Tissue studies during recovery from immobilization atrophy

Immobilization of one hind leg of puppies was produced at 12 weeks of age. After 6 weeks of immobilization, the immobilized muscles were restored to weight bearing. The opposite leg was the control leg. To study recovery from atrophy in these muscles, biochemical analyses and histochemical patterns of the muscles were used. Recovery periods varied from 55 to 300 days. In the 91-day remobilization group there were increased values in the interfiber constituents as well as decreases in the intrafiber constituents, but values were not as large as in immobilization only. After 300 days of remobilization the formerly atrophic muscles had regained the same concentration as in the control muscles, indicating recovery. The histochemical patterns of 1 kg of control muscle and remobilized muscle were traced. The ultrafiltrate volume in the groups up to 91 days of remobilization was increased in amounts over the control volumes, but the increases were not as large as in immobilization only. In 300-day group all volumes were the same as in the control, indicating recovery from atrophy, according to these criteria.