Differential effects of 10-Hz and 50 Hz-stimulation of the tibialis anterior on the ipsilateral, unstimulated soleus muscle.

Twelve rabbits were cast-immobilized for 4 weeks during which either 10- or 50-Hz stimulation was applied transcutaneously to the anterior compartment muscles. After the treatment period, tibialis anterior and soleus muscle contractile and histochemical properties were measured. Tibialis anterior stimulation at either 10 or 50 Hz had significantly different effects on the ipsilateral, unstimulated soleus muscles. Whereas soleus muscles of both groups demonstrated significant atrophy relative to nonstimulated, nonimmobilized soleus muscles, the soleus muscles from the 50-Hz group demonstrated significantly less atrophy than did the soleus muscles from the 10-Hz group as indicated by significantly greater muscle mass, maximum tetanic tension, and fast fiber area. The results indicate that muscle stimulation may have beneficial effects on ipsilateral muscles that are passively stretched secondary to stimulation. In addition, passive tension, not just muscle activation, appears to have an important role in regulating muscle size.