Many of us notice a strong link between exercise and our sleep habits. In general, regular exercise promotes sleep, and good sleep promotes a body that’s more receptive to exercise. Scientific research supports exercise as an important lifestyle factor for improving sleep quality and duration by boosting melatonin production. Exercise reduces cortisol levels, increases endorphins, and helps regulate your circadian rhythm (or internal clock), which promotes regular sleeping and waking. But can this mutually beneficial relationship go wrong? The answer is… maybe.
Research on how exercise affects sleep is controversial. Studies are often small and analyze only certain aspects of sleep and exercise. These shortcomings make it challenging to give overall advice on how to optimize your exercise routine for better sleep, but here’s what we do know:
Intensity: Overall, exercise intensity does not impact sleep – low, moderate, to high intensity exercise all improve a variety of sleep parameters when compared to no exercise. High intensity exercise can improve sleep by reducing wakefulness when compared to low intensity exercise, as long as overtraining is avoided, which can cause chronic muscle soreness, achiness and injury that can all interfere with sleep. However, high intensity exercise performed in the evening may negatively impact sleep quality, reducing rapid eye movement (REM) sleep – the 4th sleep stage important for brain development and emotional processing.
Takeaway: Reserve high intensity exercise for the first half of the day and avoid over-training. If you participate in low intensity exercise and have sleep disturbances, try upping your intensity.
Timing: Most experts recommend completing exercise between 2 and 4 hours before bedtime or in the morning. Exercise temporarily increases your heart rate, blood pressure, core body temperature, and cortisol and adrenaline levels, so it’s important to leave time for your body to return to its normal functioning when prepping for sleep. A 2019 study found that moderate exercise in the morning had the most benefit on sleep and was superior to vigorous morning exercise or vigorous evening exercise.
Earlier in the day has been the traditional advice on exercise timing and sleep, but in a review of 23 studies on exercise and sleep, researchers found that a single session of moderate exercise (for example, strength training or aerobic activity like running, swimming or biking) in the evening does not affect sleep, and in fact, it may help promote shorter time spent falling asleep and a longer duration of deep sleep. Other studies have found similar findings.
Try exercising at the same time every day. Studies show this can promote exercise’s effect on your circadian rhythm and improve your ability to fall asleep, especially when working out in the mornings.
Takeaway: If you’re having sleep issues and tend to be an evening exerciser, try morning/early afternoon workouts instead, and for an extra benefit, exercise at the same time each day to improve your circadian rhythm.
Duration: Studies show that participating in prolonged periods of exercise can interfere with sleep quality. This includes rigorous, prolonged occupational activity, as well as ultra exercising like marathons, triathlons, and iron man competitions. Prolonged exercise increases cortisol levels for extended periods of time, which can interfere with quality sleep parameters. While 1 hour of exercise daily proves more beneficial for sleep than 30 minutes, exercising for too long can sometimes have the opposite effect.
Takeaway: Long exercise routines may negatively impact your sleep quality, although not exercising for long enough can have the same effect. Find your sweet spot, which for most people is about 1 hour.
Overall, exercise is incredibly beneficial for sleep. If you exercise and sleep well keep doing what you’re doing. If you exercise and are struggling with your sleep, look at the intensity, duration, and timing of your workouts. You might need to increase your duration and/or intensity, stop overtraining, or change the timing of your workouts.
