The Effects of Exercise as a Countermeasure for Fatigue in Sleep-Deprived Aviators

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

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.

Planning Ability and Alertness After Nap Deprivation: Beneficial Effects of Acute Moderate-Intensity Aerobic Exercise Greater Than Sitting Naps

Nap deprivation is regarded as a sleep loss for habitual nappers. The beneficial effects of napping and moderate-intensity aerobic exercise on the reduction in planning ability following nighttime sleep deprivation have been proven. However, it is still unknown whether it can improve the performance decline caused by daytime nap deprivation in habitual nappers. Seventy-four healthy adults who had a long-term habit of taking naps were assigned to three interventions after receiving nap deprivation: (1) Control group (no intervention); (2) Nap group (15-min sitting naps); (3) Exercise group (15-min aerobic exercise), in which subjective alertness, mood, fatigue, and task performance in objective alertness (Psychomotor Vigilance Task, PVT) and planning ability (the Tower of London Task) were measured. Results showed that nap deprivation negatively influenced some performance on the psychomotor vigilance (i.e., response times and 10% slowest response time) and planning ability (i.e., planning time). And acute moderate-intensity aerobic exercise improved psychomotor alertness (i.e., response times) and planning ability (i.e., execution accuracy, execution time), a 15-min sitting naps only alleviated subjective fatigue, whereas some performance (i.e., response times) deteriorated when no intervention was used. These findings suggested that acute moderate-intensity aerobic exercise has a better restorative effect on the reduced planning ability and objective alertness due to nap deprivation compared to sitting naps.

Efficacy and safety of electroacupuncture treatment in the prevention of negative moods in healthy young men after 30 h of total sleep deprivation: study protocol for a single-center, single-blind, parallel-arm, randomized clinical trial

Background

Sleep deprivation (SD) among young adults is a major public health concern. In humans, it has adverse effects on mood and results in serious health problems. Faced with SD, persons may take precautionary measures to try and reduce their risk. The aim of this study is to evaluate the efficacy and safety of electroacupuncture (EA) for the prevention of negative moods after SD. In addition, we will do a comparison of the effects of EA on mood after SD at different time points.

Methods

This randomized controlled trial (RCT) will be performed at the First Affiliated Hospital of Changchun University of Chinese Medicine in China. The Standards for Reporting Interventions in Clinical Trials of Acupuncture 2010 will be strictly adhered to. Forty-two healthy male volunteers will be distributed into acupoints electroacupuncture (AE) group, non-acupoints electroacupuncture (NAE) control group, or blank control group. This trial will comprise 1-week baseline (baseline sleep), 1-week preventative treatment, 30-h total sleep deprivation (TSD), and 24-h after waking follow-up period. Participants in the AE group and the NAE control group during the preventative treatment period will be administered with EA treatment once daily for 1 week. Participants in the blank control group will not be administered with any treatment. The primary outcome will be the Profile of Mood States (POMS) Scale. Secondary outcome measures will include changes in the Noldus FaceReader (a tool for automatic analysis of facial expressions) and Positive and Negative Affect Schedule (PANAS) Scale. Total sleep deprivation will be 30 h. During the 30-h TSD period, participants will be subjected to 11 sessions of assessment. Adverse events will be recorded.

Discussion

This study is designed to evaluate the efficacy and safety of EA for the prevention of negative moods after SD. The results of this trial will allow us to compare the effects of EA on mood after SD at different time points. Moreover, the findings from this trial will be published in peer-reviewed journals.

Trial registration

Chinese Clinical Trial Registry Chi2000039713. Registered on 06 November 2020

Exercising the Sleepy-ing Brain: Exercise, Sleep, and Sleep Loss on Memory

ABSTRACT

We examine the novel hypothesis that physical exercise and sleep have synergistic effects on memory. Exercise can trigger mechanisms that can create an optimal brain state during sleep to facilitate memory processing. The possibility that exercise could counteract the deleterious effects of sleep deprivation on memory by protecting neuroplasticity is also discussed.

Beneficial effects of exercise training on cognitive performances during total sleep deprivation in healthy subjects

OBJECTIVE

Exercise training has been shown to improve learning and memory, and to protect against the negative impact of sleep deprivation. The aim of this study was to investigate the effects of seven weeks of moderate- and high-intensity interval exercise training on vigilance/sustained attention, inhibition processes and working memory during 40-h total sleep deprivation (TSD) in 16 healthy young men.

METHODS

The subjects were evaluated before (Baseline, BAS) and during TSD, and the day after a night of recovery sleep (Recovery, REC).

RESULTS

Exercise training significantly decreased errors and increased speed assessed by the psychomotor vigilance task (PVT) during TSD and REC while no difference was found in executive inhibition (Go-noGo task) and working memory (2-Back task) performances. The multiple sleep latency test results were higher during BAS and REC at Post-exercise training, and no difference occurred in subjective sleepiness and daytime microsleeps over the 40-h TSD. The PVT speed was positively correlated with maximal oxygen consumption and maximal aerobic power measured before entry in the in-laboratory TSD protocol, and stage 3 sleep duration measured during the first night in the in-laboratory TSD protocol (N-1). Exercise training effects on sleep were found during the night recovery with lower stage-3 sleep and higher rapid eye movement (REM) sleep durations. An exercise training effect was also found on free insulin-like growth factor I levels with lower levels during TSD at Post-exercise training.

CONCLUSIONS

In healthy young men, exercise training reduced sleep pressure at baseline and protected against sustained attention deficits induced by TSD with persistent effect after one night of recovery sleep. Nevertheless, exercise training was not effective in reducing deficits in executive inhibition and working memory induced by TSD.

The Crossroads of Posttraumatic Stress Disorder and Physician Burnout: A National Review of United States Trauma and Nontrauma Surgeons

Posttraumatic stress disorder (PTSD) among trauma surgeons is three times that of the general population, and physician burnout (PBO) among surgeons is rising. Given that PTSD and PBO are both stress-based syndromes, we aim to identify the prevalence and risk factors for PTSD among trauma and nontrauma surgeons, and determine if a relationship exists. A cross-sectional survey of surgeons was conducted between September 2016 and May 2017. Respondents were screened for PTSD and PBO. Traumatic stressors were identified, and 20 potential risk factors were assessed. The respondents (n = 1026) were grouped into trauma (n = 350) and nontrauma (n = 676). Between the cohorts, there was no significant difference in prevalence of screening positive for PTSD (17% vs 15%) or PBO (30% vs 25%). A relationship was found between PTSD and PBO (P < 0.001). The most common traumatic stressor was overwhelming work responsibilities. Potential risk factors for PTSD differed, but overlapping risk factors included hospital culture, hospital support, and salary (P < 0.05). Our findings of an association between PTSD and PBO is concerning. Interventions to reduce rates of PTSD should target changing the existing culture of surgery, improving hospital support, and ensuring equitable pay.

Physiological and psychological determinants of whole-body endurance exercise following short-term sustained operations with partial sleep deprivation

Purpose

The study examined the effects of short-term field-based military training with partial sleep deprivation on whole-body endurance performance in well-trained individuals.

Methods

Before and after a 2-day sustained operations (SUSOPS), 14 cadets performed a 15-min constant-load cycling at 65% of peak power output (PPO; CLT₆₅), followed by an exhaustive constant-load trial at 85% of PPO (CLT₈₅). Physiological [oxygen uptake (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot {V}$$\end{document}V˙O₂), heart rate (HR), mean arterial pressure (MAP), cardiac output (CO), and regional oxygenation (TOI) in the frontal cerebral cortex and vastus lateralis muscle] and psychological [effort perception (RPE), affective valence (FS), and perceived activation (FAS)] variables were monitored during exercise.

Results

SUSOPS reduced time to exhaustion in CLT₈₅ by 29.1% (p = 0.01). During the CLT₆₅ trial, SUSOPS potentiated the exercise-induced elevations in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot {V}$$\end{document}V˙O₂ and HR (p < 0.05), and blunted MAP (p = 0.001). CO did not differ between trials. Yet, towards the end of both CLT₈₅ trials, CO tended to decline (p ≤ 0.08); a response that occurred at an earlier stage in the SUSOPS trial. During CLT₆₅, SUSOPS altered neither cerebral nor muscle TOI. The SUSOPS CLT₈₅ trial, however, was terminated at similar leg-muscle deoxygenation (p > 0.05) and lower prefrontal cortex deoxygenation (p < 0.01). SUSOPS increased RPE at submaximal intensities (p = 0.05), and suppressed FAS and FS throughout (p < 0.01).

Conclusions

The present findings indicate, therefore, that a brief period of military sustained operations with partial sleep deprivation augment cardiorespiratory and psychological strain, limiting high-intensity endurance capacity.

The impact of breaking up prolonged sitting on glucose metabolism and cognitive function when sleep is restricted

Objectives

To investigate the acute benefits of breaking up prolonged sitting with light-intensity physical activity on (i) glucose metabolism under conditions of sleep restriction, and (ii) cognitive deficits associated with sleep restriction.

Methods

This counterbalanced, crossover trial consisted of two five-day (5 night) experimental conditions separated by a two-week washout period. On the first night, participants were given a 9-h sleep opportunity to allow the collection of steady-state baseline measures the following day. This was followed by three consecutive nights of sleep restriction (5-h sleep opportunity). In the sitting condition (SIT), participants remained seated between 1000 and 1800 h. In the physical activity condition (ACT), participants completed 3-min bouts of light-intensity walking every 30 min on a motorised treadmill between 1000 and 1800 h. At all other times, in both conditions, participants remained seated, except when walking to the dining room or to use the bathroom (max distance = 32 m). Six physically inactive, healthy males were randomised to one of two trial orders, 1) SIT then ACT, or 2) ACT then SIT. Continuous measures of interstitial glucose were measured at 5-min intervals. A cognitive and subjective test battery was administered every two hours during wake periods. Analyses were conducted using a series of linear mixed-effect ANOVAs.

Results

No differences in interstitial glucose concentration or cognitive performance were observed between the SIT condition and the ACT condition. Participants reported higher levels of sleepiness, and felt less alert in the SIT condition compared with the ACT condition.

Conclusions

There were no observable benefits of breaking up prolonged sitting on glucose metabolism under conditions of sleep restriction. These findings have implications for behaviour change interventions. Future studies will need to include larger, less homogenous study populations and appropriate control conditions (i.e., 8–9 h sleep opportunities).

The Immediate and Sustained long-Term Changes in Daytime Sleepiness After Participation in a Workplace Pedometer Program: A Prospective Cohort Study

OBJECTIVE

To assess the potential benefit of a workplace physical activity program on daytime sleepiness.

METHODS

A total of 685 participants of a 4-month workplace physical activity program were assessed for daytime sleepiness (Epworth Sleepiness Scale [ESS]) at baseline, 4 months (postprogram), and 12 months. Changes in ESS were analyzed using multilevel mixed linear regression.

RESULTS

In the total population, no changes in ESS scores were observed; 0 to 4 months: -0.2 (95% CI: -0.5 to 0.0), 4 to 12 months: 0.1 (95% CI: -0.2 to 0.4). In participants with baseline excessive daytime sleepiness (ESS > 10, n = 109), ESS scores improved significantly by -2.2 (95% CI: -3.0 to -1.4) at 4 months, sustained at 12 months; and almost half no longer had excessive daytime sleepiness by end of program.

CONCLUSIONS

This study suggests that for employees with excessive daytime sleepiness, short- and long-term improvement in daytime sleepiness may be an unforeseen benefit of workplace physical activity programs.

Relationship between Changes in Fatigue and Exercise by Follow-Up Period

BACKGROUND

Fatigue is one of the most common presenting symptoms in primary care in Korea. In this study, we aimed to determine the effect of exercise intervention on the severity of fatigue of unknown medical cause during a period of follow-up.

METHODS

We used the data collected from an outpatient fatigue clinic in Seoul National University Bundang Hospital. The study was conducted from March 3, 2010 to May 31, 2014. We measured the body mass index of each patient and evaluated variables including lifestyle factors (smoking, alcohol consumption, and regular exercise), quality of sleep, anxiety, depression, stress severity, and fatigue severity using questionnaires. A total of 152 participants who completed questionnaires to determine changes in fatigue severity and the effect of exercise for each period were evaluated. We used univariate analysis to verify possible factors related to fatigue and then conducted multivariate analysis using these factors and the literature.

RESULTS

Of 130 patients with the complaint of chronic fatigue for over 6 months, over 90 percent reported moderate or severe fatigue on the Fatigue Severity Scale and Brief Fatigue Inventory questionnaires. The fatigue severity scores decreased and fatigue improved over time. The amount of exercise was increased in the first month, but decreased afterwards.

CONCLUSION

There was no significant relationship between changes in the amount of exercise and fatigue severity in each follow-up period. Randomized controlled trials and a cohort study with a more detailed exercise protocol in an outpatient setting are needed in the future.

Current and future directions in clinical fatigue management: An update for emergency medicine practitioners

Physicians worldwide are working round the clock to meet the demands of healthcare systems, especially in acute medical settings such as EDs. Demanding shift work schedules cause fatigue and thus deterioration in mood and motor performance. This article explores the effects of sleep deprivation, focusing on cognition, executive decision-making and the implications for clinical care. Humans are capable of functioning and even adapting to sleep restriction; however, clinicians should be aware of pitfalls and absolute minimums for sleep. Fatigue management training shows promise in enhancing safety in aviation and might have a role in medical shift work. Strategic napping improves performance during night shift in the ED, but does not fully negate fatigue. Drugs offer limited benefit for performance under sleep-deprived conditions, and whenever possible, sleep and/or strategic napping takes precedence.

Sleep and exercise: a reciprocal issue?

Sleep and exercise influence each other through complex, bilateral interactions that involve multiple physiological and psychological pathways. Physical activity is usually considered as beneficial in aiding sleep although this link may be subject to multiple moderating factors such as sex, age, fitness level, sleep quality and the characteristics of the exercise (intensity, duration, time of day, environment). It is therefore vital to improve knowledge in fundamental physiology in order to understand the benefits of exercise on the quantity and quality of sleep in healthy subjects and patients. Conversely, sleep disturbances could also impair a person's cognitive performance or their capacity for exercise and increase the risk of exercise-induced injuries either during extreme and/or prolonged exercise or during team sports. This review aims to describe the reciprocal fundamental physiological effects linking sleep and exercise in order to improve the pertinent use of exercise in sleep medicine and prevent sleep disorders in sportsmen.

Effect of caffeine and taurine on simulated laparoscopy performed following sleep deprivation

Background

Sleep deprivation affects surgical performance and has the potential to endanger patient safety. Pharmacological stimulants may counter this consequence of long working hours. This study aimed to investigate whether commonly available stimulants can counter the effects of fatigue on technical and neurocognitive skill.

Methods

This was a single-blind crossover study of surgical novices trained to proficiency on the Minimally Invasive Surgical Trainer—Virtual Reality laparoscopic simulator. Participants were acutely sleep-deprived three times each, followed by administration of either placebo, 150 mg caffeine, or 150 mg caffeine combined with 2 g taurine before simulated laparoscopy. Outcome measures were: laparoscopic psychomotor skill, cognitive performance and the Stanford Sleepiness Scale (range 1–7). Rested baselines were gathered following completion of test sessions.

Results

Baseline performance was recorded for 18 participants in the rested state. Sleep-deprived participants receiving the placebo took longer (median 41 versus 35 s; P = 0·016), were less economical with movement (3·25 versus 2·95 m; P = 0·016) and made more errors (66 versus 59; P = 0·021) on the laparoscopic task compared with the rested state. Caffeine restored psychomotor skills to baseline for time taken (37 versus 35 s; P = 0·101), although the number of errors remained significantly greater than in the rested state (63 versus 59; P = 0·046). Sleep-deprived subjects receiving placebo had slower reaction times (377 versus 299 ms; P = 0·008) and a higher score on the Stanford Sleepiness Scale (6 versus 2 points; P = 0·001) than rested surgeons. Negative effects of sleep deprivation on reaction time were reversed when caffeine (307 ms versus 299 ms in rested state; P = 0·214) or caffeine plus taurine (326 versus 299 ms; P = 0·110) was administered. Subjective sleepiness was also improved, but not to baseline levels.

Conclusion

Sleep deprivation affects laparoscopic psychomotor skills, reaction time and subjective measures of sleepiness in novice surgical subjects. Caffeine and taurine restore simulated laparoscopic performance to rested levels, but do not reduce errors.

Brief hourly exercise during night work can help maintain workers' performance

Increased night work is an important issue because of its implications on workers' health, safety and performance. This study examined the effects of brief hourly exercise as a countermeasure against the adverse effects of night work, especially for workers requiring sustained attention while working in a prolonged sitting posture. During simulated night work (22:00-08:00), participants were required to follow an hourly schedule comprising a 30-min task, 15-min test and 15-min break. The study included 2 experimental conditions: (1) hourly exercise (HE; hourly exercise for 3 min during breaks) and (2) control (without exercise during breaks). Throughout the test period, work performance in the last 10 min of each 30-min task was better under the HE condition than under the control condition (p<0.01). During the second half of the test period, exercise showed an effect on sustained attention (p=0.02). Parasympathetic nerve activity under the HE condition was less than that under the control condition (p<0.01). However, exercise was not effective in reducing subjective fatigue and sleepiness. These results suggest that brief hourly exercise acts as a restraint on parasympathetic nerve activity and is capable of sustaining attention levels during the circadian rhythm nadir that occurs during early morning.

Comparative sensitivity of outcome variables of a software-based Behavioral Sleep Resistance Task

Unintentional sleep and performance impairment due to extended wakefulness are often the cause of traffic and work accidents. Therefore, large-scale screening instruments assessing the ability to resist falling asleep during monotonous tasks are needed. The current widespread computer use in industrial and home settings offers the possibility to use software-based instruments as an alternative for expensive hardware interfaces to assess sleep resistance. Therefore, we propose a software-based sleep resistance task based on the procedure of the Oxford SLEep Resistance test (OSLER): the Behavioral Sleep Resistance Task (BSRT). In order to validate this instrument we submitted 36 healthy individuals to four 40-min sleep resistance challenges during a night of extended wakefulness (14, 16, 18 and 20 h). Subjective sleepiness was assessed by means of the Karolinska Sleepiness Scale and a Visual Analogue Scale for sleepiness/alertness and objective sleepiness by means of a 4-min EEG-monitored fixation task. Our results show significant correlations of BSRT hit ratio, error profiles and sleep onset latency variables with subjective sleepiness and of BSRT hit ratio and 3-6 error profiles with High-Beta Central EEG activity. Additionally, using a distribution- and scale-free sensitivity index, we found that subjective sleepiness measures are the most sensitive to the effects of sustained wakefulness, closely followed by the BSRT hit ratio and BSRT error profile 3-6.

Recovery of cognitive performance from sleep debt: do a short rest pause and a single recovery night help?

We studied the recovery of multitask performance and sleepiness from acute partial sleep deprivation through rest pauses embedded in performance sessions and an 8 h recovery sleep opportunity the following night. Sixteen healthy men, aged 19-22 yrs, participated in normal sleep (two successive nights with 8 h sleep) and sleep debt (one 2 h night sleep followed by an 8 h sleep the following night) conditions. In both conditions, the participants performed four 70 min multitask sessions, with every other one containing a 10 min rest pause with light neck-shoulder exercise. The multitask consisted of four simultaneously active subtasks, with the level of difficulty set in relation to each participant's ability. Physiological sleepiness was assessed with continuous electroencephalography/electro-oculography recordings during themultitask sessions, and subjective sleepiness was self-rated with the Karolinska Sleepiness Scale. Results showed that multitask performance and physiological and subjective sleepiness were impaired by the sleep debt ( p > .001). The rest pause improved performance and subjective sleepiness for about 15 min, regardless of the amount of prior sleep ( p > .01-.05). Following recovery sleep, all outcome measures showed marked improvement ( p < .001), but they failed to reach the levels observed in the control condition ( p < .001-.05). A correlation analysis showed the participants whose multitask performance deteriorated the most following the night of sleep loss tended to be the same persons whose performance was most impaired following the night of the recovery sleep ( p < .001). Taken together, our results suggest that a short rest pause with light exercise is not an effective countermeasure in itself for sleep debt-induced impairments when long-term effects are sought. In addition, it seems that shift arrangements that lead to at least a moderate sleep debt should be followed by more than one recovery night to ensure full recovery. Persons whose cognitive performance is most affected by sleep debt are likely to require the most sleep to recover.

Privação de sono e exercício físico

A privação do sono é a remoção ou supressão parcial do sono, e esta condição pode causar diversas alterações: endócrinas, metabólicas, físicas, cognitivas, neurais e modificações na arquitetura do sono, que em conjunto comprometem a saúde e a qualidade de vida do sujeito nestas condições. Já o exercício físico praticado regularmente promove benefícios como melhora do aparato cardiovascular, respiratório, endócrino, muscular e humoral, além disso, pode melhorar a qualidade do sono. Entretanto, a associação desses dois parâmetros não tem sido bem explorada, em parte pela dificuldade conseguir voluntários que se submetam a essa condição principalmente sem nenhum tipo de compensação financeira. A maioria dos estudos que investigaram o binômio exercício físico e privação de sono focou os efeitos no desempenho aeróbio. Embora ainda haja controvérsias, os estudos apontam para pequena ou nenhuma alteração desse parâmetro quando as duas situações se fazem presentes. Em relação à potência anaeróbia e força não tem sido encontrados alterações significativas, mas para eventos prolongados, parece haver uma interação entre a privação de sono e o exercício físico, o que sugere um mecanismo de proteção. Entretanto, é importante considerar que uma das alterações mais importantes causadas pela privação do sono é o aumento na percepção subjetiva, que por si só já representa um fator para diminuição e comprometimento do desempenho físico e pode representar um elemento de "mascaramento" dos efeitos deletérios da privação. Assim, o objetivo da presente revisão é o de discutir os diferentes aspectos da relação entre o exercício físico e a privação de sono, evidenciando seus efeitos e reflexos no desempenho físico.

Effects of sleep deprivation and exercise on cognitive, motor performance and mood

This study examined the effect of 30 h of sleep deprivation and intermittent physical exercise, on both cognitive and psychomotor function as well subjective ratings of mood. Six subjects with the following physical characteristics participated in the study (Mean +/- S.D.): age 22 +/- 0.3 years, height 180 +/- 5 cm, body mass: 77 +/- 5 kg, VO2peak 44 +/- 5 ml kg(-1) min(-1). Three subjects engaged in normal sedentary activities while three others cycled on a cycle ergometer at 50% VO2peak for 20 min out of every 2 h during 30 h of sleep deprivation. One week later sleep deprivation was repeated with a cross over of subjects. Every 4 h, subjects completed simple and two-choice reaction time tasks at both rest and during exercise, a computerized tracking task, a number cancellation task, and an assessment of subjective mood state as measured by the POMS questionnaire. A 3 x 4 repeated measures ANOVA revealed that resting but not exercising reaction times were significantly slower with sleep deprivation. Sleep deprivation was also associated with significantly greater negative disturbances to subjective vigour, fatigue and depression assessed by the Profile of Mood States questionnaire. Compared to those who have been deprived of sleep alone, individuals that performed 5 h of intermittent moderate exercise during 30 h of sleep deprivation appeared to be more vulnerable to negative mood disturbances and impairment in reaction times. This could result in greater risk of accident due to a reduced capacity to respond quickly.