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The Post-Lunch Dip in Performance
Abstract
For some performance variables, and some individuals, there is a dip in performance during the midafternoon hours (referred to as the post-lunch dip) that is linked to an increase in sleep propensity at that time of day. The post-lunch dip is a real phenomenon that can occur even when the individual has had no lunch and is unaware of the time of day. This dip has its roots in human biology, and may be linked to the size of the 12-hour harmonic in the circadian system. It is certainly exacerbated by a high-carbohydrate lunch, and may be more likely to occur in extreme morning-type individuals.
... The post-lunch dip is an early afternoon phenomenon causing a bi-circadian rise in sleepiness and fatigue between 1-4 pm (Monk, 2005). It has been linked to a transient with a temporary decline in brain function, including cognition, attentiveness, and arousal (Monk, 2005;Nagano et al., 2022). ...
... The post-lunch dip is an early afternoon phenomenon causing a bi-circadian rise in sleepiness and fatigue between 1-4 pm (Monk, 2005). It has been linked to a transient with a temporary decline in brain function, including cognition, attentiveness, and arousal (Monk, 2005;Nagano et al., 2022). Besides the primary peak of sleep propensity at night, some individuals experience a secondary phase or post-lunch dip in the afternoon (Iskra-Golec et al., 2017;Monk, 2005), even in the absence of meals, posture changes, or time awareness (Monk et al., 1996), suggesting the circadian alertness drive is insufficient to counter increased sleep pressure. ...
... It has been linked to a transient with a temporary decline in brain function, including cognition, attentiveness, and arousal (Monk, 2005;Nagano et al., 2022). Besides the primary peak of sleep propensity at night, some individuals experience a secondary phase or post-lunch dip in the afternoon (Iskra-Golec et al., 2017;Monk, 2005), even in the absence of meals, posture changes, or time awareness (Monk et al., 1996), suggesting the circadian alertness drive is insufficient to counter increased sleep pressure. ...
The current literature lacks comprehensive knowledge regarding the relative and combined effects of task-related factors, such as driving in monotonous environments, and the 'post-lunch dip'-n afternoon bi-circadian increase in sleepiness-articularly within a specific chronotype group. This study aims at investigating the impact of post-lunch driving and time-on-task on fatigue and performance among well-rested morning-type individuals during simulated driving. 12 male participants with a morningness chronotype completed a series of lane change test simulated driving tasks, comprising three 20-minute blocks both before and after lunch. The results demonstrated a significant main effect of the 'post-lunch dip' on reaction time, alertness, and self-reported sleepiness. However, neither the time spent on the task nor the interaction between sleep-and task-related factors yielded significant effects on the measured variables. Furthermore, medium to high correlations among all pairs of measures suggest a good agreement for detecting fatigue and sleepiness in driving tasks.
... Lowden et al. (2004) investigated the effects of lunch on simple reaction time task and found significant performance deficit. Monk (2005) and Mahoney, Taylor and Kanarek (2005) reported that the consumption of lunch is usually followed by a decrease in performance on measures of sustained attention and alertness. The post-lunch dip in performance tends to peak about an hour after meal consumption and the extent of the dip depends upon characteristics of the person eating the meal, size of meal and types of task tested. ...
... The results are, therefore, consistent with the findings of Blake (1967), Colquhoun (1971), Craig Baer andDiekmann (1981), Monk and Folkard (1985), Smith (1985), Craig (1986), Smith andfyiiles (1986a, 1986b), Carskadon and Dement (1992), Lowden et al., (2004) and Monk, (2005) who also reported that th_ e consumption of meal produces acute effects on some type of cognitive processing in adults. . . ...
... Consumption of lunch has been observed to result in decreased alertness and performance efficiency (Smith, Ralph and McNeil, 1991 ), (Llyod, Green & Rogers, 1994). Afternoon propensity for sleep is the reason of the post-lunch dip (Monk, 2005). Changes in mood and cognitive performance are due to altered levels of neurotransmitters produced by food consumption. ...
... Therefore, restbreak structures in working life are firmly established by government law and specified by labor legislation. Although rest breaks in private life can be taken rather flexibly, even there a rhythmic structure can be observed, consisting of a change from strenuous activity to rest and vice versa (Tucker et al., 2003;Monk, 2005;Wendsche and Lohmann-Haislah, 2017). Because daily routines are similar for the majority of people, enabling similar experiences, hardly anyone would not agree with the proposal that breaks have a positive effect on feelings or mental performance (Poffenberger, 1928;Bills, 1943;Wyles et al., 2016). ...
... Since research on rest and recovery is a relatively broad and interdisciplinary field, relevant to many scientific domains including sports sciences, school psychology, work and occupational psychology, and cognitive-experimental psychology and neuroscience, it is rather impossible to organize the manuscript in the style of a classic meta-analysis, where study results are statistically aggregated to generate a quantitative estimate of an empirical phenomenon (e.g., the rest-break effect, etc.). Specifically, while it is viable to aggregate studies in well-defined work field situations, like the aftereffect of lunch breaks on performance (Monk, 2005), or the effects of shift-work on well-being (Kantermann et al., 2007(Kantermann et al., , 2012, considering variations across studies as random factor, this is neither possible nor feasible in a purely experimental situation. This would actually reduce a rather complex research question to whether an effect exist or not (or what size an effect is on average) while ignoring crucial aspects of theorizing, design, and measurement methodology that is absolutely crucial for a deeper understanding of behavioral phenomena. ...
... As already indicated, the long break is the most relevant break in the regular working life. It is an integral part of the classic 8-h workday and can only be investigated in this context (Chmiel et al., 1995;Folkard, 1997;Monk, 2005). It is neither possible nor feasible to manipulate critical experimental conditions in real-work contexts, such as to vary the break's length and content, so only the observation of those aspects that are naturally occurring during the workday remain suitable for investigation (Lombardi et al., 2014). ...
In this work, we evaluate the status of both theory and empirical evidence in the field of experimental rest-break research based on a framework that combines mental-chronometry and psychometric-measurement theory. To this end, we (1) provide a taxonomy of rest breaks according to which empirical studies can be classified (e.g., by differentiating between long, short, and micro-rest breaks based on context and temporal properties). Then, we (2) evaluate the theorizing in both the basic and applied fields of research and explain how popular concepts (e.g., ego depletion model, opportunity cost theory, attention restoration theory, action readiness, etc.) relate to each other in contemporary theoretical debates. Here, we highlight differences between all these models in the light of two symbolic categories, termed the resource-based and satiation-based model, including aspects related to the dynamics and the control (strategic or non-strategic) mechanisms at work. Based on a critical assessment of existing methodological and theoretical approaches, we finally (3) provide a set of guidelines for both theory building and future empirical approaches to the experimental study of rest breaks. We conclude that a psychometrically advanced and theoretically focused research of rest and recovery has the potential to finally provide a sound scientific basis to eventually mitigate the adverse effects of ever increasing task demands on performance and well-being in a multitasking world at work and leisure.
... 10,11,[20][21][22][23][24] Post-lunch dips in variables such as muscle strength have also been noted in some studies but not all. 11,25,26 For instance, it has been shown that although short-term maximal performance varied with time of day, no time of day effect on muscle fatigue was observed, which plays a large role in performance variation and can affect when an athlete may peak. 12 One mediating factor that may play a role is chronotype which can result in interindividual differences in circadian rhythmicity and consequently performance. ...
... 9,33 Accuracy did not reflect a learning effect and was worst in the afternoon, possibly indicating a post-lunch dip, which has been shown more broadly. 11,17,25 This dip occurring mid-afternoon is superimposed only on some variables and in some individuals, which is perhaps why the decrement was seen in accuracy and not speed (or any other variables). 25 These results suggest the circadian effect was greater than the learning effect for accuracy of delivery, because even though the bowlers train at 14:30, their bowling accuracy was still worst at that time. ...
... 11,17,25 This dip occurring mid-afternoon is superimposed only on some variables and in some individuals, which is perhaps why the decrement was seen in accuracy and not speed (or any other variables). 25 These results suggest the circadian effect was greater than the learning effect for accuracy of delivery, because even though the bowlers train at 14:30, their bowling accuracy was still worst at that time. Although the changes in accuracy were small, they can be a 'game changer' in a cricket game. ...
The game of cricket is played at various times of the day and no studies have investigated the time of day effects on perceptual, physical and performance measures of cricketers. Therefore, the purpose of this study was to focus on adolescent fast bowlers and their responses when bowling at different times of the day. First team, adolescent male fast bowlers (N = 5, Mean age 17.00 ± 0.55 years; stature 185.2 ± 6.5 cm and mass 86.06 ± 17.56 kg) were required to complete a fast-bowling simulation protocol whereby perceptual, physical and bowling-specific performance measures were tested at three different times of day (10:30, 14:30, 18:30). Over all the spells over one was significantly slower than all the other overs. There were no significant changes in bowling speed between the time intervals. However, there was a large increase in bowling speed at 14:30 compared to 10:30 (ES – 1.25) and a moderate increase in bowling speed (ES = 0.67) between 10:30 and 18:30. There was no significant change in accuracy at the different time intervals although it was best at 10:30 followed by 18:30 although the latter had a greater variance. In conclusion, this investigation found time of day did not significantly impact the responses, but the effects sizes show that bowling accuracy was worst at 14:30 despite the other parameters, such as speed of delivery, being best at this time, which may suggest a speed-accuracy trade-off. Additionally, both 10:30 and 18:30 were found to be times conducive to bowling performance with regards to accuracy.
... Post-lunch dip in psychomotor performance is a commonly observed phenomena that has been linked to a 12-hour harmonic in 24-hour circadian rhythm. 1,2 It is a common practice to consume coffee or tea during this period in order to enhance the work performance. Caffeine present in coffee or tea is well known to positively influence various domains of psychomotor performance like reaction time, concentration, attention time and vigilance. ...
... [8][9][10][11] Addition of caffeine tablets to decaffeinated coffee has also been found to improve attention span and mood of the DOI: https://dx.doi.org/10.18203/2319-2003.ijbcp20212924 1 Department of Pharmacology, 2 Department of Biostatistics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India individual during post-lunch period. 2 Coffee is either consumed as black coffee in plain water or with milk and sugar. Milk and sugar reduce the bitterness of coffee without affecting the bioavailability of phenolic acids present in it and is the traditional way of coffee consumption in India. ...
... Post-lunch dip in both cognitive and physical performance in individuals during afternoon hours has been a commonly observed phenomena that has been more likely to occur in individuals who wake up very early in the morning. 1,2,17 Such an effect has also been attributed to the high carbohydrate content of lunch. 1 It is a usual practice to consume coffee or tea to counteract this lassitude. The present study was carried out to evaluate the effect of caffeine on psychomotor performance in post-lunch period in healthy volunteers having low to moderate caffeine intake. ...
Background: This study aimed to compare the effect of regular coffee and decaffeinated coffee on psychomotor performance in healthy volunteers during post-lunch period.Methods: In this randomized double-blind cross-over study, adult healthy volunteers were given hot coffee (3 g each of regular or decaffeinated coffee) during post-lunch period. Psychomotor functions (critical flicker-fusion frequency (CFF), choice reaction time (CRT) and error count in hand-steadiness test (HST)), blood pressure and heart rate were measured pre-lunch, pre-coffee (1-hour post-lunch) and 1-hour post-coffee consumption. Subjective ratings of sleepiness and mood were also assessed during post-lunch sessions.Results: The mean age of the participants (n=16) was 27.4±2.7 years with a male: female ratio of 7:9. There was no significant deterioration in psychomotor performance post-lunch when compared to pre-lunch on both the days. The mean CFF, CRT, errors committed in HST and cardiovascular parameters did not differ significantly between regular coffee and decaffeinated groups during post-lunch sessions. There was no significant difference in values of cardiovascular parameters as well as subjective ratings of sleep and mood between two groups.Conclusions: In healthy adult individuals’ consumption of both regular coffee and decaffeinated coffee during the post-lunch period did not affect psychomotor performance.
... Outside the field of thermal comfort research, studies have identified variations in cognitive performance and subjective alertness/attention linked to the time of day (Valdez, 2019a(Valdez, , 2019b. Moreover, a so-called "post-lunch dip" or "midafternoon dip", which describes a decline in cognitive performance, has been observed (Valdez, 2019a(Valdez, , 2019bMonk, 2005;Valdez et al., 2008). Although the term "post-lunch dip" might suggest an association with the midday meal, this dip occurs independently of lunch and is primarily associated with the time of day (Monk, 2005). ...
... Moreover, a so-called "post-lunch dip" or "midafternoon dip", which describes a decline in cognitive performance, has been observed (Valdez, 2019a(Valdez, , 2019bMonk, 2005;Valdez et al., 2008). Although the term "post-lunch dip" might suggest an association with the midday meal, this dip occurs independently of lunch and is primarily associated with the time of day (Monk, 2005). This daily fluctuation was observed in our CC condition with decreased cognitive performance scores and less energetic arousal post-lunch. ...
In the design of buildings with minimal environmental impact, the incorporation of higher energy flexibility is becoming increasingly relevant. This approach is associated with dynamic modulations in setpoint temperatures. Until now, a link between indoor temperatures and cognitive performance of workers has been assumed, leading to high energy consumption and overcooling of office environments in summer conditions. However, research focusing on the relationship between thermal indoor environments and cognitive performance has rarely considered the influence of dynamic temperatures or temporal effects. This is the first experimental study aiming to understand the impact of temperature in relation to time of day on the subjective perception of cognitive load and performance under various thermal conditions in real-world office environments. The results indicated no observable relationship between temperature setpoints (25-30 • C) and cognitive performance. Instead, the temporal dynamics of cooling rather than fixed and static temperature setpoints appeared to have an impact.
... Daytime napping is another behavioral trait known for shaping nightly sleep quotas 52 . The propensity of contemporary humans to experience a mid-afternoon dip in alertness (linked to circadian oscillations of body temperature and performance) is well recognized 33,53 . Since it has been hypothesized that a napping episode during the mid-afternoon would occur under "natural", rural conditions but would be inhibited by industrial lifestyles 22,33 , we expected to find higher napping rates in agricultural adolescents than in urban participants. ...
... The propensity of contemporary humans to experience a mid-afternoon dip in alertness (linked to circadian oscillations of body temperature and performance) is well recognized 33,53 . Since it has been hypothesized that a napping episode during the mid-afternoon would occur under "natural", rural conditions but would be inhibited by industrial lifestyles 22,33 , we expected to find higher napping rates in agricultural adolescents than in urban participants. Additionally, we reasoned we would observe greater nap ratios during school nights, derived from nightly short sleep quotas 54 . ...
Comparing the nature of adolescent sleep across urban and more isolated, rural settings through an ecological, cross-cultural perspective represents one way to inform sleep nuances and broaden our understanding of human development, wellbeing and evolution. Here we tested the Social Jetlag Hypothesis, according to which contemporary, urban lifestyles and technological advances are associated with sleep insufficiency in adolescents. We documented the adolescent sleep duration (11–16 years old; X̅ = 13.7 ± 1.21; n = 145) in two small agricultural, indigenous and one densely urban context in Mexico to investigate whether adolescents in socio-ecologically distinct locations experience sleep deprivation. Sleep data was assembled with actigraphy, sleep diaries and standardized questionnaires. We employed multilevel models to analyze how distinct biological and socio-cultural factors (i.e., pubertal maturation, chronotype, napping, gender, working/schooling, access to screen-based devices, exposure to light, and social sleep practices) shape adolescent sleep duration. Results suggest that the prevalence of adolescent short sleep quotas is similar in rural, more traditional environments compared to highly urbanized societies, and highlight the influence of social activities on the expression of human sleep. This study challenges current assumptions about natural sleep and how adolescents slept before contemporary technological changes occurred.
... Studies reported a high prevalence of daytime napping in older adults as a result of several factors: health conditions, medications, excessive daytime sleepiness, boredom, lack of physical activity and changes in sleep patterns implying lower night-time sleep quantity and quality. Further, it is well known that diurnal sleepiness induced by circadian rhythms occurs in the afternoon (Mitler et al., 1988;Broughton and Mullington, 1992;Monk, 2005;Waterhouse et al., 2007). This phenomenon is called post-lunch dip and is characterized by a dip in performance for some variables during mid-afternoon hours (Monk, 2005), especially for people who have been partially deprived of sleep (Romdhani et al., 2019). ...
... Further, it is well known that diurnal sleepiness induced by circadian rhythms occurs in the afternoon (Mitler et al., 1988;Broughton and Mullington, 1992;Monk, 2005;Waterhouse et al., 2007). This phenomenon is called post-lunch dip and is characterized by a dip in performance for some variables during mid-afternoon hours (Monk, 2005), especially for people who have been partially deprived of sleep (Romdhani et al., 2019). In this context, several studies proposed mid-afternoon as the best time to onset nap (Waterhouse et al., 2007;Romdhani et al., 2021;Souabni et al., 2021). ...
A growing body of evidence indicates that napping is common among older adults. However, a systematic review on the effect of napping on the elderly is lacking. The aim of this systematic review was to (i) determine how studies evaluated napping behavior in older adults (frequency, duration and timing); (ii) explore how napping impacts perceptual measures, cognitive and psychomotor performance, night-time sleep and physiological parameters in the elderly (PROSPERO CRD42022299805). A total of 738 records were screened by two researchers using the PICOS criteria. Fifteen studies met our inclusion criteria with a mean age ranging from 60.8 to 78.3 years and a cumulative sample size of n = 326. Daytime napping had an overall positive impact on subjective measures (i.e., sleepiness and fatigue), psychomotor performances (i.e., speed and accuracy) and learning abilities (i.e., declarative and motor learning). Additionally, studies showed (i) consistency between nap and control conditions regarding sleep duration, efficiency and latency, and proportion of sleep stages, and (ii) increase of 24 h sleep duration with nap compared to control condition. Based on the findings of the present review, there is minimal evidence to indicate that napping is detrimental for older adults' nighttime sleep. Future studies should consider involving repeated naps during a micro-cycle in order to investigate the chronic effect of napping on older adults.
Systematic review registration
identifier: CRD42022299805.
... Participants were always tested at the same time of the day to avoid circadian confounds. SRT practice during post-lunch dip (13-14 h) was avoided (Monk, 2005). ...
... Reduced motor speed may be explained in part by MS-related physical disabilities (EDSS > 3.5), but may also likely be a reflection of a general cognitive processing slowdown with the evolution of MS disease (Guimara˜es and Sa´, 2012). Additionally, motor learning slopes and interference effects were similar in controls and patients during the learning phase and 20 min later, which is also in line with previous studies indicating a preserved capacity to acquire motor sequential knowledge in MS, at least in patients with minimal disability (EDSS > 2) (Monk, 2005). It remains to be ascertained how motor and sequential learning capabilities are impacted in the context of the progression of neurological impairments in the course of MS pathology, besides basic motor restrictions. ...
Studies investigating motor learning in patients with Multiple Sclerosis (MS) disease highlighted that MS patients exhibit similar learning performance than healthy controls, but that learning can be hampered by the progression of MS eventually leading to impaired efficiency of subcortical-cortical networks. We aimed at investigating whether the long-term, overnight consolidation of sequential motor memories is preserved in MS disease. 31 patients with MS and two healthy control groups (27 young and 14 middle age) were tested over two consecutive days using a serial reaction time task. Performance was tested (a) 20 minutes after the end of learning at Day 1 to monitor transient offline, short-term increase in motor and sequential performance and (b) after 24h on Day 2 to quantify overnight delayed changes in performance reflecting memory consolidation. Besides a slower overall RT in patients with MS, motor performance similarly evolved in all groups. Sequence learning as assessed by interference effects was similar in patients with MS and both control groups on Day 1 (Learning and 20-min test). In contrast, while interference effects keep increasing on Day 2 after 24h (Relearning) in healthy control groups, it reverted to levels reached at the end of learning for patients with MS. Long-term consolidation of sequential knowledge is impaired in patients with MS. At the motor level, learning and overnight consolidation abilities are preserved in MS disease.
... The post-lunch dip (PLD) is characterized by an endogenous increase of sleepiness (e.g., higher sleep propensity and shorter sleep onset latency), favorizing daytime sleep (Monk, 2005;Bes et al., 2009). It is common for athletes to compete or to train during this time of the day (Bes et al., 2009;Romdhani et al., 2019). ...
... It is common for athletes to compete or to train during this time of the day (Bes et al., 2009;Romdhani et al., 2019). Therefore, behavioral (i.e., napping) and pharmacological (i.e., caffeine) countermeasure were suggested to enhance alertness during the PLD (Hayashi et al., 2003;Monk, 2005;Waterhouse et al., 2007;Horne et al., 2008;Bes et al., 2009;Romdhani et al., 2020Romdhani et al., , 2021a. Recent evidence suggest that the PLD could be severer after partial sleep deprivation (PSD), yet, these effects were more disturbing after PSD caused by early awakening compared to PSD caused by late bedtime (Romdhani et al., 2019). ...
Purpose: To investigate the effects of placebo (PLA), 20 min nap opportunity (N20), 5mg·kg⁻¹ of caffeine (CAF), and their combination (CAF+N20) on sleepiness, mood and reaction-time after partial sleep deprivation (PSD; 04h30 of time in bed; study 1) or after normal sleep night (NSN; 08h30 of time in bed; study 2).
Methods: Twenty-three highly trained athletes (study 1; 9 and study 2; 14) performed four test sessions (PLA, CAF, N20 and CAF+N20) in double-blind, counterbalanced and randomized order. Simple (SRT) and two-choice (2CRT) reaction time, subjective sleepiness (ESS) and mood state (POMS) were assessed twice, pre- and post-intervention.
Results: SRT was lower (i.e., better performance) during CAF condition after PSD (pre: 336 ± 15 ms vs. post: 312 ± 9 ms; p < 0.001; d = 2.07; Δ% = 7.26) and NSN (pre: 350 ± 39 ms vs. post: 323 ± 32 ms; p < 0.001; d = 0.72; Δ% = 7.71) compared to pre-intervention. N20 decreased 2CRT after PSD (pre: 411 ± 13 ms vs. post: 366 ± 20 ms; p < 0.001; d = 2.89; Δ% = 10.81) and NSN (pre: 418 ± 29 ms vs. post: 375 ± 40 ms; p < 0.001; d = 1.23; Δ% = 10.23). Similarly, 2CRT was shorter during CAF+N20 sessions after PSD (pre: 406 ± 26 ms vs. post: 357 ± 17 ms; p < 0.001; d = 2.17; Δ% = 12.02) and after NSN (pre: 386 ± 33 ms vs. post: 352 ± 30 ms; p < 0.001; d = 1.09; Δ% = 8.68). After PSD, POMS score decreased after CAF (p < 0.001; d = 2.38; Δ% = 66.97) and CAF+N20 (p < 0.001; d = 1.68; Δ% = 46.68). However, after NSN, only N20 reduced POMS (p < 0.001; d = 1.05; Δ% = 78.65) and ESS (p < 0.01; d = 0.71; Δ% = 19.11).
Conclusion: After PSD, all interventions reduced sleepiness and only CAF enhanced mood with or without napping. However, only N20 enhanced mood and reduced sleepiness after NSN. Caffeine ingestion enhanced SRT performance regardless of sleep deprivation. N20, with or without caffeine ingestion, enhanced 2CRT independently of sleep deprivation. This suggests a different mode of action of napping and caffeine on sleepiness, mood and reaction time.
... This fluctuation often reaches a low point after midday, characterized by increased sleepiness and fatigue, along with a decrease in alertness and core body temperature. This phenomenon is often referred to as post lunch dip and typically occurs between 13:00 and 16:00 (Monk 2005). Athletes generally nap during this period, which align with their circadian rhythm and thus achieves more excellent physical performance (Bellastella et al. 2019;Irandoust et al. 2019;Ayala et al. 2021). ...
Athletes generally suffer from insufficient sleep duration, lower sleep efficiency, and a high overall prevalence of insomnia. Daytime napping has been demonstrated to supplement nighttime sleep in athletes; however, recent controversial findings warrant further consideration. This review synthesized existing studies on the effects of daytime naps on athletes, explored potential mechanisms of daytime napping, and analyzed instances of ineffective interventions or negative outcomes. Daytime napping functions as a restorative strategy to counteract sleep deprivation or the post-lunch dip, assisting athletes in recovering anaerobic capacity, agility, reaction time, and alertness, with potential mechanisms including the reduction of sleepiness through adherence to circadian rhythms, decreased subjective soreness and fatigue attributed to autonomic functioning, and improved respiratory performance. The optimal nap period occurs between 13:00 and 15:00, with a 5–6 h interval between morning awakening and nap initiation. Depending on the athlete’s nighttime sleep, opt for a 20 ~ 40 or 60 ~ 90 min nap with at least 60 min between the nap and subsequent exercise to reduce sleep inertia. The intervention efficacy of daytime napping was correlated with exercise intensity. A nap program must be developed based on the specific athletic demands of the sport in practical application.
... Contudo, estudos mostram que no período referido como pós-almoço, estimado entre 14h e 16h, o impulso circadiano para o estado de alerta diurno não é suficientemente forte para se opor ao aumento da pressão homeostática do sono, causando a sonolência neste período [6]. Em decorrência desse fenômeno é comum o descanso pós-almoço, institucionalizado em diversos países com uma pausa comercial neste horário. ...
O estado da arte das pesquisas em iluminação incita a caracterização do efeito do ambiente construído nos usuários sob a ótica da iluminação circadiana. Assim, o objetivo deste trabalho é investigar o efeito de vidros com distribuição espectral distinta, no estado de alerta de indivíduos por meio de teste de atenção visual concentrada. Para isso, foi realizado um estudo transversal em sessões de exposição controlada, em uma câmara climática iluminada naturalmente. Participaram aos pares 48 voluntários expostos a 3 tipos de vidro, totalizando 72 sessões. O estado de alerta foi medido pelo teste de atenção d2-R. Os resultados foram analisados estatisticamente considerando-se a vista do usuário, o tipo de céu e o horário de exposição. A uma significância de 5% aceitou-se a hipótese de que o tipo de vista (a janela ou a parede) não impactou o desempenho dos voluntários no teste. Já o tipo de céu, bem como a alteração dos vidros, afetou o seu desempenho. Por fim, houve diferença de desempenho entre o grupo da manhã e o da tarde. Concluiu-se que as características luminosas da fonte de luz (céu e vidro) e o período do ciclo circadiano podem afetar o estado de alerta do usuário.
... The experiment was performed in the early afternoon hours, starting either at 12.00 or 14.00, to benefit from the so-called post-lunch dip phase, when a natural decline in alertness occurs. As a meal enhances the post-lunch dip phase, [20][21][22] it was decided to provide a meal before the main experiment. ...
The non-image forming effects of light are moderated by various aspects such as dose, spectrum or temporal and spatial patterns. One of them, the spatial distribution of light within the field of view, has been scarcely researched. Although few studies suggest effects on melatonin secretion during night-time, the daytime effects remain unknown. In this project, we investigated the effect of three light directions – from above, below and the side – each illuminating different retinal regions. The luminance and the size of the light source were kept constant, thus realising the same vertical illuminance and melanopic irradiance at the eye for all scenes. Forty participants underwent a two hour protocol of cognitive tasks and subjective assessments of alertness and performance. Our results suggest stronger non-image forming-effects stimulation with lighting from above, whereas the effect of lighting from below and side differed slightly.
... Therefore, for a good recovery during the day, many people perform a short afternoon nap. Indeed, a propensity to sleep after lunch (i.e., the post lunch dip) has been reported and was related to a reduction in central temperature and vigilance and an increase in the sensation of sleep (4). ...
Sleep is fundamental for recovery and good mental, cognitive and physical performance. Many factors could affect the sleep of the physical active people or athletes such as: late night training sessions or competition, Ramadan fasting and jetlag. These conditions that affect the sleep quality have significant negative effects on mental, cognitive and physical performance. Thus, scientists have to find strategies to overcome the perturbation of sleep and to optimize mental, cognitive and physical performance especially for physical active people and athletes. One of the proposed strategies is the nap opportunity. Otherwise, in their routinely training sessions, athletes are required to perform short-term repetitive maximal sprints. One of the utilized exercise for testing or training is the 5-m shuttle run test (5mSRT). Recent studies concluded that a nap opportunity has a positive effect on performance during the 5mSRT. These studies reported that this positive effect depends on the duration and the time of day of the nap opportunity. Indeed, the positive effect of the nap opportunity was better after a duration of 45-minutes compared to a 25-minutes. Also, this positive effect was reported when the nap opportunity was performed at 14h00 or 15h00. However, no-positive effect was reported when the nap opportunity was realized at 13h00.
... The circadian system, one of two additive processes that determine the sleep-wake schedule, has natural variations in multiple physiological functions across a 24-hr period (Lack & Wright, 2007a). For example, an individual with an average timed sleep pattern (i.e., 11 p.m.-7 a.m.) has a dip in alertness between approximately 2 and 4 p.m. (Monk, 2005). Importantly, these variations have been found to influence athletic performance (Walsh et al., 2021). ...
The overall aim of the present study was to examine the daily patterns and relationships between sleep behavior, anxiety, mood (i.e., depression symptoms) and cognitive performance (i.e., reaction time) in esports athletes competing in an Oceanic Rocket League Championship Series regional event. Sixteen participants completed a daily sleep diary, evening anxiety measure, and an afternoon mood measure and cognitive performance task. Measures were taken (i) pre-competition), (ii) across the competition days, and (iii) post-competition. We found that participants’ lights out time was earliest across the competition nights. Sleep onset latency gradually lengthened pre-competition and across the competition nights, eventually exceeding normal limits. Wake after sleep onset was longest across the competition nights but remained within normal limits. Wake-up time was earliest at the start of the competition period but consistently late on most other days. Total sleep time was generally adequate but mildly reduced the night before the first day of competition. There was no significant relationship between anxiety and subsequent sleep, nor a relationship between total sleep time and next day mood or cognitive performance. Future research should investigate whether these findings generalize to esports athletes from other games, at higher levels of competition, and different start times.
... Previous research has shown that naps are able to counteract fatigue and improve subjective ratings of cognition, vigilance and psychomotor ability (Lovato and Lack 2010). When sleep restricted the time since awake component is greater and the corresponding elevation of subjective fatigue values in the late afternoon are likely to result in impaired function (Monk 2005). By implementing the nap, our results suggest the nap, offset symptoms and improved cognitive variables by reducing sleep propensity and decreasing the number of test errors. ...
We have investigated the effects that partial-sleep-restriction (PSR0, 4-h sleep retiring at 02:30 and waking at 06:30 h for two consecutive nights) have on 07:30 and 17:00 h cognitive and submaximal weightlifting; and whether this performance improves at 17:00 h following a 13:00 h powernap (0, 30 or 60-min). Fifteen resistance-trained males participated in this study. Prior to the experimental protocol, one repetition max (1RM) bench press and back squat, normative habitual sleep and food intake were recorded. Participants were familiarised with the testing protocol, then completed three experimental conditions: (i) PSR with no nap (PSR0); (ii) PSR with a 30-min nap (PSR30) and (iii) PSR with a 60-min nap (PSR60). Conditions were separated by 7 days with trial order counterbalanced. Intra-aural temperature, Profile of Mood Scores, word-colour interference, alertness and tiredness values were measured at 07:30, 11:00, 14:00, 17:00 h on the day of exercise protocol. Following final temperature measurements at 07:30 h and 17:00 h, participants completed a 5-min active warm-up before performing three repetitions of left and right-hand grip strength, followed by three repetitions at each incremental load (40, 60 and 80% of 1RM) for bench press and back squat, with a 5-min recovery between each repetition. A linear encoder was attached perpendicular to the bar used for the exercises. Average power (AP), average velocity (AV), peak velocity (PV), displacement (D) and time-to-peak velocity (tPV) were measured (MuscleLab software) during the concentric phase of the movements. Data were analysed using general linear models with repeated measures. The main findings were that implementing a nap at 13:00 h had no effect on measures of strength (grip, bench press or back squat). There was a main effect for time of day with greatest performance at 17:00 h for measures of strength. In addition to a significant effect for "load" on the bar for bench press and back squat where AP, AV, PV, D values were greatest at 40% (P < 0.05) and decreased with increased load, whereas tPV and RPE values increased with load; despite this no interaction of "load and condition" were present. A post lunch nap of 30- and 60-minute durations improved mood state, with feelings of alertness, vigour and happiness highest at 17:00 h, in contrast to confusion, tiredness and fatigue (P < 0.05), which were greater in the morning (07:30 h). The word-colour interference test, used as an indicator of cognitive function, reported significant main effect for condition, with the highest total test score in PSR60 condition (P = 0.015). In summary, unlike strength measures the implementation of a 30 or 60-minute nap improved cognitive function when in a partially sleep restricted state, compared to no nap.
... Importantly, human performance (i.e., tasks that require concentration, alertness, and attention, as well as physical tasks that require speed and muscle strength) tends to be reduced in response to the post-lunch dip phenomenon [8][9][10], which occurs between 13:00 h and 16:00 h, due to an increase in the tendency to sleep and decreases in core temperature and vigilance [11]. Therefore, daytime napping is regarded as a recovery strategy often used to counteract impaired performances as a consequence of the post-lunch dip [12]. ...
Abstract Background Daytime napping is used by athletes as a strategy to supplement night time sleep and aid physical performance. However, no meta-analytical overview regarding the impact of napping following a night of normal sleep (7–9 h) on physical performance is available. Objective The aim of this study was to evaluate the effect of daytime napping following normal night-time sleep on physical performance in physically active individuals and athletes. Methods This systematic review and meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Seven electronic databases (i.e., PubMed, Web of Science, Scopus, SPORTDiscus, CINAHL, SCIELO, and EBSCOhost) were used to search for relevant studies that investigated the impact of daytime napping, following normal night-time sleep, on physical performance in physically active individuals and athletes, published in any language, and available before September 01, 2022. Studies that included assessments of any physical performance measures were included. QualSyst was used to assess the methodological quality of the studies. Results Of 18 selected articles, 15 were of strong quality and 3 were of moderate quality. Compared with no-nap conditions, physically active individuals and athletes who napped experienced an increase in highest distance (effect size [ES] 1.026; p < 0.001) and total distance (ES 0.737; p < 0.001), and a decrease in fatigue index (ES 0.839, p = 0.008) during the 5-m shuttle run test (5MSRT). However, napping yielded no effect on muscle force (ES 0.175; p = 0.267). No effect of napping was found in one study that measured sprint performance and in two studies that measured performance during the 30-s Wingate test. Two of three studies reported an increase in jump performance after napping. Two of three studies reported an increase in repeated sprints after napping. One study reported an increase in upper-body power performance after napping, and napping was beneficial for endurance performance in one of two studies. Conclusion Following normal sleep, napping is beneficial for the performance of the 5MSRT, with no significant effect on muscle force. No firm conclusions can be drawn regarding other physical performance measures due to the limited number of studies.
... Importantly, human performance (i.e., tasks that require concentration, alertness, and attention, as well as physical tasks that require speed and muscle strength) tends to be reduced in response to the post-lunch dip phenomenon [8][9][10], which occurs between 13:00 h and 16:00 h, due to an increase in the tendency to sleep and decreases in core temperature and vigilance [11]. Therefore, daytime napping is regarded as a recovery strategy often used to counteract impaired performances as a consequence of the post-lunch dip [12]. ...
Background
Daytime napping is used by athletes as a strategy to supplement night time sleep and aid physical performance. However, no meta-analytical overview regarding the impact of napping following a night of normal sleep (7–9 h) on physical performance is available.
Objective
The aim of this study was to evaluate the effect of daytime napping following normal night-time sleep on physical performance in physically active individuals and athletes.
Methods
This systematic review and meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Seven electronic databases (i.e., PubMed, Web of Science, Scopus, SPORTDiscus, CINAHL, SCIELO, and EBSCOhost) were used to search for relevant studies that investigated the impact of daytime napping, following normal night-time sleep, on physical performance in physically active individuals and athletes, published in any language, and available before September 01, 2022. Studies that included assessments of any physical performance measures were included. QualSyst was used to assess the methodological quality of the studies.
Results
Of 18 selected articles, 15 were of strong quality and 3 were of moderate quality. Compared with no-nap conditions, physically active individuals and athletes who napped experienced an increase in highest distance (effect size [ES] 1.026; p < 0.001) and total distance (ES 0.737; p < 0.001), and a decrease in fatigue index (ES 0.839, p = 0.008) during the 5-m shuttle run test (5MSRT). However, napping yielded no effect on muscle force (ES 0.175; p = 0.267). No effect of napping was found in one study that measured sprint performance and in two studies that measured performance during the 30-s Wingate test. Two of three studies reported an increase in jump performance after napping. Two of three studies reported an increase in repeated sprints after napping. One study reported an increase in upper-body power performance after napping, and napping was beneficial for endurance performance in one of two studies.
Conclusion
Following normal sleep, napping is beneficial for the performance of the 5MSRT, with no significant effect on muscle force. No firm conclusions can be drawn regarding other physical performance measures due to the limited number of studies.
... Another plausible factor that needs to be considered is that the daytime nap may relieve sleep pressure and adenosine buildup in the brain, which increases throughout wake periods [44]. Sleep pressure has been shown to increase in the afternoon [45,46] and has been associated with reductions in alertness and increased fatigue [47]. Furthermore, adenosine buildup inhibits neurotransmitters within the brain, causing an increase in sleepiness and negatively affecting alertness and fatigue [48]. ...
Daytime napping are used by elite athletes in both training and match-day settings. Currently, there are limited interventional studies on the efficacy of napping on physical performance in elite team-sport athletes. Therefore, the objective was to investigate the effect of a daytime nap (<1 h) on afternoon performance of peak power, reaction time, subjective wellness, and aerobic performance in professional rugby union athletes. A randomised cross-over design was carried out amongst 15 professional rugby union athletes. Athletes performed nap (NAP) and no nap (CON) conditions on two occasions, separated by one week. Baseline testing of reaction time, subjective wellness, and 6-s peak power test on a cycle ergometer was completed in the morning, followed by 2 x 45-minute training sessions, after which athletes completed the NAP or CON condition at 1200h. Following the nap period, baseline measures were retested in addition to a 30-minute fixed intensity interval cycle and a 4-minute maximal effort cycling test. A significant group x time interaction was determined for 6-s peak power output (+157.6 W, p<0.01, d=1.53), perceived fatigue (-0.2 AU, p=0.01, d=0.37) and muscle soreness (-0.1 AU, p=0.04, d=0.75) in favor of the NAP condition. A significantly lower perceived exertion rating (-1.2 AU, p<0.01, d=1.72) was recorded for the fixed intensity session in favour of NAP.
This study highlights that utilizing daytime naps between training sessions on the same day improved afternoon peak power and lower perceptions of fatigue, soreness, and exertion during afternoon training in professional rugby union athletes.
... In addition, sleep deprivation due to long working hours could be enhanced by the postlunch dip (Monk, 2005). Most people feel a significant reduction in alertness and concentration between 2 and 4 pm, leading to poor judgment and increased human error, increasing the accident rate and reduced performance in the workplace (Williamson et al., 2011). ...
Uber and other on-demand business platforms drivers experience unparalleled flexibility in work hours, and many are using this model instead of working a fixed-hours job. The option of working more hours a day and, as a result, increasing the remuneration received is often chosen by drivers even at the expense of sleep. Due to their professional obligation, this population is at risk of excessive sleepiness due to sleep deprivation or poor sleep quality, increasing the risk of detrimental effects on health and the risk of car accidents. Considering that sleep is essential for general health, it is mandatory to create strategies to address these issues, such as limiting the maximum number of hours worked a day under the laws regulating labor rights and periodically assessing drivers' alertness.
... Fatigue appears generally during the afternoon and increases as the day gets closer to regular sleep times. The daily averaged scores suggest a subtle fatigue peak after midday that could be associated with what has been referred in the literature as postlunch dip in performance [42]. This consensus with sleep and performance studies supports our hypothesis that keystroke dynamics can be used to quantify daily fatigue in computer users in an objective and unobtrusive manner. ...
Background
Mental fatigue is a common and potentially debilitating state that can affect individuals’ health and quality of life. In some cases, its manifestation can precede or mask early signs of other serious mental or physiological conditions. Detecting and assessing mental fatigue can be challenging nowadays as it relies on self-evaluation and rating questionnaires, which are highly influenced by subjective bias. Introducing more objective, quantitative, and sensitive methods to characterize mental fatigue could be critical to improve its management and the understanding of its connection to other clinical conditions.
Objective
This paper aimed to study the feasibility of using keystroke biometrics for mental fatigue detection during natural typing. As typing involves multiple motor and cognitive processes that are affected by mental fatigue, our hypothesis was that the information captured in keystroke dynamics can offer an interesting mean to characterize users’ mental fatigue in a real-world setting.
Methods
We apply domain transformation techniques to adapt and transform TypeNet, a state-of-the-art deep neural network, originally intended for user authentication, to generate a network optimized for the fatigue detection task. All experiments were conducted using 3 keystroke databases that comprise different contexts and data collection protocols.
Results
Our preliminary results showed area under the curve performances ranging between 72.2% and 80% for fatigue versus rested sample classification, which is aligned with previously published models on daily alertness and circadian cycles. This demonstrates the potential of our proposed system to characterize mental fatigue fluctuations via natural typing patterns. Finally, we studied the performance of an active detection approach that leverages the continuous nature of keystroke biometric patterns for the assessment of users’ fatigue in real time.
Conclusions
Our results suggest that the psychomotor patterns that characterize mental fatigue manifest during natural typing, which can be quantified via automated analysis of users’ daily interaction with their device. These findings represent a step towards the development of a more objective, accessible, and transparent solution to monitor mental fatigue in a real-world environment.
... Academic radiology and other applied research fields have consistently demonstrated an impact of fatigue on performance (e.g., Krupinski, 2015;Taylor-Phillips & Stinton, 2019;Vosshenrich et al., 2021). For example, research has shown that radiologists' performance varies over the course of the day, generally peaking in the early evening, but suffering in the middle of the day following lunch (Monk, 2005). This "post-lunch dip effect" corresponds to a well-studied period of postprandial fatigue after the midday meal (Stahl et al., 1983). ...
Visual search-looking for targets among distractors-underlies many critical professions (e.g., radiology, aviation security) that demand optimal performance. As such, it is important to identify, understand, and ameliorate negative factors such as fatigue-mental and/or physical tiredness that leads to diminished function. One way to reduce the detrimental effects is to minimize fatigue itself (e.g., scheduled breaks, adjusting pre-shift behaviors), but this is not always possible or sufficient. The current study explored whether some individuals are less susceptible to the impact of fatigue than others; specifically, if conscientiousness, the ability to control impulses and plan, moderates fatigue's impact. Participants (N = 374) self-reported their energy (i.e., the inverse of fatigue) and conscientiousness levels and completed a search task. Self-report measures were gathered prior to completing the search task as part of a large set of surveys so that participants could not anticipate any particular research question. Preregistered linear mixed-effect analyses revealed main effects of energy level (lower state energy related to lower accuracy) and conscientiousness (more trait conscientiousness related to higher accuracy), and, critically, a significant interaction between energy level and conscientiousness. A follow-up analysis, that was designed to illustrate the nature of the primary result, divided participants into above- vs. below-median conscientiousness groups and revealed a significant negative relationship between energy level and accuracy for the below median, but not above-median, group. The results raise intriguing operational possibilities for visual search professions, with the most direct implication being the incorporation of conscientiousness measures to personnel selection processes.
... Namun, peningkatan sleep propensity (kecenderungan tidur) ini tidak tergantung dari makanan, jadi merupakan proses sirkadian berupa penurunan suhu tubuh. 22,23 Ditemukannya phase advance dari circadian dip pada kelompok bangun dini memperkuat temuan phase advance suhu maksimum kelompok yang sama. Jadi memang terjadi phase advance irama sirkadian pada kelompok bangun dini sebanyak 1-2 jam. ...
Banyak orang harus bangun lebih pagi sebelum matahari terbit karena tuntutan pekerjaan, sekolah, atau agama. Hal ini kemungkinan akan memengaruhi irama sirkadian. Tujuan penelitian mencari perubahan irama sirkadian pada orang yang bangun dini hari melalui perubahan suhu inti tubuh, dan perubahan proses homeostasis. Metode penelitian analitik pendekatan potong lintang, sampel penelitian 18 mahasiswa FKIK Ukrida angkatan 2016-2019 (21-24 tahun). Dibagi menjadi 2 kelompok, 13 subjek bangun jam 4-5 pagi (kelompok A) dan 5 subjek bangun jam 6-7 pagi (kelompok B). Suhu inti tubuh subjek diukur dengan termometer digital di ketiak setiap jam bangun selama 3 hari berturut-turut. Subjek mengisi kuesioner Epsworth Sleepiness Scale versi bahasa Indonesia. Analisis statistik menggunakan Chi-square. Hasil penelitian pada kelompok A suhu tubuh maksimum tercapai pada jam 18.00, kelompok B jam 19.00. Pada kelompok A circadian dip pada pukul 13.00, kelompok B pukul 15.00. Kelompok A 84,6% mengantuk berlebihan, kelompok B hanya 20% (p=0,022). Hasil penelitian sesuai perkiraan bahwa terjadi perubahan irama sirkadian pada orang yang bangun dini. Simpulan terjadi phase advance 1-2 jam irama sirkadian subjek bangun dini. Jadi sinar matahari tidak cukup kuat untuk entrainment pada subjek yang bangun dini. Selain itu subjek yang bangun dini lebih banyak mengalami mengantuk berlebihan sehingga menggambarkan pengaruh proses homeostasis.
... The 2-h period was chosen to allow enough time for one sleep cycle. To align with the post-lunch circadian dip (Monk, 2005), the nap occurred at approximately 1:00 p.m. ...
Relatively little is known regarding the interaction between encoding-related neural activity and sleep-based memory consolidation. One suggestion is that a function of encoding-related theta power may be to “tag” memories for subsequent processing during sleep. This study aimed to extend previous work on the relationships between sleep spindles, slow oscillation-spindle coupling, and task-related theta activity with a combined Deese-Roediger-McDermott (DRM) and nap paradigm. This allowed us to examine the influence of task- and sleep-related oscillatory activity on the recognition of both encoded list words and associative theme words. Thirty-three participants (29 females, mean age = 23.2 years) learned and recognised DRM lists separated by either a 2 h wake or sleep period. Mixed-effects modelling revealed the sleep condition endorsed more associative theme words and fewer list words in comparison to the wake group. Encoding-related theta power was also found to influence sleep spindle density, and this interaction was predictive of memory outcomes. The influence of encoding-related theta was specific to sleep spindle density, and did not appear to influence the strength of slow oscillation-spindle coupling as it relates to memory outcomes. The finding of interactions between wakeful and sleep oscillatory-related activity in promoting memory and learning has important implications for theoretical models of sleep-based memory consolidation.
... Fatigue appears generally during the afternoon and increases as the day gets closer to regular sleep times. The daily averaged scores suggest a subtle fatigue peak after midday that could be associated with what has been referred in the literature as post-lunch dip in performance 31 . This consensus with sleep and performance studies supports our hypothesis that keystroke dynamics can be used to quantify in an objective and unobtrusive manner daily fatigue in computer users. ...
In this paper we study the feasibility of employing keystroke biometrics for mental fatigue detection during natural typing. For this task, we employ TypeNet, a state-of-the-art deep neuronal network, originally intended for user authentication at large scale using keystroke dynamics. We adapted TypeNet for fatigue detection by leveraging the information embedded in TypeNet for person recognition, and applying that information to a different but related task as it is fatigue detection by employing domain adaptation techniques. All experiments were conducted using three keystroke databases that comprise different contexts and data collection protocols. Our preliminary results showed performances ranging between 72.2% and 80.0% for fatigue versus rested sample classification, which is aligned with previously published models on daily alertness and circadian cycles. This demonstrates the potential of our proposed system to characterize mental fatigue fluctuations via natural typing patterns. Finally, we studied the feasibility of an active detection approach that utilizes the continuous monitoring of keystroke biometric patterns for the real-time assessment of subject fatigue.
... The impermanent decline in alertness and performance during the afternoon, known as post-lunch dip, is thought to be the result of daytime sleepiness. [1][2][3] The introduction of naps is a practical countermeasure to overcome daytime sleepiness, which has been reported to significantly influence alertness, cognitive performance, decision-making, and social interactions in humans. [4][5][6][7] In fact, napping for 10-45 minutes after lunch has been verified to promote afternoon performance to varying degrees, including learning ability, memory, executive function, and vigilance. ...
Purpose
Previous epidemiological and psychological studies have assessed the effects of napping on individual performance and health. However, these studies did not distinguish between spontaneous and passive napping due to sleep disorders. Therefore, this study aimed to explore the potential motivation for napping among Chinese college students and to assess the relationship between different nap motivations and sleep.
Patients and Methods
This cross-sectional study was conducted at a university in Shanghai in March 2021 using convenience sampling. A total of 564 Chinese college students with self-reported napping habits participated in this study. Exploratory factor analysis (EFA) was employed to analyze 34 self-rated motivations for napping to derive a potential structural model of napping motivation. Correlation and multiple linear regression analyses were performed to determine the influence of nap motivation on sleep behavior.
Results
Chinese college students mainly take naps to reduce fatigue, usually in the form of frequent and long naps (6.25 ± 1.24 days; 64.62 ± 23.70 min). A structural model of nap motivation named the I-DREAM model was proposed, consisting of six factors: restorative, induced, mindful, appetitive, dysregulative, and exercise naps. There were also sex differences in nap motivation, as women preferred restorative naps and appetitive naps, while men preferred exercise naps (p < 0.01, p < 0.05). Furthermore, there was a significant correlation between nap motivation on nap duration, frequency and nighttime sleep quality (R²= 2.70–18.9%).
Conclusion
The proposed I-DREAM model implies that there are population differences in napping motivation. Different motivations also have different relationships with napping patterns and nighttime sleep. In understanding the relationship between naps and health status, nap motivation may be an extremely important influencing factor.
... The two-hour period was chosen to allow enough time for one sleep cycle. To align with the post-lunch circadian dip (Monk, 2005), the nap occurred at approximately 1:00pm. ...
Relatively little is known regarding the interaction between encoding-related neural activity and sleep-based memory consolidation. One suggestion is that a function of encoding-related theta power may be to 'tag' memories for subsequent processing during sleep. This study aimed to extend previous work on the relationships between sleep spindles, slow oscillation-spindle coupling and task-related theta activity with a combined Deese-Roediger-McDermott (DRM) and nap paradigm. This allowed us to examine the influence of task- and sleep-related oscillatory activity on the recognition of both encoded list words and associative theme words. Thirty-three participants (29 females, mean age = 23.2 years) learned and recognised DRM lists separated by either a 2hr wake or sleep period. Mixed-effects modelling revealed the sleep condition endorsed more associative theme words and fewer list words in comparison to the wake group. Encoding related theta power was also found to influence sleep spindle density, and this interaction was predictive of memory outcomes. The influence of encoding-related theta was specific to sleep spindle density, and did not appear to influence the strength of slow oscillation-spindle coupling as it relates to memory outcomes. The finding of interactions between wakeful and sleep oscillatory-related activity in promoting memory and learning has important implications for theoretical models of sleep-based memory consolidation.
... Interestingly, regardless of the nocturnal sleep the prior night, human performance decreases in the mid-day, as a result of "post-lunch dip" phenomenon, 21 which is related to an innate propensity for sleep during the early afternoon hours (2 a.m. to 4 a.m.). 22 Accordingly, mid-day napping is considered as countermeasure to impaired performance caused not only by sleep loss but also as a result of the "post-lunch dip" in human performance. A nap is commonly referred to as "short sleep". ...
Mid‐day napping has been recommended as a countermeasure against sleep debt and an effective method for recovery, regardless of nocturnal sleep duration. Herein, we summarize the available evidence regarding the influence of napping on exercise and cognitive performance as well as the effects of napping on athletes’ perceptual responses prior to or during exercise. The existing studies investigating the influence of napping on athletic performance have revealed equivocal results. Prevailing findings indicate that following a normal sleep night or after a night of sleep loss, a mid‐day nap may enhance or restore several exercise and cognitive performance aspects, while concomitantly provide benefits on athletes’ perceptual responses. Most, but not all, findings suggest that compared to short‐term naps (20‐30 min), long‐term ones (>35‐90 min) appear to provide superior benefits to the athletes. The underlying mechanisms behind athletic performance enhancement following a night of normal sleep or the restoration after a night of sleep loss are not clear yet. However, the absence of benefits or even the deterioration of performance following napping in some studies is likely the result of sleep inertia. The present review sheds light on the predisposing factors that influence the post‐nap outcome, such as nocturnal sleep time, mid‐day nap duration and the time elapsed between the end of napping and the subsequent testing, discusses practical solutions and stimulates further research on this area.
... around 15:00). 21 In mid-to-late March 2020, many federal and state-level governments around the world issued stay-at-home orders and recommendations in an effort to limit the spread and severity of the COVID-19 pandemic. In the U.S., this resulted in the closure of many nonessential business, the loss of roughly 16 million civilian jobs between March and May 2020 22 and 35% of the civilian workforce shifting to teleworking specifically due to the pandemic by May 2020. ...
Lighting for workplaces and schools is typically specified to meet the needs of the visual system without sufficient regard to the lighting characteristics that are required by the human circadian system. In 2020, many workers and student were compelled by the COVID-19 pandemic to work and study from home, where light levels are typically even lower than those found in most schools and workplaces. The aim of this study was to quantify potential changes in daytime light exposures resulting from teleworking or self-isolating at home and how those changes might have affected self-reported sleep quality, psychological health, and emotional health. The study employed electronic surveys to collect subjective response data for measures of both daily indoor and outdoor light exposures, as well as measures of sleep quality and wellbeing. The first survey (project Phase 1) was administered in early May 2020, and the second survey (project Phase 2) was administered in September 2020. The survey results were compared for respondents staying or working at home full-time during the lockdown to responses from individuals still staying or working at home full-time or working part or full-time at their places of work after the stay-at-home orders had been lifted.
... 27 There is some evidence of a dip in performance after lunch. 28 Circadian rhythms have been hypothesised to apply to radiology accuracy, with some studies reporting that diagnostic accuracy is worse when the interpretation of images takes place later in the day than when it takes place earlier in the day. 29,30 Other studies do not support this. ...
Fatigue in radiologists may be responsible for a large number of medical errors. This review describes the latest research on fatigue in radiology. This includes measurement methods, and recent evidence on how fatigue affects accuracy in laboratory test conditions and in clinical practice. The extensive opportunities for future research in the area are explored, including testing interventions to reduce fatigue-related error, and further understanding of which fatigue measures correlate with errors. Finally we explore the possibility of answering these questions using large population-based observational studies and pragmatic integrated randomised controlled trials. This publication is the reprint with Russian translation from original: Taylor-Phillips S, Stinton C. Fatigue in radiology: a fertile area for future research. Br J Radiol. 2019;92:20190043. doi: 10.1259/bjr.20190043.
... The timing of the afternoon learning sessions may also be an important factor, occurring in close proximity to the circadian dip 30 . Several studies have examined split sleep schedules in the context of shift work 32-37 , suggesting vigilance and subjective alertness are optimal when sleep is scheduled during circadian low points 35,36 . ...
Daytime naps have been linked with enhanced memory encoding and consolidation. It remains unclear how a daily napping schedule impacts learning throughout the day, and whether these effects are the same for well-rested and sleep restricted individuals. We compared memory in 112 adolescents who underwent two simulated school weeks containing 8 or 6.5 h sleep opportunities each day. Sleep episodes were nocturnal or split between nocturnal sleep and a 90-min afternoon nap, creating four experimental groups: 8 h-continuous, 8 h-split, 6.5 h-continuous and 6.5 h-split. Declarative memory was assessed with picture encoding and an educationally realistic factual knowledge task. Splitting sleep significantly enhanced afternoon picture encoding and factual knowledge under both 6.5 h and 8 h durations. Splitting sleep also significantly reduced slow-wave energy during nocturnal sleep, suggesting lower homeostatic sleep pressure during the day. There was no negative impact of the split sleep schedule on morning performance, despite a reduction in nocturnal sleep. These findings suggest that naps could be incorporated into a daily sleep schedule that provides sufficient sleep and benefits learning.
... However, the current results showed that the short nap was more beneficial than the long one after NSN. In fact, the PLD is a transient naturally occurring decline in performances even when athletes obtain a sufficient amount of nocturnal sleep [2,3]. Therefore, a short nap could be scheduled when athletes feel sleepy during the day, despite having a normal sleep during the previous night. ...
To compare the effects of two nap opportunities (20 and 90 min) to countermeasure the transient naturally occurring increased sleepiness and decreased performances during the post-lunch dip (PLD). Fourteen highly trained judokas completed in a counterbalanced and randomized order three test sessions (control (Nonap), 20- (N20) and 90-min (N90) nap opportunities). Test sessions consisted of the running-based anaerobic sprint test (RAST), simple and multiple-choice reaction times (MCRT) and the Epworth sleepiness scale (ESS). From the RAST, the maximum (Pmax), mean (Pmean) and minimum (Pmin) powers were calculated. Blood samples were taken before and after the RAST to measure the effect of pre-exercise napping on energetic and muscle damage biomarkers and antioxidant defense. N20 increased Pmax and Pmean compared to No-nap (p < 0.001, d = 0.59; d = 0.66) and N90 (p < 0.001, d = 0.98; d = 0.72), respectively. Besides, plasma lactate and creatinine increased only when the exercise was performed after N20. Both N20 (p < 0.001, d = 1.18) and N90 (p < 0.01, d = 0.78) enhanced post-exercise superoxide dismutase activity compared to No-nap. However, only N20 enhanced post-exercise glutathione peroxidase activity (p < 0.001, d = 1.01) compared to pre-nap. Further, MCRT performance was higher after N20 compared to No-nap and N90 (p < 0.001, d = 1.15; d = 0.81, respectively). Subjective sleepiness was lower after N20 compared to No-nap (p < 0.05, d = 0.92) and N90 (p < 0.01, d = 0.89). The opportunity to nap for 20 min in the PLD enhanced RAST, MCRT performances, and antioxidant defense, and decreased sleepiness. However, the opportunity of 90 min nap was associated with decreased repeated sprint performances and increased sleepiness, probably because of the sleep inertia.
... The effect of the time awake on inexperienced radiologists was notable and may be related to the time of day the reporting took place [15,18,36,37]. The lowest lesion sensitivity was observed during reporting at <2 and 4 to <6 h of wakefulness, when performance was significantly lower than the highest performance points, which were noted at 8 to <10 h of wakefulness. ...
... 8 Thus, PLD seems to be the perfect time to nap, because sleep propensity is higher and sleep latency is shorter. 9 Furthermore, PSD increases muscle, hepatic, and cardiac damage and decreases antioxidant defense after a single bout of exercise, 3,6,10 which would potentially affect recovery. Therefore, upcoming training and competition would be potentially affected by the incomplete recovery process. ...
Purpose:
To compare the effect of a 20-minute nap opportunity (N20), a moderate dose of caffeine (CAF; 5 mg·kg-1), or a moderate dose of caffeine before N20 (CAF+N) as possible countermeasures to the decreased performance and the partial sleep deprivation-induced muscle damage.
Methods:
Nine male, highly trained judokas were randomly assigned to either baseline normal sleep night, placebo, N20, CAF, or CAF+N. Test sessions included the running-based anaerobic sprint test, from which the maximum (Pmax), mean (Pmean), and minimum (Pmin) powers were calculated. Biomarkers of muscle, hepatic, and cardiac damage and of enzymatic and nonenzymatic antioxidants were measured at rest and after the exercise.
Results:
N20 increased Pmax compared with placebo (P < .01, d = 0.75). CAF+N increased Pmax (P < .001, d = 1.5; d = 0.94), Pmin (P < .001, d = 2.79; d = 2.6), and Pmean (P < .001, d = 1.93; d = 1.79) compared with placebo and CAF, respectively. Postexercise creatine kinase increased whenever caffeine was added, that is, after CAF (P < .001, d = 1.19) and CAF+N (P < .001, d = 1.36). Postexercise uric acid increased whenever participants napped, that is, after N20 (P < .001, d = 2.19) and CAF+N (P < .001, d = 2.50) and decreased after CAF (P < .001, d = 2.96).
Conclusion:
Napping improved repeated-sprint performance and antioxidant defense after partial sleep deprivation. Contrarily, caffeine increased muscle damage without improving performance. For sleep-deprived athletes, caffeine before a short nap opportunity would be more beneficial for repeated sprint performance than each treatment alone.
Background and Objectives: Volleyball demands high levels of anaerobic strength, flexibility, agility, and mental focus. Adequate sleep has been shown to enhance athletic performance and cognitive function. This study investigates the impact of post-lunch naps of varying durations (25 and 45 min) on the physiological performance and cognitive focus of elite volleyball players. Materials and Methods: Sixteen elite volleyball players (8 male, 8 female) with at least 7 years of competitive experience participated in a randomized crossover study. They underwent three experimental conditions: no nap (No-Nap), a 25-min nap (N25), and a 45-min nap (N45). Physical performance was measured through counter-movement jumps (CMJ) and volleyball agility tests, while cognitive function was assessed using the D2 attention test. Statistical analysis included repeated measures ANOVA to examine the differences between nap conditions and gender-specific responses. Results: Significant improvements in both physical performance and cognitive focus were observed in the N25 and N45 conditions compared to the No-Nap condition (indicating the effectiveness of short naps in enhancing both physical and mental performance). Males outperformed females in most physical metrics, while females scored higher on the D2 attention test (suggesting possible gender-specific responses to napping). The 25-min nap showed slightly better results in terms of sleep quality and subsequent performance (confirming that shorter naps may be more beneficial). Conclusions: Post-lunch naps, especially of 25 or 45 min, enhance both physiological and cognitive performance in elite volleyball players. These findings suggest that integrating short naps into athletes’ training regimens can improve performance and focus, with potential gender-specific benefits. Further research is needed to explore long-term effects and variations across other sports.
Objective:
Evaluate compliance, symptom reactivity, and acceptability/experience ratings for an ecological momentary assessment (EMA) protocol involving ultra-brief ambulatory cognitive assessments in adolescent and young adult patients with concussion.
Setting:
Outpatient concussion clinic.
Participants:
116 patients aged 13 to 25 years with concussion.
Design:
Prospective research design was used to examine compliance, symptom reactivity, and acceptability/experience for the Mobile Neurocognitive Health Project (MNCH); an EMA study of environmental exposures, symptoms, objective cognitive functioning, and symptom reactivity involving 4, daily EMA surveys (7:30 am, 10:30 am, 3:00 pm, 8:00 pm) for a period of 7 days following concussion. Overall compliance rates, symptom reactivity scores, and participant acceptability/experience ratings were described. A series of non-parametric Friedman Tests with post-hoc Wilcoxon signed-rank tests were used to examine differences in compliance and reactivity related to time of day and over the course of the protocol (first 3 days [Early Week] vs last 4 days [Late Week]).
Main measures:
Compliance rates, symptom reactivity scores, participant experience/acceptability.
Results:
Overall median compliance was 71%, and there were significantly fewer 7:30 am surveys completed compared to the 10:30 am (Z = -4.88,P ≤ .001), 3:00 pm (Z = -4.13,P ≤ .001), and 8:00 pm (Z = -4.68, P ≤ .001) surveys. Compliance for Early Week surveys were significantly higher than Late Week (Z = -2.16,P = .009). The median symptom reactivity score was 34.39 out of 100 and was significantly higher for Early Week compared to Late Week (Z = -4.59,P ≤ .001). Ninety-nine percent (89/90) of the sample agreed that the app was easy to use, and 18% (16/90) indicated that the app interfered with their daily life.
Conclusion:
Adolescents and young adults with concussion were compliant with the MNCH EMA protocol. Symptom reactivity to the protocol was low and the majority of participants reported that the app and protocol were acceptable. These findings support further investigation into applications of EMA for use in concussion studies.
Objectives
“WKUP GT”, a low caffeine beverage consisting of carob, Guarana, Green Tea and Elderberry extracts was studied on attention and cognitive functions post‐lunch in a pilot randomized double blind placebo controlled trial.
Methods
Thirty healthy volunteers were included in a crossover design trial, presenting five beverages randomly assigned to the following groups: placebo, “WKUP GT” (single, double or triple doses), or “caffeine” as an active control. Hemodynamic measurements were assessed as safety outcomes.
The Cambridge Neuropsychological Test Automated Battery (CANTAB), was used to evaluate the patients when beverages were consumed 30 and 120 min after lunch (respectively Delta30 and Delta120 considering baseline).
Results
Drinking “caffeine” or “WKUP GT” after lunch, showed significant improvement ( p < 0.05) in rapid visual information processing compared to placebo (Delta120 of “caffeine”, “WKUP” single and double). In addition, improvement in Multitasking Test (Delta30 for “WKUP” double, and Delta120 for “caffeine” and “WKUP” triple compared to placebo) was observed. “WKUP” triple also showed significant improvement for “memory” when compared to placebo (Delta120). Compared to “caffeine”, WKUP GT did not increase systolic blood pressure.
Conclusion
“WKUP GT” showed improvements for attention, memory, psychomotor and executive function tasks after lunch without increase in pulse rate.
Drosophila melanogaster was first used for research in the early 1900’s by scientists located in the northeastern corridor of the United States, gaining prominence with the establishment of the famous “fly room” by Thomas Hunt Morgan at Columbia University circa1908. Several reasons for using D. melanogaster in research are well known; easy and inexpensive to breed, short lifespan, amongst others. But why was this insect species flourishing in a temperate northeast region of the New World during the late 1800’s when they originated in the tropical forests of sub-Saharan Africa millions of years ago? The purpose of this review is to provide an overview of the experimental underpinnings for a temperature sensitive mechanism that likely contributed to the rather unique ability of Drosophila melanogaster to successfully colonize temperate regions on a global scale. It also furnishes an interesting historical insight into how ancestral genetics serendipitously held the keys to the journey of D. melanogaster becoming such a popular research organism. While numerous papers have been published detailing different aspects of the work, this is the first comprehensive review. Herein, I discuss the discovery of a small thermosensitive intron in D. melanogaster (termed dmpi8) that controls midday siesta levels. Like many day-active animals, Drosophila exhibits a robust genetically based midday siesta that is protective in warm climates. Yet long bouts of daytime inactivity might be counterproductive in temperate climates, especially since daylength in these regions is shorter during the cooler months. Evidence discussed in this review strongly indicates that targeting of dmpi8 splicing efficiency by natural selection enhanced the ability of D. melanogaster to scale daytime sleep levels commensurate with a wide range of local climates. Surprisingly, dmpi8 splicing regulates midday siesta levels in trans by controlling the expression of a nearby anti-siesta gene called daywake. The “fortuitous” genetic arrangement of a thermosensitive intron in proximity to an anti-siesta gene might have contributed to the cosmopolitan nature of D. melanogaster and its historical journey in becoming a popular research organism.
This study aims to investigate the impact of a 40‐min nap opportunity on perceived recovery, exertion, and maximal voluntary isometric contraction (MVIC) following the 5‐m shuttle run test (5SRT), after 1 night of normal sleep. In a randomised, counterbalanced, cross‐over design, 17 trained men (mean [SD] age 20 [3] years, height 173 [6] cm, body mass 68 [6] kg) performed a 5SRT under two conditions: a 40‐min nap opportunity and no‐nap condition. After both conditions, electromyography signals during a 5‐s isometric knee extension were recorded before and immediately after the 5SRT. Two electrical nerve stimulations at the femoral nerve were measured during and after the MVIC. Force, voluntary activation level, M‐wave amplitudes, potentiated twitch, and electromyography signals (root mean square) were measured during each MVIC. Perceived exertion was recorded after each repetition of the test and perceived recovery was determined after the end of the MVIC. Compared to the no‐nap condition, the 40‐min nap resulted in significant enhancements in both the highest distance ( p < 0.01, Δ = +7.6%) and total distance ( p < 0.01, Δ = +7.5%). Before and after exercise, values for MVIC, root mean square, M‐wave amplitudes, and voluntary activation level were improved after the 40‐min nap opportunity compared to no‐nap condition (all p ≤ 0.01). Values for perceived exertion and recovery were improved after the 40‐min nap opportunity in comparison with no‐nap condition ( p ≤ 0.01). A 40‐min nap opportunity improved repeated high‐intensity short‐term maximal performance, perceived recovery, associated neuromuscular responses, and reduced perceived fatigue. Therefore, our findings suggest that central and peripheral processes are involved in the improvements of 5SRT performance after napping.
Background & Aims: The role of nutrition in modulating the inflammatory response is increasingly recognized. The phytonutrient sulforaphane shows promise for clinical use due to its effect on inflammatory pathways, favorable pharmacokinetic profile, and high bioavailability. The inflammatory status has been linked to autonomic activity, which can be assessed by the study of heart rate variability (HRV). However, monitoring of HRV for assessment of inflammation in humans has hardly been used. We investigated the potential of HRV as a non-invasive tool to monitor inflammation induced by the caloric load and assessed the effects of sulforaphane on caloric load-induced inflammation in healthy participants. Methods: In this double-blind, crossover, randomized, placebo-controlled trial twelve healthy participants (26.9 (3.6) years) were administered 25 mg of sulforaphane, or placebo followed over 90 min by the standardized high-calorie drink PhenFlex given to induce an inflammatory response. Levels of high-sensitivity C-reactive protein (hs-CRP) and interleukin (IL)-6 were measured in plasma before and two hours after the PhenFlex challenge. Changes in the autonomic function were assessed by HRV on four timepoints. Results: The caloric challenge triggered a significant increase in total power (TP) (P = 0.028) and very low frequency (VLF) component (P = 0.013) 30 min after its administration. Those changes were followed by reduction of TP (P = 0.028) and low frequency (LF) component (P = 0.005), suggesting marked decrease in the sympathetic activity two hours after the caloric load. When sulforaphane was given prior to the caloric challenge, decreased parasympathetic activity was observed via a reduction of RMSSD (P = 0.007), pNN50 (P = 0.013) and HF (P = 0.047). In addition, sulforaphane elicited a pro-inflammatory response as measured by the change of hs-CRP with caloric exposure (sulforaphane 2.7 (4.2) vs. placebo -1.8 (3.1) ng/mL, P = 0.048). The pro-inflammatory effect of sulforaphane was associated with vagal withdrawal and sympathetic dominance as suggested by correlations between the changes in hs-CRP and HF (rs = -0.68, P = 0.029) as well as LF/HF (rs = 0.56, P = 0.093) components assessed before and two hours after the PhenFlex challenge. Conclusions: Monitoring of HRV might be a sensitive tool to follow activity of the inflammatory response in various clinical conditions. The standardized caloric PhenFlex challenge induced significant changes in the autonomic regulation in healthy young individuals. Administration of sulforaphane prior to the caloric challenge caused a pro-inflammatory effect which was accompanied by vagal withdrawal and sympathetic dominance. Trial registration number: NCT05146804 at www.clinicaltrials.gov.
Based on the Conservation of Resources theory, we develop dual mechanisms by which lunchtime recovery activities predict creativity. Specifically, by conceptualizing the quality of lunchtime naps and meals as examples of recovery activities, we expect these recovery activities help individuals replenish their psychological resources in the form of more work engagement (affective process) and less cognitive depletion (cognitive process). Further, individuals are expected to utilize these available psychological resources to generate creative ideas. To test our model, we used a group‐mean centering approach to focus on within‐person effects by recruiting 230 employees working at construction sites in South Korea. Overall, after removing 242 invalid observations (omitting at least two items and not reporting the duration of a nap), we finalized a total of two‐wave 1598 daily questionnaires. A high quality of lunchtime naps and meals helps individuals recover their emotional resources (more work engagement) and cognitive resources (less cognitive depletion), which predict individuals' creativity. Finally, although indirect effects of the two recovery activities on creativity via affective and cognitive processes were generally supported, the indirect effect of lunch nap quality on creativity via work engagement was not significant, suggesting most of the effect is due to meal quality rather than nap quality.
Background:
This study explores whether listening to preferred music after a stressful situation affects putting and swinging performance, heart rate (HR), HR variability (HRV), and anxiety among amateur golfers.
Methods:
Twenty healthy amateur collegiate golfers voluntarily participated in this study (age 20.1 ± 1.17 yrs., height = 173.8 ± 7.74 cm, body weight = 72.35 ± 12.67 kg). Pre- and post-intervention HR and HRV measurements were taken, along with a self-report of the State-Trait Anxiety Inventory (STAI-S) and Triple Factor Anxiety Inventory (TFAI). Participants were exposed to a stressful situation through the Stroop Colour and Word Test (SCWT) and then instructed to perform three golf-practice sessions in a golf simulator, separated by 48–72 hours of recovery, under different conditions: control, pre-task music, and synchronised music.
Results:
No significant difference was identified between the experimental conditions for swinging (in terms of total distance ( p = 0.116), carry distance ( p = 0.608), speed of the ball ( p = 0.819), and launch angle ( p = 0.550) and putting performance (the number of successful putts on target ( p > 0.05) and distance error between the target and ball ( p = 0.122). No main effect for condition and time of intervention, as well as no interaction between these two factors was found for HR, HRV, and STAI-S ( p = 0.116). However, the pre and post-intervention percentages of physiological items of the TFAI indicated a large, significant difference in synchronised music trial ( p = 0.012, pre-task trial = −1.92% < control trial = 0% < synchronised trial = 4.58%).
Conclusions:
The results imply that following a stressful situation, listening to preferred music before and/or during golf has no immediate effect on golf performance, anxiety, and psychophysiological responses in collegiate golfers.
The objective of the present work was to investigate the impacts of energetic and restorative naps on subjective levels of arousal, and on aspects of cognitive and physical performances in the afternoon in healthy habitual nappers. To meet our objective, three experimental studies were implemented. We investigated the impacts of the nap in different sleep environments, namely the bed, the reclining chair, and the SOMBOX sleep product which we contributed to its development and validation. We found that regardless of the sleep environments, all the naps enhanced daytime arousal and improved cognitive performances, with longer lasting effects observed after taking a nap in the bed compared to a nap in the box or the reclining chair. Accordingly, we recommend napping in a bed. Regarding the impacts of the energetic nap on cognitive performances, we found that the nap enhanced daytime arousal and improved sustained attention, mental rotation, and information processing speed in the simple reaction time and the delayed match-to-sample tests. However, a negative impact of napping was observed in the visual scanning test. Concerning the effects of the energetic nap on physical performances, the results demonstrated that there were no improvements in muscular power, maximal jump high, and endurance performances compared to the no-nap condition. Nevertheless, the nap enhanced speed and directional ability. Together, these findings suggested that the effects of the energetic nap on cognitive and physical performances are highly task-dependent. Regarding the effects of the restorative nap, we found that the deficit in cognitive and physical performances induced by partial sleep deprivation was restored following the nap. We assume that the beneficial effects of the energetic and restorative naps on performances depend on a fine balance between the input of the circadian system and the sensitivity level of the performed task to the homeostatic pressure.
To investigate the effect of 20 min nap opportunity (N20), 5 mg · kg-1 of caffeine (CAF) and their combination (CAF+N20) on the biochemical response (energetic biomarkers, biomarkers of muscle damage and enzymatic antioxidants) to the running-based anaerobic sprint test. Fourteen highly trained male athletes completed in a double-blind, counterbalanced and randomized order four test sessions: no nap with placebo (PLA), N20, CAF and CAF+N20. Compared to PLA, all treatments enhanced maximum and mean powers. Minimum power was higher [(mean difference) 58.6 (95% confidence interval = 1.31–116) Watts] after CAF and [102 (29.9–175) Watts] after CAF+N20 compared to N20. Also, plasma glucose was higher after CAF [0.81 (0.18–1.45) mmol·l-1] and CAF+N20 [1.03 (0.39–1.64) mmol·l-1] compared to N20. However, plasma lactate was higher [1.64 (0.23–3.03) mmol ·l-1] only after N20 compared to pre-exercise, suggesting a higher anaerobic glycolysis during N20 compared to PLA, CAF and CAF+N20. Caffeine ingestion increased post-exercise creatine kinase with [54.3 (16.7–91.1) IU·l-1] or without napping [58.9 (21.3–96.5) IU·l-1] compared to PLA. However, superoxide dismutase was higher after napping with [339 (123–554) U·gHB-1] or without caffeine [410 (195–625) U·gHB-1] compared to PLA. Probably because of the higher aerobic glycolysis contribution in energy synthesis, caffeine ingestion resulted in better repeated sprint performance during CAF and CAF+N20 sessions compared to N20 and PLA. Caffeine ingestion resulted in higher muscle damage, and the short nap enhanced antioxidant defence with or without caffeine ingestion.
Internet of things (IoT) and Radio Frequency Identification (RFID) technologies are gradually adopted in manufacturing recently. With the aid of them, numerous data is generated from daily manufacturing operations. Big data analytics is used in locating deficiencies and thus improving the productivity of a manufacturing shopfloor. Many studies have also examined the effect of “Blue Monday” and “post-lunch slump” on worker’s performance. This paper provides a big data approach on analyzing worker’s performance with the data collected from a manufacturing shopfloor. By evaluating the worker’s performance at different time periods, a better decision can be arranged for improving overall productivity.
Background and objective:
The ever-increasing fatality rate due to traffic and workplace accidents, resulting from drowsiness have been a persistent concern during the past years. An efficient technology capable of monitoring and detecting drowsiness can help to alleviate this concern and has potential applications in driver vigilance monitoring, vigilance monitoring in air traffic control rooms and other safety critical work places. In this paper, we present the feasibility of a wearable light weight wireless consumer grade Electroencephalogram (EEG)-based drowsiness detection.
Methods:
A set of informative features were extracted from short daytime nap EEG signals and their applicability in discriminating between alert and drowsy state was studied. We derived an optimal set of EEG features, that give maximum detection rate for the drowsy state. In addition, heart rate was also recorded concurrently with EEG and correlation between heart rate and the EEG features corresponding to drowsiness was also studied.
Results:
Using the selected features, the EEG data is shown to be capable of classifying alert and drowsy states with an accuracy of 78.3% using Support Vector Machine classifier employing cross subject validation. The feature selection results also revealed that, the EEG features extracted from the temporal electrodes are more significant for drowsiness detection than the features from frontal electrodes. In addition, EEG features extracted from the temporal electrodes yielded higher correlation coefficient with heart rate, which was in concordance with the feature selection results.
Conclusions:
The results reveal that using the proposed drowsiness detection algorithm, it is possible to perform drowsiness detection using a single EEG electrode placed behind the ear.
Episodic memory is reconstructive and is thus prone to false memory formation. Although false memories are proposed to develop via associative processes, the nature of their neural representations, and the effect of sleep on false memory processing is currently unclear. The present research employed the Deese-Roediger-McDermott (DRM) paradigm and a daytime nap to determine whether semantic false memories and true memories could be differentiated using event-related potentials (ERPs). We also sought to illuminate the role of sleep in memory formation and learning. Healthy participants (N = 34, 28F, mean age = 23.23, range = 18-33) completed the learning phase of the DRM task followed by an immediate and a delayed recognition phase. The two recognition phases were separated by either a 2hr daytime nap or an equivalent wake period. Linear mixed modelling of effects at delayed recognition revealed larger LPC amplitudes for true memories in contrast to false memories for those in the wake group, and larger P300 amplitudes for false compared to true memories across sleep and wake groups. Larger LPC amplitudes for true memories were associated with enhanced true memory recognition following sleep, whilst larger P300 amplitudes were associated with similar true and false memory recognition rates. These findings are argued to reflect sleep’s ability to promote memory generalisation associated with pattern completion, whilst also enhancing true memory recognition when memory traces have a strong episodic basis (linked to pattern separation). The present research suggests that true and false memories have differing neural profiles and are reflective of adaptive memory processes.
Consistent effects of time of day have been observed in digit span/sequence performance, and in the immediate memory for information presented in prose. However, studies using syntactically unstructured word lists have yielded inconsistent results. Three experiments were conducted that examined the free recall of 15 word lists. In all three, immediate recall from the pre-recency positions was found to be superior in the morning to the afternoon. This superiority disappeared after a 20-min delay (Experiment 1) and under articulatory suppression (Experiment III), but was unaffected by a manipulation that equated recall order (Experiment II). Immediate recall from the recency positions showed a W-shaped trend over the day (Experiment I) that might account for the inconsistencies previously reported. It is suggested that the changes in recall from the pre-recency positions may reflect a decrease in maintenance, and increase in elaboration, over the day. Such a change in processing strategy could itself reflect an increase in attentional selectivity associated with the changes in basal arousal level commonly held to occur over the day.
An English language self-assessment Morningness-Eveningness questionnaire is presented and evaluated against individual differences in the circadian vatiation of oral temperature. 48 subjects falling into Morning, Evening and Intermediate type categories regularly took their temperature. Circadian peak time were identified from the smoothed temperature curves of each subject. Results showed that Morning types and a significantly earlier peak time than Evening types and tended to have a higher daytime temperature and lower post peak temperature. The Intermediate type had temperatures between those of the other groups. Although no significant differences in sleep lengths were found between the three types, Morning types retired and arose significantly earlier than Evening types. Whilst these time significatly correlated with peak time, the questionnaire showed a higher peak time correlation. Although sleep habits are an important déterminant of peak time there are other contibutory factors, and these appear to be partly covered by the questionnaire. Although the questionnaire appears to be valid, further evaluation using a wider subject population is required.
Accurate estimation of the phases and amplitude of the endogenous circadian pacemaker from constant-routine core-temperature series is crucial for making inferences about the properties of the human biological clock from data collected under this protocol. This paper presents a set of statistical methods based on a harmonic-regression-plus-correlated-noise model for estimating the phases and the amplitude of the endogenous circadian pacemaker from constant-routine core-temperature data. The methods include a Bayesian Monte Carlo procedure for computing the uncertainty in these circadian functions. We illustrate the techniques with a detailed study of a single subject's core-temperature series and describe their relationship to other statistical methods for circadian data analysis. In our laboratory, these methods have been successfully used to analyze more than 300 constant routines and provide a highly reliable means of extracting phase and amplitude information from core-temperature data.
Previous research has shown that caffeine increases alertness and improves sustained attention. In contrast to this, consumption of lunch leads to a decline in the ability to maintain attention. The main aim of the present study was to determine whether caffeine removes or reduces the postlunch drop in performance, an issue which is of considerable practical importance and theoretical interest. The results showed that caffeine improved performance on the Bakan vigilance task and removed the post-lunch dip observed in the decaffeinated condition. Similar effects were observed in one of the conditions of a mental rotation task. The lunch X caffeine interaction observed in the Bakan task did not change over the course of the task. In contrast to the performance data, lunch X caffeine interactions were not observed in analyses of cardiovascular function or subjective mood.
"Morning" and "evening" persons, defined according to a modified version of the Horne and Ostberg questionnaire, performed the 7/13 min sleep-waking schedule under attempting sleep condition after sleeping for one night in the laboratory, and under the resisting sleep condition after one night of sleep deprivation. Morning types slept significantly more under the attempting sleep condition and showed an earlier rise in nocturnal sleepiness. After sleep deprivation, morning types had a more distinct sleep propensity pattern with well-defined midafternoon and nocturnal sleep gates. In this condition there was a significant interaction between type and time of day with respect to amount of sleep: morning types slept more during the night, and evening types slept more during the day. Based on their amounts of sleep, subjects were also divided into "sleepy" and "alert" types, which were independent from the chronotypology.
Following the 1986 annual meeting of the Association of Professional Sleep Societies (Columbus, Ohio, U.S.A., June 15–22, 1986), a committee of scientists was formed to review recent reports and related information on the role of human sleep and brain clocks (time-of-day variation in physiology and alertness) in the occurrence of medical and human error catastrophes. This is a report of the committee's findings and recommendations.
The purpose of this study was to evaluate homeostatic and circadian sleep process in 'larks' and 'owls' 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 'working' 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 = 0.01) and 2 h (P = 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 = 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 = 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.
There is now a wealth of physiological evidence that man’s internal body chemistry changes predictably as a function of time of day. It is thus hardly surprising that there are equivalent predictable changes in his mood and performance efficiency, and it is to these psychological circadian rhythms that the present chapter is primarily addressed. In particular, it will be concerned with circadian performance rhythms, the history of their study, the methodological problems connected with measuring them, the forms of rhythms usually found, and the arousal model conventionally used to explain them. A final section is then concerned with some of the practicalities of measuring psychological rhythms, and the direction in which future developments might be expected to lead.
The most marked ‘ morning ’ and ‘evening ’ types in a psychology class were identified by means of a questionnaire, and asked to record their oral temperatures and food intakes throughout the day during a 4-week and a 4-day period respectively. The morning group had its mean circadian temperature maximum 5 h earlier than the evening group, and had its cumulative food intake distribution curve 1¾ h ahead of the evening group. After adjusting the food distributions by 1¾ h in the time base to get a least-square fit, significant differences between the distributions remained. It is suggested that morning types have a more autonomous 24-hour-periodicity than evening types. It is concluded that the questionnaires have the power to discriminate extreme morning and evening types of individuals in terms of oral temperature and food intake. Food intake seems to be a sensitive enough measure to be included in studies of inter-individual differences of circadian rhythms.
PERFORMANCE ON 8 TASKS RANGING FROM NOVEL LABORATORY TESTS TO HIGHLY PRACTICED FAMILIAR SKILLS WAS MEASURED AT 5 TIMES OF DAY BETWEEN 8 AM AND 9 PM. 5 TASKS SHOWED A CONSISTENT TENDENCY FOR IMPROVEMENT IN EFFICIENCY; IN 1 TASK THERE WAS DETERIORATION; AND IN THE REMAINING 2 THE EFFECTS WERE NOT SIGNIFICANT. RESULTS SUGGEST THAT THE OBSERVED TRENDS ARE RELATED TO THE UNDERLYING STATE OF AROUSAL AS INDICATED BY BODY TEMPERATURE. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
There were 15 healthy female subjects, differing in their position on the “morningness-eveningness” scale, studied for 7 consecutive days, first while living a sedentary lifestyle and sleeping between midnight and 08:00 and then while undergoing a “constant routine.” Rectal temperature was measured at regular intervals throughout this time, and the results were subjected to cosinor analysis both before and after “purification” for the effects of physical activity. Results showed that there was a phase difference in the circadian rhythm of core temperature that was associated with the morningness score, with calculations that “morning types” would be phased earlier than “evening types” by up to about 3h. This difference in phase (which was also statistically significant when the group was divided by a median split into a “morning group” and an “evening group”) could not be attributed to effects of waking activity and existed in spite of the subjects keeping the same sleep-wake schedule. Moreover, it persisted when the subjects' data had been purified and when the data were obtained from the constant routine. That is, there was an endogenous component to this difference in phase of the core temperature. The morning group also showed a greater fall of core temperature during sleep; this was assessed in two ways, the main one being a comparison of constant routine and nychthemeral data sets after correction for any effects of activity. Even though the morning group was sleeping at a later phase of their circadian temperature rhythm than was the evening group, neither group showed a fall of temperature due to sleep that varied with time elapsed since the temperature acrophase. It is concluded that another factor that differs between morning and evening types is responsible for this difference. (Chronobiology International, 18(2), 227–247, 2001)
This study explored the relationship between circadian performance rhythms and rhythms in rectal temperature, plasma cortisol, plasma melatonin, subjective alertness and well-being. Seventeen healthy young adults were studied under 36 h of «unmasking» conditions (constant wakeful bedrest, temporal isolation, homogenized «meals») during which rectal temperatures were measured every minute, and plasma cortisol and plasma melatonin measured every 20 min. Hourly subjective ratings of global vigour (alertness) and affect (well-being) were obtained followed by one of two performance batteries. On odd-numbered hours performance (speed and accuracy) of serial search, verbal reasoning and manual dexterity tasks was assessed. On even-numbered hours, performance (% hits, response speed) was measured at a 25–30 min visual vigilance task. Performance of all tasks (except search accuracy) showed a significant time of day variation usually with a nocturnal trough close to the trough in rectal temperature. Performance rhythms appeared not to reliably differ with working memory load. Within subjects, predominantly positive correlations emerged between good performance and higher temperatures and better subjective alertness; predominantly negative correlations between good performance and higher plasma levels of cortisol and melatonin. Temperature and cortisol rhythms correlated with slightly more performance measures (5/7) than did melatonin rhythms (4/7). Global vigour correlated about as well with performance (5/7) as did temperature, and considerably better than global affect (1/7). In conclusion: (1) between-task heterogeneity in circadian performance rhythms appeared to be absent when the sleep/wake cycle was suspended; (2) temperature (positively), cortisol and melatonin (negatively) appeared equally good as circadian correlates of performance, and (3) subjective alertness correlated with performance rhythms as well as (but not better than) body temperature, suggesting that performance rhythms were not directly mediated by rhythms in subjective alertness.
In this study, we report the effects of sleep loss upon circadian rhythm parameters analyzed by the cosine curve fitting (cosinor)
method. Rhythm alterations are described as reductions in rhythm strength, increases in individual variations producing an
increase in the 95% confidence limits, and reductions in rhythm amplitude. Subjects worked continuously at tasks for 45 h
with time-of-day cues. Circadian cycles in physiological and mood variables remained intact, but rhythms in some task performance
measures no longer showed significant 24-h/cycle activities. The relationship between oral temperature, mood, and pulse rhythms
continued undisturbed during the continuous work period; however, the performance linkage to oral temperature was lost. These
findings direct attention to individual difference in susceptibility to continuous work periods and suggest that 24-h rhythms
in some performance and physiological measures perhaps are more readily responsive to an altered wake/sleep cycle than other
circadian rhythms.
Forty students performed on a perceptual discrimination task both before and after a mid-day lunch interval. Half of the students
consumed a three-course lunch during the interval, the remaining half abstained from lunch. It was found that the actual ability
to discriminate between events was significantly impaired following the consumption of lunch, but did not alter when no food
was ingested. The magnitude of the post-lunch dip in discrimination efficiency was significantly greater in the less “neurotic”
and the more “extraverted” individuals, according to scores on the Eysenck Personality Inventory, and was also significantly
though negatively related to the extent of the drop in sublingual temperature that occurred over the lunch interval. It is
concluded that operational efficiency and safety may be at risk following lunch.
Previous studies have led to the beliefs: (1) that short-term memory is best during the night when the body temperature is at its nadir, and (2) that the circadian rhythms of short-term memory and subjective alertness are driven by oscillators independent from each other and from the body temperature cycle. Unfortunately, these conclusions, which would have major implications for understanding the organization of the human circadian timing system, are largely based on field and laboratory studies, which in many cases sampled data infrequently and/or limited data collection to normal waking hours. In order to investigate these points further, we have monitored behavioural variables in two different protocols under controlled laboratory conditions: (1) during a period of 36-60 h of sustained wakefulness; and (2) during forced desynchrony between the body temperature and sleep/wake cycles, allowing testing of non-sleep-deprived subjects at all circadian phases. Contrary to earlier findings, we report here that the circadian rhythm of short-term memory varies in parallel with the circadian rhythms of subjective alertness, calculation performance, and core body temperature under both these experimental conditions. These results challenge the notion that short-term memory is inversely linked to the body temperature cycle and suggest that the human circadian pacemaker, which drives the body temperature cycle, is the primary determinant of endogenous circadian variations in subjective alertness and calculation performance as well as in the immediate recall of meaningful material.
For half a century, Sleep and Wakefulness has been a valuable reference work. It discusses phases of the sleep cycle, experimental work on sleep and wakefulness, sleep disorders and their treatment, and such sleep-like states as hypnosis and hibernation.
Three complementary studies examined the effect of lunch within the context of diurnal variation recording of blood glucose, autonomic indices, body temperature, mood and performance efficiency in male and female subjects.The parasympathetic control of insulin is suggested as a mechanism which may underpin postprandial increases in deactivated mood. Sex differences in autonomic indices are related to possible sex differences in response to the laboratory environment and procedure.
The "post-lunch dip" is a common behavioral phenomenon, though perhaps a misnomer. Biphasic models of the human sleep tendency rhythm suggest an alternative explanation for the afternoon decline in alertness. Sleep tendency was measured with the Multiple Sleep Latency Test (MSLT) at 2-hour intervals in 16 volunteers from three age groups (ages 10-12, ages 16-17, ages 62-74 years) during a constant routine in which small meals were given each hour. Baseline scores showed no significant Time of Day effect, although a trend for an afternoon dip was present in the eldest group. During the constant routine, a significant Time of Day effect was found for the two older groups and not for the prepubertal group. The results indicate a midday increase in sleep tendency that is unrelated to food intake but that may be related to developmental or maturational processes.
This study tested the hypothesis that the impaired sleep of healthy 71-91 year olds might be due to circadian dysfunction stemming from irregularity of life-style. Twenty-five old women, 20 old men and 21 young controls (19-28 years old) were studied in relation to 1) objective sleep as measured in the laboratory, 2) subjective sleep quality as measured by the Pittsburgh sleep quality index (PSQI) and 3) the social rhythm metric (SRM), an instrument to quantify the daily rhythms of life. Contrary to prediction, the SRM scales revealed that the older group had just as many activities completed and just as much other-person involvement as the young. Moreover, they showed a significantly greater regularity in daily life-style than the young, despite showing reliably impaired subjective and objective sleep. This suggests either that these seniors have always been regular in their life-style and that this has been protective of their health and vigor, or that their regularity has been developed as an adaptive response to age-related changes in the circadian system.
To examine differences between healthy elderly and young adults in daytime napping, nocturnal sleep, and 24-hour sleep/wake patterns. A second objective was to determine whether elderly subjects with more and less frequent naps differed in their clinical features or nocturnal sleep.
Survey by sleep/wake logs and polysomnography. Comparison by age.
Sleep/wake logs were completed in the subjects' homes. Polysomnographic studies were conducted on an outpatient basis in a sleep and chronobiology research laboratory.
Convenience samples of forty-five healthy subjects over 78 years of age (21M, 24F) and 33 healthy adults between 20 and 30 years of age (20M, 13F).
Using self-reports, we estimated the frequency and timing of daytime naps; timing, duration, and quality of nocturnal sleep; and 24-hour patterns of sleep and wakefulness. Also polysomnographic sleep measures.
Compared to young adults, elderly subjects reported a greater mean number of daytime naps (P = .004), shorter nocturnal sleep with more wakefulness and earlier sleep hours (P less than .003 for each), and a trend for a shorter 24-hour sleep fraction. Among the elderly, more-frequent and less-frequent nappers did not differ in clinical ratings, self-report sleep measures, or polysomnographic measures. There was a trend for more sleep-disordered breathing and periodic limb movements in more frequent nappers.
These findings are consistent with an age-related decrease in amplitude of the circadian sleep propensity rhythm, or with the expression of a semi-circadian (12-hour) sleepiness rhythm. However, we cannot exclude the additional possibility that napping results from lifestyle factors and nocturnal sleep pathologies in a subset of the elderly.
Thirty-six undergraduate subjects were divided into 'larks' and 'owls' by median split using the morningness test devised by Horne and Ostberg. Each was given a battery of two performance tests at six times of day, in a design that counter-balanced for practice effects. Oral temperatures were also recorded. Slight (1 hr) phase differences (in the predicted direction) were observed between 'larks' and 'owls' in temperature rhythm, and in the performance test that paralleled temperature (a serial search task). Much more striking differences, though, were observed in the cognitive (logical reasoning) performance test which (as predicted) peaked earlier in the day, on average, than the serial search task. Not only did 'larks' peak much earlier in the day than 'owls', but there were also quite dramatic differences between the two groups in amplitude and shape. Possible mechanisms regarding oscillatory control and performance strategy are discussed.
P átkai , P. Interindividual differences in diurnal variations in alertness, performance, and adrenaline excretion . Acta physiol. scand. 1971. 81 . 35–46.
Subjects classified as habitual morning vs. evening workers on the basis of their answers to a questionnaire, were compared with regard to day‐time variations in catecholamine excretion and performance. Adrenaline excretion in morning workers was highest in the morning and decreased gradually during the day, while evening workers showed nearly constant excretion values. The performance of morning workers did not vary during the day, while evening workers showed a steady improvement, performing best in the evening. In addition, a significant difference between the two groups was found in the personality dimension of extraversion‐introversion, showing that evening workers were more extravert and morning workers more introvert. The constancy of individual diurnal rhythms and their relations to personality traits, are discussed.
Two groups of subjects identified as either morning (M) or evening (E) types, determined by a self-assessment questionnaire, were measured for performance efficiency at a simulated production-line inspection task given for 15 sessions at different times of the waking day. Systematic fatigue and practice effects were minimised by a random presentation of these sessions over a series of days. Although there were no significant within- or between-group changes with circadian trends for items erroneously rejected, significant differences were apparent with the number of items correctly rejected. M types' correct rejection levels were significantly better than E types' in the morning, whereas they were worse during the evening. Whilst E types showed a steady improvement throughout the day, M types showed a general decline. A post-lunch dip in performance was quite evident for M types, but not for E types. In addition, the circadian trends in correct rejection levels and body temperature were highly positively correlated for E types, but a significant negative relationship between these parameters was found for M types. These findings are discussed.
The deterioration of nocturnal sleep and increase in daytime napping that accompany aging may represent changes in homeostatic or circadian aspects of sleep regulation. We addressed these possibilities by examining patterns of unintended sleep episodes, subjective sleepiness and mood during 36 hours of constant wakeful bed rest in 17 healthy 20-30-year-olds (n = 9 men, n = 8 women) and 18 healthy 80-year-olds (n = 11 men, n = 7 women). Subjects had continuous electroencephalographic (EEG) monitoring and core body temperature measurements and completed visual analog scale ratings of sleepiness and mood each hour. Young and elderly groups both showed significant linear and circadian trends in sleep episodes across the interval. Group x time interaction effects revealed a stronger linear trend in the young vs. elderly group, but no difference in circadian trends. Analysis of age groups by sex demonstrated more complex interactions, with elderly men showing weaker rhythmic (circadian) trends than elderly women. Subjective ratings of sleepiness and mood showed no difference in temporal trends between young and elderly groups. These data support the hypothesis that age-related sleep changes result primarily from decreases in homeostatic, rather than circadian, sleep propensity. They also confirm the presence of sex differences in sleep patterns among the elderly and support the distinction between objective and subjective measures of sleepiness.
This study compared rectal temperature rhythms in groups of subjects who either did (n = 5) or did not (n = 7) show a clear postlunch dip in performance at a monotonous (25-30 min) vigilance task. Performance was tested every 2h in a standardized routine with lunch replaced by hourly liquid food supplements. Those showing the postlunch performance dip had a higher amplitude and later peaking 12h component to their rectal temperature rhythm that those who did not, resulting in flat, rather than rising, temperatures over the 10:00-15:00 time interval. The effect could not be explained by intergroup differences in prior sleep, morningness, or gender, although there was a trend (p = 0.09) for the "dip" group to be slightly younger (21.8y vs. 24.2y). The postlunch dip appears to be an endogenous phenomenon individually determined, but related to the strength of the (12h) harmonic of the circadian system.
In dealing with inter-individual phase differences in overt circadian rhythms, it is often difficult to distinguish the impact of the endogenous circadian oscillator from that of an individual's habitual lifestyle. In an attempt to resolve this uncertainty about the role of masking influences, two groups of subjects, morning-type and evening-types, were selected and monitored during entrained, habitual sleep-wake conditions and during 24 h of controlled wakefulness in a laboratory-based constant-routine procedure. Under both conditions significant differences were observed in the circadian phases of body temperature and subjective alertness. During constant routine mean between-group differences for these two variables were 2.21 and 4.28 h, respectively. Thus, evidence is provided for the endogenous nature of morningness-eveningness.
Unlabelled:
This study explored the relationship between circadian performance rhythms and rhythms in rectal temperature, plasma cortisol, plasma melatonin, subjective alertness and well-being. Seventeen healthy young adults were studied under 36 h of 'unmasking' conditions (constant wakeful bedrest, temporal isolation, homogenized 'meals') during which rectal temperatures were measured every minute, and plasma cortisol and plasma melatonin measured every 20 min. Hourly subjective ratings of global vigour (alertness) and affect (well-being) were obtained followed by one of two performance batteries. On odd-numbered hours performance (speed and accuracy) of serial search, verbal reasoning and manual dexterity tasks was assessed. On even-numbered hours, performance (% hits, response speed) was measured at a 25-30 min visual vigilance task. Performance of all tasks (except search accuracy) showed a significant time of day variation usually with a nocturnal trough close to the trough in rectal temperature. Performance rhythms appeared not to reliably differ with working memory load. Within subjects, predominantly positive correlations emerged between good performance and higher temperatures and better subjective alertness; predominantly negative correlations between good performance and higher plasma levels of cortisol and melatonin. Temperature and cortisol rhythms correlated with slightly more performance measures (5/7) than did melatonin rhythms (4/7). Global vigour correlated about as well with performance (5/7) as did temperature, and considerably better than global affect (1/7).
In conclusion:
(1) between-task heterogeneity in circadian performance rhythms appeared to be absent when the sleep/wake cycle was suspended; (2) temperature (positively), cortisol and melatonin (negatively) appeared equally good as circadian correlates of performance, and (3) subjective alertness correlated with performance rhythms as well as (but not better than) body temperature, suggesting that performance rhythms were not directly mediated by rhythms in subjective alertness.
This brief review is concerned with how human performance efficiency changes as a function of time of day. It presents an overview of some of the research paradigms and conceptual models that have been used to investigate circadian performance rhythms. The influence of homeostatic and circadian processes on performance regulation is discussed. The review also briefly presents recent mathematical models of alertness that have been used to predict cognitive performance. Related topics such as interindividual differences and the postlunch dip are presented.
The purpose of this study was to describe and compare the circadian rhythm of body temperature and cortisol, as well as self-reported clock times of sleep onset and offset on weekdays and weekends in 19 healthy adult "larks" (morning chronotypes) and "owls" (evening chronotypes), defined by the Home and Ostberg questionnaire. Day-active subjects entered the General Clinical Research Center, where blood was sampled every 2 h over 38 h for later analysis for cortisol concentration by enzyme immunoassay. Rectal body temperature was measured continuously. Lights were turned off at 22:30 for sleep and turned on at 06:00, when subjects were awakened. The acrophases (peak times) of the cortisol and temperature rhythms occurred 55 minutes (P < or = .05) and 68 minutes (P < .01), respectively, earlier in the morningness group. The amplitude of the cortisol rhythm was lower in the eveningness than in the morningness group (P = n.s.). Subject groups differed on all indices of habitual and preferred timing of sleep and work weekdays and weekends (P = .05-.001).
To determine the effects of a 90-minute afternoon nap regimen on nocturnal sleep, circadian rhythms, and evening alertness and performance levels in the healthy elderly.
Nine healthy elderly subjects (4m, 5f, age range 74y-87y) each experienced both nap and no-nap conditions in two studies each lasting 17 days (14 at home, 3 in the laboratory). In the nap condition a 90-minute nap was enforced between 13:30 and 15:00 every day, in the no-nap condition daytime napping was prohibited, and activity encouraged in the 13:30-15:00 interval. The order of the two conditions was counterbalanced.
N/A INTERVENTIONS: N/A MEASUREMENTS: Diary measures, pencil and paper alertness tests, and wrist actigraphy were used at home. In the 72 hour laboratory studies, these measures were augmented by polysomnographic sleep recording, continuous rectal temperature measurement, a daily evening single trial of a Multiple Sleep Latency Test (MSLT), and computerized tests of mood, activation and performance efficiency.
By the second week in the "at home" study, an average of 58 minutes of sleep was reported per siesta nap; in the laboratory, polysomnography confirmed an average of 57 minutes of sleep per nap. When nap and no-nap conditions were compared, mixed effects on nocturnal sleep were observed. Diary measures indicated no significant difference in nocturnal sleep duration, but a significant increase (of 38 mins.) in 24-hour Total Sleep Time (TST) when nocturnal sleeps and naps were added together (p<0.025). The laboratory study revealed a decrease of 2.4% in nocturnal sleep efficiency in the nap condition (p<0.025), a reduction of nocturnal Total Sleep Time (TST) by 48 mins. in the nap condition (p<0.001) which resulted primarily from significantly earlier waketimes (p<0.005), but no reliable effects on Wake After Sleep Onset (WASO), delta sleep measures, or percent stages 1 & 2. Unlike the diary study, the laboratory study yielded no overall increase in 24-hour TST consequent upon the siesta nap regimen. The only measure of evening alertness or performance to show an improvement was sleep latency in a single-trial evening MSLT (nap: 15.6 mins., no nap: 11.5 mins., p<0.005). No significant change in circadian rhythm parameters was observed.
Healthy seniors were able to adopt a napping regimen involving a 90-minute siesta nap each day between 13:30 and 15:00, achieving about one hour of actual sleep per nap. There were some negative consequences for nocturnal sleep in terms of reduced sleep efficiency and earlier waketimes, but also some positive consequences for objective evening performance and (in the diary study) 24-hour sleep totals. Subjective alertness measures and performance measures showed no reliable effects and circadian phase parameters appeared unchanged.
A self-assessment questionnaire to determine morningness-eveningness in human circadian rhythms [33] Kerkhof GA, Van Dongen HP. Morning-type and evening-type individuals differ in the phase position of their endogenous circadian oscillator
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Short-term memory, alertness and performance: a re-appraisal of their relationship to body temperature
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Circadian performance rhythms Hours of work: temporal factors in work scheduling
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Folkard S, Monk TH. Circadian performance rhythms. In: Folkard S, Monk TH, editors. Hours of work: temporal factors in work scheduling. New York7 John Wiley & Sons; 1985. p. 37 – 52.
Chronobiological aspects and models of sleep and napping Sleep and alertness: chronobiological, behavioral, and medical aspects of napping
- Rj Broughton
Broughton RJ. Chronobiological aspects and models of sleep and napping. In: Dinges DF,
Broughton RJ, editors. Sleep and alertness: chronobiological, behavioral, and medical aspects
of napping. New York7 Raven Press; 1989. p. 71-98.
Napping patterns and effects in human adults Sleep and alertness: chronobiological, behavioral, and medical aspects of napping
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Dinges DF. Napping patterns and effects in human adults. In: Dinges DF, Broughton RJ, editors.
Sleep and alertness: chronobiological, behavioral, and medical aspects of napping. New York7
Raven Press; 1989. p. 171-204.
Napping patterns and effects in human adults
- Dinges
Chronobiological aspects and models of sleep and napping
- Broughton
Circadian variations in mental efficiency
- Colquhoun