Mechanics and fatigability of the rat soleus muscle during early reloading.
In order to elucidate muscle functional changes by acute reloading, contractile and fatigue properties of the rat soleus muscle were investigated at three weeks of hindlimb suspension and the following 1 hr, 5 hr, 1 d, and 2 weeks of reloading. Compared to age-matched controls, three weeks of unloading caused significant changes in myofibrillar alignments, muscle mass relative to body mass (-43%), normalized tension (-35%), shortening velocity (+143%), and response times. Further significant changes were not observed during early reloading, because the transitional reverse process was gradual rather than abrupt. Although most of the muscle properties returned to the control level after two weeks of reloading, full recovery of the tissue would require more than the two-week period. Delayed recovery due to factors such as myofibrillar arrangement and fatigue resistance was apparent, which should be considered for rehabilitation after a long-term spaceflight or bed-rest.
Lee
Kisoo
K
Department of Life Science, College of Liberal Arts and Science, Yonsei University, 234 Maeji-Ri, Heungup-Myon, Wonju, Gangwon-do 222-710, Korea.
Lee
Youn Sun
YS
Lee
Moonyong
M
Yamashita
Masamichi
M
Choi
Inho
I
D000818:Animals; D019417:Hindlimb Suspension; D019344:Lactic Acid / Q000378:metabolism; D008854:Microscopy, Electron; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000502:physiology*; D009210:Myofibrils / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D016474:Weight-Bearing / Q000502:physiology
D019344:Lactic Acid