Abstract

Nine well-trained male adults were orally supplemented with 360 mg/die Mg2+ for one month. Before and after Mg administration, each subject underwent a short-time high intensity exercise, in order to evaluate modifications in plasma and erythrocyte Mg2+ and Zn2+ levels. Magnesium administration was accompanied by a significant increase in plasma Mg2+ at rest (+ 3.54) but not under physical effort. The opposite was noticed in red blood cells, with higher Mg2+ concentrations only after exercise (+ 14.21). Furthermore, a significant augmentation in the time of the cycle ergometer test was noticed, as a consequence of supplementation (+ 14.73). Concerning the effect of the strenuous muscle exercise, a significant reduction in plasma MG2+ was found both before and after the cation administration (- 9.86; - 9.16), when results were corrected for the plasma volume reduction. No effect was induced on erythrocyte Mg2+ in unsupplemented subjects whereas increased levels were observed after supplementation (+ 7.06). Limited reduction in plasma Zn2+ were found after the exercise, with no modification in erythrocytes. Our results suggest that during brief and intense muscle activity, hypomagnesemia represents the effect of a rapid intercompartmental shift of the cation, independently of the dietary intake. We then propose to measure Mg2+ in erythrocytes as a more useful indicator to evaluate the positive effect of oral supplementation of this electrolyte. Verf.-Referat