High intensity exercise can be maintained for only short periods of time. Cessation of short term, high intensity exercise is generally associated with muscular fatigue and discomfort, particularly in working muscles. Currently, the literature indicates that muscular fatigue resulting from high intensity exercise is due, partly, to a decrease in intramuscular pH.[l] The metabolic demands of high intensity exercise are met primarily by the nonoxidative breakdown of glucose, resulting in the production of metabolic acids such as lactic acid (see equation 3), which decrease the pH of exercising muscles [2]. The onset of muscular fatigue is associated with a rapid increase in the production of metabolic acids. The tolerance of high intensity exercise may be limited by the ability of the body to counteract decreases in intracellular (muscle) and extracellular (blood) pH through its intrinsic buffering systems. The majority of hydrogen ions (H+) dissociated from metabolic acids produced during exercise are buffered by the bicarbonate ion (HC03-) system, as depicted in the following equation:

H+ + HC03- ↔ H2C03 ↔ H20 + C02 (Eq.l)

Intracellular and extracellular lactic acid levels increase as a function of the duration of high intensity exercise [3], and, similarly, C03- levels decrease during high intensity exercise [3,4]. Associated with these metabolic changes are a decrease in pH and muscular fatigue. A positive linear correlation has been reported between H+ levels in muscle and a decrease in muscle fatigue [1]. Furthermore, recovery was associated with the rapid removal of lactate and H+ from muscle cells [1]. Thus, it has been hypothesised that increasing the body's buffering capacity (i.e. increasing the amount of circulating HC03-) would protect against acidosis and thereby delay the onset of muscle fatigue during exercise [1, 5-20]. It is this hypothesis that is the basis of the use of exogenous sodium bicarbonate (NaHC03) as a method of increasing buffering capacity, delaying the onset offatigue and increasing exercise performance. The purpose of this article is to briefly discuss the mechanisms involved in this hypothesis, review results of numerous investigations testing this hypothesis and to discuss related practical and ethical considerations.