Effects of Walking and Weight-bearing Exercise on Soleus Muscle in Hindlimb-suspended Rat

[Purpose] This study examined the effects of walking exercise and weight-bearing exercise on the prevention of disuse muscle atrophy. [Subjects and Method] Male Wistar rats aged 7 weeks were used. They were randomly divided into control groups and experimental groups (n=8). After hindlimb-suspension for 7 days, the experimental groups were 1) hindlimb-suspended (HS), 2) exercised by treadmill walking (EX), 3) body weight-loaded (WB) and 4) re-loaded (RL) for 1 (day-8) or 7 (day-14) more days. The right soleus muscle was used for histology and stained with hematoxylin eosin and the left soleus muscle was used to measure the MyoD and mechano growth factor mRNA expressions. [Result] Soleus muscle wet weights and cross-sectional areas of RL-14 and WB-14 were significantly greater than those of HS-14, although those of EX-14 were not. Mechano growth factor mRNA expression of RL-8 was significantly higher than those of HS-8 and WB-8, but there were no significant differences between the values for RL-8 and EX-8. MyoD mRNA expression of RL-8 was significantly higher than those of the other groups.[Conclusion] Walking exercise couldn't prevent disuse muscle atrophy any more than weight-bearing exercise, even though the mechanical stress of walking exercise was greater than that of the weight-bearing exercise.