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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.

The purpose of this study was to examine the time-of-day effects on short-term performances in boys. In a balanced and randomized study design, 20 boys performed four anaerobic tests of strength and power (grip strength, Squat-Jump, Five-jump and cycle Wingate tests) at 08:00, 14:00 and 18:00 hr on separate days. The results showed a time-of-day effect on oral temperature. Analysis of variance revealed a significant time-of-day effect for short-term performances for strength, cycle, and jump tests. The post hoc analysis revealed that performances improved significantly from morning to afternoon but no significant differences were noticed between 14:00 and 18:00 hr. The differences between the morning and the afternoon (the highest value measured either at 14:00 or at 18:00 hr) reached 5.9% for grip strength, 3.5% for the squat jump test, 5% for the five jump test, and 5.5% for P(peak) and 6% for P(mean) during the Wingate test. A significant positive correlation was found between temperature and short-term performances. In conclusion, a time-of-day effect in the child's maximal short-term exercise performances exists in relation with core temperature. Such variations would have pronounced effects when expressed in training programs and competitions.

The purpose of this study was to determine whether delaying bedtime or advancing rising time by 4 h affects anaerobic performance of individuals the following day in the morning and afternoon. Eleven subjects participated in the study, during which we measured the maximal, peak, and mean powers (i.e., P(max) [force-velocity test], P(peak), and P(mean) [Wingate test], respectively). Measurements were performed twice daily, at 07:00 and 18:00 h, following a reference normal sleep night (RN), a partial sleep deprivation timed at the beginning of the night (SDB), and a partial sleep deprivation timed at the end of the night (SDE), and oral temperature was measured every 4 h. Each of the three experimental conditions was separated by a one-week period. Our results showed a circadian rhythm in oral temperature, and analysis of variance revealed a significant sleep x test-time effect on peak power (P(peak)), mean power (P(mean)), and maximal power (P(max)). These variables improved significantly from the morning to the afternoon for all three experimental conditions. Whereas the morning-afternoon improvement in the measures was similar after the RN and SDB conditions, it was smaller following the SDE condition. There was no significant difference in the effect of the two sleep-deprivation conditions on anaerobic performances at 07:00 and at 18:00 h under the SDB condition in comparison with the post-reference night. However, the performance variables were significantly lower at 18:00 h after the SDE condition. In conclusion, a 4 h partial sleep deprivation at the end of the night appears to be more disturbing than partial sleep deprivation at the beginning of the night.

This study examined the effects of Ramadan fasting on anaerobic performances and their diurnal fluctuations. In a balanced and randomized study design, 12 subjects were measured for maximal power (P(max); force-velocity test), peak power (P(peak)), and mean power (P(mean)) with the Wingate test at 07:00, 17:00, and 21:00 h on four different occasions: one week before Ramadan (BR), the second week of Ramadan (SWR), the fourth week of Ramadan (ER), and two weeks after Ramadan (AR). There was an interval of 28 h between any two successive tests. Oral temperature was measured before each test. Under each condition, the results showed a time-of-day effect on oral temperature. Analysis of variance revealed a significant (Ramadanxtime-of-day of test) interaction effect on P(max). This variable improved significantly from morning to evening before Ramadan (1.1+/-0.2 W x kg(-1)), during the second week of Ramadan (0.6+/-0.2 W x kg(-1)), and two weeks after the end of Ramadan (0.9+/-0.2 W x kg(-1)). However, daily fluctuations disappeared during the fourth week of Ramadan. For P(peak) and P(mean), there was no significant Ramadan x test-time interaction. These variables improved significantly from morning to evening before Ramadan ([1+/-0.3 W x kg(-1)] for P(peak) and [1.7+/-1.6 W x kg(-1)] for P(mean)) and in the second week of Ramadan ([0.9+/-0.6 W x kg(-1)] for P(peak) and [1.7+/-1.5 W x kg(-1)] for P(mean)). However, they were not affected by time-of-day in the fourth week of Ramadan. Considering the effect of Ramadan on anaerobic performances, in comparison with before Ramadan, no significant difference was observed during Ramadan at 07:00 h. The variables were significantly lower in the second week of Ramadan and in the fourth week of Ramadan at 17:00 h and 21:00 h. P(mean) was not affected during the second week of Ramadan. In conclusion, the time-of-day effect on anaerobic power variables tends to disappear during Ramadan. In comparison with the period before Ramadan, anaerobic performances were unaffected in the morning but impaired in the evening during Ramadan.