Abstract
The purpose of this study was to determine the morphologic effect of immobilization on rat soleus muscles in shortened and lengthened positions. Sixteen male Wister rat were divided into two groups, an immobilization (n=8) and a control (n=8) groups. In an immobilization group, both ankles were immobilized with a cast for four weeks, so that the right ankle was in a full plantar-flexion, and the left in a full dorsiflexion. Thus, soleus muscles were immobilized in shortened and lengthened positions. After experiments, the soleus muscle was then extracted and morphological study was conducted using a light and scanning electron microscope. The soleus muscle in the shortened position became more atropied compared to lengthened position. Amount of connective tissue increased, sarcomere lengths decreased, and the transverse component of collagen fibrilles increased in the shortened position. But sarcomere lengths in the lengthened position did not significantly differ from that for the control, and the longitudinal component of collagen fibrilles increased in the lengthened position. The results suggest that muscle stretch may play a preventive role in disuse atrophy, shortening of muscle fibers and endomysium, and the decrease in muscle extensibility.
