Meeting Abstract

82.5  Friday, Jan. 7  Do skeletal levers have a trade-off between speed and force? MCHENRY, MJ*; STROTHER, JA; UC Irvine mmchenry@uci.edu

The mechanical advantage, MA, determines how much force may be generated by a skeletal lever system. MA is the distance from input force to a joint, divided by the distance from the joint to the output force. If the input force drives the lever at a fixed input velocity, then the output velocity is inversely proportional to MA. For this reason, it is thought that skeletal levers possess an inherent trade-off between their capacity for force and speed. The present study challenges this view with a mathematical model that demonstrates how the speed of a lever system is independent of MA if driven by elastic energy storage. However, a force-velocity trade-off is predicted for lever systems driven by a muscle, due to the strain-rate dependency of force generation by muscle. We present a general model that relates lever geometry and the dynamic properties of a muscle to the speed that a lever system may generate.