Histological and Ultrastructural Alterations in Regenerating Skeletal Muscle of Older Adults Following Exercise-Induced Damage

Abstract

Morphological studies have reported fewer muscle fibers in older men suggesting fewer motor units and therefore more force absorbed per muscle fiber. Physiologic studies concur with this information, reporting decreases in lean body mass and muscular strength, and lower levels of fitness (i.e. aerobic capacity) in older subjects. Muscle specimens taken from older adults have shown a greater occurance of non specific ultrastructural alterations, including Z disk thickening, myofibrillar focal damage, and lipufuscin granules. These findings suggest that skeletal muscle of older adults may be more susceptible to environmental stress and may not regenerate as effectively following trauma. Our laboratory has investigated the ultrastructure of thigh muscle in young adults following an exercise scheme designed to stress muscle during lengthening (i.e. eccentric exercise) and result in muscle damage. The vulnerability of the ultrastructure of older adults to exercise induced muscle damage has not been investigated. The purpose of this study is to compare the frequency of occurance of non specific myofibrillar disturbances in young and older adults, and describe the fine structure of skeletal muscle of older adults prior to, immediately following, and at a time when muscle regeneration is expected to occur.