Exercise, free radical generation, and aging.

Advancing age is associated with profound alterations in body composition and exercise capacity. Skeletal muscle mass declines on average of 6% per decade after age thirty and this change impacts both basal energy requirements and maximal aerobic exercise capacity. While skeletal muscle has one of the highest requirements of all tissues for oxygen, exercise increases total oxygen consumption by approximately 10-fold, causing an increased rate of production of reactive oxygen species (ROS). Biological aging is thought to be influenced by ROS generation and older individuals may be more susceptible to exercise-induced oxidative damage. However, aging is also associated with increases in antioxidant enzymes and controversy still exists as to whether exercise training further upregulates the expression of these free radical scavenging enzymes. Older individuals who participate in regular exercise may have higher requirements for antioxidant vitamins to compensate for the deficit of endogenous antioxidants.