Effect of exercise and heat stress before hindlimb suspension on prevention of the skeletal muscle atrophy

Effect of exercise and heat stress applied before hindlimb suspension on prevention of muscle atrophy was examined in the rat soleus muscle. Male Wistar rats were randomly divided into 4 groups: 1) control (C), 2) hindlimb suspension for 2 weeks (HS), 3) exercise before HS (Ex-HS), and 4) heat stress before HS (Heat-HS). Before hindlimb suspension, the rats in the Ex-HS were exercised by running on an incline treadmill, and those in the Heat-HS were placed 4 times in a week, in a heat chamber. After 2-week hindlimb suspension, the soleus muscles were isolated and their wet weight was examined. Cross sections of each muscle were cut in and stained for ATPase to distinguish fiber types, and alkaline phosphatase to visualize the capillaries. Muscle wet weight, fiber diameter, ratio of type I fiber, and capillary-to-fiber (C/F) ratio in the HS were significantly smaller than the C. The muscle wet weight, diameter and ration of type I fiber and C/F ratio in the Ex-HS and heat-HS were significantly larger than the HS. These findings suggested that the exercise and heat stress applied as pre-emptive countermeasures have considerable benefits to inhibit muscle atrophy and regression alterations.