Diurnal variation in temperature, mental and physical performance, and tasks specifically related to football (soccer)

Football (soccer) training and matches are scheduled at different times throughout the clay. Association football involves a variety of fitness components as well as psychomotor and game-related cognitive skills. The purpose of the present research, consisting of two separate studies, was to determine whether game-related skills varied with time of day in phase with global markets of both performance and the body clock. In the first study, eight diurnally active male association football players (19.1 +/- 1.9 yrs of age; mean +/- SD) with 10.8 +/- 2.1 yrs playing experience participated. Measurements were made on different days at 08:00, 12:00, 16:00, and 20:00 It in a counterbalanced manner. Time-of-day changes in intra-aural temperature (used as a marker of the body clock), grip strength, reaction times, flexibility (markers of aspects of performance), juggling and dribbling tasks, and wall-volley test, (football-specific skills) were compared. Significant (repeated measures analysis of variance, ANOVA) diurnal variations were found for body temperature (p < 0.0005), choice reaction time (p < 0.05), self-rated alertness (p < 0.0005), fatigue (p < 0.05), forward (sit-and-reach) flexibility (p < 0.02), and right-hand grip strength (p < 0.02), but not left-hand grip strength (p = 0.40) nor whole-body (stand-and-reach) flexibility (p = 0.07). Alertness was highest and fatigue lowest at 20:00 h. Football-specific skills of juggling performance showed significant diurnal variation (p < 0.05, peak at 16:00 h), whereas performance on the wall-volley test tended to peak at 20:00 It and dribbling showed no time-of-day effect (p = 0.55). In a second study, eight diurnally active subjects (23.0 +/- 0.7 yrs of age) completed five test sessions, at the same times as in the first study but with a second session at 08:00 h. Test-re-test comparisons at 08:00 It for all components indicated good reliability. Intra-aural temperature showed a significant time-of-day effect (p < 0.001) with mean temperature at 16:00 h (36.4 degrees C) higher than at 08:00 h (35.4 degrees C). There was no significant effect of chronotype on the temperature acrophase (peak time) (p > 0.05). Diurnal variation was found for performance tests, including sit-and-reach flexibility (p < 0.01) and spinal It yper-ex tension (p < 0.05). Peaks