ABSTRACT

　Disuse of skeletal muscle leads to a reduction in muscle mass and alterations in mitochondrial function. We previously found that treadmill exercise primarily performed by forelimbs during a period of hindlimb muscle disuse attenuated atrophy and decrease in mitochondrial protein contents in the immobilized hindlimb muscles. In this study, we investigated the effects of treadmill exercise mainly performed by forelimb during bilateral hind limb immobilization on the adaptations in soleus muscle following cast removal in mice. Male Institute of Cancer Research （ICR）mice were divided into three groups: a control group without immobilization（CON），a remobilized group subjected to 14 days of hindlimb cast immobilization followed by 3 days of remobilization period （R）， and an exercise-remobilized group that performed treadmill exercise during the immobilization period, followed by a 3 days of remobilization period（ER）．After the intervention, the soleus muscles were harvested and analyzed. The results showed that both R and ER groups had significantly lower total average cross-sectional area （CSA） and levels of mitochondrial-related proteins in the soleus muscle compared to those of the CON group. The average CSA of type IIa and IIx/b fibers were significantly lower in the R group compared to the CON group, while no significant difference was observed between the CON and ER groups. These findings suggest that treadmill exercise mainly performed by forelimb during hindlimb immobilization may induce fiber?type?specific responses in remobilized muscles.

DECENTE SPORTS SCIENCE Vol.47/The DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE