Interaction between elastic energy utilization and active state development within the work enhancing mechanism during countermovement

Abstract: The purpose of this study was to investigate the interaction between elastic energy utilization and the time available for active state development during countermovement, and to determine the contributions of these factors in enhancing work output from a quantitative standpoint. Especially, we focused on the effect of length variation of the series elastic element (SEE) and the speed of active state development. A Hill-type model of the muscle tendon complex (MTC) was constructed. A range of SEE lengths (between 0.625 and 10 times the optimal length of the contractile element) and a range of active state development rates were investigated. Forward dynamics simulations were performed to evaluate the causal factors for the gain in height during concentric (CO) and countermovement (CM) conditions. Simulated outputs suggested that the contribution of the time available for active state development was larger than the contribution of elastic energy utilization for a shorter SEE muscle. On the other hand, the contribution of the elastic energy utilization was larger for a longer SEE muscle. Additionally, the work output of the SEE in CM was considerably augmented due to increasing the speed of active state development. As results, two main findings were obtained. First, a quantitative discussion was developed regarding how the elastic energy utilization and the time available for active state development are contributing within the work enhancing mechanism. Second, it was found that elastic energy utilization and the time available for active state development have a synergistic effect during countermovement. [Copyright &y& Elsevier]