The influence of eccentric exercise-induced muscle weakness on the history dependence of force
Following active lengthening or shortening, force production in subsequent isometric contractions are increased (residual force enhancement; rFE) or decreased (residual force depression; rFD), respectively, compared to fixed-end isometric reference contractions at same muscle lengths and activation levels. These intrinsic properties of muscle are collectively known as the history dependence of force. The purpose of this thesis was to investigate how rFE and rFD are modified in a weakened state. Participants performed electrically stimulated, and submaximal and maximal voluntary contractions (MVC) prior to, and following eccentric exercise. Following eccentric exercise; MVC torque was decreased, prolonged low frequency force depression was present, and both rFE and rFD increased for all maximal and submaximal conditions. Thus, rFE seems to be increased due to concomitant maintenance and reductions in passive and active forces, respectively. Furthermore, we speculate that the increase in rFD is due to mechanical, but not metabolic alterations in the weakened state.