It is demonstrated that endurance exercise performance is enhanced in the evening compared with the morning and suggested that behavioural markers of circadian phenotype are associated with the magnitude of diurnal variation in performance.
A. Singh, Sanjida Ahmed, S. Hesketh· European Journal of Applied...· 0 citations
OBJECTIVE
Rapid eye movement (REM) sleep is implicated in fear inhibition processes critical for trauma recovery. However, prior experimental models of REM sleep disruption have lacked ecological validity by manipulating sleep without accounting for circadian timing. Circadian misalignment frequently occurs in occupations at high risk of trauma exposure. The present study examined the relationship between REM sleep and fear inhibition in the context of experimentally induced circadian misalignment.
METHOD
A total of 42 healthy adults (Mage = 24.89, SD = 5.11) were randomized to one of three conditions for four nights: (a) normal control (n = 18), (b) circadian disruption with placebo administration (n = 14), or (c) circadian disruption with melatonin (3 mg) administration (n = 10). Circadian disruption consisted of two consecutive 4-hr phase advances. Fear inhibition was measured via the fear-potentiated startle task. Degree of circadian misalignment was measured via the phase angle between peak urinary 6-sulfatoxymelatonin and scheduled wake time.
RESULTS
Greater circadian misalignment on Night 4 significantly predicted larger reductions in both REM% (p = .010) and REM minutes (p = .002) that night. Controlling for changes in total sleep time and slow wave sleep, reductions in REM minutes on Night 4 significantly predicted poorer extinction recall the following day (ΔR² = .12, p = .040), whereas reductions in REM% showed a nonsignificant small-to-moderate association (p = .087).
CONCLUSIONS
Individuals experiencing greater reductions in REM sleep under circadian misalignment demonstrated poorer extinction recall. Interestingly, circadian misalignment predicted the same change in sleep (reduced REM minutes) also linked to poor extinction recall. Given the role of extinction recall in trauma-related psychopathology, these findings may have implications for frontline personnel at increased risk for posttraumatic stress disorder. However, larger samples are needed to confirm these preliminary findings. (PsycInfo Database Record (c) 2026 APA, all rights reserved).
V. Vuong, Elise McGlashan, Sonia Birch et al.· Psychological Trauma· 0 citations
Sports nutrition, which uses ergogenic substances, has emerged as an important tool that favors athletes’ performance. Like caffeine, melatonin has been investigated as a potential ergogenic aid; however, its effects are not yet fully understood. This study aimed to evaluate the effects of acute melatonin and caffeine intake on performance and sleepiness of runners in the 1 mile physical test. A total of 24 healthy, active, and experienced male runners were selected. Participants completed a 1 mile run under three supplementation conditions (placebo, melatonin, and caffeine), each separated by a 1 week washout period. All evaluations were carried out at the same time. Sleepiness was assessed for 5 h after each supplementation. The results showed that performance over 1 mile across the three supplementation conditions did not differ. Melatonin consumption maintained an increase in sleepiness up to 5 h after the test. These findings caution against melatonin for performance, particularly when used outside its sleep-promoting context.
Nádia Esteves dos Santos, B. Franco, V. Sanz-Milone et al.· Sport Sciences for Health· 0 citations
BACKGROUND
Poor sleep and affect are common, co-occurring symptoms in postmenopausal women. However, the temporal associations between these symptoms - whether sleep disturbances trigger next day changes in affect and/or whether affect disrupts next night sleep - is unknown. Here we examined the day-to-day bidirectional association of sleep with positive and negative affect in midlife postmenopausal women.
METHODS
Midlife postmenopausal women (N = 240, mean age 59.42 ± 4.11 years, 82.08% White) completed 72 h of sleep and affect monitoring. Sleep characteristics (wake after sleep onset, sleep efficiency, total sleep time) were assessed via wrist actigraphy. Positive affect (energetic, interested/involved) and negative affect (angry/irritated, nervous/anxious, stressed) were assessed via ecological momentary assessment. Multiple linear regression models were conducted for all analyses. Moderation of the associations between sleep and affect by vasomotor symptoms and depressive symptoms was also examined.
RESULTS
Better sleep (i.e., lower wake after sleep onset, higher sleep efficiency, and moderate total sleep time) was associated with higher next day positive affect but not negative affect. Higher positive affect was associated with shorter next night total sleep time. There was little evidence of vasomotor symptoms and depressive symptoms moderating these associations.
CONCLUSION
Findings support day-to-day associations between sleep and positive affect rather than negative affect. More robust associations were observed in the direction of sleep to next day positive affect compared with the positive affect to next night sleep direction. These findings highlight the potential to enhance positive affect in midlife postmenopausal women through sleep improvement.
Shelby C. Wood, R. Thurston, Yue-Fang Chang et al.· Sleep Medicine· 0 citations
The phase delay on the sleep-wake cycle resulting from biopsychosocial changes related with adolescence is exacerbated by the level of urbanization. However, early school start times conflict with this delay, leading to several negative consequences. This study aims to compare sleep habits and quality, daytime sleepiness, and attention between adolescents from morning and afternoon shifts across different urbanization levels. A total of 159 Brazilian adolescents from technical high school (15.3 ± 0.8 years old; 101 girls/58 boys) completed the following questionnaires: "Health and Sleep," the Pittsburgh Sleep Quality Index, and the Pediatric Daytime Sleepiness Scale, in addition to a 10-d sleep diary that included the Maldonado Sleepiness Scale. Attention was evaluated by a continuous performance task. Sleep and attention were compared between shifts (Morning: n = 78/Afternoon: n = 81) and degrees of urbanization (High: n = 97/Low: n = 62) using MANCOVA. Independent of urbanization level, morning-shift students woke-up earlier, had a shorter time in bed at night and over a 24-h period (nocturnal sleep + nap), showing higher irregularities in wake-up times, along with higher sleep debt at night and over 24-h, social jetlag, daytime sleepiness, sleepiness upon wake-up time, frequency of naps, and non-spontaneous waking during the week than those in the afternoon shift. However, there were no differences in attention performance. Independent of shift, students from higher urbanization regions showed later bed and wake-up times and a shorter time in bed at night and over 24 h on weekends, and higher sleepiness upon wake-up time on weekdays. Despite longer reaction time in phasic alertness and selective attention, they showed a lower percentage of wrong responses in tonic and phasic alertness, selective attention, and a higher time‑on‑task stability. Thus, early school starting time is a strong modulator for adolescents' sleep-wake cycle regardless of the urbanization level. Further studies are necessary to analyze the relationship between attention and school shift.
Z. C. M. Bessa, F. M. C. Diogo, A. M. Câmara et al.· Chronobiology International· 0 citations
Background Endurance running has a substantial influence on sleep, while insufficient or disturbed sleep prior to exercise may impair endurance performance. However, these interactions remain poorly characterized under real-life conditions. The aim of this field study was to examine sleep patterns in athletes before and after an ultra-trail race. Methods Eighteen athletes (mean age 34.6 ± 8.13, 3 women) underwent an ultra-trail race at 03:30 a.m. (Ultra Marathon des Cirques, La Réunion, France, 64 km, 5000 m of elevation gain, June 2024). After completing various questionnaires to assess their sleep, all participants filled out a sleep diary and all wore an actimeter for six nights before and after the event. Results The athletes reported modest subjective sleep alterations, mainly a later wake-up time and reduced sleep quality on the night following the race (p < 0.05). However, actigraphy-based sleep measurements revealed objective sleep changes, including reduced sleep efficiency (p < 0.05), longer nocturnal wake time (p < 0.05), an increased number of awakenings (p < 0.05), and wake after sleep onset (p < 0.05), lasting up to four nights after the race. Conclusions Participants reported minor sleep complaints following the ultra-trail, whereas more pronounced sleep disruptions can persist for up to four nights postrace. These disruptions are characterized by sleep fragmentation and reduced sleep efficiency. The mechanisms underlying these alterations remain to be elucidated and may involve factors such as sleep deprivation, cumulative fatigue, hypoxia, and hyperthermia.
Fanny Fachan, Franck Vilcourt, B. Lemarchand et al.· Sleep Medicine: X· 0 citations
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