Sleep is extremely important for performance, learning, development and physical and mental health.3 Some of the consequences of inadequate sleep include: a reduction in academic performance, mood disturbance, increases in risk-taking behaviour and drowsy driving.11 From an athletic perspective, reductions in performance, decision- making ability, learning and cognition can occur alongside reductions in immune function and an increased susceptibility to weight gain. While this chapter will outline the importance of sleep for all athletes, additional focus will be placed on the adolescent athlete. It is becoming increasingly clear that adolescence (ages 12–18 yrs) is a period of development where sleep is particularly important. What is also becoming obvious is that many adolescents do not obtain the recommended amount of sleep.11 This chapter will discuss consequences of reduced sleep, how much sleep is required, reasons for poor sleep and strategies that can be utilized to enhance sleep quality, and quantity in athletes and adolescents.
CONSEQUENCES OF REDUCED SLEEP
While there is limited research on exercise performance and sleep, a small number of studies have examined the effect of partial sleep deprivation on athletic performance in adults. Reilly and Deykin13 reported decrements in a range of psychomotor functions after only one night of restricted sleep; however, muscle strength, lung power and endurance running were unaffected.13 Reilly and Hayles14 reported similar effects in females following partial sleep deprivation, with gross motor functions being less affected by sleep loss than tasks requiring fast reaction times.14 Reilly and Percy15 found a significant effect of sleep loss on maximal bench press, leg press and dead lifts, but not maximal bicep curl. Submaximal performance, however, was significantly affected on all four tasks and to a greater degree than maximal efforts. The greatest impairments were found later in the protocol, suggesting an accumulative effect of fatigue from sleep loss.15
From the available research it appears that submaximal prolonged tasks may be more affected than maximal efforts, particularly after the first two nights of partial sleep deprivation.15
There are a number of other biological functions that can be altered following sleep deprivation. Changes in glucose metabolism and neuroendocrine function as a result of chronic, partial sleep deprivation may result in alterations in carbohydrate metabolism, appetite, food intake, and protein synthesis. Ultimately these factors can all negatively influence an athlete’s nutritional, metabolic and endocrine status and hence potentially reduce athletic performance.
EFFECTS OF SLEEP EXTENSION
Another means of examining the effect of sleep on performance is to extend the amount of sleep an athlete receives and determine the effects on subsequent performance. Mah et al,9 instructed six basketball players to obtain as much extra sleep as possible following two weeks of normal sleep habits. Faster sprint times and increased free-throw accuracy was observed at the end of the sleep extension period. Mood was also significantly improved, with increased vigour and decreased fatigue.9 While limited, this data suggests that increasing the amount of sleep an athlete receives may significantly enhance performance.
EFFECTS OF NAPPING
Athletes suffering from some degree of sleep loss may benefit from a brief nap, particularly if a training session is to be completed in the afternoon or evening. Waterhouse et al16 are one of the only groups to investigate the effects of a lunchtime nap on sprint performance following partial sleep deprivation (4 h of sleep). Following a 30-min nap, 20-m sprint performance was increased (compared to no nap), alertness was increased, and sleepiness was decreased. In terms of cognitive performance, sleep supplementation in the form of napping has been shown to have a positive influence on cognitive tasks following a night of sleep deprivation (2 h).12 Naps can markedly reduce sleepiness and can be beneficial when learning skills, strategy or tactics.12 Napping may be beneficial for athletes who have to routinely wake early for training or competition and for athletes who are experiencing sleep deprivation.16
HOW MUCH SLEEP ARE ATHLETES GETTING?
According to a 2005 Gallup Poll in the USA, the average self-reported sleep duration of healthy individuals is 6.8 h on weekdays and 7.4 h on weekends.7 However, the sleep habits of elite athletes have only recently been investigated. Leeder et al8 compared the sleep habits of 26 elite athletes from Olympic Sports (Canoeing, n=11; Diving, n=14; Rowing, n=10; Short-track speed skating, n=11) using actigraphy over a four- day period to that of age-and sex-matched non-sporting controls. The athlete group had a total time in bed of 8:36 ± 0:53 hr:min, compared to 8:07 ± 0:20 in the control group. Despite the longer time in bed, the athlete group had a longer sleep latency (time taken to fall asleep) (18.2 ± 16.5 min vs. 5.0 ± 2.5 min), a lower sleep efficiency (estimate of sleep quality) than controls (80.6 ± 6.4% vs. 88.7 ± 3.6%), resulting in a similar time asleep (6:55 ± 0:43 vs. 7:11 ± 0:25 hr:min). The results demonstrated that while athletes had a comparable quantity of sleep to controls, significant differences were observed in quality of sleep between the two groups.8
While the above data was obtained during a period of normal training without competition, athletes may experience disturbed sleep prior to important competition or games. Erlacher et al4 administered a questionnaire to 632 German athletes to assess possible sleep disturbances prior to competition. Of these athletes, 66% (416) reported that they slept worse than normal at least once prior to an important competition. Of these 416 athletes, 70% reported problems falling asleep, 43 reported waking up early in the morning and 32% reported waking up at night. Factors such as thoughts about competition (77%), nervousness about competition (60%), unusual surroundings (29%) and noise in the room (17%) were identified as reasons for poor sleep.4
In a study from the Australian Institute of Sport, athletes and coaches ranked sleep as the most prominent problem when they were asked about the causes of fatigue/tiredness.5 Sleep characteristics ranked first when athletes were asked about the aspects of the clinical history that they thought were important.
Therefore, it appears that sleep disturbances in athletes can occur at two time points: 1) prior to important competitions and 2) during normal training. This sleep disruption during normal training may be due to poor routine as a consequence of early training sessions, poor sleep habits (i.e., watching television in bed), nocturnal waking to use the bathroom, caffeine use, and excessive thinking/worrying/ planning. While not documented in the literature, anecdotal evidence also suggests that athletes such as soccer players who compete at night also have significant difficulties falling asleep post competition.
HOW MUCH SLEEP DO ADOLESCENTS NEED?
Research suggests that the sleep needs of adolescents do not differ from that of younger children.10 Evidence suggests that when adolescents are allowed to sleep as much as they want, they sleep for an average of 9.25 hrs per night.2 Further, during mid-puberty, there is an increased desire to sleep during the day even when sufficient sleep occurred at nighttime.2 From the literature available, it appears that adolescents require a minimum of 9 hrs per night of sleep.
HOW MUCH SLEEP ARE ADOLESCENTS GETTING?
Despite the recommendation that 12–18 year olds obtain a minimum of 9 hrs of sleep per night, research shows that adolescents sleep between 7.5 and 8.5 hrs per night.11 While there is certainly going to be individual differences, it is clear that many adolescents are not meeting the minimum requirements for the recommended hours of sleep.
CAUSE OF POOR SLEEP IN ADOLESCENTS
There are a number of factors that may explain the poor sleep observed in adolescents, and these can be broken down to internal and external factors.
A shift in circadian rhythm occurs during puberty as a result of changes in the timing of melatonin release.11 Melatonin is a hormone that when released precipitates sleepiness. The delay in release of melatonin in adolescents results in the later feelings of sleepiness, the later subsequent bedtime, and the later wake-up time.
As mentioned above, adolescents have a propensity to go to bed later and wake up later the following morning based on biological factors. However, due to school and extracurricular activities, most adolescents do not have the opportunity to wake later in the morning on school nights and potentially weekends, depending on their sporting schedule. This significantly reduces their sleep opportunity.
Adolescence is usually associated with increased social demands. This can include time spent “in person” or electronically. There is an increasing trend for adolescents to communicate via telephone, SMS, email, Facebook and Twitter into the late evening. As many adolescents experience sleep deprivation, they have increased levels of daytime sleepiness, which may result in caffeine and/or energy drink intake to feel alert and more awake. Caffeinated beverages can have a significant impact on the time taken to fall asleep.
WHEN DO ADOLESCENTS SLEEP?
The changes that occur with development result in adolescents feeling sleepy later in the evening when compared to children.11 Specifically, sleep onset time (time at which a person falls asleep) occurs later in the evening, and wake-up time is later in the morning.6 The reasons for this delay will be discussed below; however, the result of the delay is most often reduced total sleep time due to the requirement to attend school or training the following morning.
One study found that in a group of 20 healthy adolescents, average sleep onset time was 12:44 a.m. with a rise time of 8:18 a.m., resulting in 7.7 hrs of sleep.1 In addition, adolescents tend to have more variable sleep patterns across the week when compared to children and adults.6 This is evidenced by significant differences between school-night and weekend sleep onset time, wake-up time and total sleep times. Reports suggest that adolescents delay their bedtime by 1–2 hrs on weekends, and they may sleep in 3–4 hrs later on weekends compared to school nights.10 This typically results in more sleep obtained on weekends, as the adolescent is able to fit his or her sleep pattern to their more favoured bedtime and wake-up time due to no influence of school schedules. However, this also results in significantly altered routines across a 7-day week.
HOW TO ASSESS SLEEP
A simple sleep diary in which information on bedtime, wake-up time, total sleep time, caffeine consumed prior to sleep, activities performed before going to bed, perceptions of sleep quality, and daytime functioning is recorded can be very useful. The National Sleep Foundation (http:// www.sleepfoundation.org/) has excellent resources including diaries for adults and teens, which can be helpful to gain insight into sleep habits. A sleep clinician can conduct a detailed sleep history and assessment to determine if the athlete has a clinical sleep disorder. Psychiatric and medical conditions may need to be considered due to their interaction with sleep. A sleep clinician may conduct sleep assessments using actigraphy (wearing of a wristwatch to detect movement during sleep) or polysomnography (overnight stay in a sleep laboratory to measure brain activity and other physiological functions).
SOLUTIONS TO SLEEP PROBLEMS
Many of the strategies suggested for optimising sleep in adults also apply to the adolescent. However, there are some specific tips and tricks that may be useful for this age group. Table 1 includes some of the guidelines from The National Sleep Foundation (www. sleepfoundation.org).
Sleep is one of the body’s most important biological functions with roles in performance, cognition, learning, development and mental and physical health. While there are numerous consequences as a result of inadequate sleep, identifying sleep problems and following the recommended sleep guidelines can help ensure sporting performance is maximized.
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Mah, C.D., K.E. Mah, E.J. Kezirian, and W.C. Dement (2011). The effects of sleep extension on the athletic performance of collegiate basketball players. Sleep. 34:943-950.
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Moore, M., and L.J. Meltzer (2008). The sleepy adolescent: causes and consequences of sleepiness in teens. Paediatr. Respir. Rev. 9:114-20; quiz 20-1.
Postolache, T.T., and D.A. Oren (2005). Circadian phase shifting, alerting, and antidepressant effects of bright light treatment. Clin. Sports Med. 24:381-413.
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Reilly, T., and A. Hales (1988). Effects of partial sleep deprivation on performance measures in females. In: E.D. McGraw (ed). Contemporary Ergonomics. London: Taylor and Francis, pp. 509-513.
Reilly, T., and M. Piercy (1994). The effect of partial sleep deprivation on weight-lifting performance. Ergonomics. 37:107-15.
Waterhouse, J., G. Atkinson, B. Edwards, and T. Reilly (2007). The role of a short post- lunch nap in improving cognitive, motor, and sprint performance in participants with partial sleep deprivation. J. Sports Sci. 25:1557-66.