Exercise Training Effects on Mitochondrial Enzyme Activity, Ubiquinones and Vitamin E

It is well-known that endurance exercise training leads to an overall increase in the oxidative capacity of oxidative type (red) skeletal muscles through increased biogenesis of mitochondria (1, 2). While overall muscle mitochondrial content increases, the mitochondrial lipid/protein ratio and the specific activities of mitochondrial enz37mes remain constant (2). Besides their known physiological function as providers of ATP through oxygen reduction, mitochondria are also potential sites of oxygen free radical formation by erroneous, incomplete electron transfer to oxygen, most probably at the site of ubiquinone oxidoreduction (3). Mitochondrial free radical production is likely to increase with the massive increase in oxygen consumption during physical activity. This suggests that exercise should result in an increased demand on antioxidant systems to respond to the increased production of oxygen-derived and other free radicals.