Small stretches applied during isometric contractions revealed that contractile force enhancement was greater in rat soleus muscle, while noncontractile enhancement was greater in EDL muscle.
When an active muscle is stretched, the force increases due to strain of contractile and noncontractile proteins. We examined this force enhancement in rat extensor digitorum longus (EDL) and soleus muscles, which differ in their composition of these proteins, and their susceptibility to damage. Small stretches were applied at different velocities during isometric contractions from which we quantified the velocity-dependent contractile and velocity-independent noncontractile contributions to force enhancement. Whereas the contractile contribution was significantly greater in soleus than EDL, the noncontractile force enhancement was significantly greater in EDL than soleus, and increased ≈6-fold after damaging eccentric contractions. The increased contractile stiffness may be functionally beneficial in slow muscle, as resistance to lengthening is fundamental to maintaining posture. Following stretch-induced muscle damage this capacity is compromised, leading to increased strain of noncontractile proteins that may facilitate the activation of signaling pathways involved in muscle adaptation to injury.
Ramsey et al. (Thu,) reported a other. Small stretches during isometric contractions vs. Extensor digitorum longus (EDL) vs soleus muscles was evaluated on Velocity-dependent contractile and velocity-independent noncontractile contributions to force enhancement. Small stretches applied during isometric contractions revealed that contractile force enhancement was greater in rat soleus muscle, while noncontractile enhancement was greater in EDL muscle.