The Role of Fiber Dynamics in Strain-Induced Muscle Damage

Although global measures of muscle force and strain magnitude during exercise are often employed to quantify muscle function or damage, there is evidence that these measures may not be accurate. Recent studies in our lab have shown that the magnitude of muscle strain is not a valid predictor of muscle damage or fiber strains in-vivo. This may be due, in part, to the complexity of force sharing amongst synergists, as well as the complexity of the muscle architecture, and tendon properties during ambulation and exercise. Current evidence indicates that muscle fibers are highly mechanosensitve, thus previously measured regional variations in the adaptive response to eccentric exercise may be due to the regional variations in fiber strain magnitudes experienced within compartments of the muscle. Here, we propose to directly measure local mechanical stimuli within and between synergist muscles in-vivo using an established animal model of eccentric exercise. This will allow the direct measurement of local fiber dynamics within and between muscles, and subsequent calculation of the division of labor between them. In addition, we will determine the relationship between fiber strain and muscle damage for synergists, and assess the possible interrelationship between muscle architecture, force sharing and subsequent damage during exercise.