Ultradian rhythmicity and induced changes in salivary testosterone

Testosterone and cortisol respond to exercise stimuli and modulate adaptation. Episodic basal secretion of these hormones may modify the responsiveness of these hormones. We sought to identify episodic steroid secretion via frequent salivary sampling and investigate any interaction between ultradian rhythmicity and induced changes in testosterone. Salivary testosterone and cortisol concentrations of seven males (age 20–40 years) were measured every 10 min between 0800 and1600 h on three consecutive days. On either the second or third day, three interventions designed to elicit a hormonal response were randomly assigned: sprint exercise (two 30-s maximal efforts on a cycle ergometer); boxing (two 30-s maximal punching efforts); and a violent video game (10 min of player vs. player combat). On the other days subjects were inactive. Testosterone data on non-intervention days suggested pulsatile secretion with a pulse interval of 47 ± 9 min (mean ± SD). The sprint intervention substantially affected hormones: it elicited a small transient elevation in testosterone (by a factor of 1.21; factor 90% confidence limits ×/÷1.21) 10 min after exercise, and a moderate elevation in cortisol peaking 50 min post-exercise (factor 2.3; ×/÷2.6). The testosterone response correlated with the change in testosterone concentration in the 10 min prior to the sprint (r = 0.78; 90% CL 0.22–0.95) and with a measure of randomness in testosterone fluctuations (r = 0.83; 0.35–0.96). Thus, the salivary testosterone response to exercise may be dependent on the underlying ultradian rhythm and aspects of its regulation. This interaction may have important implications for adaptation to exercise.