Magnesium is used in the body to regulate heart beat, keep muscles and nerves functioning optimally, promote bone health and boost the immune system. About 50 percent of your body’s magnesium store is found in your bones, with most of the rest located in your tissues and organs. Approximately 1 percent is found in the blood at a concentration that the body attempts to keep fairly constant. Research has shown that magnesium influences the effect of exercise on the body, and that the magnesium concentrations in the body change in response to exercise.
Magnesium and Exercise Tolerance in Heart Patients
The “British Journal of Sports Medicine” published a 2006 study that focused on the effect of oral magnesium supplementation on exercise tolerance in patients with coronary artery disease . Subjects were given 15 mmoles of magnesium twice per day for six months. The study showed that magnesium improved exercise tolerance and heart function in the test subjects. The researchers contended that magnesium reduced the chest pain usually brought on by exercise in patients with coronary artery disease.
The “Journal of Nutrition” reported on a study in 2002 that examined the effect of magnesium depletion on cardiac function and energy needs during exercise. Post-menopausal women were put on a diet supplemented with 200 mg of magnesium, followed by a non-supplemented diet. The restriction of dietary magnesium resulted in decreased magnesium concentrations in the body, which translated to poor cardiovascular function and poor energy during exercise, the study showed.
Effect of High Intensity Exercise on Magnesium Concentration
A 2006 review by Forrest Nielson and associates reported in the journal “Magnesium Research” stated that your body responds to exercise by redistributing its supply of magnesium. Concentration of magnesium in the blood increases by 5 to 15 percent after short bouts of high-intensity exercise. An increase is also seen after moderate exercise that is done over an extended period. This is a transient change, however, with plasma levels returning to normal within a day. Possible explanations put forward for this phenomenon include decreased plasma volume, muscle breakdown and transfer of magnesium out of the muscles during contractions.
Endurance Exercise and Magnesium
According to the Nielson study, there is evidence that cross country skiing, marathon running and other extended endurance exercises decrease plasma magnesium concentration. This may be the effect of increased loss of magnesium through sweat and urine, and the movement of magnesium into other areas of the body. The explanation seems to be that your body sends magnesium to the parts of the body with the greatest metabolic need, where increased energy production is required.