Plasma and red blood cell magnesium levels and plasma creatinine after a 100 km race

Magnesium homeostasis is critical for exercise performance. In this report the effect of long distance race on the erythrocyte and plasma magnesium concentration is determined in a group of 7 well-trained male amateur runners. After a 100 km race the plasma Mg2+ levels increased significantly from 0.845 +/- 0.074 to 0.934 +/- 0.099 mmol.l-1 (p < 0.05). However, the intra-erythrocyte Mg2+ concentrations were not modified significantly (2.10 +/- 0.2 mmol.l-1 versus 2.14 +/- 0.12 mmol.l-1). Creatinine plasma levels increased significantly from 73.4 +/- 3.5 mumol.l-1 to 117.6 +/- 19.4 mumol.l-1 (p < 0.01), suggesting impairment of the renal function. A significant positive correlation between plasma magnesium and plasma creatinine, r = +0.65 (p < 0.01) was found. These results suggest that an increase in the magnesium plasma levels could be related to renal failure during long-distance running.