Time-of-day effects on physical performance and perceptual responses in Brazilian Jiu-Jitsu athletes

This study investigated how the time of day affects physical performance and perceptual responses in Brazilian Jiu-Jitsu (BJJ) athletes. Given the significance of circadian rhythms on athletic capabilities, we aimed to determine whether performance variations occur across different times of the day (morning, 10:00-11:00h; afternoon, 14:00-15:00h; and evening, 18:00-19:00h) and if these effects differ by sex. In total, 23 BJJ athletes (9 females, 14 males) participated in this study. The athletes performed physical tests including the maximal isometric handgrip strength test (HGS), Kimono Grip Strength Endurance Test (KGST), and a BJJ-specific test (BJJST) in the morning, afternoon, and evening. Perceptual responses (RPE) were also collected before the BJJST. Results showed enhanced physical performance in the evening for most tests, including increased HGS and superior performance in the KGST and BJJST for both sexes (p < 0.05). No significant differences were observed in perceptual responses (RPE) or between sexes (p > 0.05). We conclude that BJJ athletes generally perform better in the evening compared to other times of the day, with notable improvements in HSG and specific BJJ tests. The study highlights the importance of aligning training schedules with an athlete's circadian rhythm to optimize performance, leading to more efficient training sessions and improved long-term performance outcomes.