Comparison of the effects of acute Resistance-Aerobic training in the morning and evening on cortisol, testosterone, and insulin levels in male and female bodybuilders

Introduction: Circadian rhythm is one of the factors interfering with hormonal responses to a training session. Therefore, the aim of the present study was to compare the effect of acute resistance-aerobic training in the morning and evening on the levels of cortisol, testosterone, and insulin hormones in male and female bodybuilders. Material & Methods: Subjects included 15 male (age 27.70±3.99 years) and 15 female (age 25.90±4.10 years) bodybuilders voluntarily participated in this semi-experimental study. After obtaining informed consent, blood samples were collected before and after the training session in two separate times (8:00 a.m. and 5:00 p.m.), with a three-day recovery interval between sessions. resistance training was performed for 30 minutes, including upper and lower body resistance movements at 80% of one repetition maximum, and after a 3-minute rest, aerobic training was performed, including running on a treadmill for 20 minutes at an intensity of 75% of maximum heart rate. Blood samples were collected immediately before and after each session to assess serum cortisol, testosterone, and insulin concentrations using ELISA method. Data were analyzed using the Shapiro–Wilk test for normality, paired and independent t-tests, and repeated-measures ANOVA (p≤0.05). Results: Between-group comparisons showed that, after a session of Resistance-Aerobic training, the decrease in both cortisol and insulin hormones was greater in women in the evening and in men in the morning (p<0.05). However, the increase in testosterone in both women and men was greater in the evening (p<0.05). Conclusion: The results of the present study showed that circadian rhythm affects the responses of cortisol, testosterone, and insulin hormones to acute aerobic-resistance training in male and female bodybuilders; therefore, gender and training time in the morning and evening are intervening factors on different hormonal responses to a training session.