Does time of day and player chronotype impact tennis-specific skills and physical performance?

Tennis players' success relies on tennis skills, such as groundstrokes and serves, and physical attributes, such as strength, speed and endurance. This study aimed to determine if players' tennis skills and physical attributes are influenced by time of day, chronotype or sleep-wake behaviour (SWB). Twelve male tennis players (age (years): 28.17 +/- 7.85) competing in state-level competitions wore a wrist-worn activity monitor (GT3X, Actigraph) and completed a modified version of the Consensus Sleep Diary to measure SWB. The Chalder Fatigue Scale and Morningness and Eveningness Questionnaire were used to measure players' fatigue and preferred chronotype. Mid-sleep with a sleep correction was used to determine players' current chronotype. After the baseline period, players were tested at 8:00 am, 2:00 pm and 8:00 pm, with the order of testing sessions randomised for each player. Testing sessions were separated by at least 48 hours. Players' groundstrokes, serve speed, agility, overhead medicine ball throw and Hit and Turn Test performance were measured in each session. General linear modelling revealed that backhand consistency was less in the evening compared to the morning by 17% (p = 0.020) and afternoon by 15% (p = 0.040). Maximal service velocity was less in the evening compared to the afternoon by 10.5 km/h (p = 0.041). Chronotype did not influence tennis skills or physical performance. Average and maximal backhand velocities were reduced for every hour that time at lights out, and sleep-onset time was postponed. Tennis skills, but not physical performance tests, were influenced by time of day and SWB.