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Sleep and Exercise - The Apeiron Life Perspective

7 min read

Updated: Oct 24, 2022


What it is:

The relationship between exercise and sleep is bidirectional. An improvement in one is often reflected in the other. Similarly, when one suffers, the other tends to as well. Knowing this allows us to understand how we can sleep our way to a better exercise routine and exercise our way to better sleep.

Poor sleep leaves us tired and less likely to exercise. It also makes us more susceptible to injury and impairs the muscle recovery required for training. However, the amount of movement that we get can impact our sleep. If we don’t exercise enough, we can become restless, and our rest can suffer. Tossing and turning at night is typically followed by next-day exhaustion and insufficient energy to exercise, which perpetuates the cycle.



Purported claims:

  • Regular, moderate exercise can improve sleep quality, including fewer nighttime awakenings, shorter sleep onset, and greater slow wave activity.

  • Sufficient sleep prevents injury, promotes protein synthesis and muscle growth, and improves coordination and motor skills.

  • The time of day we exercise can determine our sleep timing and help us build better habits.


What the science says:

Physical activity is essential for total mind and body health. The health benefits are numerous, including:

  • Promotes longevity

  • Supports posture by strengthening bones and muscles

  • Boosts mental health

  • Prevents cardiovascular disease

  • Combats fatigue

  • Reduces cancer risk

  • Potent stress-busting tool

When we don’t exercise regularly, we might feel sluggish and stressed, increase the risk of certain diseases, and even struggle to sleep. Transient insomnia affects more than half of the population from time to time, typically brought about by stress or significant life changes. But chronic pain, injury, and illness can also be to blame. While it isn’t immediately apparent, exercise can also prevent these problems.

Movement makes us stronger, and this goes a long way in preventing injury and chronic pain. Exercise also powers up the immune system, preventing infection and illness, and serves as a potent anti-inflammatory agent.

Physical discomfort from illness or injury can make it difficult to get comfortable enough to fall asleep or cause us to wake up during the night. When this happens, we might have to turn to medications with undesirable side effects, which can present their own challenges. In terms of chronic pain, insufficient sleep lowers our pain threshold, making symptoms seem worse than they might otherwise be, further disrupting sleep, and negatively affecting mood.

Exercise can affect sleep acutely, as well as produce long-term benefits. A large 2015 meta-analysis of 66 studies (using data from 2,863 participants) found that acute (less than one week off) exercise was associated with fewer sleep disturbances. This same analysis found that regular exercise resulted in moderate-to-large positive effects on general sleep quality, including the time to fall asleep and total sleep duration. They also found that cycling tended to be more beneficial than running because cycling has a lower impact and results in fewer injuries than running.

Consolidated sleep is essential for hormone regulation. Growth hormone peaks during our deepest sleep stages, which is important for protein synthesis and new muscle growth. Prolactin also peaks during the night. This hormone involves many aspects of our physiology, from reproductive behavior to developing new blood vessels, the immune system, and neural plasticity.

Beyond hormones, sleep is essential for memory formation, decision-making, hand-eye coordination, and movement. If these become impaired, we cannot perform at our peak and even increase our risk of injury. Most sports benefit from muscle memory, or the ability to execute specific actions without thinking much about them. The learning required to embed these motions in our physiology so that we can perform them on autopilot requires specific brain activities that can only occur during sleep.

Sleep restriction blunts the complete restoration of muscle glycogen stores after intense activity. This hinders next-day performance of sustained exercise. While many athletes sleep poorly before an important event due to nerves, regular training offers a potent preventative. That being said, it is still essential to prioritize sufficient sleep opportunity the night before endurance activities so that skeletal muscles are primed and ready to go.

As well as priming the muscles, sleep is essential for their recovery after exercise. Insufficient sleep increases inflammation which can slow the rate of muscle repair. This means it takes longer to recover back to baseline after a workout which leaves us vulnerable to injury.



Does exercise timing matter?

Chronobiology is a relatively new field of research that focuses on the optimal timing of daily activities such as food intake, exercise, and pharmaceutical use to maximize their benefits. Several studies have sought to determine whether there is an optimal time of day to exercise, but unfortunately, there is no one-size-fits-all prescription. This is due to nuances in chronotype (our innate circadian rhythms, as determined by genetics), lifestyle, and environmental factors.

The general rule of thumb on most sleep hygiene pamphlets is that exercising within two hours of bedtime can disrupt sleep by elevating heart rate and core body temperature. This can make it difficult for our brain’s “sleep switch” to activate. However, one study challenged this by looking at the effects of nighttime exercise on individuals with insomnia and found that it helped some while hindering others, showing that significant individual differences exist.

Our circadian rhythm uses external time cues (known as “zeitgebers”) to synchronize the central pacemaker in our brain, the suprachiasmatic nucleus (SCN), and the downstream clock genes in the many other cells of our body. The most potent time cue is light, but meal and exercise timing are also profound influences. One study showed that exercise can modulate the circadian rhythm to the same extent as light.

For some individuals with a “phase delay” (meaning that they fall asleep later than is ideal,) shifting exercise to earlier in the day can make them feel sleepy earlier at night, thus moving sleep timing earlier. However, other studies have also shown that evening exercise can also shift sleep timing earlier, so the jury is out on which is superior, and it appears to come down to the individual.

About 20% of the US population is thought to work out within four hours of bedtime. A meta-analysis of 275 participants from 23 different studies didn’t find that evening exercise resulted in many significant changes to sleep compared to exercising at any other time of day. Still, they reported that training generally tended to result in more deep (slow-wave) sleep than not exercising at all.

Interestingly, a recent study showed that blood pressure recovered fastest following afternoon exercise (around 5 pm) compared to morning exercise. However, this study was a small sample size.

In terms of maximizing overnight muscle recovery, several researchers have looked at the timing of protein consumption and whether pre-sleep consumption of casein, whey, or plant-based protein improves muscle mass. This protocol appears to be effective for young men, but more studies must be conducted on women and older adults to determine if this rule applies more broadly.



Our take:

While exercise timing, intensity, and duration vary dramatically between individuals based on need and preference, numerous studies show that moderate physical activity benefits overall sleep quality. Taking steps to get more sleep and prioritize exercise can improve all aspects of health and well-being.

The optimal time to exercise varies from person to person and largely depends on many lifestyle factors, including work, family, and social obligations. If you only have one opportunity to exercise during the day, it’s better to pursue it and trust its many benefits rather than worrying about whether the timing is perfect. However, if you have some flexibility and can switch things up, consider shifting the timing and see how your mood, energy, and sleep respond.



Will this benefit you?

Much like any habit, starting a regular exercise routine can be challenging if you haven’t prioritized it until now. However, the benefits of sleep can be significant and come without any side effects associated with medication. The good news is that you don’t need to perform like an Olympic athlete to reap the rewards. The data show that resistance training just 2-3 times per week is sufficient to build and maintain strength. Additionally, the American Heart Association recommends just 150 minutes of moderate or 75 minutes of vigorous exercise per week to protect cardiovascular health. Yet, many people find advantages to exercising more than this recommendation.


If you still want to try it, here’s what to look out for:

When something isn’t right with our health, changes in sleep behavior can be one of the first signs. Trouble sleeping can come from a lack of movement and the associated physical discomfort or buildup of stress that ensues.

Remember that exercise is a powerful tool for helping your body ease into sleep by promoting a well-earned type of tiredness. Just be mindful of not overdoing it. Over-exercising can induce a stress response that can leave you exhausted during the daytime and disturb sleep. You’ll know when you’re getting the right amount of exercise because it will leave you feeling energized and strong rather than depleted.

Also, remember that there are other benefits to exercise timing in addition to better sleep. For example, just 20 minutes of light walking after a meal can dramatically reduce blood glucose levels. This serves as a powerful tool in reducing the risk of diabetes and other cardiovascular diseases.

Lastly, remember that you can use your exercise timing to help you build better habits. For example, if you have a happy hour habit that you would like to kick, consider moving your exercise to the late afternoon. This might allow you an extra hour in bed in the morning and come with some of the blood pressure benefits that you read about earlier. Find the time that works best for you and stick with it – you have everything to gain.



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