Aerobic exercise as a countermeasure for microgravity-induced bone loss and muscle atrophy in a rat hindlimb suspension model.
BACKGROUND
Loss of bone and skeletal muscle atrophy resulting from non-weight-bearing are major concerns associated with microgravity environment and spaceflight deconditioning. The objective of this research was to address the fundamental issue of whether bone loss and muscle atrophy could be attenuated using weight-bearing aerobic exercise on a treadmill as a countermeasure in rats subjected to simulated weightlessness by hindlimb suspension.


METHODS
Bone and muscle from control and hindlimb-suspended groups with and without exercise were evaluated by bone mineral density (BMD), mechanical tests, bone histomorphometry and muscle mass.


RESULTS
Femoral BMD of hindlimb-suspended (HS) rats subjected to treadmill exercise was significantly greater than femoral BMD of HS rats without exercise and also was equivalent to that of weight-bearing controls. Muscle mass from HS rats exercised on a treadmill was significantly greater than muscle mass from HS rats that did not exercise. Exercise did not result in muscle mass equal to that of controls, however. In addition, histomorphometric analysis of the metaphysis of the proximal tibia revealed that HS rats that exercised did not maintain bone formation equivalent to controls. No other bone parameters were found to vary significantly between groups.


CONCLUSIONS
It was concluded that moderate aerobic exercise on a treadmill did attenuate bone loss and muscle atrophy due to simulated weightlessness by hindlimb suspension, however its effectiveness differed by tissue, anatomical site and parameter investigated.
Norman
T L
TL
Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown 26506-9196, USA. tnorman@wvu.edu
Bradley-Popovich
G
G
Clovis
N
N
Cutlip
R G
RG
Bryner
R W
RW
D000818:Animals; D001696:Biomechanical Phenomena; D001835:Body Weight; D015519:Bone Density; D001862:Bone Resorption / Q000175:diagnosis / Q000209:etiology* / Q000517:prevention & control*; D004195:Disease Models, Animal; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D005269:Femur / Q000473:pathology; D019417:Hindlimb Suspension / Q000009:adverse effects*; D009133:Muscular Atrophy / Q000175:diagnosis / Q000209:etiology* / Q000517:prevention & control*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013977:Tibia / Q000473:pathology; D016474:Weight-Bearing; D018474:Weightlessness Simulation / Q000009:adverse effects*