Triathlon competition induced a transient immunosuppressive change in the peripheral blood of athletes.

This study was designed to determine whether or not physical and psychological stress of triathlon competition causes an immunosuppressive change in the peripheral blood of athletes, if it does occur, how long does it take to recover. Fifteen healthy men, aged 19 to 40, volunteered for this study. Peripheral blood was drawn four times at approximately the same time on the following days; one day before the race, immediately after, one day and eight days after, and served for determining circulating leucocyte and lymphocyte subset counts, in vitro lymphocyte proliferative response and natural killer activity. The results showed that triathlon competition caused considerable changes in the cell counts of peripheral blood leucocyte and lymphocyte subsets, and a transient reduction in vitro lymphocyte proliferative response and natural killer activity, all of which returned to pre-race levels in one to eight days after the race.