Characterization of skeletal muscle performance and morphology following acute and chronic mechanical loading paradigms

Unaccustomed muscular activity (incorporating lengthening-type movements) results in skeletal muscle damage, yet effects in performance and muscle morphology from movements such as stretch-shortening contractions (which are common-type movements in daily activities) are not well characterized or quantified. Thus, determining time- and dose-dependent responses resulting from acute mechanical exposure will aid critically in understanding muscle injury kinetics and the role of repair and regeneration following this type of exposure. Furthermore, skeletal muscle mass and function declines with age and these events result in a significant impact on the aging workforce. Differentiating the response following both acute and chronic adaptive exposures in young and aged populations will advance our understanding of how the regenerative capacity of skeletal muscle may differ with age. In the absence of overt muscle damage, oxidative stress mismanagement may influence the adaptive/mal-adaptive response following high-intensity mechanical loading. The glutathione system greatly impacts multiple pathways and functions directly as a reducing agent, serving as a substrate for glutathione peroxidase (and other enzymes), and functioning in the recycling of radicals generated from other molecules in skeletal muscle. The adaptive response ensuing from manipulating the glutathione system was ascertained with respect to age following chronic mechanical exposures. Surprisingly, the impact of oxidative stress was negligible, irrespective of age following SSC exposure. However, our results suggest initial muscle regeneration is a critical element in assuring successful, long-term adaptation. Remarkably the capacity to respond efficiently to an initial mechanical stimulus as one ages, may be one of the most important factors that ultimately influences adaptation of skeletal muscle