CHANGES IN THE CONCENTRATIONS OF PLASMA AND ERYTHROCYTE MAGNESIUM ANDOF 2,3-DIPHOSPHOGLYCERATE DURING A PERIOD OF AEROBIC TRAINING

Physical exercise appears to affect both blood magnesium status and er ythrocyte 2,3-diphosphoglycerate (2,3-DPG) concentration. Concentratio ns of erythrocyte and plasma magnesium (ErMg and PlMg) and erythrocyte 2,3-DPG were measured three times over a period of 2 months in a grou p of 11 athletes who were training for a marathon. The concentration o f 2,3-DPG was found to be significantly increased at the end of the 1s t month (P < 0.05) compared to its level at the beginning of the study . However, at the end of the 2nd month, it was significantly lower (P < 0.05) than at the end of the 1st month. This decrease might have bee n due to the reduction in the intensity of training, despite an increa se in the training distance. Both ErMg and PlMg did not change signifi cantly after the 1st and 2nd months of training. However, the decrease of total circulating magnesium, i.e. whole blood magnesium was signif icant, after both the 1st and 2nd months, This decrease may have been due to an increased loss of magnesium or to a shift of magnesium from the blood to other compartments. We observed a significant negative co rrelation between ErMg and 2,3-DPG after the 1st month: r = -0.59, P < 0.05. We hypothesized that this inverse relationship might have been due to the sympathetic stimulation secondary to physical stress. Furth ermore, in view of the mechanism of binding ErMg and 2,3-DPG by haemog lobin, the negative correlation between ErMg and 2,3-DPG might have be en due to the relative tissue hypoxia that accompanies aerobic exercis e.