Abstract
The purpose of this study was to determine the effect of periodic low-intensity exercise during hindlimb suspension on the mass, relative weight, myofibrillar protein content in soleus, plantaris and gastrocnemius muscles. To examine the effectiveness of periodic low-intensity exercise on mass, and myofibrillar protein content of hindlimb muscles, adult female Wistar rats were suspended(HS) and half of these rats walked on a treadmill for 45min/day(15 min every 4h) at 5m/min and a $15^{\circ}$ grade(HS-EX). Soleus wet weight was 33.51% significantly smaller(p<0.005) and relative soleus weight of hindlimb suspended rats was 31.96% smaller(p<0.005) compared with those of control rats following seven days of hindlimb suspension. Plantaris wet weight was 7.5% smaller(p<0.01) and relative plantaris weight was 11.83% smaller(p<0.05) compared with those of control rats following seven days of hindlimb suspension. Gastrocnemius wet weight was 11.31% significantly smaller(p<0.005) and relative gastrocnemius weight was 17.13% significantly smaller(p<0.005) compared with those of control rats following seven days of hindlimb suspension. Soleus wet weight while increased by relative soleus weight increased by 25.13%, 27.59% each through periodic low intensity exercise during hindlimb suspension(p<0.05, p<0.05). Plantaris wet weight and relative plantaris weight increased by 1.04%, 10.98%(p<0.05) each, and gastrocnemius wet weight and relative gastrocnemius weight increased by 1.98%, 12.02%(p<0.05) each through periodic low intensity exercise during hindlimb suspension. Wet weight of soleus, plantaris and gastrocnemius in HS-EX rats did not recover to control level. Myofibrillar protein content of soleus, plantaris and gastrocnemius was 48.24%, 40.85% and 37.33% significantly smaller(p<0.005) respectively compared with those of control rats following seven days of hindlimb suspension. Myofibrillar protein content of soleus, plantaris and gastrocnemius increased by 40.68%, 25.07% and 17.93%(p<0.005) each through periodic low intensity exercise during hindlimb suspension. Myofibrillar protein content of soleus, plantaris, and gastrocnemius in HS-EX rats did not recover to control level. The results suggest that periodic low intensity exercise can attenuate hindlimb muscle atrophy induced by hindlimb suspension.