Short-term changes in the series elastic component after an acute eccentric exercise of the elbow flexors

We have studied the effect of a unique eccentric exercise session on the series elastic component (SEC) properties of human elbow flexors. Ten active females performed five sets of ten maximal eccentric contractions on an isokinetic ergometer. Maximal isometric (MVC) torque, and the corresponding myoelectrical activity (RMS) of the biceps brachii and the triceps brachii muscles were recorded before, immediately after, 48 h after, and 1 week after the exercise session. SEC compliance was also measured, using the in situ quick-release technique. Maximal eccentric torque declined significantly among the five sets of the exercise session (P < 0.01). The exercise session induced a significant decrease of the MVC over the post-exercise 48-h period. MVC returned to its control value 1 week after the exercise session. The neuromuscular efficiency calculated from the MVC torque:RMS ratio did not change throughout the experimental period, suggesting an optimisation of the neural drive to muscle force production capacity. The compliance values increased when force values decreased, but the slope of the relationship between both compliance and force logarithmic values was not significantly modified by the experimental procedure, indicating that the intrinsic properties of the SEC were not affected by the eccentric exercise session. The contractility-elasticity coupling was also maintained at a constant level during the recovery period. In other words, after an acute eccentric exercise, the evolution of SEC compliance was closely linked to force changes.