As salts of the amino acid aspartic acid, aspartates are commonly bound to the minerals magnesium, potassium, calcium, and zinc in dietary supplements to facilitate enhanced absorption. Beyond being naturally produced in the body, thus nonessential in nature, aspartate can be obtained from the diet through sugar cane, molasses, dairy, and meat. Ties to human performance originated in the late 1950s when human trials demonstrated magnesium and potassium aspartate supplements reduced muscle fatigue, helping to extend endurance in athletes.
During physical training, especially that of high intensity, the exhaustion of high energy molecules within the muscles (called ATP) during contraction causes lactate and ammonia levels to rise; increases in these levels are postulated to contribute to the onset of muscle fatigue and reduced endurance capacity in athletes. It is thought that aspartates reduce muscle fatigue by accelerating the conversion of ammonia to urea, thereby lowering levels of ammonia in the muscles and allowing more ATP energy to be produced for enhanced endurance. Furthermore, it is hypothesized that aspartate salts promote a faster rate of glycogen resynthesis during exertion, helping to protect against the fatigue-inducing glycogen depletion commonly known in sports as hitting the wall and bonking.