Increase of free and total testosterone during submaximal exercise in normal males.

The serum levels of testosterone, free testosterone, prolactin, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were measured at rest, during 45 min of exercise on a bicycle ergometer at 50% of the subjects' previously determined maximal oxygen uptake (VO2max), and during a 30-min recovery period. Ten healthy, untrained males were used as subjects. Mean serum testosterone levels increased significantly (P less than .05) over resting values at 15 min of exercise. Mean peak serum testosterone and free testosterone were significantly (P less than .01) increased during the exercise period as compared to resting values. No significant changes were measured for serum levels of LH, FSH, or prolactin during exercise. It appeared that bicycle exercise of moderate intensity significantly increased both free and total testosterone in untrained males.