The Effect of Heavy Resistance Exercise on Circadian Rhythm of Salivary Cortisol in Male Body Building Athletes. (English)

Background: The aim of the present study was to evaluate the effect of heavy resistance exercise on the circadian rhythm of salivary cortisol in male body building athletes. Methods: In this balanced, crossover study, 15 healthy resistance-trained men (mean age, weight and height: 21.45 ± 1.10 years, 76.50 ± 4.20 kg, and 178.30 ± 3.60 cm, respectively) with three years of previous experience in resistance exercise were selected. At the time of study, the subjects were involved in a resistance training program of at least three sessions per week. The testing period included two test days per week, incorporating a total of two days of "rest" and two days of "exercise". Subjects were randomly selected to participate on the "rest" and "exercise" days. The heavy resistance exercise protocol consisted of three, ten-repetition sets using 75% of one repetition maximum (1RM). Saliva samples were obtained every two hours for a maximum of 16 hours during each testing day. The repeated measures analysis of variance (ANOVA) was followed by post-hoc LSD test. The significance level was considered as P ≤ 0.05. Findings: There was a significant increase in the level of salivary cortisol immediately after the heavy resistance exercise session (P ≤ 0.05). There were no significant differences between the exercise and control days in circadian rhythm of salivary cortisol (P ≥ 0.05). Conclusion: This study showed that heavy resistance exercise had a significant effect on cortisol release immediately post exercise, but did not significantly affect the waking circadian rhythm in male body building athletes. [ABSTRACT FROM AUTHOR]

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