The difference in plasma zinc levels is dependent on the intensity of exercise. It is evident that there are temporary effects of exercise on metabolism of zinc. Also, it has been revealed that a high level of persistent exercise can have long-standing effects on metabolism of zinc. It has also been stated that runners have lower plasma zinc levels than control population. Long-term endurance training has reported to reduce the resting serum zinc levels significantly in both male and female athletes as compared to the sedentary control population.

Muscle function gets affected with severe zinc deficiency. One of the results of low serum zinc levels might be reduction in muscle zinc concentrations. As zinc is essential for several enzyme activities in energy metabolism, it could be expected that low muscle zinc levels could lead to a decrease in endurance capacity. Zinc could be acting directly at membrane level, whereas changes in extracellular zinc levels have been documented to stimulate twitch-tension relationship in muscle. Few investigators have linked acute and exhaustive exercise with reduced immune function. The mechanisms of physical stress modify immune capability that is complex, which involves both immune and neuroendocrine messengers.

Muscular fatigue is of vital importance and has been the focus of several investigators. Even though various factors are identified, but a clear cause remains unclear. Factors that are discussed include energy supply, unconventional work, the accumulation of metabolites, immune dysfunctions, etc. It has also been revealed that daily high and maintained physical training for an extended period of time, i.e. 7 months, provokes distinct modifications in the immune system of best sportsmen, which is accompanied by a psychological and biochemical stress level.

Source: Cordova A, Alvarez-Mon M. Behaviour of zinc in physical exercise: a special reference to immunity and fatigue. Neurosci Biobehav Rev. 1995; 19(3):439-445. doi:10.1016/0149-7634(95)00002-v