Title page for ETD etd-0711102-184930

Type of Document Dissertation
Author Prisby, Rhonda Dianne
Author's Email Address rprisby@hotmail.com
URN etd-0711102-184930
Title Effects of High-Load Eccentric Exercise Training on Rat Soleus Muscle Myofibrillar Disruption Following One-Week of Hindlimb Suspension Unloading and Subsequent Reloading
Degree Doctor of Philosophy (Ph.D.)
Department Kinesiology
Advisory Committee
Advisor Name Title
Arnold Nelson Committee Chair
Maren Hegsted Committee Member
Mike Keenan Committee Member
Robert Wood Committee Member
Changaram Venugopal Dean's Representative
  • repeated bout effect
  • intersitial area
  • resistance training
  • muscle reloading
  • myofibrillar damage
  • muscle damage
  • fiber area
  • glucose-6-phosphate dehydrogenase
Date of Defense 2002-06-25
Availability unrestricted
Purpose: This investigation evaluated the effects of a high-load (50% body weight) eccentric exercise training protocol on reloading myofibrillar damage in soleus (SOL) and extensor digitorum longus (EDL) muscles in rats following 7 days (d) of hindlimb suspension unloading (HSU). Methods: 48 female Sprague-Dawley rats were randomly stratified to four experimental groups; exercise + hindlimb suspension unloading (ExHSU), hindlimb suspension unloading (HSU), exercise (Ex) and control (C). The ExHSU and Ex groups underwent a high-load eccentric exercise protocol for ~2.5 weeks. Following exercise training, the ExHSU and HSU groups underwent 7 d of hindlimb suspension unloading and a subsequent 16-19 h reloading period. ANOVA was used to determine significance between groups for the following variables: body weight (BW) across time, BW at sacrifice, Glucose-6-phosphate dehydrogenase (G-6-PDH) activity, fiber area, fiber area to body-weight ratio, % myofibrillar damage, SOL and EDL wet, dry and wet-weight to body-weight ratios, % interstitial area, adrenal weights and adrenal weight to body-weight ratios, tibia lengths and tibia bone mineral content. Results: ANOVA revealed no significant differences (p > .10) between the ExHSU and HSU groups for BW at sacrifice, fiber area, fiber area to body-weight ratio, SOL and EDL wet, dry and wet-weight to body-weight ratios, adrenal weights and adrenal weight to body-weight ratios and tibia lengths and bone mineral content. Yet a post analysis t-test revealed a significantly higher % of myofibrillar damage in the HSU vs. the ExHSU group. Further, G-6-PDH activity and % interstitial area approached significance (p = 0.134 and p = 0.152, respectively). Conclusions: The high-load eccentric exercise training protocol prior to HSU attenuated the % of myofibrillar damage during reloading. Further, the % of interstitial area and G-6-PDH activity tended to be smaller in the ExHSU group vs. the HSU group. Therefore, eccentric exercise prior to HSU may elicit a repeated bout effect and attenuate the amount damage incurred by the muscle during reloading. Additionally, this investigation was the first to demonstrate increased G-6-PDH activity with reloading myofibrillar damage.
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