Unaccustomed eccentric muscle exercise causes structural damage to muscle fibers, hypothesized to be driven by fiber strain magnitude and oxidative capacity rather than absolute stress.
This review proposes that exercise-induced muscle injury is driven by fiber strain magnitude and occurs early during eccentric exercise, predominantly affecting fast-twitch glycolytic fibers.
It is well documented in both animal and human studies that unaccustomed, particularly eccentric, muscle exercise may cause damage of muscle fiber contractile and cytoskeletal components. These injuries typically include: Z-band streaming and dissolution, A-band disruption, disintegration of the intermediate filament system, and misalignment of the myofibrils. The mechanical basis for this damage is suggested to be due to the fiber strain magnitude rather than the absolute stress imposed on the fiber. We hypothesize that eccentric contraction-induced damage occurs early in the treatment period, i.e., within the first few minutes. The structural abnormalities predominate in the fast-twitch glycolytic fibers. In the final section of this paper, we hypothesize a damage scheme, based on the muscle fiber oxidative capacity as a determining factor.
Fridén et al. (Fri,) conducted a review in Exercise-induced muscle injury. Unaccustomed eccentric muscle exercise was evaluated on Muscle fiber contractile and cytoskeletal damage. Unaccustomed eccentric muscle exercise causes structural damage to muscle fibers, hypothesized to be driven by fiber strain magnitude and oxidative capacity rather than absolute stress.
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