Effects of chronotype and time of day on mood responses to CrossFit training.

Morningness-eveningness, time of day, and physical exercises have been shown to influence mood states. This study aimed to test whether impact of physical exercise on mood depends on time of day and chronotype. Ninety-four participants (age 32 ± 6 years; 34% females; weekly training volume 4 ± 1 hours) filled the Composite Scale of Morningness and reported their current mood using the UWIST Mood Adjective Checklist before and after a 60-min long CrossFit training session which took part in the morning (beginning at 6:30 or 7:45) or in the evening (beginning at 19:30 or 20:45). In this quasi-experiment the measurements were taken by the occasion of the participants' usual training, in their preferred hours. There were only a few evening-types in the studied sample, while morning and intermediate chronotypes were over-represented. Participation in CrossFit training resulted in mood improvement consisting of increase in energetic arousal (η2 = 0.29) and hedonic tone (η2 = 0.47) and reduction of tense arousal (η2 = 0.14), all significant at p = 0.001. Furthermore, CrossFit training during morning hours boosted mood in the intermediate/evening chronotype group to the levels observed in morning chronotypes (η2 = 0.29, p < 0.05, for the three-way interaction effect). We conclude that participation in intense physical exercise, such as CrossFit training, may allow compensation for the negative effects of non-optimal time of day on experienced moods, particularly in the case of neither/evening-types.