Chronobiology international
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Fatigue is recognized as an important safety concern in the transportation industry. In this study, our goal was to investigate how circadian and sleep-wake dependent factors influence St-Lawrence River pilots' sleep-wake cycle, alertness and psychomotor performance levels at work. A total of 18 male St-Lawrence River ship pilots were recruited to a 16-21-day field study. ⋯ In individuals, earlier phases in psychomotor performance were correlated with earlier chronotype. This study indicates that both circadian and homeostatic processes modulate alertness and psychomotor performance levels with worst levels reached when long shifts ended in the morning. This work has potential applications as it indicates fatigue countermeasures considering both processes are scientifically based.
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Comparative Study
Changes in growth and sleep across school nights, weekends and a winter holiday period in two Australian schools.
Studies suggest that there may be an association between sleep and growth; however, the relationship is not well understood. Changes in biology and external factors such as school schedule heavily impact the sleep of adolescents, during a critical phase for growth. This study assessed the changes in sleep across school days, weekends and school holidays, while also measuring height and weight changes, and self-reported alterations in food intake and physical activity. ⋯ This may be related to sleep restriction. Despite sleep being both later and longer during the school holidays, participants' growth slowed during the holiday period. It is possible that this may be a reflection of other behavioural changes in the holidays (increased food intake and reduced physical activity), as sleep timing during the school period was related to growth.
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Comparative Study
Circadian variations in the clinical presentation of headaches among migraineurs: A study using a smartphone headache diary.
Migraines occur within certain time frames. Nevertheless, information regarding circadian variation in the clinical presentation of migraine is limited. We investigated circadian variations in the clinical presentation of migraine using a smartphone headache diary (SHD). ⋯ All headaches, migraine-type headaches and non-migraine-type headaches occurred most frequently between 06:00 and 11:59, and least frequently between 18:00 and 23:59, and between 00:00 and 05:59. Migrainous headache characteristics, such as unilateral pain, pulsating quality, severe headache intensity, aggravation by movement, nausea, photophobia, and phonophobia presented most frequently between 06:00 and 11:59, and least frequently between 18:00 and 23:59, and 00:00 and 05:59 among 1491 all headache attacks. Headache clinical presentation as well as headache occurrence exhibited circadian periodicity among migraineurs.
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Randomized Controlled Trial Comparative Study
Morphological, molecular and hormonal adaptations to early morning versus afternoon resistance training.
It has been clearly established that maximal force and power is lower in the morning compared to noon or afternoon hours. This morning neuromuscular deficit can be diminished by regularly training in the morning hours. However, there is limited and contradictory information upon hypertrophic adaptations to time-of-day-specific resistance training. ⋯ Resting cortisol declined significantly from pre- to post-training in all three groups (p < 0.05). In conclusion, similar levels of muscle strength and hypertrophy could be achieved regardless of time of the day in previously untrained men. However, at the level of skeletal muscle signalling, the extent of adaptation in some parameters may be time of day dependent.
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The guidelines for night and shift workers recommend that after night work, they should sleep in a dark environment during the daytime. However, staying in a dark environment during the daytime reduces nocturnal melatonin secretion and delays its onset. Daytime bright-light exposure after night work is important for melatonin synthesis the subsequent night and for maintaining the circadian rhythms. ⋯ No significant differences were found in any sleep parameter. Our study demonstrated that daytime sleeping under bright-light conditions after night work could not reduce late evening melatonin secretion until midnight or delay the phase of melatonin secretion without decreasing the quality of the daytime sleeping. Thus, these results suggested that, to enhance melatonin secretion and to maintain their conventional sleep-wake cycle, after night work, shift workers should sleep during the daytime under bright-light conditions rather than dim-light conditions.