Yonsei Med J.  2004 Aug;45(4):690-702. 10.3349/ymj.2004.45.4.690.

Mechanics and Fatigability of the Rat Soleus Muscle During Early Reloading

• Lee K
• Lee YS
• Lee M
• Yamashita
• Choi I

• KMID: 721422
• DOI: http://doi.org/10.3349/ymj.2004.45.4.690

Abstract

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.

Keyword

Contractility; fatigability; hindlimb suspension; lactate; reloading

MeSH Terms

Animals
Hindlimb Suspension
Lactic Acid/metabolism
Microscopy, Electron
Muscle Contraction/*physiology
Muscle Fatigue/*physiology
Muscle, Skeletal/cytology/*physiology
Myofibrils/ultrastructure
Rats
Rats, Sprague-Dawley
Research Support, Non-U.S. Gov't
Weight-Bearing/physiology