Abstract Summary
In vivo studies of joint moment-velocity relationships usually do not breakdown the contributions of individual muscles. Namely, force contributions of individual muscles may change according to muscle group isotonic load. To address this question, we measured the in situ force-velocity (F-V) properties of the kangaroo rat plantarflexor group and used two models to estimate the contributions of individual muscles. In the first model, each muscle’s percent contribution was assumed constant across all group forces. In the second model, we assumed that the F-V relationships for the fibers of each muscle were identical, but due to muscle architectural differences, each muscle’s contribution would change with group force. We found that the second model predicted the contributions better when compared to independent estimates based upon sonomicrometry of muscles’ lengths during isotonic loading. This shows that architecture differences influence how muscles contribute to the group F-V properties.
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