Heat tolerance after total and partial acute sleep deprivation

Sleep deprivation (SD) is suggested to be associated with reduced thermo-regulatory functions. This study aimed to quantify the effect of partial (PSD) and total (TSD) 24?h SD using a standard heat tolerance test (HTT). Eleven participants underwent HTT after well-rested state, PSD and TSD. No significant physiological differences were found between the exposures but subjective discomfort was higher after TSD. Evening chronotypes' temperature during HTT was higher after TSD compared with PSD (p = 0.017). After TSD, evening chronotypes compared to intermediate chronotypes' temperature was higher during the first hour of the HTT (p?<?0.05), suggesting that thermo-regulatory function during exercise in the heat is influenced by chronotype.     

The effects of sleep deprivation and time of day on cognitive performance

The extent to which the diurnal fluctuations of different cognitive processes could be affected by sleep loss may be explored to predict performance decrements observed in the real world. Twenty healthy male subjects voluntarily took part in 8 test sessions at 06:00, 10:00, 14:00, and 18:00 h, following either a night with or without sleep in random order. Measurements included oral temperature, simple reaction time, sign cancelation, Go/NoGo, and the Purdue pegboard test. The results indicate that simple reaction time and motor coordination had morning–afternoon variations closely following the rhythms of temperature and vigilance. Inhibitory attention (Go/NoGo) presented no morning–afternoon variations. Sleep deprivation may affect the profiles of cognitive performance depending on the processes solicited. Sustained and inhibitory attention are particularly affected in the morning (after 24 and 28 waking hours), while a complex task (visuo-motor coordination) would be affected after 32 waking hours only.     

Caffeine ingestion does not affect afternoon muscle power and fatigue during the Wingate test in elite judo players

The purpose of the present study was to evaluate the effect of caffeine ingestion on elite judo players’ mood states, simple reaction time, and muscle power during the Wingate test in the afternoon. Ten elite judo players (age: 21.08 ± 1.16 years, body mass: 83.75 ± 20.2 kg, height: 1.76 ± 0.07 m) took part in this study. The performance variables were measured during two test sessions scheduled at 17:00 h, after placebo or caffeine (5 mg/k) ingestion. The results revealed an increase in anxiety and vigour (p < 0.05) and a reduction in simple reaction time (p < 0.005) following caffeine ingestion. However, muscle power and fatigue during the Wingate test were unaffected. It is concluded that afternoon caffeine ingestion has no ergogenic effect on anaerobic performance.     

Effects of partial sleep deprivation after prolonged exercise on metabolic responses and exercise performance on the following day

[Purpose]We determined the effect of partial sleep deprivation (PSD) after an exercise session on exercise performance on the following morning.[Methods]Eleven male athletes performed either a normal sleep trial (CON) or a PSD trial. On the first day (day 1), all subjects performed an exercise session consisting of 90 min of running (at 75% V˙O2max) followed by 100 drop jumps. Maximal strength (MVC) was evaluated before and after exercise. In the CON trial, the sleep duration was 23:00–7:00, while in the PSD trial, the sleep duration was shortened to 40% of the regular sleep duration. On the following morning (day 2), MVC, the metabolic responses during 20 min of running (at 75% V˙O2max), and time to exhaustion (TTE) at 85% V˙O2max were evaluated.[Results]On day 2, neither the MVC nor V˙O2 during 20 min of running differed significantly between the two trials. However, the respiratory exchange ratio was significantly lower in the PSD trial than in the CON trial (p = 0.01). Moreover, the TTE was significantly shorter in the PSD trial than in the CON trial (p = 0.01).[Conclusion]A single night of PSD after an exercise session significantly decreased endurance performance without significantly changing muscle strength or cardiopulmonary response.     

Caffeine reversal of sleep deprivation effects on alertness,mood and repeated sprint performances in physical education students

The aim of this study was to evaluate the effects of caffeine ingestion and partial sleep deprivation on mood and cognitive and physical performances. In randomised order, 12 healthy male physical education students completed four test sessions at 18:00 h after placebo or 5 mg/kg of caffeine ingestion during a baseline night (RN) (bed time: from 22:00 to 07:00 h), or during a night of partial (four hrs) sleep deprivation (PSD). During each test session, participants performed a reaction time test, a vigilance test, the 10 s Wingate cycling test during (measuring peak power (PP) and anaerobic capacity), and the 5 m multiple shuttle test (measuring peak distance (PD), total distance (TD), and fatigue index (FI)). Compared to RN, simple reaction time, vigilance, PP, PD, TD, and FI were altered by PSD the following day after placebo ingestion with increased reaction time and FI and reduced PP, PD, TD, and vigilance (p < 0.001). Moreover, during PSD condition, PP, PD, and TD were significantly higher after caffeine ingestion in comparison with placebo ingestion (p < 0.05). However, both simple reaction times and vigilance were significantly lower after caffeine ingestion in comparison with placebo during PSD (p < 0.05). Caffeine is an effective strategy to maintain physical and cognitive performances the day after PSD.     

Melatonin ingestion after exhaustive late-evening exercise improves sleep quality and quantity,and short-term performances in teenage athletes

ABSTRACT

The present study aimed to explore the effects of a single 10-mg dose of melatonin (MEL) administration after exhaustive late-evening exercise on sleep quality and quantity, and short-term physical and cognitive performances in healthy teenagers. Ten male adolescent athletes (mean ± SD, age = 15.4 ± 0.3 years, body-mass = 60.68 ± 5.7 kg, height = 167.9 ± 6.9 cm and BMI = 21.21 ± 2.5) performed two test sessions separated by at least one week. During each session, participants completed the Yo-Yo intermittent-recovery-test level-1 (YYIRT-1) at ~20:00 h. Then, sleep polysomnography was recorded from 22:15 min to 07:00 h, after a double blind randomized order administration of a single 10-mg tablet of MEL (MEL-10 mg) or Placebo (PLA). The following morning, Hooper wellness index was administered and the participants performed the Choice Reaction Time (CRT) test, the Zazzo test and some short-term physical exercises (YYIRT-1, vertical and horizontal Jumps (VJ; HJ), Hand grip strength (HG), and five-jump test (5-JT)). Evening total distance covered in the YYIRT-1 did not change during the two conditions (p > 0.05). Total sleep time (Δ = 24.55 mn; p < 0.001), sleep efficiency (Δ = 4.47%; p < 0.001), stage-3 sleep (N3 sleep) (Δ = 1.73%; p < 0.05) and rapid-eye-movement sleep (Δ = 2.15%; p < 0.001) were significantly higher with MEL in comparison with PLA. Moreover, sleep-onset-latency (Δ = –8.45mn; p < 0.001), total time of nocturnal awakenings after sleep-onset (NA) (Δ = –11 mn; p < 0.001), stage-1 sleep (N1 sleep) (Δ = –1.7%; p < 0.001) and stage-2 sleep (N2 sleep) (Δ = ?1.9%; p < 0.05) durations were lower with MEL. The Hooper index showed a better subjective sleep quality, a decrease of the subjective perception of fatigue and a reduced level of muscle soreness with MEL. Moreover, MEL improved speed and performance but not inaccuracy during the Zazzo test. CRT was faster with MEL. Morning YYIRT-1 (Δ = 82 m; p < 0.001) and 5-JT (Δ = 0.08 m; p < 0.05) performances were significantly higher with MEL in comparison with PLA. In contrast, HG, VJ and HJ performances did not change during the two conditions (p > 0.05). The administration of a single dose of MEL-10 mg after strenuous late-evening exercise improved sleep quality and quantity, selective attention, subjective assessment of the general wellness state, and some short-term physical performances the following morning in healthy teenagers.     

Effect of bright light therapy on delayed sleep/wake cycle and reaction time of athletes participating in the Rio 2016 Olympic Games

This study investigated the effect of using an artificial bright light on the entrainment of the sleep/wake cycle as well as the reaction times of athletes before the Rio 2016 Olympic Games. A total of 22 athletes from the Brazilian Olympic Swimming Team were evaluated, with the aim of preparing them to compete at a time when they would normally be about to go to bed for the night. During the 8-day acclimatization period, their sleep/wake cycles were assessed by actigraphy, with all the athletes being treated with artificial light therapy for between 30 and 45 min (starting at day 3). In addition, other recommendations to improve sleep hygiene were made to the athletes. In order to assess reaction times, the Psychomotor Vigilance Test was performed before (day 1) and after (day 8) the bright light therapy. As a result of the intervention, the athletes slept later on the third (p = 0.01), seventh (p = 0.01) and eighth (p = 0.01) days after starting bright light therapy. Regarding reaction times, when tested in the morning the athletes showed improved average (p = 0.01) and minimum reaction time (p = 0.03) when comparing day 8 to day 1. When tested in the evening, they showed improved average (p = 0.04), minimum (p = 0.03) and maximum reaction time (p = 0.02) when comparing day 8 to day 1. Light therapy treatment delayed the sleep/wake cycles and improved reaction times of members of the swimming team. The use of bright light therapy was shown to be effective in modulating the sleep/wake cycles of athletes who had to perform in competitions that took place late at night.     

Uncertain call likelihood negatively affects sleep and next-day cognitive performance while on-call in a laboratory environment

ABSTRACT

On-call working arrangements are employed in a number of industries to manage unpredictable events, and often involve tasks that are safety- or time-critical. This study investigated the effects of call likelihood during an overnight on-call shift on self-reported pre-bed anxiety, sleep and next-day cognitive performance. A four-night laboratory-based protocol was employed, with an adaptation, a control and two counterbalanced on-call nights. On one on-call night, participants were instructed that they would definitely be called during the night, while on the other on-call night they were told they may be called. The State-Trait Anxiety Inventory form x-1 was used to investigate pre-bed anxiety, and sleep was assessed using polysomnography and power spectral analysis of the sleep electroencephalographic analysis. Cognitive performance was assessed four times daily using a 10-min psychomotor vigilance task. Participants felt more anxious before bed when they were definitely going to be called, compared with the control and maybe conditions. Conversely, participants experienced significantly less non-rapid eye movement and stage two sleep and poorer cognitive performance when told they may be called. Further, participants had significantly more rapid eye movement sleep in the maybe condition, which may be an adaptive response to the stress associated with this on-call condition. It appears that self-reported anxiety may not be linked with sleep outcomes while on-call. However, this research indicates that it is important to take call likelihood into consideration when constructing rosters and risk-management systems for on-call workers.     

Time or retiring and sleep quality may be predictors of academic performance and psychosomatic disorder in university students

In an effort to improve school performance, we have examined the effect of sleep–wake patterns, particularly time in bed, and morning psychosomatic conditions in adolescents. A psychosomatic disorder questionnaire was administered to 135 physically healthy students, who were divided into four groups according to time they went to bed: 23–24, 24–01, 01–02 and 02–03 h. (1) The 23–24 and 24–01 h groups had significantly higher grade point averages than the 02–03 h group. (2) Partial correlations, controlling for sleep quality, revealed significant associations between time to bed and psychosomatic disorder, with regard to whole-body fatigue, lack of motivation and the desire to rest. Our results suggest that the sleep–wake pattern, especially the time of retiring, may predict academic performance and psychosomatic disorder.