High cortisol awakening response measured on day following high-intensity exercise

Recent field studies have reported the effects of exercise on the cortisol awakening response (CAR); however, no study has experimentally examined the effects. The purpose of this study was to investigate the effect of exercise intensity on CAR among 14 healthy male university students. Participants rested for 20 min (control condition) and exercised on a cycle ergometer for 20 min at 40% (low), 60% (moderate), and 80% (high) intensity of V・O2max on separate days. Saliva samples were collected 10 times as follows: 1) before and 2) immediately after the experimental session, 3) 10 min, 4) 20 min, and 5) 30 min into the recovery period, 6) 9 PM and 7) 11 PM in the evening following the session, 8) immediately after awakening, 9) 15 min, and 10) 30 min post-awakening the day after the session. Cortisol concentration increased after the high-intensity exercise and recovered in the evening following the session. The 30 min post-awakening sampling point the day after the session of high-intensity exercise was higher than the control condition (p = .039). In addition, the higher intensity exercise condition led to the magnitude of change in CAR (CARc) (p = .006) and the area of cortisol increased under the curve (AUCi) (p = .034), making it higher than the control condition. There were no significant differences in other confounders. These results suggest that CAR showed a higher value in healthy male university students the day after performing high-intensity exercise.