Free Radical Or Mitochondrial Theory of Aging

The free radical or mitochondrial theory of aging has received increasing recognition during the last 20 years. A basic tenet of this theory is that the fundamental changes associated with the aging process are the cumulative result of the reactive oxygen species (ROS) which are normal by-products of aerobic life. Physical exercise is an integral part of daily life. Prominent changes, which occur during exercise, include: an increased metabolic rate, an enhanced rate of mitochondrial respiration, and oxidative phosphorylation.

During maximal muscular contraction in men, it has been estimated that oxygen consumption can be as much as 100 times the resting level for local muscle fibers and 20 times for the whole body. This high rate of oxygen flux may lead to increased electron "leakage" found at the resting condition and poses an oxidative stress to the mitochondria and other critical cellular organelles [1]. During aging, the skeletal muscle is under increasing oxidative stress, as evidenced by higher levels of lipid peroxidation and antioxidant defense in aged muscles.

The theory states the mitochondria are the major source of toxic oxidants, which are capable of reacting with and destroying cell constituents and which accumulate with age. The consequence of this destructive activity is an inefficient cell and a body we recognize as aged (wrinkled skin, low energy level). The gradual loss of energy with age is paralleled by a decrease in number of mitochondria per cell, as well as the health and energy-producing efficiency of those remaining mitochondria.

1- Jenkins, RR and Goldfarb, A. Introduction: oxidant stress, aging, and exercise. Med Sci Sports Exerc. 1993 Feb;2(2) :210-2