Meeting Abstract

P3.54  Tuesday, Jan. 6  Net joint work as a function of speed in a small running bird, the chukar. MARSH, Richard L.*; HANSEN, Eric; WATSON, Rebecca; PROPERT, Matthew W.G.; Northeastern University; Northeastern University; Northeastern University; Northeastern University r.marsh@neu.edu

Little information is available on the mechanical work done at individual joints in small running animals. We calculated the net work done at the joints of chukars running over a force plate at approximately constant speeds ranging from 0.27 to 2.7 m/s. Using simultaneous high-speed video to measure joint kinematics and measures of segment properties, we calculated net joint work using 2-D inverse dynamics. As expected for constant-speed runs the positive and negative work summed across all joints were approximately equal. However, the individual joints showed large differences in the amount and sign of the work done. Positive joint work showed the highest values at the hip and the ankle, but, whereas the ankle showed an almost equal amount of negative work, very little negative work was done at the hip. Negative work predominates to varying degrees at the tarsometatarsal-phalangeal, and inter-phalangeal joints. Although, these values cannot be interpreted directly in terms of muscle work, they provide valuable guidelines regarding which muscles likely provide positive work and which are involved energy storage, and braking. Supported by NIH AR47337 and NSF IOB-0542795.