To exercise or to sleep… that is the question

Science is a fast-moving business. New research is always coming out and suggesting novel ways to keep our minds and bodies healthy. But throughout everything, two activities that have consistently been shown to be central to health are exercise and sleep.

We’ve often written about how doing a good amount and variety of exercise and maintaining healthy sleeping patterns are the best way to guarantee a long life. However, we haven’t yet discussed the complex ways in which these two cornerstones of longevity influence one another.

In this blog, we’ll look at the science of how exercise and sleep impact each other, and when you should prioritize one over the other. 

How does exercise impact sleep?

We all know the glorious feeling of settling down for a good night’s rest after an active day, and plenty of research supports the idea that exercise leads to better sleep. In a study published last month, participants aged 18-40 performed 3-minute bodyweight 'exercise breaks’ - consisting of chair squats, calf raises and standing straight-leg knee raises - every 30 minutes across a 4-hour period in the evening. As a result, they slept on average 27 minutes more than when they were sat down all evening. ^[1]

Many other studies have supported the idea that low- or moderate-intensity exercise in the evening improves sleep. ^{[2, 3]} It does so primarily by stimulating the release of melatonin, a hormone which helps regulate sleep-wake cycles, and by lowering mental stress. ^[4] However, some evidence suggests that high-intensity exercise late in the evening (less than 2 hours before bed) can disrupt sleep, because it increases body temperature and heart rate which opposes the natural cooling down and calming effect that helps you get to sleep. ^{[5, 6]} 

Do different types of exercise have different effects?

Different types of exercise also seem to have slightly different effects. One study found that performing resistance exercise at any point in the day resulted in better sleep, but the time taken to fall asleep was significantly shorter when participants exercised in the evening. ^[7]

Any form of aerobic exercise generally seems to improve sleep too. However, one large meta-analysis that included 23 separate studies found that, while any evening exercise up to 1 hour before bedtime improved sleep, running resulted in significantly less waking during the night than cycling. ^[8] 

If you do want to (or have to) exercise late in the evening, it's best to do something low-intensity and that incorporates breathwork and stretching. Both yoga and Tai Chi have been proven to improve sleep when performed in the evening. ^[9]

So what does this all mean practically?

• Exercise in the evening to improve sleep, but avoid high-intensity exercise within two hours of your bedtime, and avoid any exercise at all within an hour of your bedtime
• Resistance exercise in the evening appears to be better for sleep than at other times of day (contrary to the popular belief that exercise in the morning is better!)
• Try a series of 3-minute ‘exercise breaks’ every half hour in the evening to get longer sleep
• If you have to exercise very late at night, do low-intensity activities that incorporate breathwork and stretching, such as yoga and Tai Chi

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What about how sleep impacts exercise?

While exercise can make your sleep better, the relationship goes the other way too. Maintaining healthy sleeping habits allows you to perform at your best during exercise, helps you to recover and build muscle effectively after, and, in some cases, even seems to be necessary for reaping the many benefits that exercise provides.

We’ve written about the importance of proper sleep hygiene for long-term health before on this blog and, as you’d expect, sleep deprivation severely harms exercise performance. ^[10] However, better sleep can also improve performance, even from a healthy baseline. In one study, college basketball players were asked to extend their sleep as much as possible for a month. ^[11] On average they slept around 2 hours longer (going from roughly 7 to 9 hours on average) which resulted in an increased sprint speed, decreased reaction time and a 9% increase in shooting accuracy. Similar studies have also shown that longer sleep increases the serve accuracy of tennis players ^[12] and improves swimmers’ times. ^[13]

Good sleep is possibly the most important factor for recovering and building muscle effectively after exercise. You need sufficient rest to give your cells and tissues time to heal and, crucially, your body releases growth hormone during sleep which stimulates the building of new muscle. So if you’re not getting good sleep following a workout you’re unlikely to get many of the benefits you’re aiming for. This means that you also need to sleep longer if you’re doing more intense training.

It also appears that sufficient sleep is necessary for the powerful long-term cognitive benefits that regular exercise provides, as shown by a study from last year that followed people over the age of 50 for an average of 10 years. It found that doing high amounts of exercise was effective at preventing cognitive decline, but only among participants who were getting adequate amounts of sleep (6-8 hours/night). ^[14]

Tips on sleeping for better exercise

• Put as much focus and effort into your sleep protocol as you do into your exercise regime
• Aim to sleep longer after a day of particularly intense training
• Sleep as long as possible the night before an event, competition, or anything you want to be able to perform at your best in

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Which should you prioritise, sleep or exercise?

So we know that good sleep is crucial for good exercise, and vice versa. But sometimes you may have to prioritise one over the other. Say you’re struggling to get to sleep late at night, should you still set your alarm to wake up early and go on your morning run? Or, should you go to the gym after working late, even if it means you’ll push your bedtime back by an hour or two?

The answer to this age-old question is simple when considering intense exercise. Since intense exercise is almost pointless if you don’t back it up with proper sleep, you should always prioritise a good night’s sleep (i.e. a minimum of 7 hours) over a hard workout.

If you’re consistently prioritising exercise to the point of sleep deprivation - say, for example, that you are waking up at 6am to train before work, despite the fact that you struggle to sleep before midnight - then there are also some more factors to consider, beyond the fact that you won’t be benefitting from the positive impact of exercise. Even short-term sleep deprivation significantly disrupts metabolism and causes you to feel more hungry, ^[15] meaning you are more likely to undo any of the positive benefits of exercise by eating unhealthily. Poor sleep also has a severe and harmful impact on your mood and immune system, ^[16] all of which will contribute to a worse day-to-day experience and, ultimately, fewer healthier years alive.