Elsevier

Physiology & Behavior

Volume 87, Issue 2, 28 February 2006, Pages 396-408
Physiology & Behavior

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

https://doi.org/10.1016/j.physbeh.2005.11.009Get rights and content

Abstract

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 × 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.

Introduction

Although the full purpose and functions of sleep are still unclear it is well established that sleep deprivation can results in significant impairments in human cognitive and motor functioning, but not physical performance. Despite variation in the design of studies, the length of sleep deprivation period used, and type of task assessed, available literature points to sleep deprivation attenuating a person's ability to perform a variety of psychomotor tasks designed to measure neuromuscular function. Of the measures of psychomotor ability used to assess the effects of sleep deprivation, reaction times, both simple and choice are most frequently reported. For example, sleep deprivation has been associated with longer reaction times and reduced force on a simple and choice reaction time test [1]. Other studies have shown that sleep deprivation ranging from 30 to 64 h influences simple and choice reaction time significantly [2]. Similar results have been found for tasks that involve higher levels of cognitive functioning. That is, sleep deprivation resulting in decreased performance indexed by increased lapsing, cognitive slowing, memory impairment, decrease in vigilance and sustained attention and shift in optimum response capability [3], [4], [5], [6], [7], [8]. Performance decrements and the increased variation exhibited during sleep deprivation have been attributed to the inability of participants to maintain attention and alertness, thereby creating an unstable state that fluctuates within seconds (not fully awake or asleep) [9]. However, sleep deprivation of up to at least 24 h has not been shown to influence physical performance capabilities like muscular strength, and cardiovascular and respiratory responses to exercise [10], [11].

To date, no studies have shown that exercise hampers concentration, problem solving, reaction time, or discriminative ability so long as the intensity of exercise is at low or moderate levels [12]. It has been hypothesized that exercise has an inverted-U relationship on performance of cognitive tasks [13]. The explanation for this relationship being based on Easterbrook's ‘Cue Utilisation Theory’ [14]. Chmura et al. [15], for example, found that the fasted reaction times occurred whilst exercising at approximately 75% of the participant's maximal oxygen uptake (HR 164 beats/min). Following increases in workload reaction time increased rapidly, exceeding the resting level by 18% at volitional exhaustion. In a similar study it was found that 100% maximum workload as determined by a standard incremental test until exhaustion for each participant, significantly increased simple reaction times in recreational athletes in comparison to 70% of maximum workload [16]. However, more recent research evidence does not seem to support the inverted-U hypothesis between exercise and cognitive functioning. For example, experienced football players whilst undertaking moderate or maximal exercise (exercising at 70% and 100% maximum power output, respectively) showed better performance on a football decision making task than at rest [17]. In particular the speed of decision making was improved (rather than accuracy). Similarly, movement times have been significantly faster during exercise at 100% of participant's maximum power output in comparison to rest and 70% power output [18].

It has been suggested that the type of task and the fitness level of the participants are important moderating factors. With regard to the former, it is suggested that attention demanding task that make significant demands on our limited attentional capacity, are affected by exercise in a inverted-U fashion whereas simple, automatic tasks are not [19], [20]. Secondly, a high level of physical fitness is associated with superior levels of mental performance in particular when testing is conducted after the exercise bout [21].

To date, only a few studies have evaluated the extent to which exercise modifies performance induced by sleep deprivation and most of these studies have regarded exercise as an additional stressor. Participants have been found to be more alert immediately following exercise. That is, short bouts of exercise improving some of the increases in sleepiness and fatigue seen following sleep deprivation for a short period of time. However, they are not likely to prevent performance decrements [22]. Similarly, the effect of eight, intense cycling sessions (15 min at 20 km/h against a load of 2.5 kg) during 48 h of constant waking on the performance of tasks involving short-term memory, complex addition and auditory vigilance showed that sleep loss was associated with significant impairments on all tasks but none of the tasks could differentiate the bed rest from the exercise condition [23]. However, using the same tasks with an intensified (in terms of total energy expenditure) exercise protocol (10 vs. 2 h of exercise), significantly poorer performance in both the short term memory and addition tasks by the exercise group compared to the bed-rest (control) group have been reported [24]. However, in a subsequent study whilst further intensifying both the sleep loss (60 h) and exercise (20 h at 25–30% VO2max) in an attempt to maximize any potential modification of sleep loss effects by exercise, it was concluded that prolonged moderate exercise did not result in a deterioration in cognitive and motor performance [25]. Finally, it has been found that short 10 min bouts of exercise at 0%, 20%, 40% and 70% VO2max in sleep-restricted subjects showed improvements in vigilance [26]. However, Matsumoto et al. [27] suggested that exercise during an extended period of wakefulness results in an increase risk in human error. It appears that the effects of exercise on cognitive and motor performance whilst exposed to sleep deprivation are still unclear. One aim of the present study was to investigate the effects of bouts of moderate exercise and sleep deprivation on participant's cognitive and motor ability on selected tasks. The present study used an intensified exercise protocol (in terms of energy expenditure) in an attempt to amplify any sleep loss effects by exercise and increase their change of detection.

Periods without sleep have also been demonstrated to have significant adverse effects on subjective mood. For example, significant decreases in participant's mood, as measured by the Profile of Mood States questionnaire (POMS) [28], have been found after periods of constant wakefulness [29], [30]. However, habitual physical activity can moderate this effect. That is, habitually more active participants showing less negative effect after sleep deprivation. Furthermore, significant correlations have been found between self-reported mood and performance suggesting that mood-state may be a useful predictor of performance in sleep deprived subjects [31], [32]. On the other hand, it is well established that a single bout of exercise [33] as well as prolonged participation in exercise [34] result in positive changes in people's mood states. Many studies have shown enhancement in mood in different populations such as the elderly [35], [36], college students [37] and middle aged women [38] following a single bout or prolonged exercise participation. Mood benefits of exercise are not automatic and a useful taxonomy has been proposed to help to maximize mood benefits from exercise sessions [39]. The three most influential factors in this model are enjoyment, mode of exercise and practice and training guidelines.

A second aim of the present study was to investigate the effects of moderate exercise and sleep deprivation on the participant's mood and whether mood was a predictor of cognitive and motor performance.

In summary, the present study examined the effect of a period of sleep deprivation, with and without intermittent physical exercise, on responses to sub-maximal cycling. The protocol adopted in this study asked the participants to cycle at 50% of their maximal oxygen uptake. This level was selected because moderate exercise has been shown to improve cognitive and motor function as well as improve mood.

Section snippets

Participants

Six male students (age 22 ± 0.3 years, height 180 ± 5 cm, body mass: 77 ± 5 kg, VO2peak 44 ± 5 ml kg 1 min 1) took part in the study. None had previously experience of sleep deprivation studies or reported abnormal sleep patterns prior to the study. All participants were non-smokers and refrained from alcohol and heavy exercise, and in the 48 h prior to each protocol maintained normal sleeping and eating patterns. The protocol was approved by the institutional ethics committee, and all subjects gave

Results

Table 1, Table 2 provide the mean and standard deviation results for the psychomotor and cognitive performance and mood scores, respectively. Table 3 provide the results for the repeated measures ANOVA's for each of the dependent variables.

Discussion

The present study has two main findings. Firstly, neither treatment condition adversely affected reaction times during submaximal exercise. Resting simple and 2-choice reaction times, however, were significantly affected by sleep deprivation. Additionally, sleep deprivation was also associated with significantly greater negative disturbances to subjective vigour, fatigue and depression. Compared to those who have been deprived of sleep alone, individuals that performed 5 h of intermittent

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