EFFECT OF TRAINING ON ZINC-METABOLISM - CHANGES IN SERUM AND SWEAT ZINC CONCENTRATIONS IN SPORTSMEN

The purpose of this research was to determine the effects of daily phy sical training on serum and sweat zinc concentrations in professional sportsmen between October and December, during the competing season. T welve volleyball players and another 12 control subjects have particip ated in this study. Tests were made in October and December which cons isted of a progressive bicycle ergometer test (increasing 30 W every 3 min to reach maximum tolerated power). Blood samples were obtained at rest and immediately after exercise. Total serum zinc increased signi ficantly after maximal exercise in both sportsmen and control subjects . In athletes, the change after exercise was significantly higher in D ecember than in October. The percentage of ultrafiltrable zinc (ZnUf) in October was similar in sportsmen and in controls. In December, howe ver, after exercise, the percentage of ZnUf was higher in athletes. Wi th respect to sweat zinc, it was in the same range both in controls an d in sportsmen in October. In December, however, sweat zinc was signif icantly higher in athletes as compared with the situation in October a nd with respect to the control group. In October, the zinc concentrati on of urine was similar for sportsmen and controls. In December, the s portsmen showed an increase in urinary zinc excretion with respect to control subjects. Cortisol in athletes increased significantly after e xercise in December. In conclusion, a daily and maintained practice of exercise is probably responsible for an alteration of zinc metabolism . The results suggest that ZnUf control, zinc supplementation and/or s tress control appear to be indicated in athletes to prevent the diminu tion of active ZnUf. In our practical opinion we think that alteration s in zinc metabolism with increases in zinc excretion and stress level s lead to a situation of latent fatigue with a decreased endurance.