The aim of this study was to assess the effect of time-of-day-specific training on the diurnal variations of short-term performances in boys. Twenty-four boys were randomized into a morning-training-group (07:00–08:00h; MTG), an evening training-group (17:00–18:00h; ETG) and a control-group (CG). They performed four tests of strength and power (unilateral isometric maximal voluntary contraction of the knee extensor muscles, Squat-Jump, Counter-Movement-Jump and Wingate tests) at 07:00 and 17:00h just before (T0) and after 6 weeks of resistance training (T1). In T0, the results revealed that short-term performances improved and oral temperature increased significantly from morning to afternoon (amplitudes between 2.36 and 17.5% for both oral temperature and performances) for all subjects. In T1, the diurnal variations of performances were blunted in the MTG and persisted in the ETG and CG. Moreover, the training program increase muscle strength and power especially after training in the morning hours and the magnitude of gains was greater at the time-of-day-specific training than at other times. In conclusion, these results suggest that time-of-day-specific training increases the child’s anaerobic performances specifically at this time-of-day. Moreover, the improvement of these performances was greater after morning than evening training.
H. Souissi, H. Chtourou, and A. Chaouachi are with Research Laboratory “Sports Performance Optimization” National Center of Medicine and Science in Sports (CNMSS), Tunis, Tunisia. Dogui is with the Research Unit “Neurophysiology of Vigilance, Attention, and Performances” 99/UR/08-23, Service of Functional Exploration of the Nervous System, CHU Sahloul, Sousse, Tunisia. K. Chamari and N. Souissi are with Research Laboratory “Sports Performance Optimization” National Center of Medicine and Science in Sports (CNMSS), Tunis, Tunisia. Amri is with Laboratory of Functional Neurophysiology and Pathology, Faculty of Sciences Tunis, Tunisia.