Influence of time of day on the anxiolytic effects of exercise.

The purpose of this investigation was to study state anxiety responses associated with running at different times of day. Thirty volunteers (15 Female and 15 Male) who regularly exercised in the morning (n = 10), at noon (n = 10), or in the evening (n = 10) completed three running sessions at 0600 h-0800 h, 1100 h-1300 h, and 1600 h- 1800 h. A post-hoc analysis was also performed comparing individuals who ran at their preferred time (N = 18) with individuals who ran at a time different from their preferred time (N = 11). The duration and pace of these runs were based upon each runner's "preferred exertion", and this was held constant across trials for each participant. The estimated metabolic cost did not differ across the three sessions, but there was a significant difference between Female (mean = 11.4 METS) and Male (mean = 12.9 METS) runners. The dependent variables were state anxiety, perceived exertion, heart rate, tympanic temperature and blood pressure. Data were analyzed by means of repeated measures MANOVA for multifactor experiments. State anxiety was reduced significantly (p < 0.05) for both the women and men, and this effect was independent of time of day. Furthermore, this effect occurred regardless of whether or not the individual's usual exercise time was the preferred time. Perceived exertion increased significantly (p < 0.05) from half-way through to the end of the run and this response occurred regardless of time of day. None of the remaining variables were influenced by time of day. It is concluded that the anxiolytic effects of running exercise are independent of the time of day the exercise is performed.