Greg Roach

The night-time sleep and autonomic activity of male and female professional road cyclists competing in the Tour de France and Tour de France Femmes

Publisher: Cold Spring Harbor Laboratory

Date: 06-07-2023

DOI: 10.1101/2023.07.06.23292280

Abstract: The objective of this study was to examine the capacity of male and female professional cyclists to recover between daily race stages while competing in the 109 th edition of the Tour de France (2022) and the 1 st edition of the Tour de France Femmes (2022), respectively. The 17 participating cyclists were 8 males from a single team (aged 28.0 ± 2.5 years [mean ± 95% confidence interval]) and 9 females from two separate teams (aged 26.7 ± 3.1 years). Cyclists wore a fitness tracker (WHOOP 4.0) to capture recovery metrics primarily related to night-time sleep and autonomic activity. Data were collected for the entirety of the events and for 7 days of baseline before the events. The primary analyses tested for a main effect of ‘stage type’ – i.e., rest, flat, hilly, mountain or time trial for males and flat, hilly or mountain for females – on the various recovery metrics. During baseline, total sleep time at night was 7.2 ± 0.3 h for male cyclists and 7.7 ± 0.3 h for female cyclists, sleep efficiency (i.e., total sleep time as a percentage of time in bed) was 87.0 ± 4.4 % for males and 88.8 ± 2.6 % for females, resting heart rate was 41.8 ± 4.5 beats·min -1 for males and 45.8 ± 4.9 beats·min -1 for females, and heart rate variability during sleep was 108.7 ± 17.0 ms for males and 119.8 ± 26.4 ms for females. During their respective events, total sleep time at night was 7.2 ± 0.1 h for males and 7.5 ± 0.3 h for females, sleep efficiency was 86.4 ± 1.2 % for males and 89.6 ± 1.2 % for females, resting heart rate was 44.5 ± 1.2 beats·min -1 for males and 50.2 ± 2.0 beats·min -1 for females, and heart rate variability during sleep was 99.1 ± 4.2 ms for males and 114.3 ± 11.2 ms for females. For male cyclists, there was a main effect of ‘stage type’ on recovery, such that heart rate variability during sleep was lowest after mountain stages. For female cyclists, there was also a main effect of ‘stage type’ on recovery, such that the percentage of light sleep in a sleep period (i.e., lower-quality sleep) was highest after mountain stages. Some aspects of recovery were compromised in cyclists after the most demanding days of racing, i.e., mountain stages. Overall however, the cyclists obtained a reasonable amount of good-quality sleep while competing in these highly demanding endurance events. This study demonstrates that it is now feasible to assess recovery metrics in professional athletes during multiple-day endurance events using validated fitness trackers.

The impact of extended leave on sleep and alertness in the Australian rail industry

Publisher: National Institute of Industrial Health

Date: 2005

DOI: 10.2486/INDHEALTH.43.105

Abstract: In the past, scientific studies have investigated the effects of shift timing and duration on sleep and alertness in the rail industry. To our knowledge no research has been conducted to determine the effects of extended break lengths (>48 h) on these factors. Hence, this study analyses the work and rest schedules of 304 Australian rail employees (mean age 41.3 yr, standard deviation 7.4 yr) to determine the effect of prior break lengths (12-169 h) on sleep and subjective alertness at work after periods of leave. Extended break periods (>48 h) were found to increase the length of the sleep prior to returning to work and reduce the total wake time to the end of the first shift, but did not influence levels of subjective alertness immediately prior to the commencement of the first shift. Research into the influence of longer break periods (>169 h) is needed in order to make definitive conclusions regarding sensible return to work policies after extended leave within the Australian rail industry.

Daytime naps can be used to supplement night-time sleep in athletes

Publisher: Informa UK Limited

Date: 03-06-2018

DOI: 10.1080/07420528.2018.1466795

Abstract: This study examined the efficacy of daytime napping to supplement night-time sleep in athletes. Twelve well-trained male soccer players completed three conditions in a randomised, counterbalanced order: 9 h in bed overnight with no daytime nap (9 h + 0 h) 8 h in bed overnight with a 1-h daytime nap (8 h + 1 h) and 7 h in bed overnight with a 2-h daytime nap (7 h + 2 h). Sleep was assessed using polysomnography. The total amount of sleep obtained in the three conditions was similar, i.e. 8.1 h (9 h + 0 h), 8.2 h (8 h + 1 h), and 8.0 h (7 h + 2 h). Daytime napping may be an effective strategy to supplement athletes' night-time sleep.

Alternatives to polysomnography (PSG): A validation of wrist actigraphy and a partial-PSG system

Publisher: Springer Science and Business Media LLC

Date: 18-01-2014

DOI: 10.3758/S13428-013-0438-7

Abstract: The objective of this study was to assess the validity of a sleep/wake activity monitor, an energy expenditure activity monitor, and a partial-polysomnography system at measuring sleep and wake under identical conditions. Secondary aims were to evaluate the sleep/wake thresholds for each activity monitor and to compare the three devices. To achieve these aims, two nights of sleep were recorded simultaneously with polysomnography (PSG), two activity monitors, and a partial-PSG system in a sleep laboratory. Agreement with PSG was evaluated epoch by epoch and with summary measures including total sleep time (TST) and wake after sleep onset (WASO). All of the devices had high agreement rates for identifying sleep and wake, but the partial-PSG system was the best, with an agreement of 91.6% ± 5.1%. At their best thresholds, the sleep/wake monitor (medium threshold, 87.7% ± 7.6%) and the energy expenditure monitor (very low threshold, 86.8% ± 8.6%) had similarly high rates of agreement. The summary measures were similar to those determined by PSG, but the partial-PSG system provided the most consistent estimates. Although the partial-PSG system was the most accurate device, both activity monitors were also valid for sleep estimation, provided that appropriate thresholds were selected. Each device has advantages, so the primary consideration for researchers will be to determine which best suits a given research design.

The impact of altitude on the sleep of young elite soccer players (isa3600)

Publisher: BMJ

Date: 26-11-2013

DOI: 10.1136/BJSPORTS-2013-092829

Can a shorter psychomotor vigilance task be used as a reasonable substitute for the ten-minute psychomotor vigilance task?

Publisher: Informa UK Limited

Date: 2006

DOI: 10.1080/07420520601067931

Abstract: The 10 min psychomotor vigilance task (PVT) is commonly used in laboratory studies to assess the impact of sleep loss, sustained wakefulness, and/or time of day on neurobehavioral performance. In field settings, though, it may be impractical for participants to perform a test of this length. The aim of this study was to identify a performance measure that is sensitive to the effects of fatigue but less burdensome than a 10 min test. Sixteen participants (11 female, 5 male mean age = 21.7 years) slept in the sleep laboratory overnight then remained awake for 28 h from 08:00 h. During every second hour, participants completed three PVTs of differing duration (10 min, 5 min, 90 sec). For the 5 min/10 min comparison, ANOVA indicated that response time was significantly affected by test length (F1,14 = 26.9, p < .001) and hours of wakefulness (F13,182 = 46.1, p < .001) but not by their interaction (F13,182 = 1.7, ns). There was a strong correlation between response time on the 5 and 10 min PVTs (r = .88, p < .001). For the 90 sec/10 min comparison, ANOVA indicated that response time was significantly affected by test length (F1,14 = 65.9, p < .001) and hours of wakefulness (F13,182 = 29.7, p < .001) as well as by their interaction (F13,182 = 6.0, p < .001). There was a strong correlation between response time on the 90 sec and 10 min PVTs (r = .77, p < .001). The effects of hours of wakefulness on neurobehavioral performance were similar for the 5 min and 10 min PVTs. In contrast, performance on the 90 sec PVT was less affected by hours of wakefulness than on the 10 min PVT. In addition, performance on the 10 min PVT was more highly correlated with the 5 min PVT than the 90 sec PVT. These data indicate that the 5 min PVT may provide a reasonable substitute for the 10 min PVT in circumstances where a test shorter than 10 min is required.

The relationship between the rate of melatonin excretion and sleep consolidation for locomotive engineers in natural sleep settings

Publisher: Ubiquity Press, Ltd.

Date: 18-08-2006

DOI: 10.1186/1740-3391-4-8

No Effect of Chronotype on Hunger or Snack Consumption during a Night Shift with Acute Sleep Deprivation

Publisher: MDPI AG

Date: 22-03-2022

DOI: 10.3390/NU14071324

Abstract: Night shift workers experience circadian misalignment and sleep disruption, which impact hunger and food consumption. The study aim was to assess the impact of chronotype on hunger and snack consumption during a night shift with acute sleep deprivation. Seventy-two (36f, 36m) healthy adults participated in a laboratory study. A sleep opportunity (03:00–12:00) was followed by a wake period (12:00–23:00) and a simulated night shift (23:00–07:00). Subjective measures of hunger, prospective consumption, desire to eat fruit, and desire to eat fast food were collected before (12:20, 21:50) and after (07:20) the night shift. Snack opportunities were provided before (15:10, 19:40) and during (23:50, 03:30) the night shift. A tertile split of the dim light melatonin onset (DLMO) distribution defined early (20:24 ± 0:42 h), intermediate (21:31 ± 0:12 h), and late chronotype (22:56 ± 0:54 h) categories. There were no main effects of chronotype on any subjective measure (p = 0.172–0.975), or on snack consumption (p = 0.420), and no interactions between chronotype and time of day on any subjective measure (p = 0.325–0.927) or on snack consumption (p = 0.511). Differences in circadian timing between chronotype categories were not associated with corresponding differences in hunger, prospective consumption, desire to eat fruit, desire to eat fast food, or snack consumption at any measurement timepoint.

A smart microfluidic platform for rapid multiplexed detection of foodborne pathogens

Publisher: Elsevier BV

Date: 08-2020

DOI: 10.1016/J.FOODCONT.2020.107242

Simulated train driving: Fatigue, self-awareness and cognitive disengagement

Publisher: Elsevier BV

Date: 03-2007

DOI: 10.1016/J.APERGO.2006.03.006

Abstract: Fatigue is a serious issue for the rail industry, increasing inefficiency and accident risk. The performance of 20 train drivers in a rail simulator was investigated at low, moderate and high fatigue levels. Psychomotor vigilance (PVT), self-rated performance and subjective alertness were also assessed. Alertness, PVT reaction times, extreme speed violations (>25% above the limit) and penalty brake applications increased with increasing fatigue level. In contrast, fuel use, draft (stretch) forces and braking errors were highest at moderate fatigue levels. Thus, at high fatigue levels, errors involving a failure to act (errors of omission) increased, whereas incorrect responses (errors of commission) decreased. The differential effect of fatigue on error types can be explained through a cognitive disengagement with the virtual train at high fatigue levels. Interaction with the train reduced dramatically, and accident risk increased. Awareness of fatigue-related performance changes was moderate at best. These findings are of operational concern.

Wellness, fatigue and physical performance acclimatisation to a 2-week soccer camp at 3600 m (ISA3600)

Publisher: BMJ

Date: 26-11-2013

DOI: 10.1136/BJSPORTS-2013-092749

The night before night shift: Chronotype impacts total sleep and rapid eye movement sleep during a strategically delayed sleep

Publisher: Wiley

Date: 10-08-2023

DOI: 10.1111/JSR.13683

Abstract: Transition to night shift may be improved by strategically delaying the main sleep preceding a first night shift. However, the effects of delayed timing on sleep may differ between chronotypes. Therefore, the study aim was to compare the impacts of chronotype on sleep quality and architecture during a normally timed sleep opportunity and a delayed sleep opportunity. Seventy‐two (36 female, 36 male) healthy adults participated in a laboratory study. Participants were provided with a normally timed sleep opportunity (23:00–08:00) and a delayed sleep opportunity (03:00–12:00) over two consecutive nights in a sleep laboratory. Sleep was monitored by polysomnography (PSG), and chronotype was determined from dim light melatonin onset (DLMO). A tertile split of DLMO defined early (20:24 ± 0:42 h), intermediate (21:31 ± 0:12 h), and late chronotype (22:56 ± 0:54 h) categories. Although there was no main effect of chronotype on any sleep measure, early chronotypes obtained less total sleep with delayed sleep than with normally timed sleep ( p = 0.044). Intermediate and late chronotypes obtained more rapid eye movement (REM) sleep with delayed sleep than with normally timed sleep ( p = 0.013, p = 0.012 respectively). Wake was more elevated for all chronotypes in the later hours of the delayed sleep opportunity than at the start of the sleep opportunity. Strategically delaying the main sleep preceding a first night shift appears to benefit intermediate and late chronotypes (i.e., more REM sleep), but not early chronotypes (i.e., less total sleep). Circadian processes appear to elevate wakefulness for all chronotypes in the later stages of a delayed sleep opportunity.

Shiftwork experience and the value of time

Publisher: Informa UK Limited

Date: 26-02-2004

DOI: 10.1080/0014013032000157896

How Tired is Too Tired to Drive? A Systematic Review Assessing the Use of Prior Sleep Duration to Detect Driving Impairment

Publisher: Informa UK Limited

Date: 04-2023

DOI: 10.2147/NSS.S392441

The sleep, subjective fatigue, and sustained attention of commercial airline pilots during an international pattern

Publisher: Informa UK Limited

Date: 2006

DOI: 10.1080/07420520601085925

Abstract: International commercial airline pilots may experience heightened fatigue due to irregular sleep schedules, long duty days, night flying, and multiple time zone changes. Importantly, current commercial airline flight and duty time regulations are based on work/rest factors and not sleep/wake factors. Consequently, the primary aim of the current study was to investigate pilots' amount of sleep, subjective fatigue, and sustained attention before and after international flights. A secondary aim was to determine whether prior sleep and/or duty history predicted pilots' subjective fatigue and sustained attention during the international flights. Nineteen pilots (ten captains, nine first officers mean age: 47.42+/-7.52 years) participated. Pilots wore wrist activity monitors and completed sleep and duty diaries during a return pattern from Australia to Europe via Asia. The pattern included four flights: Australia-Asia, Asia-Europe, Europe-Asia, and Asia-Australia. Before and after each flight, pilots completed a 5 min PalmPilot-based psychomotor vigilance task (PVT) and self-rated their level of fatigue using the Samn-Perelli Fatigue Checklist. Separate repeated-measures ANOVAs were used to determine the impact of stage of flight and flight sector on the pilots' sleep in the prior 24 h, self-rated fatigue, and PVT mean response speed. Linear mixed model regression analyses were conducted to examine the impact of sleep in the prior 24 h, prior wake, duty length, and flight sector on pilots' self-rated fatigue and sustained attention before and after the international flights. A significant main effect of stage of flight was found for sleep in the prior 24 h, self-rated fatigue, and mean response speed (all p < 0.05). In addition, a significant main effect of flight sector on self-rated fatigue was found (p < .01). The interaction between flight sector and stage of flight was significant for sleep in the prior 24 h and self-rated fatigue (both p < .05). Linear mixed model analyses indicated that sleep in the prior 24 h was a significant predictor of self-rated fatigue and mean response speed after the international flight sectors. Flight sector was also a significant predictor of self-rated fatigue. These findings highlight the importance of sleep and fatigue countermeasures during international patterns. Furthermore, in order to minimize the risk of fatigue, the sleep obtained by pilots should be taken into account in the development of flight and duty time regulations.

The impact of training schedules on the sleep and fatigue of elite athletes

Publisher: Informa UK Limited

Date: 15-09-2014

DOI: 10.3109/07420528.2014.957306

Abstract: In any sport, successful performance requires a planned approach to training and recovery. While sleep is recognized as an essential component of this approach, the amount and quality of sleep routinely obtained by elite athletes has not been systematically evaluated. Data were collected from 70 nationally ranked athletes from seven different sports. Athletes wore wrist activity monitors and completed self-report sleep/training diaries for 2 weeks during normal training. The athletes also recorded their fatigue level prior to each training session using a 7-point scale. On average, the athletes spent 08:18 ± 01:12 h in bed, fell asleep at 23:06 ± 01:12 h, woke at 6:48 ± 01:30 h and obtained 06:30 ± 01:24 h of sleep per night. There was a marked difference in the athletes' sleep/wake behaviour on training days and rest days. Linear mixed model analyses revealed that on nights prior to training days, time spent in bed was significantly shorter (p = 0.001), sleep onset and offset times were significantly earlier (p < 0.001) and the amount of sleep obtained was significantly less (p = 0.001), than on nights prior to rest days. Moreover, there was a significant effect of sleep duration on pre-training fatigue levels (p ≤ 0.01). Specifically, shorter sleep durations were associated with higher levels of pre-training fatigue. Taken together, these findings suggest that the amount of sleep an elite athlete obtains is dictated by their training schedule. In particular, early morning starts reduce sleep duration and increase pre-training fatigue levels. When designing schedules, coaches should be aware of the implications of the timing of training sessions for sleep and fatigue. In cases where early morning starts are unavoidable, countermeasures for minimizing sleep loss - such as strategic napping during the day and correct sleep hygiene practices at night - should be considered.

A validation study of the WHOOP strap against polysomnography to assess sleep

Publisher: Informa UK Limited

Date: 26-07-2020

DOI: 10.1080/02640414.2020.1797448

Implementing a Circadian Adaptation Schedule after Eastward Flight in Young Male Athletes

Publisher: MDPI AG

Date: 25-10-2021

DOI: 10.3390/APP11219962

Abstract: This study examined the effectiveness of a circadian adaptation schedule in male cricketers after an 8.5 h eastward time zone change. Ten participants (aged 18.7 ± 0.9 y) were randomly assigned to a control group or an intervention group. Participants in the intervention group followed a light exposure schedule in which they were instructed to seek light in the three hours preceding, and avoid light in the three hours following their estimated core body temperature minimum. The rate of adaptation was assessed using the nightly excretion rate of urinary 6-sulphatoxymelatonin (aMT6s). General linear mixed models were conducted to assess the effect of condition (i.e., control and light intervention) on nocturnal secretion of aMT6s. Significant main effects of day (F(7, 35) = 10.4, p 0.001) were reflected by an increase in nocturnal melatonin excretion (i.e., all participants gradually adapted to the destination time zone). Subjective jet lag decreased by day (F(7, 54) = 22.9, p 0.001), bedtime was delayed by day (F(7, 54) = 3.1, p = 0.007) and get up time was earlier by day (F(7, 35) = 5.4, p 0.001). On average, it took 7 days for all participants to return to baseline levels following transmeridian travel. Similarly, it took 7 days for subjective jet lag to alleviate. In the initial 4 days of the protocol, the intervention group registered higher levels of nocturnal urinary melatonin, however, there was no significant differences in the rate of adaptation between the groups. It is possible that participants did not adhere to the intervention or that they followed the intervention but it was ineffective.

Effects of sleep hygiene and artificial bright light interventions on recovery from simulated international air travel

Publisher: Springer Science and Business Media LLC

Date: 12-11-2014

DOI: 10.1007/S00421-014-3043-2

Abstract: Despite the reported detrimental effects of international air travel on physical performance, a paucity of interventions have been scientifically tested and confirmed to benefit travelling athletes. Consequently, the aim of the present study was to examine the effects of sleep hygiene and artificial bright light interventions on physical performance following simulated international travel. In a randomized crossover design, 13 physically active males completed 24 h of simulated international travel with (INT) and without (CON) the interventions. The mild hypoxia and cr ed conditions typically encountered during commercial air travel were simulated in a normobaric, hypoxic room. Physical performance, subjective jet-lag symptoms and mood states were assessed in the morning and evening on the day prior to and for two days post-travel. Sleep quantity and quality were monitored throughout each trial. Sleep duration was significantly reduced during travel in both trials (P < 0.01), though total sleep duration during and following travel was almost significantly greater (P = 0.06) in INT (17.0 (16.2-17.8) h) compared to CON (15.7 (14.9-16.5) h). Maximal-sprint and countermovement jump (P 0.05) performance, were significantly reduced the evening of day 1 and 2 post-travel, with no differences between trials (P > 0.05). Furthermore, vigour was significantly greater (P = 0.04) the morning of day 2 in INT [5.3 (3.9-6.7)] compared to CON [2.8 (1.4-4.2)], and subjective jet-lag symptoms and mood states were significantly worse on day 2 in CON only (P < 0.05). Whilst reducing travel-induced sleep disruption may attenuate travel fatigue, no improvements in the recovery of physical performance were apparent.

Adaptation of performance during a week of simulated night work

Publisher: Informa UK Limited

Date: 05-02-2004

DOI: 10.1080/00140130310001617930

The effects of cold water immersion on the amount and quality of sleep obtained by elite cyclists during a simulated hill climbing tour

Publisher: Springer Science and Business Media LLC

Date: 02-01-2019

DOI: 10.1007/S11332-018-0522-6

Optimising emergency department and acute care for people experiencing mental health problems: a nominal group study

Publisher: CSIRO Publishing

Date: 19-11-2021

DOI: 10.1071/AH21092

Abstract: Objective The aim of this study was to identify potential model of care approaches and systems processes for people presenting to acute healthcare settings with mental health problems, including mental illnesses. Methods Five (consensus) nominal group technique sessions were conducted in 2019 with a purposive s le of stakeholders from health, police, ambulance and consumer agencies (n = 21). Sessions were recorded, transcribed and analysed for thematic content. Results Potential model of care approaches and systems processes for people with mental health problems in the emergency department include: a skilled collaborative approach to care consumer-focused service knowledge improvement early assessment the development of models, systems and processes and the built environment. In the broader acute care setting, the themes of formal care, linking of services, enhancing informal and innovative care options, improving information sharing and enhancing training and education were identified. Conclusions Coherent and multifaceted approaches to the provision of care to people with mental health problems and diagnosed mental illnesses who are requiring emergency care include the linking and sharing of systems and information, changing the built environment and exploring new models of service delivery. What is known about the topic? There is considerable evidence of interventions used in the emergency department and acute healthcare settings for this vulnerable group of people with mental health problems and diagnosed mental illnesses however, the evidence for appropriate model of care approaches and systems processes is limited. What does this paper add? For people with mental health problems in emergency departments and for people with diagnosed mental illnesses in acute care settings, targeted directions to further support treatment include the linking and sharing of systems and information, changing the built environment and exploring new models of service delivery. What are the implications for practitioners? Planning changes to services for mental health clients with acute problems needs to incorporate clinicians, health service planners, architects and a range of emergency services personnel.

The influence of circadian phase and prior wake on neuromuscular function

Publisher: Informa UK Limited

Date: 06-2010

DOI: 10.3109/07420528.2010.488901

Abstract: Previous forced desynchrony (FD) studies have shown that neurobehavioral function is affected by circadian phase and duration of prior wakefulness. There is some evidence that neuromuscular function may also be affected by circadian phase and prior wake, but these effects have not been systematically investigated. This study examined the effects of circadian phase and prior wake on two measures of neuromuscular function--postural balance (PB) and maximal grip strength (MGS)--using a 28-h FD protocol. Eleven male participants (mean +/- SD: 22.7 +/- 2.5 yr) lived in a sound-attenuated, light- and temperature-controlled time-isolation laboratory for 12 days. Following two training days and a baseline day, participants were scheduled to seven 28-h FD days, with the ratio between sleep opportunity and wake spans kept constant (i.e., 9.3 h sleep period and 18.7 h wake period). PB was measured during 1 min of quiet standing on a force platform. MGS of the dominant hand was measured using a dynamometer. These two measures were obtained every 2.5 h during wake. Core body temperature was continuously recorded with rectal thermistors to determine circadian phase. For both measures of neuromuscular function, in idual data points were assigned a circadian phase and a level of prior wake. Data were analyzed by repeated-measures analysis of variance (ANOVA) with two within-subjects factors: circadian phase (six phases) and prior wake (seven levels). For MGS, there was a main effect of circadian phase, but no main effect of prior wake. For PB, there were no main effects of circadian phase or prior wake. There were no interactions between circadian phase and prior wake for MGS or PB. The significant effect of circadian phase on muscle strength is in agreement with previous reports in the literature. In terms of prior wake, both MGS and PB remained relatively stable across wake periods, indicating that neuromuscular function may be more robust than neurobehavioral function when the duration of wakefulness is within a normal range (i.e., 18.7 h).

A Validation of Six Wearable Devices for Estimating Sleep, Heart Rate and Heart Rate Variability in Healthy Adults

Publisher: MDPI AG

Date: 22-08-2022

DOI: 10.3390/S22166317

Abstract: The primary aim of this study was to examine the validity of six commonly used wearable devices, i.e., Apple Watch S6, Garmin Forerunner 245 Music, Polar Vantage V, Oura Ring Generation 2, WHOOP 3.0 and Somfit, for assessing sleep. The secondary aim was to examine the validity of the six devices for assessing heart rate and heart rate variability during, or just prior to, night-time sleep. Fifty-three adults (26 F, 27 M, aged 25.4 ± 5.9 years) spent a single night in a sleep laboratory with 9 h in bed (23:00–08:00 h). Participants were fitted with all six wearable devices—and with polysomnography and electrocardiography for gold-standard assessment of sleep and heart rate, respectively. Compared with polysomnography, agreement (and Cohen’s kappa) for two-state categorisation of sleep periods (as sleep or wake) was 88% (κ = 0.30) for Apple Watch 89% (κ = 0.35) for Garmin 87% (κ = 0.44) for Polar 89% (κ = 0.51) for Oura 86% (κ = 0.44) for WHOOP and 87% (κ = 0.48) for Somfit. Compared with polysomnography, agreement (and Cohen’s kappa) for multi-state categorisation of sleep periods (as a specific sleep stage or wake) was 53% (κ = 0.20) for Apple Watch 50% (κ = 0.25) for Garmin 51% (κ = 0.28) for Polar 61% (κ = 0.43) for Oura 60% (κ = 0.44) for WHOOP and 65% (κ = 0.52) for Somfit. Analyses regarding the two-state categorisation of sleep indicate that all six devices are valid for the field-based assessment of the timing and duration of sleep. However, analyses regarding the multi-state categorisation of sleep indicate that all six devices require improvement for the assessment of specific sleep stages. As the use of wearable devices that are valid for the assessment of sleep increases in the general community, so too does the potential to answer research questions that were previously impractical or impossible to address—in some way, we could consider that the whole world is becoming a sleep laboratory.

A field study of sleep and fatigue in a regular rotating 12-h shift system

Publisher: Elsevier BV

Date: 07-2009

DOI: 10.1016/J.APERGO.2008.06.003

Abstract: The aim of this study was to examine a regular rotating 12-h shift system (2D2N4Off) at an Australian Smelter. Sleep behavior, subjective fatigue and neurobehavioral performance were investigated over a 14-day period for 20 employees. Activity monitors, sleep/wake diaries, and 5-min psychomotor vigilance tasks were used. Sleep data showed differences between day and night shifts. While sleep prior to night1 was increased relative to day shifts, a reduced sleep length carried into the period leading to night2. Total wakefulness at the end of shift, and subjective fatigue were increased for night shifts, particularly night1. Decrements in performance data supported these findings. Both prior wakefulness and prior sleep are important in a 12-h shift system. Employees may "sleep in" after day shifts, rather than taking extra sleep prior to night work. Thus, sleep between day and night shifts is based on recovery rather than preparation.

The influence of break timing on the sleep quantity and quality of Fly-in, Fly-out shiftworkers

Publisher: National Institute of Industrial Health

Date: 2014

DOI: 10.2486/INDHEALTH.2014-0102

Moderate-intensity exercise performed in the evening does not impair sleep in healthy males

Publisher: Informa UK Limited

Date: 09-05-2020

DOI: 10.1080/17461391.2019.1611934

Abstract: The aim of this study was to examine the effect of single bouts of moderate-intensity aerobic exercise and moderate-intensity resistance exercise performed in the evening on the sleep of healthy young males. The study employed a repeated-measures, counterbalanced, crossover design with three conditions (control, evening aerobic exercise, evening resistance exercise). Twelve male participants (mean ± SD age: 21.9 ± 2.7 yr) attended the laboratory on three occasions separated by one day between each visit. Between 20:45 h and 21:30 h, participants completed either no exercise, 30 min of aerobic exercise at 75%HRmax, or 30 min of resistance exercise corresponding to 75% of 10-repetition maximum. A 9-h sleep opportunity was provided between 23:00 h and 08:00 h. Core body temperature was measured using ingestible temperature capsules and sleep was measured using polysomnography. Core body temperature was higher during the aerobic exercise and resistance exercise compared to control (

Impact of layover length on sleep, subjective fatigue levels, and sustained attention of long-haul airline pilots

Publisher: Informa UK Limited

Date: 23-05-2012

DOI: 10.3109/07420528.2012.675222

Abstract: Long-haul airline pilots often experience elevated levels of fatigue due to extended work hours and circadian misalignment of sleep and wake periods. During long-haul trips, pilots are typically given 1-3 d off between flights (i.e., layover) to recover from, and prepare for, duty. Anecdotally, some pilots prefer long layovers because it maximizes the time available for recovery and preparation, but others prefer short layovers because it minimizes both the length of the trip, and the degree to which the body clock changes from "home time" to the layover time zone. The aim of this study was to examine the impact of layover length on the sleep, subjective fatigue levels, and capacity to sustain attention of long-haul pilots. Participants were 19 male pilots (10 Captains, 9 First Officers) working for an international airline. Data were collected during an 11- or 12-d international trip. The trips involved (i) 4 d at home prior to the trip (ii) an eastward flight of 13.5 h across seven time zones (iii) a layover of either 39 h (i.e., short, n = 9) or 62 h (i.e., long, n = 10) (iv) a return westward flight of 14.3 h across seven time zones and (v) 4 d off at home after the trip. Sleep was recorded using a self-report sleep diary and wrist activity monitor subjective fatigue level was measured using the Samn-Perelli Fatigue Checklist and sustained attention was assessed using the psychomotor vigilance task for a personal digital assistant (PalmPVT). Mixed-model regression analyses were used to determine the effects of layover length (short, long) on the amount of sleep that pilots obtained during the trip, and on the pilots' subjective fatigue levels and capacity to sustain attention. There was no main effect of layover length on ground-based sleep or in-flight sleep, but pilots who had a short layover at the midpoint of their trip had higher subjective fatigue levels and poorer sustained attention than pilots who had a long layover. The results of this study indicate that a short layover during a long-haul trip does not substantially disrupt pilots' sleep, but it may result in elevated levels of fatigue during and after the trip. If short layovers are used, pilots should have a minimum of 4 d off to recover prior to their next long-haul trip.

Finding DLMO: estimating dim light melatonin onset from sleep markers derived from questionnaires, diaries and actigraphy

Publisher: Informa UK Limited

Date: 07-09-2020

DOI: 10.1080/07420528.2020.1809443

The likelihood of crashing during a simulated post-work commute decreases across a week of consecutive night shifts

Publisher: Informa UK Limited

Date: 24-08-2020

DOI: 10.1080/07420528.2020.1809444

The effects of hydration on cognitive performance during a simulated wildfire suppression shift in temperate and hot conditions

Publisher: Elsevier BV

Date: 05-2019

DOI: 10.1016/J.APERGO.2018.12.018

Abstract: The effects on dehydration and cognitive performance from heat and/or physical activity are well established in the laboratory, although have not yet been studied for personnel working in occupations such as wildland firefighting regularly exposed to these types of conditions. This study aimed to investigate the effects of temperature and dehydration on seventy-three volunteer firefighters (35.7 ± 13.7 years, mean ± standard deviation) during a simulation of wildfire suppression under either control or hot (18-20 or 33-35 °C) temperature conditions. Results showed cognitive performance on the psychomotor vigilance task declined when participants were dehydrated in the heat and Stroop task performance was impaired when dehydrated late in the afternoon. Firefighters may be at risk of deteriorations in simple cognitive functions in the heat whilst dehydrated, although may also experience impairments in complex cognitive functions if dehydrated late in the day, irrespective of the environmental temperature.

The effects of different roster schedules on sleep in miners

Publisher: Elsevier BV

Date: 07-2010

DOI: 10.1016/J.APERGO.2009.12.017

Abstract: Shiftwork involving early morning starts and night work can affect both sleep and fatigue. This study aimed to assess the impact of different rostering schedules at an Australian mine site on sleep and subjective sleep quality. Participants worked one of four rosters 4 x 4 (n = 14) 4D4O4N4O 7 x 4 (n = 10) 7D4O7N40 10 x 5 (n = 17) 5D5N50 14 x 7 (n = 12) 7D7N70. Sleep (wrist actigraphy and sleep diaries) was monitored for a full roster cycle including days off. Total sleep time (TST) was longer on days off (7.0 +/- 1.9) compared to sleep when on day (6.0 +/- 1.0) and nightshifts (6.2 +/- 1.6). Despite an increase in TST on days off, this may be insufficient to recover from the severe sleep restriction occurring during work times. Restricted sleep and quick shift-change periods may lead to long-term sleep loss and associated fatigue.

Finger Twitches are More Frequent in REM Sleep Than in Non-REM Sleep

Publisher: Informa UK Limited

Date: 2020

DOI: 10.2147/NSS.S233439

Timing of Sleep in the Break Between Two Consecutive Night-Shifts: The Effect of Different Strategies on Daytime Sleep and Night-Time Neurobehavioural Function

Publisher: Informa UK Limited

Date: 02-2022

DOI: 10.2147/NSS.S336795

Changes in the concentration of urinary 6-sulphatoxymelatonin during a week of simulated night work

Publisher: National Institute of Industrial Health

Date: 2005

DOI: 10.2486/INDHEALTH.43.193

Abstract: The aim of the study was to examine the adaptation of participants to a common night work schedule using urinary 6-sulphatoxymelatonin (aMT6s) concentration as the circadian phase marker. Fifteen adults (7 male, 8 female, age = 21.9 yr) spent nine consecutive nights in the laboratory, including: (i) adaptation sleep, (ii) baseline sleep, and (iii) seven simulated night shifts (23:00-07:00 h) followed by daytime sleep. During the baseline and daytime sleeps, participants collected urine s les which were subsequently assayed for aMT6s. The concentration of aMT6s in urine for the first three day sleeps was significantly lower than for the baseline sleep, but there was no difference in aMT6s concentrations between any of the last three day sleeps and the baseline sleep. The data indicate that people may adapt to a pattern of work that includes seven consecutive night shifts if they adhere to a fixed sleep schedule, if their exposure to morning sunlight is minimised, and if they are provided with an ideal sleep environment.

Driving when distracted and sleepy: The effect of phone and passenger conversations on driving performance

Publisher: Informa UK Limited

Date: 03-06-2018

DOI: 10.1080/07420528.2018.1466799

Abstract: This study investigates the effect of passenger and phone conversations on sleep-restricted driving. Six volunteers (50% male, mean age 24.8 ± 4.3 years) had their sleep restricted to 4 h in bed followed by a 20-min simulated drive on three separate occasions. Each drive included either a passenger conversation, a mobile phone conversation or a quiet passenger. The effect size of a phone conversation on lane deviation was large while passenger conversation was small. The main effect of conversation on lane deviation was non-significant (F(2,10) = 2.57, p = 0.126). Combining sleep-restricted driving with conversations warrants further investigation.

The relative contributions of the homeostatic and circadian processes to sleep regulation under conditions of severe sleep restriction

Publisher: Oxford University Press (OUP)

Date: 07-2012

DOI: 10.5665/SLEEP.1956

The evidence that cyclic alternating pattern subtypes affect cognitive functioning is very weak

Publisher: Elsevier BV

Date: 09-2010

DOI: 10.1016/J.SLEEP.2010.04.005

Sleep/wake behaviour of endurance cyclists before and during competition

Publisher: Informa UK Limited

Date: 08-08-2015

DOI: 10.1080/02640414.2014.942690

Abstract: Good sleep is critical for optimising recovery and athletic performance. Yet, few studies have investigated how athletes sleep before and during competition. The aim of this study was to determine whether such sleep is poorer than that before a usual training day. Twenty-one male endurance cyclists' (age: 19.9 ± 1.7 years) sleep/wake behaviour was assessed using wrist activity monitors for 11 nights, including a six-night baseline training phase, three nights before competition and two nights during competition. Cyclists had less sleep on the night before competition (6.5 ± 0.9 h) and during the first night of competition (6.8 ± 0.8 h) than at baseline (7.4 ± 0.6 h). Cyclists also went to bed and woke up earlier during competition than at baseline. Competition schedules and competition itself can disrupt the sleep/wake behaviour of athletes during competition. Future investigations should examine sleep during three stages of competition (i.e. before, during and after competition). This will help coaches develop a greater understanding of how sleep changes during different phases of competition and enable them to plan post-competition training programmes to ensure appropriate rest and recovery is obtained.

Predicting pilot's sleep during layovers using their own behaviour or data from colleagues: Implications for biomathematical models

Publisher: Elsevier BV

Date: 03-2012

DOI: 10.1016/J.AAP.2011.09.019

Abstract: Biomathematical models are used in industry to estimate how much sleep people are likely to get on different work patterns, and how efficient and safe people are likely to be at work. Since there is evidence to suggest that in iduals respond differently to sleep loss, there has been a recent focus on trying to account for in idual differences. One possible approach could use past behaviour to predict future responses to similar working conditions. This study investigated the predictive value of sleep timing and duration data for a particular in idual on a break between shifts relative to data from their colleagues. Sleep diaries and wrist actigraphy were collected from 306 international long-haul pilots for at least 2-weeks. Fifty layovers, equivalent in origin and destination, length and timing, were completed twice by in idual pilots. Matched layovers done by other pilots (n=2311) were also identified. Layover periods were analysed for minute-by-minute correspondence of sleep or wake (yes/no), and total sleep time (TST). Using an in idual's own data improved concordance by approximately 5% relative to using a large s le of different pilots, and by 10% relative to using a random s le of 50 different pilots. Using an in idual's own TST to predict their TST on an equivalent layover yielded an r value of 0.83, compared to r=0.78 when data from a colleague was used, and r=0.73 using different pilots in a random s le of equivalent size. The mean difference in TST using pilots' own data was <20 min, compared to <40 min using data from colleagues. However, the confidence limits on these differences were large (up to 8h). Results suggest that for international pilots on specific layover patterns, knowing the past behaviour of an in idual may only represent a modest improvement over knowing the length and timing of a colleague's sleep, when it comes to predicting their sleep behaviour.

Consecutive Nights of Moderate Sleep Loss Does Not Affect Mood in Healthy Young Males

Publisher: MDPI AG

Date: 20-08-2021

DOI: 10.3390/CLOCKSSLEEP3030031

Abstract: Sleep loss causes mood disturbance in non-clinical populations under severe conditions, i.e., two days/nights of sleep deprivation or a week of sleep restriction with 4–5 h in bed each night. However, the effects of more-common types of sleep loss on mood disturbance are not yet known. Therefore, the aim of this study was to examine mood disturbance in healthy adults over a week with nightly time in bed controlled at 5, 6, 7, 8 or 9 h. Participants (n = 115) spent nine nights in the laboratory and were given either 5, 6, 7, 8 or 9 h in bed over seven consecutive nights. Mood was assessed daily using the Profile of Mood States (POMS-2). Mixed-linear effects models examined the effect of time in bed on total mood disturbance and subscales of anger-hostility, confusion-bewilderment, depression-dejection, fatigue-inertia, tension-anxiety, vigour-activity and friendliness. There was no effect of time in bed on total mood disturbance (F(4, 110.42) = 1.31, p = 0.271) or any of the subscales except fatigue-inertia. Fatigue-inertia was higher in the 5 h compared with the 9 h time in bed condition (p = 0.012, d = 0.75). Consecutive nights of moderate sleep loss (i.e., 5–7 h) does not affect mood but does increase fatigue in healthy males.

Do short international layovers allow sufficient opportunity for pilots to recover?

Publisher: Informa UK Limited

Date: 2006

DOI: 10.1080/07420520601062387

Abstract: For Australian pilots, short layovers (<40 h) are a feature of many international patterns. However, anecdotal reports suggest that flight crew members find patterns with short slips more fatiguing than those with a longer international layover, as they restrict the opportunity to obtain sufficient sleep. The current study aimed to determine whether pilots operating international patterns with short layovers have sufficient opportunity to recover prior to the inbound flight. Nineteen international pilots (ten captains, nine first officers) operating a direct return pattern from Australia to Los Angeles (LAX) with a short (n = 9) 9+/-0.8 h (mean+/-S.D) or long (n = 10) 62.2+/-0.9 h LAX layover wore an activity monitor and kept a sleep/duty diary during the pattern. Immediately before and after each flight, pilots completed a 5 min PalmPilot-based psychomotor vigilance task (Palm-PVT). Flights were of comparable duration outbound (3.5+/-0.6 h) and inbound (14.3+/-0.6 h) and timing. The amount of sleep obtained in-flight did not significantly vary as a function of layover length. However, pilots obtained significantly more sleep during the inbound (3.7+/-0.8 h) than the outbound flight (2.2+/-0.8 h). Pilots with the shorter layover obtained significantly less sleep in total during layover (14.0+/-2.7 h vs. 19.6+/-2.5), due to significantly fewer sleep periods (3.0+/-0.7 vs. 4.0+/-0.9). However, neither mean sleep duration nor the sleep obtained in the 24 h prior to the inbound flight significantly differed as a function of layover length. Response speed significantly varied across the pattern, and a significant interaction was also observed. For pilots with a short layover, response speed was significantly slower at the end of both the outbound and inbound flight, and prior to the inbound flight (i.e., at the end of layover), relative to response speed at the start of the pattern (pre-trip). Similarly, response speed for the longer layover was slower at the end of the outbound flight compared to pre-trip (approaching significance, p = 0.073). However, response speed at the beginning of the inbound flight was significantly faster than pre-trip and did not significantly differ from pre-trip at the end of the inbound flight. The data suggest that short slips (<40 h) do not allow pilots the opportunity to obtain sufficient sleep to reverse the effects of fatigue accumulated during the outbound flight. As a result, their response speed prior to the inbound flight is substantially slower than the response speed of flight crew with a longer layover.

Performance on a simple response time task: Is sleep or work more important for miners?

Publisher: Elsevier BV

Date: 2011

DOI: 10.1016/J.APERGO.2010.06.010

Abstract: The purpose of the current study was to investigate the impact of work- and sleep-related factors on an objective measure of response time in a field setting. Thirty-five mining operators working 12-h shift patterns completed daily sleep and work diaries, wore activity monitors continuously and completed palm-based psychomotor vigilance tests (palmPVT) at the start and end of each shift. Linear mixed models were used to test the main effects on response time of roster, timing of test, sleep history and prior wake. The time at which the test occurred was a significant predictor of response time (F₃(,)₄₀₃(.)₄ = 6.72, p < .01) with the end of night shifts being associated with significantly slower response times than the start of night shifts, and the start or end of day shifts. Further, the amount of sleep obtained in the 24h prior to the test was also a significant predictor of response time (F₃(,)₄₀₇(.)₀ = 3.05, p < .01). The results suggest that, as expected, the end of night shift is associated with changes in response time indicative of performance impairments. Of more interest however is that immediate sleep history was also predictive of changes in response time with lower amounts of prior sleep related to slower response times. The current data provides further evidence that sleep is a primary mediator of performance, independent of roster pattern.

A model of shiftworker sleep/wake behaviour

Publisher: Elsevier BV

Date: 03-2012

DOI: 10.1016/J.AAP.2011.09.017

Abstract: Software-based biomathematical models of alertness provide a means to estimate fatigue-related risk in advance of a schedule being worked. Obtaining a good estimate of employees' sleep/wake behaviour during non-work periods is critical in obtaining accurate estimates of alertness. This is because estimates of alertness are generated based on estimated sleep and wake times, not rest and work times per se. The purpose of the current analysis was to evaluate the predictive validity of a novel version of a previously published sleep predictor model. This model was originally designed to predict sleep probability for aviation pilots in connection with long-haul flight operations. It has since been modified to predict sleep periods for industrial shiftwork rosters in non-transmeridian environments. The algorithm uses two procedures to predict sleep timing and duration: (1) estimate the total amount of sleep likely to be obtained in a given rest period and then (2) estimate the timing and duration of sleep periods within that rest period. The sleep periods predicted in the second procedure are generated such that their combined sum is a priori equivalent to the total amount of sleep predicted in the first procedure. The model was parameterized and validated based on a s le of 225 train drivers who collected work/rest and sleep/wake data for two weeks during normal commercial operations. Agreement between observed and predicted sleep periods was robust (percent agreement=85%) and compared favourably with agreement levels between sleep behaviours exhibited by the same in idual on distinct occasions but where shift sequences were repeated. These results are discussed within the context of ongoing efforts to develop in idualized biomathematical models of alertness.

Sleep restriction masks the influence of the circadian process on sleep propensity

Publisher: Informa UK Limited

Date: 23-05-2012

DOI: 10.3109/07420528.2012.675256

Abstract: Previous forced desynchrony studies have highlighted the close relationship between the circadian rhythms of core body temperature (CBT) and sleep propensity. In particular, these studies have shown that a "forbidden zone" for sleep exists on the rising limb of the CBT rhythm. In these previous studies, the length of the experimental day was either ultrashort (90 min), short (20 h), or long (28 h), and the ratio of sleep to wake was normal (i.e., 1:2). The aim of the current study was to examine the relative effects of the circadian and homeostatic processes on sleep propensity using a 28-h forced desynchrony protocol in which the ratio of sleep to wake was substantially lower than normal (i.e., 1:5). Twenty-seven healthy males lived in a time-isolation sleep laboratory for 11 consecutive days. Participants completed either a control (n = 13) or sleep restriction (n = 14) condition. In both conditions, the protocol consisted of 2 × 24-h baseline days followed by 8 × 28-h forced desynchrony days. On forced desynchrony days, the control group had 9.3 h in bed and 18.7 h of wake, and the sleep restriction group had 4.7 h in bed and 23.3 h of wake. For all participants, each 30-s epoch of time in bed was scored as sleep or wake based on standard polysomnography recordings, and was also assigned a circadian phase (360° = 24 h) based on a cosine equation fitted to continuously recorded CBT data. For each circadian phase (i.e., 72 × 5° bins), sleep propensity was calculated as the percentage of epochs spent in bed scored as sleep. For the control group, there was a clear circadian rhythm in sleep propensity, with a peak of 98.5% at 5° (~05:20 h), a trough of 64.9% at 245° (~21:20 h), and an average of 82.3%. In contrast, sleep propensity for the sleep restriction group was relatively high at all circadian phases, with an average of 96.7%. For this group, the highest sleep propensity (99.0%) occurred at 60° (~09:00 h), and the lowest sleep propensity (91.3%) occurred at 265° (~22:40 h). As has been shown previously, these current data indicate that with a normal sleep-to-wake ratio, the effect of the circadian process on sleep propensity is pronounced, such that a forbidden zone for sleep exists at a phase equivalent to evening time for a normally entrained in idual. However, these current data also indicate that when the ratio of sleep to wake is substantially lower than normal, this circadian effect is masked. In particular, sleep propensity is very high at all circadian phases, including those that coincide with the forbidden zone for sleep. This finding suggests that if the homeostatic pressure for sleep is sufficiently high, then the circadian drive for wakefulness can be overridden. In future studies, it will be important to determine whether or not this masking effect occurs with less severe sleep restriction, e.g., with a sleep-to-wake ratio of 1:3.

Yin and yang, or peas in a pod? Individual-sport versus team-sport athletes and altitude training

Publisher: BMJ

Date: 19-11-2013

DOI: 10.1136/BJSPORTS-2013-092764

The sleep of elite athletes at sea level and high altitude: A comparison of sea-level natives and high-altitude natives (ISA3600)

Publisher: BMJ

Date: 26-11-2013

DOI: 10.1136/BJSPORTS-2013-092843

Perceptions of labour pain by mothers and their attending midwives

Publisher: Wiley

Date: 22-07-2001

DOI: 10.1046/J.1365-2648.2001.01834.X

Abstract: The aim of the current study was to examine the perception of pain by labouring women and their attendant midwife, from the onset of labour to delivery. Accurate measurement and appropriate management of pain is a significant problem for attendant medical and nursing personnel. Both the experience and perception of pain are regarded as subjective and are therefore difficult to measure objectively. Indeed, much of the literature reports that pain is often under- or over-estimated by nursing staff who as a consequence consistently fail to administer adequate analgesia. Few studies have specifically examined the ability of midwives to assess the pain of labouring women. The short form McGill Pain Questionnaire (SF-MPQ), routinely used to assess pain in obstetric environments, was used to determine pain perception. Thirteen labouring women and nine midwives completed the SF-MPQ every 15 minutes beginning at the time of admittance to the delivery suite. Peak pain ratings for the preceding 15 minutes were obtained without reference to prior ratings or each other's scores. Further, midwives in the maternity unit of The Queen Elizabeth Hospital (TQEH), Adelaide, South Australia completed a survey investigating the cues they use to assess pain during labour. On each measure of pain on the SF-MPQ, the midwives scores correlated with the mothers' scores across the entire pain range. Further analysis showed that mothers' and midwives' pain scores were similar at mild-moderate pain levels, but midwives significantly underestimated pain intensity at levels that mothers described as severe. The survey responses indicated that midwives rely on both verbal and nonverbal cues to assess pain levels. The cues used by midwives to differentiate pain intensities and qualities are similar to those used in other clinical settings, but may have limited discriminatory value as pain levels become severe.

Concordance of Chronotype Categorisations Based on Dim Light Melatonin Onset, the Morningness-Eveningness Questionnaire, and the Munich Chronotype Questionnaire

Publisher: MDPI AG

Date: 17-06-2021

DOI: 10.3390/CLOCKSSLEEP3020021

Abstract: Chronotype reflects circadian timing and can be determined from biological markers (e.g., dim light melatonin onset DLMO), or questionnaires (e.g., Morningness-Eveningness Questionnaire MEQ, or Munich Chronotype Questionnaire MCTQ). The study’s aim was to quantify concordance between chronotype categorisations based on these measures. A total of 72 (36f) young, healthy adults completed the MEQ and MCTQ and provided saliva s les hourly in dim light during the evening in a laboratory. The corrected midpoint of sleep on free days (MSFsc) was derived from MCTQ, and tertile splits were used to define early, intermediate and late DLMO-CT, MEQ-CT and MSFsc-CT chronotype categories. DLMO correlated with MEQ score (r = −0.25, p = 0.035) and MSFsc (r = 0.32, p = 0.015). For early, intermediate and late DLMO-CT categories, mean(SD) DLMO were 20:25(0:46), 21:33(0:10) and 23:03(0:53). For early, intermediate and late MEQ-CT categories, mean(SD) MEQ scores were 60.5(5.3), 51.4(2.9) and 40.8 (5.0). For early, intermediate and late MSFsc-CT categories, mean(SD) MSFsc were 03:23(0:34), 04:37(0:12) and 05:55(0:48). Low concordance of categorisations between DLMO-CT and MEQ-CT (37%), and between DLMO-CT and MSFsc-CT (37%), suggests chronotype categorisations depend on the measure used. To enable valid comparisons with previous results and reduce the likelihood of misleading conclusions, researchers should select measures and statistical techniques appropriate to the construct of interest and research question.

A Validation Study of a Commercial Wearable Device to Automatically Detect and Estimate Sleep

Publisher: MDPI AG

Date: 08-06-2021

DOI: 10.3390/BIOS11060185

Abstract: The aims of this study were to: (1) compare actigraphy (ACTICAL) and a commercially available sleep wearable (i.e., WHOOP) under two functionalities (i.e., sleep auto-detection (WHOOP-AUTO) and manual adjustment of sleep (WHOOP-MANUAL)) for two-stage categorisation of sleep (sleep or wake) against polysomnography, and (2) compare WHOOP-AUTO and WHOOP-MANUAL for four-stage categorisation of sleep (wake, light sleep, slow wave sleep (SWS), or rapid eye movement sleep (REM)) against polysomnography. Six healthy adults (male: n = 3 female: n = 3 age: 23.0 ± 2.2 yr) participated in the nine-night protocol. Fifty-four sleeps assessed by ACTICAL, WHOOP-AUTO and WHOOP-MANUAL were compared to polysomnography using difference testing, Bland–Altman comparisons, and 30-s epoch-by-epoch comparisons. Compared to polysomnography, ACTICAL overestimated total sleep time (37.6 min) and underestimated wake (−37.6 min) WHOOP-AUTO underestimated SWS (−15.5 min) and WHOOP-MANUAL underestimated wake (−16.7 min). For ACTICAL, sensitivity for sleep, specificity for wake and overall agreement were 98%, 60% and 89%, respectively. For WHOOP-AUTO, sensitivity for sleep, wake, and agreement for two-stage and four-stage categorisation of sleep were 90%, 60%, 86% and 63%, respectively. For WHOOP-MANUAL, sensitivity for sleep, wake, and agreement for two-stage and four-stage categorisation of sleep were 97%, 45%, 90% and 62%, respectively. WHOOP-AUTO and WHOOP-MANUAL have a similar sensitivity and specificity to actigraphy for two-stage categorisation of sleep and can be used as a practical alternative to polysomnography for two-stage categorisation of sleep and four-stage categorisation of sleep.

Correction: Bellenger et al. Wrist-Based Photoplethysmography Assessment of Heart Rate and Heart Rate Variability: Validation of WHOOP. Sensors 2021, 21, 3571

Publisher: MDPI AG

Date: 18-04-2022

DOI: 10.3390/S22083090

Abstract: The authors wish to correct the following errors in the original paper [...]

Wrist-Based Photoplethysmography Assessment of Heart Rate and Heart Rate Variability: Validation of WHOOP

Publisher: MDPI AG

Date: 20-05-2021

DOI: 10.3390/S21103571

Abstract: Heart rate (HR) and HR variability (HRV) infer readiness to perform exercise in athletic populations. Technological advancements have facilitated HR and HRV quantification via photoplethysmography (PPG). This study evaluated the validity of WHOOP’s PPG-derived HR and HRV against electrocardiogram-derived (ECG) measures. HR and HRV were assessed via WHOOP 2.0 and ECG over 15 opportunities during October–December 2018. WHOOP-derived pulse-to-pulse (PP) intervals were edited with WHOOP’s proprietary filter, in addition to various filter strengths via Kubios HRV software. HR and HRV (Ln RMSSD) were quantified for each filter strength. Agreement was assessed via bias and limits of agreement (LOA), and contextualised using smallest worthwhile change (SWC) and coefficient of variation (CV). Regardless of filter strength, bias (≤0.39 ± 0.38%) and LOA (≤1.56%) in HR were lower than the CV (10–11%) and SWC (5–5.5%) for this parameter. For Ln RMSSD, bias (1.66 ± 1.80%) and LOA (±5.93%) were lowest for a 200 ms filter and WHOOP’s proprietary filter, which approached or exceeded the CV (3–13%) and SWC (1.5–6.5%) for this parameter. Acceptable agreement was found between WHOOP- and ECG-derived HR. Bias and LOA in Ln RMSSD approached or exceeded the SWC/CV for this variable and should be interpreted against its own level of bias precision.

Sleep or swim? Early-morning training severely restricts the amount of sleep obtained by elite swimmers

Publisher: Informa UK Limited

Date: 06-07-2014

DOI: 10.1080/17461391.2012.696711

Abstract: Good sleep is essential for optimal performance, yet few studies have examined the sleep/wake behaviour of elite athletes. The aim of this study was to assess the impact of early-morning training on the amount of sleep obtained by world-class swimmers. A squad of seven swimmers from the Australian Institute of Sport participated in this study during 14 days of high-intensity training in preparation for the 2008 Olympic Games. During these 14 days, participants had 12 training days, each starting with a session at 06:00 h, and 2 rest days. For each day, the amount of sleep obtained by participants was determined using self-report sleep diaries and wrist-worn activity monitors. On nights that preceded training days, participants went to bed at 22:05 h (s=00:52), arose at 05:48 h (s=00:24) and obtained 5.4 h (s=1.3) of sleep. On nights that preceded rest days, participants went to bed at 00:32 h (s=01:29), arose at 09:47 h (s=01:47) and obtained 7.1 h (s=1.2) of sleep. Mixed model analyses revealed that on nights prior to training days, bedtimes and get-up times were significantly earlier (p<0.001), time spent in bed was significantly shorter (p<0.001) and the amount of sleep obtained was significantly less (p<0.001), than on nights prior to rest days. These results indicate that early-morning training sessions severely restrict the amount of sleep obtained by elite athletes. Given that chronic sleep restriction of <6 h per night can impair psychological and physiological functioning, it is possible that early-morning schedules actually limit the effectiveness of training.

Changes in blood gas transport of altitude native soccer players near sea-level and sea-level native soccer players at altitude (ISA3600)

Publisher: BMJ

Date: 26-11-2013

DOI: 10.1136/BJSPORTS-2013-092761

Observations of age-related differences in neurobehavioral performance in a 12-hour shift system

Publisher: Springer Science and Business Media LLC

Date: 06-2006

DOI: 10.1111/J.1479-8425.2006.00196.X

The effects of fatigue on train handling during speed restrictions

Publisher: Elsevier BV

Date: 07-2006

DOI: 10.1016/J.TRF.2006.01.003

Does variation in workload affect fatigue in a regular 12-hour shift system?

Publisher: Springer Science and Business Media LLC

Date: 2007

DOI: 10.1111/J.1479-8425.2006.00249.X

The effects of a split sleep-wake schedule on neurobehavioural performance and predictions of performance under conditions of forced desynchrony

Publisher: Informa UK Limited

Date: 15-09-2014

DOI: 10.3109/07420528.2014.957763

Abstract: Extended wakefulness, sleep loss, and circadian misalignment are factors associated with an increased accident risk in shiftwork. Splitting shifts into multiple shorter periods per day may mitigate these risks by alleviating prior wake. However, the effect of splitting the sleep-wake schedule on the homeostatic and circadian contributions to neurobehavioural performance and subjective assessments of one's ability to perform are not known. Twenty-nine male participants lived in a time isolation laboratory for 13 d, assigned to one of two 28-h forced desynchrony (FD) schedules. Depending on the assigned schedule, participants were provided the same total time in bed (TIB) each FD cycle, either consolidated into a single period (9.33 h TIB) or split into two equal halves (2 × 4.67 h TIB). Neurobehavioural performance was regularly assessed with a psychomotor vigilance task (PVT) and subjectively-assessed ability was measured with a prediction of performance on a visual analogue scale. Polysomnography was used to assess sleep, and core body temperature was recorded to assess circadian phase. On average, participants obtained the same amount of sleep in both schedules, but those in the split schedule obtained more slow wave sleep (SWS) on FD days. Mixed-effects ANOVAs indicated no overall difference between the standard and split schedules in neurobehavioural performance or predictions of performance. Main effects of circadian phase and prior wake were present for both schedules, such that performance and subjective ratings of ability were best around the circadian acrophase, worst around the nadir, and declined with increasing prior wake. There was a schedule by circadian phase interaction for all neurobehavioural performance metrics such that performance was better in the split schedule than the standard schedule around the nadir. There was no such interaction for predictions of performance. Performance during the standard schedule was significantly better than the split schedule at 2 h of prior wake, but declined at a steeper rate such that the schedules converged by 4.5-7 h of prior wake. Overall, the results indicate that when the total opportunity for sleep per day is satisfactory, a split sleep-wake schedule is not detrimental to sleep or performance. Indeed, though not reflected in subjective assessments of performance capacity, splitting the schedule may be of some benefit, given its reduction of neurobehavioural impairment at night and its association with increased SWS. Therefore, for some industries that require operations to be sustained around the clock, implementing a split work-rest schedule may be of assistance.

The effect of sleep restriction, with or without high‐intensity interval exercise, on behavioural alertness and mood state in young healthy males

Publisher: Wiley

Date: 11-07-2023

DOI: 10.1111/JSR.13987

Abstract: Mood state and alertness are negatively affected by sleep loss, and can be positively influenced by exercise. However, the potential mitigating effects of exercise on sleep‐loss‐induced changes in mood state and alertness have not been studied comprehensively. Twenty‐four healthy young males were matched into one of three, 5‐night sleep interventions: normal sleep (NS total sleep time (TST) per night = 449 ± 22 min), sleep restriction (SR TST = 230 ± 5 min), or sleep restriction and exercise (SR + EX TST = 235 ± 5 min, plus three sessions of high‐intensity interval exercise (HIIE)). Mood state was assessed using the profile of mood states (POMS) and a daily well‐being questionnaire. Alertness was assessed using psychomotor vigilance testing (PVT). Following the intervention, POMS total mood disturbance scores significantly increased for both the SR and SR + EX groups, and were greater than the NS group (SR vs NS 31.0 ± 10.7 A.U., [4.4–57.7 A.U.], p = 0.020 SR + EX vs NS 38.6 ± 14.9 A.U., [11.1–66.1 A.U.], p = 0.004). The PVT reaction times increased in the SR ( p = 0.049) and SR + EX groups ( p = 0.033) and the daily well‐being questionnaire revealed increased levels of fatigue in both groups (SR p = 0.041, SR + EX p = 0.026) during the intervention. Despite previously demonstrated physiological benefits of performing three sessions of HIIE during five nights of sleep restriction, the detriments to mood, wellness, and alertness were not mitigated by exercise in this study. Whether alternatively timed exercise sessions or other exercise protocols could promote more positive outcomes on these factors during sleep restriction requires further research.

How well does a commercially available wearable device measure sleep in young athletes?

Publisher: Informa UK Limited

Date: 11-05-2018

DOI: 10.1080/07420528.2018.1466800

Abstract: The validity of a commercially available wearable device for measuring total sleep time was examined in a s le of well-trained young athletes during night-time sleep periods and daytime naps. Participants wore a FitBit HR Charge on their non-dominant wrist and had electrodes attached to their face and scalp to enable polysomnographic recordings of sleep in the laboratory. The FitBit automatically detected 24/30 night-time sleep periods but only 6/20 daytime naps. Compared with polysomnography, the FitBit overestimated total sleep time by an average of 52 ± 152 min for night-time sleep periods, and by 4 ± 8 min for daytime naps. It is important for athletes and practitioners to be aware of the limitations of wearable devices that automatically detect sleep duration.

Can we put the first night effect to bed? An analysis based on a large sample of healthy adults

Publisher: Informa UK Limited

Date: 11-10-2022

DOI: 10.1080/07420528.2022.2133611

Abstract: The 'first night effect' refers to in iduals experiencing poorer sleep during their first night in a laboratory. The effect is attributed to sleeping in a new environment, as well as wearing electrodes on the head and face, and is often cited as a reason for including an adaptation night in sleep research protocols. However, in the time since the 'first night effect' was initially reported, the conditions and equipment used in modern sleep laboratories have changed considerably, which may reduce the 'first night effect.' The aim of this study was to examine the impact of the 'first night effect' on sleep in a s le of healthy adults. Participants (n = 124 22.7 ± 3.6 years) were given a 9-hour sleep opportunity (23:00-08:00 h) on two consecutive nights in a time-isolated sleep laboratory with sleep measured via polysomnography. Differences in dependent sleep variables between Night 1 and Night 2 were examined using paired t-tests. There was no difference in sleep onset latency (p = .295), total sleep time (p = .343), wake after sleep onset (p = .410), or sleep efficiency (p = .342) between Nights 1 and 2. However, participants spent more time in stage one (p = .001), and less time in stages two (p = .029) and three (p = .013) on Night 1 compared with Night 2. This suggests that, where primary sleep variables are the focus and not sleep architecture or arousals (e.g., where sleep is used as an independent variable), including an adaptation night may not be necessary.

Flat-out napping: The quantity and quality of sleep obtained in a seat during the daytime increase as the angle of recline of the seat increases

Publisher: Informa UK Limited

Date: 03-06-2018

DOI: 10.1080/07420528.2018.1466801

Abstract: Some shiftwokers in the long-haul transportation industries (i.e. road, rail, sea, air) have the opportunity to sleep in on-board rest facilities during duty periods. These rest facilities are typically fitted with a seat with a maximum back angle to the vertical of 20°, 40°, or 90°. The aim of this study was to examine the impact of "back angle" on the quantity and quality of sleep obtained in a seat during a daytime nap. Six healthy adults (3 females aged 27.0 years and 3 males aged 22.7 years) each participated in three conditions. For each condition, participants had a 4-h sleep opportunity in a bed (02:00-06:00 h) followed by a 4-h sleep opportunity in a seat (13:00-17:00 h). The only difference between conditions was in the back angle of the seat to the vertical during the seat-based sleep periods: 20° (upright), 40° (reclined), and 90° (flat). Polysomnographic data were collected during all sleep episodes. For the seat-based sleep episodes, there was a significant effect of back angle on three of four measures of sleep quantity, i.e. total sleep time, slow-wave sleep, and rapid eye movement (REM) sleep, and three of four measures of sleep quality, i.e. latency to REM sleep, arousals, and stage shifts. In general, the quantity and quality of sleep obtained in the reclined and flat seats were better than those obtained in the upright seat. In particular, compared to the flat seat, the reclined seat resulted in similar amounts of total sleep and slow-wave sleep, but 37% less REM sleep and the upright seat resulted in 29% less total sleep, 30% less slow-wave sleep, and 79% less REM sleep. There are two main mechanisms that may explain the results. First, it is difficult to maintain the head in a comfortable position for sleep when sitting upright, and this is likely exacerbated during REM sleep, when muscle tone is very low. Second, an upright posture increases sympathetic activity and decreases parasympathetic activity, resulting in a heightened level of physiological arousal.

Long-haul pilots use in-flight napping as a countermeasure to fatigue

Publisher: Elsevier BV

Date: 2011

DOI: 10.1016/J.APERGO.2010.06.016

Abstract: The aim of this study was to examine the effects of fatigue on the amount of in-flight sleep obtained by airline pilots during long-haul duty periods. A total of 301 pilots collected sleep/wake and work/rest data for a period of at least 2 weeks each. Fatigue likelihood, i.e. low, moderate, high, or extreme, was estimated for each duty period based on a pilot's sleep/wake behaviour prior to duty and the time of day that the duty period occurred. Participants obtained 1.8 h of sleep (i.e. 27% of their rest time) during duty periods with low fatigue likelihood and 3.7 h of sleep (i.e. 54% of their rest time) during duty periods with extreme fatigue likelihood. These results indicate that (i) long-haul pilots obtain substantially more sleep during duty periods when fatigue is likely to be extreme than when fatigue is likely to be low and (ii) long-haul pilots use in-flight napping as a fatigue countermeasure, but more could be done to increase its efficacy.

How well do truck drivers sleep in cabin sleeper berths?

Publisher: Elsevier BV

Date: 03-2012

DOI: 10.1016/J.APERGO.2011.06.019

Abstract: The aim of this study was to evaluate the sleep obtained by livestock transport truck drivers while resting in truck sleeper berths during long-haul commercial operations. Operations were carried out in the very remote regions of Australia. The s le comprised of 32 drivers who wore wrist activity monitors and reported bed-times for a two-week period. Drivers had a mean (±standard deviation) age of 35.41 (± 9.78) years and had worked as truck drivers for 13.83 (± 9.11) years. On average, they obtained 6.07 (± 1.18) hours of sleep/24-h period. The majority of sleep occurred at night, but drivers occasionally supplemented their main sleep with a daytime nap. Consistent with operational demands, drivers were most likely to sleep in cabin sleeper berths (n = 394, 77%). Only a small proportion of sleeps were s led at home (n = 63, 12%) or at truck depots (n = 56, 11%). Mixed-model ANOVA revealed that while earlier bed-times at home yielded more sleep, there were only marginal differences in sleep quality across location. No intrinsic safety concerns associated with the use of sleeper berths were identified across consecutive days of long-haul transport operations.

Duty periods with early start times restrict the amount of sleep obtained by short-haul airline pilots

Publisher: Elsevier BV

Date: 03-2012

DOI: 10.1016/J.AAP.2011.09.020

Abstract: Most of the research related to human fatigue in the aviation industry has focussed on long-haul pilots, but short-haul pilots also experience elevated levels of fatigue. The aim of this study was to examine the impact of early start times on the amount of sleep obtained prior to duty and on fatigue levels at the start of duty. Seventy short-haul pilots collected data regarding their duty schedule and sleep/wake behaviour for at least two weeks. Data were collected using self-report duty/sleep diaries and wrist activity monitors. Mixed-effects regression analyses were used to examine the effects of duty start time (04:00-10:00 h) on (i) the total amount of sleep obtained in the 12h prior to the start of duty and (ii) self-rated fatigue level at the start of duty. Both analyses indicated significant main effects of duty start time. In particular, the amount of sleep obtained in the 12h prior to duty was lowest for duty periods that commenced between 04:00 and 05:00 h (i.e. 5.4h), and greatest for duty periods that commenced between 09:00 and 10:00 h (i.e. 6.6h). These data indicate that approximately 15 min of sleep is lost for every hour that the start of duty is advanced prior to 09:00 h. In addition, self-rated fatigue at the start of duty was highest for duty periods that commenced between 04:00 and 05:00 h, and lowest for duty periods that commenced between 09:00 and 10:00 h. Airlines should implement a fatigue risk management system (FRMS) for short-haul pilots required to work early-morning shifts. One component of the FRMS should be focussed on the production of 'fatigue-friendly' rosters. A second component of the FRMS should be focussed on training pilots to optimise sleep opportunities, to identify circumstances where the likelihood of fatigue is elevated, and to manage the risks associated with fatigue-related impairment.

The sensitivity of a palm-based psychomotor vigilance task to severe sleep loss

Publisher: Springer Science and Business Media LLC

Date: 02-2008

DOI: 10.3758/BRM.40.1.347

Abstract: In this study, we evaluated the sensitivity of a 5-min personal digital assistant-psychomotor vigilance test (PDA-PVT) to severe sleep loss. Twenty-one participants completed a 10-min PVT-192 and a 5-min PDA-PVT at two hourly intervals during 62 h of sustained wakefulness. For both tasks, response speed and number of lapses (RTs > 500) per minute significantly increased with increasing hours of wakefulness. Overall, standardized response speed scores on the 5-min PDA-PVT closely tracked those of the PVT-192 however, the PDA-PVT was generally associated with more lapses/minute. Closer inspection of the data indicated that when the level of sleep loss and fatigue became more severe (i.e., Day 3), the 5-min PDA-PVT was not quite as sensitive as the 10-min PVT-192 when 2- to 10-sec foreperiods were used for both. It is likely, however, that the observed differences between the two devices was due to differences in task length. Thus, the findings provide further evidence of the validity of the 5-min PDA-PVT as a substitute for the 10-min PVT-192, particularly in circumstances in which a shorter test is required and/or the PVT-192 is not as practical.

The influence of circadian time and sleep dose on subjective fatigue ratings

Publisher: Elsevier BV

Date: 03-2012

DOI: 10.1016/J.AAP.2011.09.026

Abstract: Subjective ratings of fatigue are increasingly being used as part of a suite of tools to assess fatigue-related risk on the road and in the workplace. There is some debate however, as to whether in iduals can accurately gauge their own fatigue states, particularly under conditions of sleep restriction. It is also unclear which references are used by in iduals to assess fatigue - for ex le prior sleep, time of day, workload, or previous ratings. The current study used a sophisticated laboratory protocol to examine the independent contributions of sleep, circadian phase and sleep debt to fatigue ratings. Importantly, participants had no knowledge of time of day, how much sleep they were getting, or how long they were awake. Twenty-eight healthy, young males participated in one of two conditions of a 28 h forced desynchrony protocol - severe sleep restriction (4.7h sleep and 23.3h wake) or moderate sleep restriction (7h sleep and 21 h wake). Fatigue ratings were provided prior to and following each sleep period using the Samn-Perelli fatigue scale. Repeated measures ANOVAs were used to analyse the effects of circadian phase, sleep dose and study day. Results demonstrated an effect of circadian phase on both pre-sleep and post-sleep fatigue ratings. The significant effect of study day is interpreted as an effect of circadian time, as opposed to accumulating sleep debt. An effect of sleep dose was only seen in post-sleep fatigue ratings. The findings suggest that post-sleep fatigue ratings may be sensitive to prior sleep and may be useful as an indicator of fatigue-related risk, particularly when triangulated with information about recent total sleep time.

No Effect of Chronotype on Sleepiness, Alertness, and Sustained Attention during a Single Night Shift

Publisher: MDPI AG

Date: 07-2021

DOI: 10.3390/CLOCKSSLEEP3030024

Abstract: The study’s aim was to examine the effect of chronotype on cognitive performance during a single night shift. Data were collected from 72 (36f) young, healthy adults in a laboratory study. Participants had a 9 h sleep period (03:00–12:00) followed by an 8 h night shift (23:00–07:00). During the night shift, participants completed five test sessions, which included measures of subjective sleepiness, subjective alertness, and sustained attention (i.e., psychomotor vigilance task PVT). Dim light melatonin onset (DLMO) was derived from saliva s les taken during the evening preceding the night shift. A tertile split of DLMO was used to determine three chronotype categories: earlier (DLMO = 20:22 ± 0:42), intermediate (DLMO = 21:31 ± 0:13), and later (DLMO = 22:54 ± 0:54). There were (a) significant main effects of test session (all p 0.001) (b) no main effects of chronotype and (c) no interaction effects between chronotype and test session on sleepiness, alertness, PVT response time, and PVT lapses. The results indicate that under controlled sleeping conditions, chronotype based on dim light melatonin onset did not affect nighttime performance. Differences in performance during night shift between chronotypes reported by field studies may be related to differences in the amount and/or timing of sleep before or between night shifts, rather than circadian timing.

Athletes underestimate sleep quantity during daytime nap opportunities

Publisher: Informa UK Limited

Date: 29-05-2018

DOI: 10.1080/07420528.2018.1466787

Abstract: This study examined the difference between athletes' self-reported and objective sleep durations during two nap opportunities. Twelve well-trained male soccer players' sleep durations were assessed using polysomnography and a self-report question during a 60- and 120-min nap opportunity. Participants underestimated sleep compared to objective sleep assessments for both the 60-min nap opportunity (p = 0.004) and 120-min nap opportunity (p = 0.001). Soccer players underestimated their sleep duration by approximately 10 min per hour of nap opportunity. It is yet to be determined if athletes are likely to underestimate sleep duration during their main nighttime sleep period.

The effect of sleep restriction on snacking behaviour during a week of simulated shiftwork

Publisher: Elsevier BV

Date: 03-2012

DOI: 10.1016/J.AAP.2011.09.028

Abstract: Due to irregular working hours shiftworkers experience circadian disruption and sleep restriction. There is some evidence to indicate that these factors adversely affect health through changes in snacking behaviour. The aim of this study was to investigate the impact of sleep restriction, prior wake and circadian phase on snacking behaviour during a week of simulated shiftwork. Twenty-four healthy males (age: 22.0 ± 3.6 years, mean ± SD) lived in a sleep laboratory for 12 consecutive days. Participants were assigned to one of two schedules: a moderate sleep restriction condition (n=10) equivalent to a 6-h sleep opportunity per 24h or a severe sleep restriction condition (n=14) equivalent to a 4-h sleep opportunity per 24h. In both conditions, sleep/wake episodes occurred 4h later each day to simulate a rotating shiftwork pattern. While living in the laboratory, participants were served three meals and were provided with either five (moderate sleep restriction condition) or six (severe sleep restriction condition) snack opportunities daily. Snack choice was recorded at each opportunity and assigned to a category (sweet, savoury or healthy) based on the content of the snack. Data were analysed using a Generalised Estimating Equations approach. Analyses show a significant effect of sleep restriction condition on overall and sweet snack consumption. The odds of consuming a snack were significantly greater in the severe sleep restriction condition (P<0.05) compared to the moderate sleep restriction condition. In particular, the odds of choosing a sweet snack were significantly increased in the severe sleep restriction condition (P<0.05). Shiftworkers who are severely sleep restricted may be at risk of obesity and related health disorders due to elevated snack consumption and unhealthy snack choice. To further understand the impact of sleep restriction on snacking behaviour, future studies should examine physiological, psychological and environmental motivators.

Position statement-Altitude training for improving team-Sport players' performance: Current knowledge and unresolved issues

Publisher: BMJ

Date: 26-11-2013

DOI: 10.1136/BJSPORTS-2013-093109

Glucose Concentrations from Continuous Glucose Monitoring Devices Compared to Those from Blood Plasma during an Oral Glucose Tolerance Test in Healthy Young Adults

Publisher: MDPI AG

Date: 09-12-2021

DOI: 10.3390/IJERPH182412994

Abstract: Continuous glucose monitoring devices measure glucose in interstitial fluid. The devices are effective when used by patients with type 1 and 2 diabetes but are increasingly being used by researchers who are interested in the effects of various behaviours of glucose concentrations in healthy participants. Despite their more frequent application in this setting, the devices have not yet been validated for use under such conditions. A total of 124 healthy participants were recruited to a ten-day laboratory study. Each participant underwent four oral glucose tolerance tests, and a total of 3315 out of a possible 4960 paired s les were included in the final analysis. Bland–Altman plots and mean absolute relative differences were used to determine the agreement between the two methods. Bland–Altman analyses revealed that the continuous glucose monitoring devices had proportional bias (R = 0.028, p 0.001) and a mean bias of −0.048 mmol/L, and device measurements were more variable as glucose concentrations increased. Ninety-nine per cent of paired values were in Zones A and B of the Parkes Error Grid plot, and there was an overall mean absolute relative difference of 16.2% (±15.8%). There was variability in the continuous glucose monitoring devices, and this variability was higher when glucose concentrations were higher. If researchers were to use continuous glucose monitoring devices to measure glucose concentrations during an oral glucose tolerance test in healthy participants, this variability would need to be considered.

Soccer activity profile of altitude versus sea-level natives during acclimatisation to 3600 m (ISA3600)

Publisher: BMJ

Date: 26-11-2013

DOI: 10.1136/BJSPORTS-2013-092776

Are two halves better than one whole? A comparison of the amount and quality of sleep obtained by healthy adult males living on split and consolidated sleep–wake schedules

Publisher: Elsevier BV

Date: 02-2017

DOI: 10.1016/J.AAP.2015.10.012

Abstract: The aim of this study was to compare the quantity/quality of sleep obtained by people living on split and consolidated sleep-wake schedules. The study had a between-groups design, with 13 participants in a consolidated condition (all males, mean age of 22.5yr) and 16 participants in a split condition (all males, mean age of 22.6yr). Both conditions employed forced desynchrony protocols with the activity:rest ratio set at 2:1, but the consolidated condition had one sleep-wake cycle every 28h (9.33+18.67), while the split condition had one sleep-wake cycle every 14h (4.67+9.33). Sleep was assessed using polysomnography. Participants in the split and consolidated conditions obtained 4.0h of sleep per 14h and 7.6h of sleep per 28h, respectively. Some differences between the groups indicated that sleep quality was lower in the split condition than the consolidated condition: the split sleeps had longer sleep onset latency (9.7 vs. 4.3min), more arousals (7.4 vs. 5.7 per hour in bed), and a greater percentage of stage 1 sleep (4.1% vs. 3.1%), than the consolidated sleeps. Other differences between the groups indicated that sleep quality was higher in the split condition than the consolidated condition: the split sleeps had a lower percentage of wake after sleep onset sleep (11.7% vs. 17.6%), and a greater percentage of slow wave sleep (30.2% vs. 23.8%), than the consolidated sleeps. These results indicate that the split schedule was not particularly harmful, and may have actually been beneficial, to sleep. Split work-rest schedules can be socially disruptive, but their use may be warranted in work settings where shiftworkers are separated from their normal family/social lives (e.g., fly-in fly-out mining) or where the need for family/social time is secondary to the task (e.g., emergency response to natural disasters).

Mild to Moderate Sleep Restriction Does Not Affect the Cortisol Awakening Response in Healthy Adult Males

Publisher: MDPI AG

Date: 25-11-2022

DOI: 10.3390/CLOCKSSLEEP4040054

Abstract: The cortisol awakening response (CAR) is a distinct rise in cortisol that occurs upon awakening that is thought to contribute to arousal, energy boosting, and anticipation. There is some evidence to suggest that inadequate sleep may alter the CAR, but the relationship between sleep duration and CAR has not been systematically examined. Healthy males (n = 111 age: 23.0 ± 3.6 yrs) spent 10 consecutive days/nights in a sleep laboratory. After a baseline night (9 h time in bed), participants spent either 5 h (n = 19), 6 h (n = 23), 7 h (n = 16), 8 h (n = 27), or 9 h (n = 26) in bed for seven nights, followed by a 9 h recovery sleep. The saliva s les for cortisol assay were collected at 08:00 h, 08:30 h and 08:45 h at baseline, on experimental days 2 and 5 and on the recovery day. The primary dependent variables were the cortisol concentration at awakening (08:00 h) and the cortisol area under the curve (AUC). There was no effect of time in bed on either the cortisol concentration at awakening or cortisol AUC. In all the time in bed conditions, the cortisol AUC tended to be higher at baseline and lower on experimental day 5. Five consecutive nights of mild to moderate sleep restriction does not appear to affect the CAR in healthy male adults.

Methods of the international study on soccer at altitude 3600 m (ISA3600)

Publisher: BMJ

Date: 26-11-2013

DOI: 10.1136/BJSPORTS-2013-092770

Optimisation and Validation of a Nutritional Intervention to Enhance Sleep Quality and Quantity

Publisher: MDPI AG

Date: 25-08-2020

DOI: 10.3390/NU12092579

Abstract: Background: Disturbed sleep may negatively influence physical health, cognitive performance, metabolism, and general wellbeing. Nutritional interventions represent a potential non-pharmacological means to increase sleep quality and quantity. Objective: (1) Identify an optimal suite of nutritional ingredients and (2) validate the effects of this suite utilising polysomnography, and cognitive and balance tests. Methods: The optimal and least optimal combinations of six ingredients were identified utilising 55 male participants and a Box–Behnken predictive model. To validate the model, 18 healthy, male, normal sleepers underwent three trials in a randomised, counterbalanced design: (1) optimal drink, (2) least optimal drink, or (3) placebo were provided before bed in a double-blinded manner. Polysomnography was utilised to measure sleep architecture. Cognitive performance, postural sway, and subjective sleep quality, were assessed 30 min after waking. Results: The optimal drink resulted in a significantly shorter sleep onset latency (9.9 ± 12.3 min) when compared to both the least optimal drink (26.1 ± 37.4 min) and the placebo drink (19.6 ± 32.0 min). No other measures of sleep, cognitive performance, postural sway, and subjective sleep quality were different between trials. Conclusion: A combination of ingredients, optimised to enhance sleep, significantly reduced sleep onset latency. No detrimental effects on sleep architecture, subjective sleep quality or next day performance were observed.

How well do pilots sleep during long-haul flights?

Publisher: Informa UK Limited

Date: 24-08-2010

DOI: 10.1080/00140139.2010.506246

Abstract: It is imperative that shiftworkers in safety-critical workplaces obtain sufficient sleep to operate effectively. This presents a challenge to long-haul airline pilots who are required to supplement normal bed sleep with sleep on-board an aircraft during flight. In the current study, the sleep/wake behaviour of 301 airline pilots operating long-haul flight patterns was monitored for at least 2 weeks using self-report sleep diaries and wrist activity monitors. The data indicate that sleep opportunities in on-board rest facilities during long-haul flights result in a similar amount of sleep, but only 70% as much recovery, as duration-matched bed sleeps. STATEMENT OF RELEVANCE: This study indicates that in-flight sleep provides airline pilots with 70% as much restoration as duration-matched bed sleep. To increase the restoration provided by in-flight sleep, airlines could take measures to improve the quality, or increase the amount, of sleep obtained by pilots during flights.

A Week of Sleep Restriction Does Not Affect Nighttime Glucose Concentration in Healthy Adult Males When Slow-Wave Sleep Is Maintained

Publisher: MDPI AG

Date: 14-09-2022

DOI: 10.3390/S22186962

Abstract: The aim of this laboratory-based study was to examine the effect of sleep restriction on glucose regulation during nighttime sleep. Healthy males were randomly assigned to one of two conditions: 9 h in bed (n = 23, age = 24.0 year) or 5 h in bed (n = 18, age = 21.9 year). Participants had a baseline night with 9 h in bed (23:00–08:00 h), then seven nights of 9 h (23:00–08:00 h) or 5 h (03:00–08:00 h) in bed. Participants were mostly seated during the daytime but had three bouts of treadmill walking (4 km·h−1 for 10 min) at ~14:40 h, ~17:40 h, and ~20:40 h each day. On the baseline night and night seven, glucose concentration in interstitial fluid was assessed by using continuous glucose monitors, and sleep was assessed by using polysomnography. On night seven, compared to the 9 h group, the 5 h group obtained less total sleep (292 min vs. 465 min) and less REM sleep (81 min vs. 118 min), but their slow-wave sleep did not differ (119 min vs. 120 min), and their glucose concentration during sleep did not differ (5.1 mmol·L−1 vs. 5.1 mmol·L−1). These data indicate that sleep restriction does not cause elevated levels of circulating glucose during nighttime sleep when slow-wave sleep is maintained. In the future, it will be important to determine whether increased insulin is required to maintain circulating glucose at a normal level when sleep is restricted.

Can a simple balance task be used to assess fitness for duty?

Publisher: Elsevier BV

Date: 03-2012

DOI: 10.1016/J.AAP.2011.09.030

Abstract: Human fatigue, caused by sleep loss, extended wakefulness, and/or circadian misalignment, is a major cause of workplace errors, incidents and accidents. In some industries, employees are required to undertake fitness for duty testing at the start of a shift to identify instances where their fatigue risk is elevated, so that minimisation and/or mitigation strategies can be implemented. Postural balance has been proposed as a fitness for duty test for fatigue, but it is largely untested. Therefore, the purpose of this study was to examine the impact of sleep loss, extended wakefulness and circadian phase on postural balance. Fourteen male participants spent 10 consecutive days in a sleep laboratory, including three adaptation days and eight simulated shiftwork days. To simulate a quickly rotating roster, shiftwork days were scheduled to begin 4h later each day, and consisted of a 23.3-h wake episode and a 4.7-h sleep opportunity. Every 2.5h during wake, balance was measured while standing as still as possible on a force platform with eyes open for one minute, and eyes closed for one minute. Subjective sleepiness was assessed using the Karolinska Sleepiness Scale. Core body temperature, continuously recorded with rectal thermistors, was used to determine circadian phase. For measures of postural balance and subjective sleepiness, data were analysed using three separate repeated measures ANOVA with two within-subjects factors: circadian phase (six phases) and prior wake (nine levels). For subjective sleepiness, there was a significant effect of prior wake and circadian phase. In particular, sleepiness increased as prior wake increased, and was higher during biological night-time than biological daytime. For the eyes open balance task, there was no effect of prior wake or circadian phase. For the eyes closed balance task, there was a significant effect of circadian phase such that balance was poorer during the biological night-time than biological daytime, but there was no effect of prior wake. These results indicate that postural balance may be a viable tool for assessing fatigue associated with time of day, but may not be useful for assessing fatigue associated with extended hours of wake.

23rd International Symposium on Shiftwork and Working Time: Towards a Global Consensus

Publisher: Informa UK Limited

Date: 03-06-2018

DOI: 10.1080/07420528.2018.1493690

Abstract: The Working Time Society (WTS), and the International Commission on Occupational Health (ICOH) Scientific Committee on Shiftwork and Working Time, are twin organisations focused on conducting research, and informing practice, regarding the impact of work hours in general, and shiftwork in particular, on the efficiency, productivity, safety, well-being, health, and biological rhythms, of employees. Every 2-3 years since 1969, the WTS and ICOH have conducted a series of international symposia in Europe, Asia, Australia, North America, and South America. The purpose of these symposia is to provide a forum for the exchange of knowledge, and the discussion of contested issues, with researchers, employee representatives, regulators, and employers. The most recent symposium in this series - the 23rd International Symposium on Shiftwork and Working Time, entitled "Toward a Global Consensus" - was held on 19-23 June 2017, at Yulara, Australia, near Uluru. Since 2004, Chronobiology International has released a special issue after each symposium, and that tradition continues with a special issue that includes 17 contributions based on a selection of the 128 papers that were presented at the most recent symposium. Here, we provide an overview of the papers that comprise the special issue, and we briefly comment on the implications of the findings for shiftworkers and their employers.

Evaluating the Typical Day-to-Day Variability of WHOOP-Derived Heart Rate Variability in Olympic Water Polo Athletes

Publisher: MDPI AG

Date: 06-09-2022

DOI: 10.3390/S22186723

Abstract: Heart rate (HR) and HR variability (HRV) can be used to infer readiness to perform exercise in athletic populations. Advancements in the photoplethysmography technology of wearable devices such as WHOOP allow for the frequent and convenient measurement of HR and HRV, and therefore enhanced application in athletes. However, it is important that the reliability of such technology is acceptable prior to its application in practical settings. Eleven elite male water polo players (age 28.8 ± 5.3 years [mean ± standard deviation] height 190.3 ± 3.8 cm body mass 95.0 ± 6.9 kg international matches 117.9 ± 92.1) collected their HR and HRV daily via a WHOOP strap (WHOOP 3.0, CB Rank, Boston, MA, USA) over 16 weeks ahead of the 2021 Tokyo Olympic Games. The WHOOP strap quantified HR and HRV via wrist-based photoplethysmography during overnight sleep periods. The weekly (i.e., 7-day) coefficient of variation in lnRMSSD (lnRMSSDCV) and HR (HRCV) was calculated as a measure of day-to-day variability in lnRMSSD and HR, and presented as a mean of the entire recording period. The mean weekly lnRMSSDCV and HRCV over the 16-week period was 5.4 ± 0.7% (mean ± 95% confidence intervals) and 7.6 ± 1.3%, respectively. The day-to-day variability in WHOOP-derived lnRMSSD and HR is within or below the range of day-to-day variability in alternative lnRMSSD (~3–13%) and HR (~10–11%) assessment protocols, indicating that the assessment of HR and HRV by WHOOP does not introduce any more variability than that which is naturally present in these variables.

Linkage Projects - Grant ID: LP0214128

Start Date: 02-2002

End Date: 12-2004

Amount: $326,354.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0667769

Start Date: 06-2006

End Date: 08-2010

Amount: $223,020.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0988420

Start Date: 10-2009

End Date: 03-2013

Amount: $416,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0346651

Start Date: 2003

End Date: 12-2005

Amount: $181,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP230102780

Start Date: 2023

End Date: 12-2025

Amount: $347,427.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP130104843

Start Date: 2013

End Date: 12-2017

Amount: $302,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0881338

Start Date: 12-2008

End Date: 12-2012

Amount: $210,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0990371

Start Date: 07-2009

End Date: 06-2012

Amount: $235,773.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP200103272

Start Date: 05-2020

End Date: 05-2024

Amount: $589,890.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP160104909

Start Date: 2016

End Date: 12-2020

Amount: $317,600.00

Funder: Australian Research Council