One night of reduced sleep subsequently increased food intake and, to a lesser extent, estimated physical activity-related energy expenditure in healthy men. These experimental results, if confirmed by long-term energy balance measurements, suggest that sleep restriction could be a factor that promotes obesity. This trial was registered at clinicaltrials.gov as NCT00986492.

Although sleep and exercise may seem to be mediated by completely different physiological mechanisms, there is growing evidence for clinically important relationships between these two behaviors. It is known that passive body heating facilitates the nocturnal sleep of healthy elderly people with insomnia. This finding supports the hypothesis that changes in body temperature trigger somnogenic brain areas to initiate sleep. Nevertheless, little is known about how the core and distal thermoregulatory responses to exercise fit into this hypothesis. Such knowledge could also help in reducing sleep problems associated with nocturnal shiftwork. It is difficult to incorporate physical activity into a shiftworker's lifestyle, since it is already disrupted in terms of family commitments and eating habits. A multi-research strategy is needed to identify what the optimal amounts and timing of physical activity are for reducing shiftwork-related sleep problems. The relationships between sleep, exercise and diet are also important, given the recently reported associations between short sleep length and obesity. The cardiovascular safety of exercise timing should also be considered, since recent data suggest that the reactivity of blood pressure to a change in general physical activity is highest during the morning. This time is associated with an increased risk in general of a sudden cardiac event, but more research work is needed to separate the influences of light, posture and exercise per se on the haemodynamic responses to sleep and physical activity following sleep taken at night and during the day as a nap.

The cytokines interleukin 1 (IL 1) and interferon (IFN) are immune response modifiers that are also pyrogenic and somnogenic. Tumor necrosis factor (TNF) (cachectin) is another pyrogenic monocyte product whose production can be elicited by somnogenic agents such as endotoxin. Human recombinant TNF (rTNF), therefore, was assayed for somnogenic activity. Intravenous (iv) or intracerebroventricular (ICV) injections of rTNF enhanced slow-wave sleep (SWS) and electroencephalographic slow-wave (0.5-4.0 Hz) activity. Recombinant TNF also suppressed rapid-eye-movement sleep (REM) and induced biphasic fevers whether given by intravenous or ICV injection. Responses to rTNF were compared with those elicited by human recombinant beta-IL 1 (rIL 1). Sleep responses elicited by rIL 1 were similar to those previously reported for native IL 1 and to those elicited by rTNF. However, unlike rTNF, rIL 1 induced monophasic fevers. Animal behavior and brain temperature changes that occur during the transition from one arousal state to another remained undisturbed after either rTNF or rIL 1 treatment. The fact that TNF and IL 1 as well as other immunoactive substances, e.g., IFN, muramyl peptides, and endotoxin, enhance SWS suggests that SWS is linked to the immune response. We conclude that TNF, in addition to IL 1 and IFN, is an endogenous somnogen.

The purpose of this study was to evaluate the effects of time of day on aerobic contribution during high-intensity exercise. A group of 11 male physical education students performed a Wingate test against a resistance of 0.087 kg . kg(-1) body mass. Two different times of day were chosen, corresponding to the minimum (06:00 h) and the maximum (18:00 h) levels of power. Oxygen uptake (.VO(2)) was recorded breath by breath during the test (30 sec). Blood lactate concentrations were measured at rest, just after the Wingate test, and again 5 min later. Oral temperature was measured before each test and on six separate occasions at 02:00, 06:00, 10:00, 14:00, 18:00, and 22:00 h. A significant circadian rhythm was found in body temperature with a circadian acrophase at 18:16+/-00:25 h as determined by cosinor analysis. Peak power (P(peak)), mean power (P(mean)), total work done, and .VO(2) increased significantly from morning to afternoon during the Wingate Test. As a consequence, aerobic contribution recorded during the test increased from morning to afternoon. However, no difference in blood lactate concentrations was observed from morning to afternoon. Furthermore, power decrease was greater in the morning than afternoon. Altogether, these results indicate that the time-of-day effect on performances during the Wingate test is mainly due to better aerobic participation in energy production during the test in the afternoon than in the morning.

The influence of time of day on elbow flexion torque was studied. Thirteen physical education students, 7 males and 6 females, made maximal and submaximal isometric contractions at 90 degrees of elbow flexors using a dynamometer. The torque developed was measured on each contraction. The myoelectric activity of the biceps muscle was also measured at the same time by surface electromyography (EMG) and quantified from the root mean square (RMS) activity. Torque and surface EMGs were measured at 6:00, 9:00, 12:00, 15:00, 18:00, 21:00, and 24:00 h over the same day. Oral temperature before each test session was measured on each occasion after a 30-min rest period. We observed a diurnal rhythm in elbow flexor torque with an acrophase at 18:00 h and a bathyphase at 6:00 h, in phase with the diurnal rhythm in oral temperature. However, the diurnal rhythm of temperature did not appear to have any influence on the torque. Links between neuromuscular efficiency and RMS/torque ratio were evaluated by measuring muscle activity along with torque. We also assessed variations in the level of maximal activity of the muscle under maximal voluntary contraction. Neuromuscular efficiency fluctuated during the day, with maximal and minimal efficiency at 18:00 h and 9:00 h, respectively, whereas activation level was maximal at 18:00 h and minimal at 9:00 h. The diurnal rhythm of torque was accounted for by variations in both central nervous system command and the contractile state of the muscle.

Purpose It has been suggested that napping is the best recovery strategy for athletes. However, researches on the impacts of napping on athletic performances are scarce. The aim of this study was to determine the effects of a 30-min nap after a partial sleep deprivation, or a normal night condition, on alertness, fatigue, and cognitive and physical outcomes. Methods Thirteen national-level male karate athletes were randomized to experience nap and no-nap conditions, after either a reference or a partial sleep deprivation night. The nap lasted 30 min at 1:00 pm. The postnap testing session started at 2:00 pm by quantifying subjective alertness and fatigue. Cognitive and physical performances were respectively measured before and after the karate-specific test (KST) by simple reaction time (SRT) test, lower reaction test (LRT), mental rotation test (MRT), squat jump (SJ), and counter movement jump (CMJ) tests. Results After a reference night, the nap improved alertness and cognitive outcomes (SRT, LRT, and MRT). No effects on subjective fatigue and physical performances were found. After a partial-sleep deprivation, the nap restored subjective alertness and the decrement in performances caused by sleep loss in most of the tests (MRT, LRT, and KST), but no effects were observed in subjective fatigue and CMJ. After the fatigue induced by KST, there was an ergogenic effect of the nap on the physical performances (CMJ and SJ), and a partial psychogenic effect on the cognitive performances (LRT). Conclusions A 30-min nap enhances cognitive outcomes. It is also an effective strategy to overcome the cognitive and physical deteriorations in performances caused either by sleep loss or by fatigue induced by exhaustive trainings in the afternoon.

The aim of this study was to check the combined and/or dissociated influences of time-of-day and sleep deprivation on postural control. Twenty subjects participated in test sessions which took place at 6:00 am, 10:00 am, 2:00 pm and 6:00 pm either after a normal night's sleep or after a night of total sleep deprivation. Postural control was evaluated by COP surface area, LFS ratio and Romberg's index. The results showed that postural control fluctuates diurnally according to three different periods, pronounced by sleep deprivation: (1) at 6:00 am, there was no modification by sleep deprivation; (2) at 10:00 am and 2:00 pm, an interaction effect was observed for COP surface area and LFS ratio after sleep deprivation. Values of COP surface area were significantly higher (P < 0.01) following the night of sleep deprivation than after the normal night's sleep (139.36 ± 63.82 mm² vs. 221.72 ± 137.13 mm² and 143.78 ± 75.31 mm² vs. 228.65 ± 125.09 mm², respectively); (3) at 6:00 pm, the LFS ratio was higher than during the two other periods (P < 0.001) whereas COP surface area decreased to the level observed at 6:00 am. At this time-of-day, only the LFS ratio was significantly increased (P < 0.05) by the night of sleep deprivation (0.89 ± 0.14 vs. 1.03 ± 0.30). This temporal evolution in postural control does not seem to be related to any deterioration in visual input as Romberg's index (150.09 ± 97.91) was not modified, regardless of the test session.

The purpose of the present study was to examine the effects of active warm-up duration on the diurnal fluctuations in anaerobic performances. Twelve physical education students performed a medical stress test ( progressive test up to exhaustion) and four Wingate tests (measurement of peak power [P peak ], mean power [P mean ], and fatigue index during an all-out 30 s cycling exercise). The tests were performed in separate sessions (minimum interval = 36 h) in a balanced and randomized design at 08:00 and 18:00 h, either after a 5 min (5-AWU) or a 15 min active warm-up (15-AWU). AWU consisted of pedaling at 50% of the power output at the last stage of the stress exhausting test. Rectal temperature was collected throughout the sessions. A two-way ANOVA (warm-up × time of day) revealed a significant interaction for P peak (F (1.11) = 6.48, p < 0.05) and P mean (F (1.11) = 5.84, p < 0.05): the time-of-day effect was significant ( p < 0.001) in contrast with the effect of warm-up duration ( p > 0.05). P peak and P mean improved significantly from morning to afternoon after both 5-AWU and 15-AWU, but the effect of warm-up duration was significant in the morning only. Indeed, the values of P peak or P mean were the same after both warmup protocols in the afternoon. For rectal temperature, there was no interaction between time-of-day and warm-up duration. Rectal temperature before and after both the warm-up protocols was higher in the afternoon, and the effect of warm-up duration on temperature was similar at 08:00 and 18:00 h. In conclusion, the interpretation of the results of the anaerobic performance tests should take into account time-of-day and warm-up procedures. Longer warm-up protocols are