Sleep and Exercise: A bi-directional relationship

Good sleep is essential to good fitness. Sleep gives you the energy to train better and your body the time it needs to build back stronger between workouts. At the same time, exercise has been found to be hugely beneficial to sleep quality and one of the most effective non-pharmacological remedies for sleep-related problems.

Experts describe the relationship between sleep and exercise as “bi-directional”. The benefits are cyclical: getting more exercise will help you sleep better, and getting an adequate amount of sleep will promote healthier physical activity levels during the day. Likewise, skimp on either and you could find yourself caught in a downward health spiral.

There are myriad benefits to exercising regularly. Among other things, these include a lower risk of diseases like cancer and diabetes, improved physical function, and overall improved quality of life. Exercising can also benefit certain groups. For example, pregnant women who engage in routine physical activity are less likely to gain an excessive amount of weight during pregnancy or experience postpartum depression, and elderly people who exercise are at lower risk of being injured during a fall.

Exercise can also improve sleep. Specifically, moderate-to-vigorous exercise has been found to increase an adult’s quality of sleep by reducing sleep onset – or the time it takes to fall asleep – and decrease the amount of time they lie awake in bed during the night. Additionally, physical activity can help alleviate daytime sleepiness and even reduce the need for sleep-related medication.

Exercise also has several indirect benefits to sleep. For instance, increased physical activity decreases the risk of excessive weight gain, which in turn reduces the likelihood of obstructive sleep apnea (OSA). Roughly 60% of moderate to severe OSA cases are attributed to obesity.

Numerous surveys have explored sleep and exercise habits among adults. These include the National Sleep Foundation’s 2003 “Sleep in America” poll, which surveyed adults between the ages of 55 and 84.

Among the survey’s respondents, 52% said they exercised three or more times per week and 24% said they exercised less than once a week. Respondents in the latter group were much more likely to sleep less than six hours per night, experience fair or poor sleep quality, struggle with falling and staying asleep, and receive a diagnosis for a sleep disorder such as insomnia, sleep apnea, or Restless Legs Syndrome than those who exercised more frequently.

Another “Sleep in America” poll in 2013 surveyed adults between the ages of 23 and 60 and focused on exercise and sleep, producing similar results.

Roughly 76-83% of respondents who engaged in light, moderate, or vigorous exercise reported very good sleep quality. For those who did not exercise, this figure dropped to 56%.

Similar studies and surveys have focused on the effects of exercise for subjects in other demographics. One study profiled college students during their exam periods. It found that exercise and physical activity reduced exam-related stress, which in turn led to better sleep.

Scientists have found exercise has a strong chemical effect on the brain. Physical activity creates more adenosine in the brain which makes us feel sleepy. Adenosine is actually the chemical that caffeine blocks to make you feel more alert. The harder you work out, the more of this chemical is released and the sleepier you will feel later.

Working out also helps you maintain your circadian rhythm (that is, your body’s internal clock).

There have been fewer studies conducted into the role sleep plays in our physical activity levels. Much of the research has focused on differences in physical activity between people with sleep disorders and healthy individuals. However, most of these studies have concluded that those who experience poor sleep are less active than those with healthy sleep habits.

In particular, people with certain sleep disorders are not as likely to exercise. Adults with insomnia for example tend to be less active than those without insomnia.

Some studies have noted that nightly shifts in sleep quality, latency, and efficiency can be used to predict physical activity levels. For example, one study found that a 30-minute increase in sleep onset was associated with a one-minute decrease in exercise duration the next day.

A person’s preference for morning or evening activity may also play a role. People who are early risers or “morning people” are more likely to engage in physical activity than those who sleep in or are more active in the evening. Some studies have suggested that exercise can essentially alter one’s diurnal preference over time, and may even shift circadian rhythms.

Perhaps most importantly, sleep is also a vital ingredient in the body’s recovery process between training sessions. Exercise provides the stimulus for the body to adapt and grow stronger, but the full extent of this growth can only be achieved with adequate sleep. It is only during the recovery that the body actually gets fitter..

In essence, sleep more and exercise more. Increases in sleep and exercise have numerous and significant health-related benefits.

Take advantage of the bi-directional relationship between the two. The more you exercise, the better you will sleep, and the better you sleep the more you will exercise - and benefit from exercise. If you are struggling with getting enough of one, try doing more of the other to regain a healthier lifestyle.