• Achilles;
  • dantrolene;
  • rat;
  • tendon rupture;
  • triceps surae


The incidence of skeletal muscle tendon rupture is increasing. The unloaded, shortened muscle undergoes rapid degeneration. Rehabilitation takes 10–12 weeks and includes stretch therapy. Outcomes may be improved by understanding the pathophysiological changes and stretch mechanisms. We investigated the effects of passive stretch on preventing central core lesions in a rat tenotomy model of simulated Achilles tendon rupture. Adult male rats were tenotomized bilaterally. At 7 days, 39% of the soleus fibers possessed central core lesions. Whole muscle calcium concentration progressively increased and plateaued by 4 days. Dantrolene, a calcium release blocker, injected daily for 7 days, reduced central core lesion formation and calcium build-up. Passive stretch, 20 min/day, inhibited central core lesion formation. Calcium increased at 4 days in mitochondria, and stretch prevented this increase. These findings indicate that stretch therapy reduces central core lesion occurrence by preventing calcium elevation in hypershortened muscles. Muscle Nerve 38: 1563–1571, 2008