Exercise & sleep: the relationship between the sweat and the snooze

Sleep supports our physical, neurocognitive and mental health, allowing us to function at our best. This is why sleep is so important for athletes aiming to push their bodies to the very limits of what is physically possible. Although the research on exercise and sleep is in its early stages, studies have revealed strong associations between varying levels of exercise and characteristics of sleep.

Athletes may benefit from more sleep than the average person as more intense forms of physical exercise generally require longer periods of rest to allow the body to recover. However, athletes often struggle to get the sleep that they need, averaging less than 8 hours per night across a range of sports. A lack of awareness about sleep hygiene amongst athletes, toxic overtraining cultures, disruptive training and travelling schedules, competition-related stress and anxiety, and concomitant academic pressures amongst young athletes can act as common obstacles to sleep uniquely experienced by athletes.

This article will outline what we currently know about the bidirectional relationship between exercise and sleep, before focusing on athlete-specific sleep considerations and practical tips.

How does exercise affect sleep?

Research has shown that there is a bi-directional relationship between exercise and sleep. Exercise can alleviate sleep problems and insufficient amounts of sleep or poor quality sleep can lead to lower levels of physical activity the following day.

Moderate to vigorous exercise can improve sleep quality by reducing the time it takes to fall asleep and the time spent awake after falling asleep. Physical activity can help alleviate daytime sleepiness and in some circumstances it can even reduce the need for sleep medications.

A 2003 poll revealed that those who exercise less than once a week are…

• less likely to achieve the sufficient amount or quality of sleep;
• more likely to struggle with falling and staying asleep;
• and more likely to be diagnosed with a sleep disorder.

A poll taken a decade later reported that up to 83% of those who exercise have good subjective sleep quality, while only 56% of those who do not exercise could say the same thing.

Exercise can also affect sleep indirectly. For example, moderate to vigorous exercise can decrease the risk of excessive weight gain, which in turn reduces the risk of developing the sleep disorder, obstructive sleep apnea. The mental health benefits derived from exercise can also improve sleep.

You may want to consider the timing of your exercise, however. Studies have revealed mixed findings on the sleep benefits of exercising before bedtime. On the one hand, intensive exercise in the 3 hours before bedtime can increase your heart rate, body temperature and adrenaline levels, preventing you from achieving the ideal physiological state for sleep. On the other hand, there is evidence that those who exercise in the evenings fall asleep quickly, experience adequate amounts of deep sleep and less light sleep, and wake feeling rested.

Most people don’t exercise in the hour before bed, but if you are going to, avoid vigorous exercise and opt for low-impact activities like yoga, light stretching and breathing exercises.

How does sleep affect exercise?

Research has not conclusively proven that better sleep leads to an increase in physical activity levels. However, there is growing evidence to suggest that those with poor sleep are less active than those with healthy sleep.

Some studies have shown that changes in sleep metrics at night can predict physical activity levels during the daytime. Early risers appear to be more likely to engage in physical activity than those who sleep in or are more active in the evenings. Some studies even suggest that exercise can alter circadian rhythms in the body.

A good night’s sleep can help you put you in a better frame of mind for exercise the following day, but healthy sleep alone may not be enough to change your physical activity levels. Sleep should be considered as part of a holistic plan to tackle obesity or mobility issues.

The importance of sleep for athletes

There is some evidence that better sleep improves certain aspects of an athlete’s performance, although the specific mechanisms at play are not fully understood. It appears to be the case that success in team sport competitions is related to increased sleep duration and quality.

Sleep deprivation has been consistently linked to worse performance in endurance tasks. This may be because athletes feel exhausted quicker after inadequate sleep, or because pre-exercise muscle glycogen stores are depleted following sleep loss.

The evidence is less clear for anaerobic power required for activities like jumping and skipping, and for speed and strength exercises. Perhaps shorter, maximal activities are less impacted by perceived increased exertion and muscle glycogen deficits, compared to longer, progressive activities.

Sleep deprivation and minimal sleep restriction significantly impairs accuracy and reaction times in sports such as darts, tennis and basketball. Lengthening athletes’ sleep duration has also been shown to result in greater accuracy and quicker reaction times.

Sleep deprivation is strongly associated with impairments in the learning and executive function of athletes, including significant cognitive lapses and a reduced ability to think flexibly. Sleep loss also appears to compromise the ability of athletes to control their impulses. This reflects the essential role of sleep in memory consolidation and may indicate that sleep loss impacts the performance of young athletes more as they are developing their academic and social skills while engaging in sports.

Poor sleep is associated with increased risk of injury and illness, which prevent athletes from taking part in training sessions and competitions. The mechanisms underpinning this effect are unclear, but it could be down to impaired reaction times and cognitive functioning, as well as the higher levels of fatigue that occur following sleep loss, making athletes more prone to accidents.

During sleep, the body processes cytokines, which are hormones that help the immune system to fight off infection. It is therefore unsurprising that poor sleep is linked to immunosuppression, increasing the risk of infection and disease. Adequate amounts of good quality sleep also allows the heart to rest and cells and tissues to repair. This supports the body’s recovery after physical activity and promotes cardiovascular health.

Poor sleep can cause an imbalance in the autonomic nervous system. This effect is similar to the impact of overtraining on the body. Given the pressure placed upon an athlete’s body through intense training schedules, these general health considerations make sleep vitally important.

Good quality sleep is associated with improved overall mood, the prevention of irritability and reductions in the risk of developing mental health conditions, such as depression. The mental health benefits of sleep are crucial for athletes who often struggle under the weight of the pressure to succeed in competitions.

Athlete-specific sleep tips

Beyond basic sleep hygiene and sleep environment optimisation, athletes should also be aware of potential obstacles to good sleep that are specific to their sport and training regime.

Avoid overtraining and training/competition schedules that do not make sufficient time for rest, non-sport commitments and sleep. Some athletes find that waking early has a negative impact on their performance, more so than staying up late, so it’s worthwhile considering your sleep schedule timings carefully.

Since athletes can benefit from more than the recommended hours of sleep per night (7–9 hours), some experts advise the use of ‘sleep banking’. This involves extending sleeps in the nights before a night that is likely to involve less sleep or before big events, such as travelling, competing or recovering from injury or illness. Although not advisable for the general population, napping after a period of inadequate sleep can also be advantageous for athletes. However, it is important to nap wisely: keep naps brief (no more than 30 minutes) and before 3–4pm.

Transmeridian travel and the resulting jet lag has been linked to poorer athletic performance. Athletes can combat jet lag by adjusting their sleep schedule and meal times ahead of transmeridian travel, ‘sleep banking’, using sleep aids to provide an optimal sleep environment whilst they are away from their usual bedroom, staying hydrated and avoiding caffeine and alcohol consumption.

For those responsible for supporting the wellbeing and performance of athletes, sports scientists have compiled an up-to-date programme incorporating sleep education, screening for sleep problems, and encouraging the sensible use of naps and ‘sleep banking’, which is freely available through the British Journal of Sports Medicine. Experts often highlight the importance of identifying and managing mental health issues, as well as reducing any other stressors that impede sleep and performance.

The use of a sleep monitor or daily sleep journal can be a helpful tool to track sleep duration and its impacts on daytime performance. This should be reviewed after at least 2 weeks to identify any patterns. If an athlete does need to increase their sleep duration, then this should be done incrementally.

Athletes often use over-the-counter sedating medications, such as antihistamines and melatonin. However, these medications have not been shown to benefit sleep or athletic performance. Sedative medications like benzodiazepines should be avoided as they can be addictive and there is no proof that they enhance athletic performance.