Abstract

Serum testosterone concentration was determined before and after physical activities of different duration. The subjects under study were: (1) 7 competitive walkers before and after a 20-km race (average race time 1 h 30 min); (2) 9 middle-distance runners before and after 1-h training; (3) 16 marathon runners before and after a marathon run (average running time 2 h 33 min); (4) 30 ultramarathon runners before and after a 107-km race (average running time 14 h). Serum testosterone increased by 51.8 (NS) in competitive walkers, by 38.2 in middle-distance runners, and by 44.9 in marathon runners; it decreased by 31.9 in the ultramarathon runners. These findings, and similar variations of serum testosterone observed in an ultramarathon runner during a 6-h training session, suggest that serum testosterone increases during physical activities lasting up to 3 h and decreases to or even below the preexercise values for longer physical efforts. The possible mechanisms responsible for these differences are discussed. Verf.-Referat