Authors: Dr Ian C Dunican Ph.D., MMineEng, MBA, GCASSc, BA & Ricky Krstic

Sleep, we all need it. Each night we close our eyes and aim to get between 7-9 hrs sleep per night. It is recommended teenagers get 8-10 hrs of sleep a night, while the recommendation for adults is 7-9 hours. Whilst scientists still do not know the primary reason as to why we sleep; we do know that sleep is just as important as proper nutrition and exercise.

Various high-level athletes have reported sleeping greater than 8-hrs per night. One such high profile National Basketball Association (NBA) player is the star, Lebron James. Lebron reports that he spends an average of 12 hrs a day with his lights out, while Steve Nash (NBA), tennis stars Roger Federer, Venus Williams and 100m sprint world record holder Usain Bolt, all claim to sleep an average of 10-hrs per night [1]. In this article, we will discuss sleep and the relationship between sleep and the impact on soccer players.

What happens while we’re sleeping?

With sleep accounting for one-third of our lives, it can be classified into two distinct types, being Rapid Eye Movement (REM) and Non-Rapid Eye Movement (NREM). These classifications include specific stages of sleep as categorised according to the criteria of the American Academy of Sleep Medicine (AASM). In this system, NREM sleep consists of two light stages of sleep (N1 and N2), and a deeper stage of sleep, slow-wave sleep (N3). During deep sleep, our body’s and brains slow down, allowing the process of recovery from any physical activity that we may have endured throughout the day.

Studies show that growth hormone is predominantly released in the first half of our sleep and is responsible for the growth of bone, muscle and other tissue development in childhood and adolescence. While REM sleep mostly occurs in the later in the night, typically between 02:00-07:00. During this period, we experience most of our dreams, and our brains are incredibly active. The exact purpose of REM sleep is unclear; we do know that it is linked with our memory, learning, mental restoration and cognitive performance daily. The different stages of sleep and their separate functions show that to gain full benefit from our rest, both types and stages are equally important.

Progression and maintenance of each stage are characterised by specific changes in EEG, movement, respiration, and eye movements [2]. During a typical sleep period over an 8-hr period, an individual will spend 5% in N1, 50% in N2, 20% in N3, and 25% in REM. These sleep stages, and the length of time spent in each stage of sleep oscillate throughout the night.

Figure 1 Sleep Hypnogram

Loss of sleep in athletes

It is estimated that 88% of athletes do not achieve the 7-9 hrs of sleep per night, as recommended by the Sleep Health Foundation [3]. Studies report that athletes tend to achieve an average, 6 hrs 50 min of sleep per night, with athletes from individual sports achieving slightly less than those from team sports, being 6 hrs 30 min of sleep on average per night [4, 5]. So, what happens when we don’t achieve enough sleep? Losing sleep results in adverse short term effects while the continuous loss of sleep increases risk of long-term health issues including chronic medical conditions such as heart disease, high blood pressure and diabetes[6, 7]. Loss of sleep may result in symptoms including;

• Decreased strength, stamina and focus.
• Impaired attention, memory, vigilance, speed and accuracy.
• Tiredness
• Irritability
• Depressed mood
• Difficulty learning
• Lack of motivation
• Increased appetite

Performance

Athletic performance may be negatively affected due to sleep loss after 24-hrs of wakefulness. This is commonly known as sleep deprivation. In a study examining the effects of 24-hrs of sleep loss in soccer players, it was found that soccer skills such as a continuous kicking test were negatively affected after a prolonged period of wakefulness [8]. Also, athletic performance may be adversely affected in several ways, including but not limited to:

• Reaction times
• Motor function (running, jumping, kicking, throwing, catching)
• Motivation
• Attention
• Learning and memory
• Focus
• Muscle recovery
• Decreased injury risk (Studies among adolescent athletes have shown that those who slept an average of less than 8-hrs per night were 1.4-1.7 times more likely to have suffered an injury compared to those who had an average of 8 or more hours of sleep per night) [9].

What are professional soccer teams doing?

In recent years, more and more athletes and teams are investigating the potential benefits of sleep. Along with seeking help from sleep scientists, professional organisations are also turning towards new technologies when it comes to increasing the quantity of sleep. For example, Manchester United have installed sleep pods to encourage their players to nap between training sessions to maximise sleep duration within a 24-hr period. Likewise, another professional soccer team, Manchester City, decorated the bedroom walls of their new complex with sleep-inducing wallpaper. However, this approach has no scientific backing, but it is of interest that teams are trying a multitude of interventions to support recovery. While Liverpool Football club has employed the use of wrist activity monitors devices and heart rate straps to assess and monitor their players sleep and recovery [10].

The timing and scheduling of training sessions is an essential factor in ensuring adequate opportunities for sleep in athletes to maximise performance. Evening training sessions in soccer players are found to delay the time of sleep onset, thereby potentially reducing the amount of sleep players will achieve [11]. However, if you allow adequate time for players to sleep in the next morning and delay the time they wake it will not negatively affect sleep duration. This is mainly due to the absence of scheduled next day early morning training sessions [11].

The sleep environment may have a significant impact on sleep quality. Athletes are often required to change their natural ‘home’ sleeping environment to a ‘training camp’. One such study with younger soccer athletes (16-years of age) during a 17-day training camp found no differences in sleep measures; however overall sleep duration was already significantly less than the Sleep Health Foundation recommendations (7-9hrs). To compensate for this reduction in sleep duration during the training camp, the use of daytime naps were beneficial in increasing total sleep duration over 24-hrs without being detrimental to nighttime sleep [12].  While naps are beneficial for health and performance, the timing and duration of naps are essential. Naps should be no longer than 30 mins as sleeping longer may result in the athlete going into deeper stages of sleep. There are several benefits to napping, such as improvement in vigilance, alertness, reaction time and cognitive performance, as well as aiding in the recovery from a bad night’s sleep. Naps longer than 30 minutes may initially slow mental function upon awakening due to sleep inertia and taking naps late in the afternoon/early evening late naps may affect sleep onset that night. However, in elite soccer players following a night game, sleep duration was shown to be significantly reduced with the players’ self-reported perception of recovery were significantly lower the next morning [13].

Athletes may benefit from non-pharmacologic techniques for promoting sleep, including inverted posture, temperature control, sensory withdrawal, breathing techniques, and cognitive relaxation [14]. A novel approach to improving sleep, as demonstrated in sub-elite soccer players was achieved using brainwave entrainment with binaural beats [15]. Additional actions to improve insomnia, and reduce disturbances include; sleep hygiene practices (as listed below), such as a consistent time to bed, avoidance of caffeine within six hours of sleep onset and no stimulating activities (exercise, work or exposure to electronic devices) within one hour of sleep onset, as well as a focus on nutrition [16] and hydration prior to sleep [17].

Sleep hygiene practices

1. Stay active and expose yourself to sunlight during the day.
2. Go to bed and wake up at the same time each morning/night.
3. Avoid things that may stress or excite you 1-2 hours before bed.
4. Avoid excess light (TV’s, various electronic devices).
5. Do something relaxing, under dim light.
6. Remove any distractions from the bedroom.
7. If you can’t fall asleep within 20 minutes, go to another room and continue with a relaxing activity until tired.
8. Late afternoon naps may make it harder to get to sleep.
9. Avoid drinking caffeinated beverages 4-6 hours before bed.
10. Avoid using sleep medication (unless prescribed in extreme cases).

Further information

For any further questions, you can contact Dr Dunican at Iandunican@sleep4performance.com.au

References

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