Changes of magnesium concentrations in endurance athletes.

Erythrocitary and serum magnesium (Mg) were determined in a group of 11 well-trained athletes before and after a 25-km running race, and in a group of 30 sedentary controls. The significant increase of mean erythrocitary Mg (EMg) concentration observed in the athletes after physical strain (2.58 +/- 0.34 mEq/l before, 3.10 +/- 0.45 mEq/l after the race: significance level = 5%) leads to the assumption that the possible Mg uptake is effected by the red blood cell to enhance some enzymatic reactions. The decrease of mean serum Mg concentration observed in the same subjects after the effort (1.70 +/- 0.14 mEq/l before, 1.64 +/- 0.15 mEq/l after the race) is not significant. The difference between mean Mg concentrations observed in the athletes' group before the race and in the sedentary group (EMg: 2.58 +/- 0.34 mEq/l in athletes, 3.67 +/- 0.38 mEq/l in sedentaries, significance level = 1%; serum Mg: 1.70 +/- 0.14 mEq/l in athletes, 1.96 +/- 0.15 mEq/l in sedentaries, significance level = 1%) suggests that athletes suffer from a Mg deficiency, partially due to physical exercise. The two hypotheses and the possible causes of the observed phenomena are discussed.