Muscle contraction is driven by conformational changes associated with portions of myosin molecules when they are attached to actin filaments. This shape change results in a sliding motion between these two muscle proteins and thus, shortening of the entire muscle. Attempts to understand the dymamics of this system have relied on two approaches: (1) experiments that employ rapid mechanical transients applied to activated muscle and (2) mass action models that treat these proteins as independent chemical species. Our research re-examines these two approaches with a combination of theoretical and experimental approaches. From a theoretical standpoint, we will show that rapid mechanical perturbations applied to single muscle cell preparations lead to propagating waves of internal strain and that these waves may account for the behaviors that have been incorrectly attributed to mysosin kinetics. Using recent experimental methods that employ high - speed laser diffractometry, we show such waves occur and we use such data to corroborate our theoretical predictions. We will also develop a new theoretical approach for modelling thedynamics of interacting proteins. In this new approach, we relax the assumption that each myosin molecule acts independently. Instead, we argue that the kinetics of each molecule can be represented as an oscillator whose behavior depends on the kinetics of its neighboring myosins. This system of coupled oscillators can yield kinetics of an ensemble of molecules that is vastly different from the kinetics of each individual. These two approaches challenge the classic views of muscle as a system of slow, independent molecules whose kinetics can be extracted from experiments employing rapid mechanical perturbations.//
