Eccentric exercise prior to hindlimb unloading attenuated reloading muscle damage in rats.
BACKGROUND
Antigravity muscles that are reloaded subsequent to hindlimb unloading (HU) are prone to injury. Similarities exist between muscle damage elicited from HU and subsequent reloading and damage induced by eccentric exercise (EE). Conditioning bouts of EE reduce muscle damage following a repeat bout of EE. Since damage to reloaded skeletal muscle is comparable to damage observed after EE, the mechanisms of damage are presumably similar. Therefore, EE prior to HU may attenuate reloading muscle damage. This study evaluated the effects of prior EE on rat soleus muscles (SOL) subsequent to 7 d of HU and 16-19 h of reloading.


METHODS
Sprague Dawley rats were randomly assigned to the following groups: eccentric exercise + hindlimb unloading + reloading (EEHUR; n = 9); hindlimb unloading + reloading (HUR; n = 10); eccentric exercise (EE; n = 12), or control (CON; n = 12). The exercise protocol was performed 5 d x wk(-1) for 2 wks followed by HU and reloading.


RESULTS
Fiber areas were lower in both suspended groups vs. the EE and CON groups. There was no difference in percent interstitial area among groups. However, percent myofibrillar damage was higher in the HUR group vs. all other groups. Further, glucose-6-phospate dehydrogenase activity, an indicator of muscle damage, was higher in the HUR group compared with the EE and CON groups.


CONCLUSIONS
These results provide some evidence that prior EE reduced muscle damage subsequent to HU and reloading. Therefore, EE may prove effective in minimizing recovery time in individuals suffering from muscle damage following periods of bed rest and spaceflight.
Prisby
Rhonda D
RD
Texas A&M University, Department of Health and Kinesiology, HLKN 4243 TAMU, College Station, TX 77843, USA. rprisby@hlkn.tamu.edu
Nelson
Arnold G
AG
Latsch
Elizabeth
E
D000818:Animals; D005260:Female; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D019417:Hindlimb Suspension / Q000009:adverse effects*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology*; D009210:Myofibrils / Q000473:pathology; D009929:Organ Size; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D005954:Glucosephosphate Dehydrogenase