The effect of heavy resistance exercise on the circadian rhythm of salivary testosterone in men

Circadian rhythms of serum testosterone concentrations in men have been sho wn, in general, to be highest in the morning and lowest in the evening. Thu s, the purpose of this investigation was to determine the effects of acute resistance exercise upon the waking circadian rhythm of salivary testostero ne over 2 days (with or without resistance exercise). The subjects included ten resistance-trained men (with at least 1 year of lifting experience) wi th the following characteristics [mean (SD)]: age 21.6 (1.1) years; height 177.8 (9.5) cm; body mass 80.5 (11.5) kg; percent body fat 7.9 (1.7)%. A ma tched, randomized, crossover study design was used such that each subject w as tested under both the resistance exercise and control (no exercise) cond itions. The resistance exercise protocol consisted of ten exercises perform ed for three sets of ten repetitions maximum with 2 min of rest between set s. Saliva sample 1 was collected at 0615 hours and resistance exercise bega n immediately afterwards at approximately 0620 hours, and sample 2 was coll ected at 0700 hours, which corresponded approximately to a mid-exercise (or control) time point. Saliva samples were then obtained every hour on the h our from 0800 hours until 2200 hours. No significant differences were obser ved between the exercise and resting conditions for salivary testosterone, with the exception of a significant decrease at 0700 hours during the resis tance exercise protocol. The results of this investigation indicate that re sistance exercise does not affect the circadian pattern of salivary testost erone secretion over a 16-h waking period in resistance-trained men.