Physiologic changes during a marathon, with special reference to magnesium.

Abstract

In a single case study of a moderately trained, healthy man, physiologic changes during a marathon are reported. Blood was drawn prior to the race, at 1 hour and 2 hours into the race, at the end of the race, and after 1 hour of recovery. By 1 hour into the race, norepinephrine, epinephrine, and dopamine had increased nearly nine-fold, two-fold and five-fold, respectively. After 1 hour of recovery, epinephrine had returned to the pre-race value but norepinephrine and dopamine were still elevated. Cortisol increased gradually and was more than doubled by the end of the race. It was still elevated after 1 hour of recovery. White blood cells gradually increased, reaching their maximum value at the end of the race; a four-to-five-fold increase. Thromboxane B2, which had an inverse relationship to serum magnesium, was below the pre-race value for the first 2 hours but increased nine-fold by the end of the race. Serum magnesium increased from 1.44 meq/l to 1.68 meq/l at 2 hours into the marathon, dropped to 1.07 meq/l by the end of the race, and returned to its pre-race value by 1 hour of recovery. The decrease in serum magnesium at the end of the race may be associated with increased plasma free fatty acid levels.

Alterations of ionized Mg2+ in human blood after exercise

“…However, ionized and total extracellular Mg did not change in the same relation suggesting that part of the decrease in ionized Mg 2+ was evoked by binding of Mg 2+ to chelators in serum or towards cell membranes. Franz et al suggested that increased plasma free fatty acids during and after a marathon could be responsible for the observed decrease in Mg (Franz et al, 1985). However, this mechanism seems unlikely for the present short term exercise protocol.…”

“…However, other workers have reported both increasing and decreasing values for total [Mg] i after exercise (Casoni et al, 1990;Deuster et al, 1987;Lijnen et al, 1988). The reason for these controversial findings is not yet clear and might depend on different methodological approaches and/or exercise protocols (Franz et al, 1985;Rayssiguier et al, 1990).…”

Minerals: Exercise performance and supplementation in athletes*

“…This change could reflect a redistribution of serum magnesium into either muscle tissue, adipocytes, or red blood cells (McDonald and Keen, 1988). In a case study of a marathon runner during a race, Franz et al (1985) found that during the race serum magnesium increased followed by a decrease by the end of the race. Deuster et al (1987) reported that a high intensity anaerobic exercise produced a significant increase in urinary excretion of magnesium on the day of the exercise and then returned to normal.…”

Consequences of magnesium deficiency on the enhancement of stress reactions; preventive and therapeutic implications (a review).

“…Runners exhibited increased excretion of both catecholamines and CS; Mg supplements significantly decreased their CS ex cretion [9]. A marathon runner, whose CS levels gradually increased during a race, attained twice pre-race values at the end of the race [26]. A mixed CS with glucocorticosteroid (GCS) and mineralocorticosteroid (MCS) activity caused negative Mg balance in normal volunteers, mostly by interfering with intestinal Mg absorption [27].…”