Effects of physical exercise on skeletal muscle fiber: ultrastrucural and molecular aspects.

This review briefly summarizes varies research studies attempting to examine the mechanisms of skeletal muscle adaptations to exercise. The study of adaptations of exercise training reveals a wide range of integrative approaches, from the systemic to the molecular level. Research has revealed that exercise can be effective at preventing and/or treating some of the most common chronic disease. Strenous exercise creates situations that subject structure and cell metabolism to significant stress, including those of muscle damage and oxidative stress. The cytoskeletal contractile myofilament apparatus adheres through subsarcolemmal and transmembrane molecules to the surronding extracellular matrix with integrin and dystrophin associated chains of molecules being the two main adhesion complexes. Immediately after exercise, especially when it involves eccentric contraction, some of the proteins belonging to these complexes decrease both quantitatively and qualitatively. This decrease is followed by a subsequent return to normal values after a few weeks. High-intensity exercise, aso induces ultrastructural damages and few weeks after the eccentric contraction, examination of muscle samples shows a normal ultrastructural myofibrillar profile, indicating the existence of a remodelling response after exerciseinduced damage. Responses to exercise are often highly variable among individuals, however that response may be mediated by variation in genes. At the present time, most of the mechanisms underlying the adaptation of human skeletal muscle to exercise still remain to be discovered.