Meeting Abstract

98.5  Wednesday, Jan. 7  Cost of muscle force production during legged locomotion in guinea fowl. MARSH, Richard L.*; HITCHCOCK, Amanda C.; TRUONG, Rosemary; PROPERT, Matthew W.G.; Northeastern University; Northeastern University; Northeastern University; Northeastern University r.marsh@neu.edu

We combined measures of joint moments, joint angles, and instantaneous effective moment arms at the ankle and tarsometatarsal-phalangeal joints with previous measures of muscle energy use by the stance muscles acting at these joints to estimate the cost of muscle force production by the ankle extensors and digital flexors. The resulting values were expressed in W/N (similar to organismal level cost coefficients). Preliminary data indicates that the cost of force production by the digital flexors rises at low speeds and then is relatively constant at higher speeds. However, the cost of force production by the pure ankle extensors (largely the gastrocnemius) increases at higher speeds. One hypothesis that might explain this difference is the production of larger amounts of net positive work by the gastrocnemius with increases in speed, because force per active muscle volume is expected to be reduced during shortening. Supported by NIH AR47337 and NSF IOB-0542795.