ABSTRACT
Lactic acid formed by anaerobic glycolysis is the primary acidifier during exercise. Lowered pH inhibits phosphofructokinase, the rate-limiting step in glycolysis, leading to fatigue. Thus, acidosis is one major factor causing fatigue during exercise. This statement is further supported by numerous observations of decreased exercise performance after induced metabolic or respiratory acidosis. The dispensable dicarboxylic amino acid, aspartic acid, is also a metabolic intermediate in several biochemical pathways such as the tricarboxylic acid and urea cycles. However, strenuous exercise places a metabolic demand upon carnitine function. In these cases, it is hypothesized that exogenous carnitine may facilitate greater entry of fatty acids into mitochondria and/or other functions that result in greater or longer production of muscular energy. Coenzyme Q10 supplementation has consistently shown improved physiological and physical parameters in both trained and untrained subjects, consistent with hypothetical mechanisms of action.
