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

The variations in plasma zinc levels is dependent which follows intens ivity of exercise. It is clear that there are short-term effects of ex ercise on zinc metabolism. It has also been shown that a high level of constant exercise can have long-term effects on zinc metabolism. It h as been reported that runners have lower plasma zinc levels than contr ols. Long term endurance training has been shown to significantly decr ease resting serum zinc levels in both male and female athletes compar ed to sedentary controls. Severe zinc deficiency can affect muscle fun ction. One consequence of low serum zinc levels could be a reduction i n 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 extrac ellular zinc levels have been reported to influence twitch-tension rel ationship in muscle. Some investigators have associated acute and exha ustive exercise with decreased immune function. The mechanisms by whic h physical stress modulates immune competence are complex, involving b oth immune and neuroendocrine messengers. Muscular fatigue is of criti cal importance and as such it has been the subject matter of numerous investigators. Although many factors have been identified, a clear cau se remains elusive. Factors discussed include: energy supply, the accu mulation of metabolites, eccentric work, immune dysfunctions, etc. Rec ently we have demonstrated that daily high and maintained physical tra ining over a prolonged period of time (7 mo) provokes marked modificat ions in the immune system of elite sportsmen accompanied by a psycholo gical and biochemical stress level. These data suggest that the mechan ism of muscular fatigue may be the mechanism implicated in the cause o f chronic fatigue.