So Much Work, so Little Time: Maximizing Elastic Energy Within the Duration of Muscle Contraction

Michael Rosario, Duke University

Across the tree of life, we find organisms that use elastic energy to move over great distances and/or with extreme power. For example, fleas jump to heights more than 500 times their body length and chameleons project their tongues with horsepower equivalent to that of most dirt bikes, but none of these extreme movements are possible without the use of elastic energy. Given the widespread dependence on elastic energy in biology, it is surprising that little is known about the universal principles that determine how much energy these spring systems store. Here, we probe the relationship between energy storage and muscle-spring parameters (i.e., spring constant and factors affecting muscle dynamics) to address a key question in biological spring systems: Is spring constant tuned to muscle dynamics in order to permit maximal storage of elastic energy? We developed both steady-state and dynamic simulations that connected muscles with springs and, as a case study, used muscle-spring parameters of bullfrog hindlimbs as inputs of the simulations. We found that the predicted optimal spring constant from the dynamic simulation matched measured values of bullfrog tendon while the prediction from the steady-state simulation was more than double. In this talk, we will demonstrate the limitations of our steady-state simulation and discuss how the parallelized dynamic model fundamentally changes our interpretation of the tuning of muscle-spring parameters in jumping bullfrogs.

Abstract Author(s): M.V. Rosario, G.S. Sawicki, G. Sutton, S.N. Patek