Abstract

Usually the changes caused by physical exercise on potassium (K+) are thought to be related to the intensity and duration of muscle work. Anyway the opinions are different about two aspects: a) the relation hasn't been proved in all sports; b) the plasma K+ is not considered a reliable parameter of K+ depletion caused by a high intensity exercise during training. We checked the changes of intra-erythrocyte and plasma electrolytes on two different groups of international level boxers, in different periods. The first investigation (19 athletes; mean age 19+/-2.4 yrs), before and after a 6-days training, showed a plasma K+ increase, even if not significant, and a very significant intra-erythrocyte K+ decrease (p less than 0.001); sodium (Na+), on the contrary, didn't show great changes in the intra-erythrocyte and plasma values. The second investigation (25 athletes; mean age 19+/-3.2 yrs), before and after a 12-day training, showed, at plasma level, a very significant plasma K+ increase (p less than 0.001), while the other cations (sodium, calcium, magnesium) remained almost unchanged. These ions weren't measured at intra-erythrocyte level for technical reasons. Our investigation confirm: a) the hydro-electrolytical results caused by training are related to the muscle work duration also for sports such as aerobic-anaerobic like boxing; b) the intra-erythrocyte K+ is the most reliable parameter of potassium depletion caused by training. It has been proved that K+ is ejected from cells, and also from working muscle, for exchange with sodium, neither in relation with plasma pH nor with glycogenolysis, as thought till today, but for other causes (such as adrenergic hyperactivity), acting on Na-K membrane pump. Verf.-Referat