SUMMAR Y The purpose of this study was to evaluate homeostatic and circadian sleep process in ÔlarksÕ and ÔowlsÕ under daily life conditions. Core body temperature, subjective sleepiness and waking electroencephalogram (EEG) theta-alpha activity (6.25-9 Hz) were assessed in 18 healthy men (nine morning and nine evening chronotypes, 21.4 ± 1.9 years) during a 36-h constant routine that followed a week of a normal ÔworkingÕ sleep-wake schedule (bedtime: 23.30 h, wake time: 07.30 h). The phase of the circadian rhythm of temperature and sleepiness occurred respectively, 1.5 h (P ¼ 0.01) and 2 h (P ¼ 0.009) later in evening-than in morning-type subjects. Only morning-type subjects showed a bimodal rhythm of sleep-wake propensity. The buildup of subjective sleepiness, as quantified by linear regression, was slower in evening than in morning types (P ¼ 0.04). The time course of EEG theta-alpha activity of both chronotypes could be closely fitted by an exponential curve. The time constant of evening types was longer than that of morning types (P ¼ 0.03), indicating a slower increase in sleep pressure during extended wakefulness. These results suggest that both the circadian signal and the kinetics of sleep pressure buildup differ between the two chronotypes even under prior naturalistic conditions mimicking the usual working day.k e y w o r d s alertness, circadian rhythms, electroencephalogram, homeostatic process, morningness/eveningness, spectral analysis

We measured the effects of slow-release caffeine (SRC) and melatonin (Mlt) on sleep and daytime sleepiness after a seven-time zone eastbound flight. In a double-blind, randomized, placebo-controlled study, each of three groups of nine subjects was given either 300 mg SRC on recovery day 1 (D1) to D5 (0800) or 5 mg Mlt on preflight D-1 (1700), flight day D0 (1600), and from D1 to D3 (2300), or placebo (Pbo) at the same times. Nighttime sleep was evaluated by polysomnography and daytime sleepiness from measurements of sleep latencies and continuous wrist actigraphy. Compared with baseline, we found a significant rebound of slow-wave sleep on night 1 (N1) to N2 under Pbo and Mlt and a significant decrease in rapid eye movement sleep on N1 (Pbo) and N1-N3 (Mlt). Sleepiness was objectively increased under Pbo (D1-D6) and Mlt (D1-D3). SRC reduced sleepiness but also tended to affect sleep quality until the last drug day. In conclusion, both drugs have positive effects on some jet lag symptoms after an eastbound flight: SRC on daytime sleepiness, and Mlt on sleep.

Four weeks of interval training induced an improvement in endurance performance. However, short-term exposure to hypoxia (approximately 114 min.wk(-1)) did not elicit a greater increase in performance or any hematological modifications.

This study aimed to investigate the effects of a short-term period of intermittent hypoxic training (IHT) on cycling performance in athletes. Nineteen participants were randomly assigned to two groups: normoxic (NT, n = 9) and intermittent hypoxic training group (IHT, n = 10). A 3-week training program (5 x 1 h-1 h 30 min per week) was completed. Training sessions were performed in normoxia (approximately 30 m) or hypoxia (simulated altitude of 3,000 m) for NT and IHT group, respectively. Each subject performed before (W0) and after (W4) the training program, three cycling tests including an incremental test to exhaustion in normoxia and hypoxia for determination of maximal aerobic power (VO2max) and peak power output (PPO) as well as a 10-min cycle time trial in normoxia (TT) to measure the average power output (P(aver)). No significant difference in VO2max was observed between the two training groups before or after the training period. When measured in normoxia, the PPO significantly increased (P < 0.05) by 7.2 and 6.6% in NT and IHT groups, respectively. However, only the IHT group significantly improved (11.3%; P < 0.05) PPO when measured in hypoxia. The NT group improved (P < 0.05) P(aver) in TT by 8.1%, whereas IHT group did not show any significant difference. Intermittent training performed in hypoxia was less efficient for improving endurance performance at sea level than similar training performed in normoxia. However, IHT has the potential to assist athletes in preparation for competition at altitude.

Some long work or shift work schedules necessitate an elevated and prolonged level of vigilance and performance but often result in sleep deprivation (SD), fatigue and sleepiness, which may impair efficiency. This study investigated the effects of a slow‐release caffeine [(SRC) at the daily dose of 600 mg] on vigilance and cognitive performance during a 64 h continuous wakefulness period. Sixteen healthy males volunteered for this double‐blind, randomised, placebo controlled, two‐way crossover study. A total of 300‐mg SRC or placebo (PBO) was given twice a day at 21:00 and 9:00 h during the SD period. Vigilance was objectively assessed with continuous electroencephalogram (EEG), the multiple sleep latency tests (MSLT) and wrist actigraphy. Cognitive functions (information processing and working memory), selective and divided attention were determined with computerised tests from the AGARD‐NATO STRES Battery (Standardised Tests for Research with Environmental Stressors). Attention was also assessed with a symbol cancellation task and a Stroop’s test; alertness was appreciated from visual analogue scales (VAS). Tests were performed at the hypo (02:00–04:00 h, 14:00–16:00 h) and hypervigilance (10:00–12:00 h, 22:00–00:00 h) periods during SD. Central temperature was continuously measured and safety of treatment was assessed from repeated clinical examinations. Compared with PBO, MSLT showed that SRC subjects were more vigilant from the onset (P=0.001) to the end of SD (P < 0.0001) whereas some cognitive functions were improved till the thirty third of SD but others were ameliorated through all the SD period and alertness was better from the thirteenth hour of SD, as shown by Stroop’s test (P=0.048). We showed that 300‐mg SRC given twice daily during a 64‐h SD is able to antagonize the impairment produced on vigilance and cognitive functions.