The Free Radical or Mitochondrial Theory of Aging

The Free Radical and Mitochondrial factors of the aging process.

The mitochondrial or free radical theory of aging has received a great increase in recognition during the last 20 years. A basic foundation 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 leading to prominent biophysical changes which occur during exercise, including: 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. This is evidenced by higher levels of lipid peroxidation and antioxidant defense in these aging muscles.

The theory expands on the idea that the mitochondria are the major source of toxic oxidants, which have the potential of reacting with and destroying cell constituents and which accumulate with age. The result of this destructive activity is an inefficient cell and a body that more readily displays signs of age (wrinkled skin, low energy level). The gradual loss of energy experienced with age is paralleled by a decrease in the ratio of mitochondria per cell, as well as the health and energy-producing efficiency of those remaining mitochondria.

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