Lipid peroxides production after strenuous exercise and in relation to muscle morphology and capillarization.

The antioxidative capacity of slow twitch muscle fibers has been reported to be higher than that of fast twitch ones. The purpose of this study was to relate the production of lipid peroxides during exercise to the morphology and capillarization of human muscles. Twenty-seven healthy volunteers performed a strenuous 90-min exercise. The content of malonyldialdehyde (MDA) in the middle portion of vastus lateralis muscle was found positively correlated with percentage and the relative cross-sectional area of the type 1 of muscle fibers (r = 0.46, P < 0.05, r = 0.43, P < 0.05, respectively) but negatively with type II muscle fibers (r = -0.46, P < 0.05, r = -0.43, P < 0.05, respectively), especially type IIB. The content of MDA in the vastus lateralis muscle correlated positively with the number of capillaries around type II muscle fibers (r = 0.71, P < 0.001). It is suggested that the production of lipid peroxides parallels the exercise-induced increase of oxygen uptake in the muscle, being highest in more oxidative and better perfused, oxygen-consuming muscle fibers.