Effect of hind-limb immobilization on contractile and histochemical properties of skeletal muscle

Summary Both hind limbs of male rats were immobilized in casts. After 4 weeks, serial sections of hind limb muscles were stained for myosin ATPase and NADH-diaphorase. The soleus from immobilized limbs had significantly fewer muscle fibers than the control soleus. Moreover, the soleus from immobilized limbs had a significantly lower percentage and lower number of fibers with low myosin ATPase activity than the soleus from control rats. Immobilization also resulted in the speed of contraction for the soleus being significantly faster than the soleus from control rats. There were no significant differences in the contractile properties or in the percentages of fibers with low myosin ATPase between rectus femoris muscles from immobilized and control limbs. The deep portion of the rectus femoris from immobilized limbs had a significantly smaller percentage of muscle fibers with high NADH-diaphorase activity than did the rectus femoris from control rats.The animals involved in this study were maintained in accordance with the Guide for Laboratory Animal Facilities and Care as published by the National Academy of Sciences-National Research Council.The research reported in this paper was conducted by personnel of the Environmental Sciences Division, USAF School of Aerospace Medicine, Aerospace Medical Division, AFSC, Brooks AFB, Texas. Further reproduction is authorized to satisfy the needs of the U.S. Government.