The purpose of this study was to determine the effect of regular exercise during dexamethasone injection on the body weight, weight of hindlimb muscles and adrenal gland in young rats. 80-100g Wistar rats were divided into control, exercise, dexamethasone injection(dexa), and exercise during dexamethasone injection(D+E) group. The dexa group received daily subcutaneous injection of dexamethasone at a dose of 5mg/kg body weight for 10 days. The exercise group ran on a treadmill for 60min/ day(20 minutes every 4 hour at 10m/ min and a 10degrees grade. The control group received daily subcutaneous injection of normal saline at a dose of 5mg/kg body weight for 10 days. The D+E group ran on a treadmill for 60min/day(20 minutes every 4hour) at 10m/min and a 10degrees grade. Body weight of both control and exercise group increased significantly until 10 days, the of both dexa and D+E group decreased significantly, resulting in 79.47 and 78.75% decrease respectively compared to the first day of experiment. Body weight and muscle weight of the soleus, plantaris and gastrocnemius decreased significantly with dexamethasone injection. Relative weight of the dexa group decreased significantly compared to that of the control group. Body weight and muscle weight of the soleus and plantaris of the D+E group showed a tendency to increase, and muscle weight of the gastrocnemius increased significantly compared to the dexa group. The Relative weight of the plantaris was comparable to the control group and that of the soleus and gastrocnemius tended to increase, in the exercise group. Body weight and muscle weight of the soleus and plantaris of the D+E group showed a tendency to increase, and muscle weight of the gastrocnemius increased significantly compared to the dexa group, The Relative weight of the soleus and gastrocnemius tended to increased and that of the plantaris of the D+E group increased significantly compared to the dexa group. Body weight, muscle weight and relative weight of the soleus, plantaris and gastrocnemius of the D+E group increased significantly compared to the dexa group Adrenal gland weight of the dexa and D+E group tended to increase, and that of the exercise group increased significantly. From these results. it can be suggested that regular exercise during dexamethasone injection might attenuate the decrease of body weight and hindllimb muscle weight induced by the dexamethasone injection.

The purpose of this study was to determine the effect of endurance training prior to occurrence of muscle atrophy on the mass, myofibrillar protein content and fiber crossectional area of atrophied hindlimb muscles of rats. Adult female Wistar rats were trained prior to occurrence of muscle atrophy induced by hindlimb suspension. Training began on the lst day for 10min/day at 15m/min on a 0% grade, training exercise increased daily in time and intensity so that by the 4th week rats were running 60min/day, at 34m/min on a 13.5% grade. Wet weight and relative weight of soleus, plantaris and gastrocnemius muscle decreased significantly after seven days of hindlimb suspension. Wet weight and relative weight of soleus tended to increase and that of plantaris and gastrocnemius tended to decrease in the exercise group as compared to the control group. Myofibrillar protein content of soleus and gastrocnemius tended to in crease and that of plantaris tended to decrease in the endurance trained group as compared to the control group. Fiber crossectional area of Type I, II fiber in soleus and plantaris muscle tended to increase in the exercise group as compared to the control group. Wet weight and relative weight of soleus, plantaris and gastrocnemius decreased significantly, myofibrillar protein content of soleus, plantaris and gastrocnemius increased in hindlimb suspended rats following endurance training as compared to the control group. There was no change in fiber type percentage and crossectional area of type I and II fiber in soleus muscle and that of type I and II fiber in plantaris muscle decreased in the hindlimb suspended rats following endurance training as compared to the control group. Wet weight and relative weight of soleus and plantaris tended to increase, that of gastrocnemius increased significantly, myofibrillar protein content of soleus and plantaris muscle increased significantly and that of gastrocnemius tended to increase in the hindlimb suspended rats following endurance training as compared to sedentary rats following endurance training. Crossectional area of type I fiber of soleus muscle tended to increase, that of type I fiber of plantaris muscle increased significantly and that of type II fiber tended to increase in hindlimb suspended rats following endurance training as compared to sedentary rats following endurance training. The results suggest that endurance training prior to occurrence of muscle atrophy can attenuate the decrease of mass, myofibrillar protein content and fiber crossectional area induced by hindlimb suspension.