard.edu

We wish to understand how multi-jointed legs are able to meet different terrain conditions and mechanical demands during vertical climbing jumps. We recorded ground reaction forces and hindlimb kinematics during three different climbing conditions in sub-adult male goats (N=3, 32.8±1.6 kg): a horizontal running approach jump (BJ) onto a box platform, a horizontal approach jump (CJ1) onto a climbing wall (64° slope), and a vertical approach jump from the climbing wall up onto a horizontal ledge (CJ2). Jump heights were 2.4, 2.1, and 2.0 times standing hip height for BJ, CJ1, and CJ2 respectively. Joint power (joint moment X joint angular velocity) was integrated to calculate net joint work. In accordance with these predictions, we hypothesized that joint work would be minimized in BJ by transferring horizontal kinetic energy during running approach to raise the center of mass (CoM) during the jump. In contrast, we hypothesized that in CJ2, the limited horizontal velocity and limb constraints due to the steepness of the climbing wall would necessitate increased net joint work while CJ1 would show intermediate net joint work. Total net work for a single hindlimb were 19.7±1.461 N-m in BJ, 26.3±1.603 N-m in CJ1, and 43.6±1.417 N-m in CJ2. Ankle net work ratio (ankle net work/total joint work) was 16.8±1.7% in BXJ, 39.2±1.9% in CJ1 and 56.2±1.9% in CJ2, which matched total joint net work patterns in the hind limb indicating significant work modulation at the ankle in CJ1 and even greater work modulation in CJ2 (p<0.005). Ankle joint excursion were 42.14±2.15° in BJ, 53.23±2.36°in CJ1, and 86.79±2.08° in CJ2 which were consistent with pattern seen in ankle net work across all three jump types.