Meeting Abstract
Series elastic elements, such as tendons and aponeuroses, greatly contribute to stable and efficient movement. Specifically, muscles and tendons interact to buffer the rate of energy input to the muscle and limit the rate of stretch applied to the fascicle during active lengthening. These interactions may mitigate muscle damage that occurs during active lengthening. Previous studies on active lengthening of muscle-tendon units (MTUs) have identified that the effective use of tendons relies on the timing of activation and the contractile kinetics. However, experimental work is limited in the scope of parameters that can be explored. Therefore, models of muscle-tendon units may 1) allow for examination of a broader range of parameters, 2) limit the use of experimental animals and 3) be readily adopted into larger scale musculoskeletal models. We used a model consisting of a Hill-type contractile element (CE) and a series elastic element (SEE) to explore the role of muscle tendon interactions during energy dissipating tasks. In this model, we incorporated realistic mechanical and contractile properties from bullfrog plantaris MTU. Our results suggest that contractile kinetics affect active lengthening such that slower rates of force development can limit the loading of elastic elements and faster relaxation rates can apply a faster stretch to muscle fascicles during tendon recoil. Regarding timing of activation, early activation allows lengthening to begin at shorter muscle lengths. The results of the simulations are consistent with our experimental results and therefore provide a useful framework for predicting how changes in motor control strategies, fiber type composition, or mechanical properties of tendons affect the integrated performance of the muscle-tendon unit during energy dissipating tasks.
