The purpose of this study was to investigate the existence of oxidative damage from oxidative stress, and to clarify the fluctuation of antioxidant vitamins after strenuous endurance exercise. Twenty- seven male triathletes (36.7 ± 9.6 yr) who participated in the Ironman Japan '93 in Lake Biwa (3.8 km swim, 180.2 km bike, 42.2 km run, average duration time : 10 hr 39 min.) were examined. We took blood samples before, immediately after and one day after the race to determine the serum levels of thiobarbituric acid reactive substances (TBARS) as an index of lipid peroxidation, α-tocopherol (α-Toc), β-carotene and vitamin C.
　A significant decrease in serum TBARS level and a significant increase in serum α-Toc level were observed immediately after the race. However, excess vitamin E was not taken three days prior to and during the race by the subjects. As vitamin C concentration in serum was high immediately after the race, serum vitamin C could be regenerating serum vitamin E. Furthermore, serum α-Toc may be mobilized from tissues which stored α-Toc after the strenuous endurance exercise.
　A significantly decreased β-carotene level was also observed immediately after the race. This phenomenon indicates that β-carotene was consumed to scavenge free radicals and initial lipid peroxidation had occurred in serum.
　A significant positive correlation between the rate of change in serum TBARS and serum β-carotene was found immediately after the race. This finding indicates that the decrease of serum TBARS may be partly caused by the consumption of serum β-carotene after the strenuous endurance exercise.
　These data suggest that the antioxidant system induced by prolonged exercise protects the body against oxidative damage from oxidative stress in strenuous endurance exercise.

DESCENTE SPORTS SCIENCE Vol.15/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE