Effect of strenuous exercise on serum lithium level in man.

The authors examined the effect of strenuous exercise on the serum lithium levels of four healthy, conditioned athletes who were stabilized on lithium carbonate for 7 days and who ran a 20-km race under hot, humid conditions. The subjects became substantially dehydrated during the race, and their serum lithium levels decreased, suggesting that sweat lithium loss may be substantial. (The sweat-to-serum ratio for lithium exceeded that for sodium by a factor of 4.) The authors conclude that contrary to widely held belief, heavy sweating may not increase the risk of lithium intoxication.