Variations in serum magnesium and hormonal levels during incremental exercise.

In this study, we examined the relationship between plasma magnesium levels and hormonal variations during an incremental exercise test until exhaustion in 27, well-trained, male endurance athletes. After a warm-up of 10 min at 2 W/kg, the test began at an initial workload of 2.5 W/kg and continued with increments of 0.5 W/kg every 10 min until exhaustion. Plasma magnesium, catecholamine, insulin, glucagon, parathyroid hormone (PTH), calcitonin, aldosterone and cortisol levels were determined at rest, at the end of each stage and three, five and seven minutes post-exercise. With the incremental exercise test, no variations in plasma magnesium levels were found, while plasma adrenaline, noradrenaline, PTH, glucagon and cortisol levels increased significantly. Over the course of the exercise, plasma levels of insulin decreased significantly, but those of calcitonin remained steady. During the recovery period, catecholamines and insulin returned to basal levels. These findings indicate that the magnesium status of euhydrated endurance athletes during incremental exercise testing may be the result of the interrelation between several hormonal variations.