When magnesium status is healthy and adequate, blood magnesium shows large swings during exercise, more than 10 times larger than when exercising in a marginal or deficient magnesium state. This wide range of blood magnesium inflow and outflow appears to allow the healthy body to fully function during the high magnesium need of vigorous exercise. Healthy magnesium stores allow for the large excretions of magnesium in urine and sweat that occur when the body is performing at peak capacity–without danger of going into a depleted magnesium state. These magnesium changes in blood and urine normalize within 24 hours after vigorous exercise in runners adequate in magnesium, unless a deficit has been induced by the exercise bout. In runners with marginal or deficit magnesium status, the blood levels do not show such wide swings of magnesium during performance, and urine losses are smaller. It is as if the body is conserving its precious store of magnesium by limiting the body’s ability to perform at its peak. Thus, it has been shown that supplemental magnesium given to deficient and marginally deficient runners allows measurably increased performance during athletic events.
It’s been known since 1983 that magnesium supplements can alleviate muscle spasms brought on by exercise. Vigorous exercise induces oxidative stress which adequate magnesium status allows the body to healthfully withstand. Vigorous running while magnesium deficient or marginally deficient can make the body more vulnerable to this extra oxidative stress. Immune changes are observed with strenuous exercise; a bout of vigorous physical exercise while in marginal or deficient magnesium status can make these immune changes larger.
It is always wise for a person engaged in vigorous physical activity to keep their magnesium status adequate and healthy, keeping in mind that their requirements are higher than the general population, that a strenuous race or long term training can deplete body magnesium, and that the modern processed food diet can be lower in nutritional magnesium than their high needs require.
Vigorous exercise, such as running in a 10K race, is often a goal of the most health-conscious individuals, not only because it brings a high sense of accomplishment, but because exercise is known to be a healthy lifestyle choice in our modern, sedentary society. Thus it behooves runners and those in vigorous exercise training to realize that nutritional magnesium status can affect the body’s ability to safely engage in such vigorous physical activity.
Reference: Nielsen, F. H. and H. C. Lukaski (2006). “Update on the relationship between magnesium and exercise.” Magnes Res 19(3): 180-9. httpss://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=17172008