BEHAVIOR OF ZINC IN PHYSICAL EXERCISE - A SPECIAL REFERENCE TO IMMUNITY AND FATIGUE

The variations in plasma zinc levels is dependent which follows intensivity of exercise. It is clear that there are short-term effects of exercise on zinc metabolism. It has also been shown that a high level of constant exercise can have long-term effects on zinc metabolism. It has been reported that runners have lower plasma zinc levels than controls. Long term endurance training has been shown to significantly decrease resting serum zinc levels in both male and female athletes compared to sedentary controls. Severe zinc deficiency can affect muscle function. One consequence of low serum zinc levels could be a reduction in muscle zinc concentrations. Since zinc is required for the activity of several enzymes in energy metabolism it could be predicted that low muscle zinc levels would result in a reduction in endurance capacity. Zinc may also be acting directly at membrane level; changes in extracellular zinc levels have been reported to influence twitch-tension relationship in muscle. Some investigators have associated acute and exhaustive exercise with decreased immune function. The mechanisms by which physical stress modulates immune competence are complex, involving both immune and neuroendocrine messengers. Muscular fatigue is of critical importance and as such it has been the subject matter of numerous investigators. Although many factors have been identified, a clear cause remains elusive. Factors discussed include: energy supply, the accumulation of metabolites, eccentric work, immune dysfunctions, etc. Recently we have demonstrated that daily high and maintained physical training over a prolonged period of time (7 mo) provokes marked modifications in the immune system of elite sportsmen accompanied by a psychological and biochemical stress level. These data suggest that the mechanism of muscular fatigue may be the mechanism implicated in the cause of chronic fatigue.