The pep prescription.

This article discusses findings of a study conducted by researchers from the University of Missouri which investigated the cause of fatigue among recreational athletes. The researchers measured the amount of iron in these athletes and found that 36 percent of the women and 6 percent of the men were deficient. Few of the athletes were actually anemic but the results suggest that iron levels in their muscles were very low. That can make it harder for muscles to absorb oxygen and it can lead to fatigue. There are several possible reasons: aerobic exercise, like running, slowly drains the body of iron; a little bit of blood can leak into gut; running can squish blood cells when the feet strike the ground, and iron is required to replenish them; and people lose iron in sweat.