Musculoskeletal soft tissue injuries represent a large portion of sports- related injuries. The frequency of occurrence of these injuries has increased rapidly over the last decade as participation in athletic activities and physical conditioning have increased in the United States. The junction between skeletal muscle cells and tendon collagen fibers has been implicated in a common type of soft tissue injury which occurs when active muscle is passively extended. These injuries apparently occur most frequently in inadequately trained participants which suggests that training and, conversely, disuse can influence the structure or physical properties of these myotendinous junctions (MTJs). This proposed investigation is directed toward elucidating the effects of exercise and disuse on the structure, molecular composition and mechanical strength of MTJs using frog skeletal muscle as a model. These experimental animals were selected because: 1) they are unusual in that single cell mechanical testing can be easily performed, and 2) the molecular composition and quantitative ultrastructure of their MTJs has been studied previously. In the proposed investigation, these animals will be subjected to strength-training, increased-frequency exercise, reduced-frequency exercise or denervation atrophy. At selected times in their training, representative animals from each group will be sacrificed and hind limb muscles analyzed for changes in: 1) mass, 2) aerobic capacity, 3) anaerobic capacity, 4) quantitative MTJ structure, 5) concentration of structural proteins at the MTJ, or 6) breaking strength at the MTJ. These data will provide the first information on the response of MTJs to exercise and disuse. These data will also provide the basis of a comprehensive description of the relationships between modifications in muscle cell structure and molecular composition to load-bearing at MTJs in ways that can be related to clinically-observed defects in humans.
Showing the most recent 10 out of 51 publications
