Residual force enhancement in skeletal muscle.

Residual force enhancement has been observed consistently in skeletal muscles following active stretching. However, its underlying mechanism(s) remain elusive, and it cannot be explained readily within the framework of the cross-bridge theory. Traditionally, residual force enhancement has been attributed to the development of sarcomere length non-uniformities. However, recent evidence suggests that this might not be the case. Rather, it appears that residual force enhancement has an active and a passive component. The active component is tentatively associated with changes in the cross-bridge kinetics that might be reflected in decreased detachment rates following active muscle stretching, while the passive component possibly originates from a structural protein, such as titin, whose stiffness might be regulated by calcium.