Using atomic absorption spectrophotometry, we measured serum mineral (Fe, Cu, Z n, Mg, Ca, K, Na) concentrations in blood of male athletes participating in a triathlon competition held at Nakajima, Ehime in 1989. The athletes were divided into a young group (n=9, 24.2±3.6 yr) and a middle-aged group (n=9, 49.3±4.4 yr) . Blood samples were taken on the day before the competition, at the finish, on the following day and for eight days after.
Immediately after the race, the concentrations of iron, calcium and potassium were increased significantly in sera taken from both groups, and those of copper and zinc were found to be increased only in the young group. In the middle-aged group, serum magnesium and sodium concentrations were decreased significantly. On the day after the race, most of the serum mineral concentrations had returned to values similar to those measured before the race, although the serum sodium concentration in the middle-aged group was still below the previous value, and this low level persisted for eight days after the race in both groups.
Noticeable differences between the young and middle-aged groups were that recovery of increased iron concentration in serum tended to be prolonged in the middle-aged group, and the concentrations of serum copper and zinc were higher than those in the young group throughout the measurement period, with only small changes evident before and after the race. By contrast, serum potassium concentration in the middle-aged group was lower than in the young group throughout the measurement period.