Effect of circadian rhythm on running-based anaerobic performance parameters of football players

The circadian rhythm is a fundamental biological timing mechanism that regulates numerous physiological processes, including body temperature, hormonal secretions, and muscle function. This rhythmic regulation can lead to time-of-day variations in anaerobic performance, particularly during short-duration, high-intensity efforts. In this context, the present study aimed to comparatively examine the effects of the circadian rhythm on running-based anaerobic performance and related physiological parameters in male soccer players. Twenty-one active male soccer players (mean age: 18.86 ± 1.68 years) with good sleep quality voluntarily participated in the study. Conducted with a single-group repeated-measures design, the experimental research involved the administration of the Running-Based Anaerobic Sprint Test (RAST) at three different times of day (09:00, 14:00, and 19:00). During each test session, data were recorded on body temperature, sprint times, power outputs (peak, mean, minimum, and relative power), fatigue index, heart rate (pre-test, during, and recovery phases), and ratings of perceived exertion. The findings indicated that sprint times recorded in the morning and afternoon sessions were significantly shorter compared to evening measurements (p<.05), while peak, mean, minimum, and relative power outputs were significantly higher at these earlier times (p<.05). In contrast, heart rate variables increased progressively throughout the day, with pre-test, mean, maximum, and recovery (1st and 2nd minute) heart rates being significantly higher in the evening than in the morning (p<.05). No significant differences were observed in minimum heart rate, perceived exertion, or fatigue index. Additionally, body temperature values showed significant time-of-day variations, being significantly higher at noon (14:00) compared to morning (09:00) and evening (19:00) measurements. In conclusion, the results of this study suggest that scheduling short-term, high-intensity training sessions in the morning or afternoon may be more favorable in terms of optimizing performance outcomes.