Foundations of Health: How Do Exercise and Sleep Benefit Each Other?

A good workout can make you feel more alert, but experts say regular training can improve your sleep too. We asked a sleep therapist and personal trainer how to move for a better night's snooze.

Sleep is precious - a fact you’ll know if you’re in the one-third of Americans getting less than seven hours sleep a night.

Whether you want more but are too busy to get it or can’t get to bed despite lying there for hours on end, not getting enough sleep is linked with chronic health problems including depression, diabetes and heart disease. “Sleep is the foundation for a healthy life; it is a basic human need that can not be ignored. If we compromise our sleep duration and quality, we compromise our health - and we can’t survive,” says sleep therapist Dr Kat Lederle.

Insomnia and other medical conditions that impact your sleep do need to be supported by a GP, but exercise can have a profound impact on sleep in general.

While any more moving sounds like an impossible drain when you’re already tired - and maybe even counterintuitive, given how alert a workout can make us feel - long-term fitness is associated with better sleep. In fact, a 2023 review reports that those who are physically active sleep for an average of 15 minutes longer a night which may not sound like much but adds over 90 extra hours of sleep a year.

How does exercise impact sleep?

“Regular exercise, like a regularly healthy diet, is supportive of good sleep,” agrees sleep Dr Lederle. It’s not just because exercise burns out your energy though. “Going out for one long run to exhaust yourself doesn’t mean you’ll sleep well,” she insists. Instead, it’s about regularly improving the health of your body to improve hormonal, psychological and biological factors that might stop you from sleeping well.

One such example is stress. Research suggests that high-stress levels reduce sleep quality: a review from the Journal of Clinical Endocrinology and Metabolism looked at the hormone and stress cycles in people with sleep disturbances and found that those with chronic insomnia have higher levels of stress hormone cortisol, particularly in the evening and the first part of sleep.

Exercise is a well-known tool for stress reduction - both psychologically and hormonally, lowering cortisol levels as well as perceived stress - which is why regular movement can support a better snooze. A 2017 paper put this to the test on a small number of students during a stressful exam period and found that exercise buffered the negative effects of stress on health outcomes, including sleep quality.

However, Dr Lederle notes that for some people, exercise can actually be stress inducing. “To manage stress effectively, you need to look at the source and, for many people, it comes down to a sense that there is never enough time to do it all. Adding a strict exercise schedule can add to those stress levels,” she says. Her advice is to “remember that movement in general also counts for improving health and sleep: walk more, alternate between sitting down and standing up during the day and find small moments for activity.”

What is the best time to exercise for sleep?

Another reason moving more is so good for sleep is because it’s one of the four factors that influence our circadian rhythm (known as the body clock), along with light, food, socializing and temperature. These elements signal to the brain that it’s daytime, helping to increase alertness. In turn, it sets a timer for the body to release ‘sleep time’ hormones like melatonin later in the day.

Because of that, exercising early on might be the best way to manage a good wake-sleep rhythm. Indeed, research - such as a 2020 paper from the University of Kentucky - shows morning exercise has the greatest potential to alleviate circadian misalignment or irregular sleep patterns.

However, circadian rhythms are personal. Some people are naturally set to being early birds while others are night owls - known as chronotypes - and the research shows that moving in line with your natural rhythm is the best way to ensure a good night’s sleep. The same 2020 paper found that late chronotypes may benefit from exercise in the morning or evening, but evening exercise can exacerbate sleep issues in early chronotypes.

All in all, finding a time that works for you and sticking with it might be best, says Dr Lederle. “If you exercise at a regular time then it can help stabilize the clock and support the body to ‘tell the time’ i.e. ‘if she’s running now then that must mean she will soon have dinner and then settle down for the evening’,” she explains.

Is It harmful to exercise right before bed?

Perhaps the most important thing to bear in mind when exercising for better sleep is to avoid intense workouts right before bed. “Exercise, particularly vigorous exercise, may lead to an increase in heart rate and lower parasympathetic nervous system activity - putting us more into ‘fight or flight’ mode - rather than a relaxed state. And it can also increase our core body temperature,” explains Dr Lederle. That’s in direct contrast to what the body typically needs to get to sleep - a lower body temperature, slower heart rate and drop in cortisol.

Lots of research shows nighttime training can negatively impact sleep - a 2020 review into female athlete health found that evening training or competitions shift circadian rhythm by 30 minutes, while a 2023 study found that exercising up to three hours before bed reduced sleep quality in students.

However, other studies suggest that late training might have less of a drastic short-term effect on sleep, but “overall I err on the side of caution and recommend people avoid high-intensity exercise close to bedtime,” says Dr Lederle.

If 9pm is genuinely the only time you can move, she suggests opting for gentle exercise. “Low-intensity exercise such as yoga, Pilates or walking may help let go of inner arousal to relax before bed,” she says.

Personal trainer Sarah Campus, founder of Ldn Mums Fitness, agrees: “For better sleep, I recommend exercising at least two or three hours before going to bed to give your body time to recover, rest and relax before sleep. If you need to exercise right before bed then try something relaxing like yoga,” she suggests.

How does sleep impact exercise?

The effects of sleep and exercise are bi-directional, which means sleep can change how you move. Just one night of poor sleep has been shown to reduce performance, with studies showing a sleepless night exhausted volleyball players faster, reduced 3 km time trials by 4% in cyclists and runners shave half a kilometer off their 30-minute running distance when sleep deprived.

Athletes who have poor sleep in the long term are also worse off. A 2014 paper found that chronically sleeping for fewer than eight hours a night made athletes 70% more likely to injure themselves.

But these problems only matter if you can even get to the gym. “A bad night’s sleep negatively affects your mood, energy, motivation and drive, which is why sleep deprivation can lead to individuals to be less physically active,” notes Campus. “The number one priority for better motivation, safety, performance and results in your training is sleep.”

Yet, a new piece of research shows that exercise can actually counteract the impact of a poor night’s sleep. The study by The University of Portsmouth found that a 20-minute bout of moderate-intensity exercise can restore cognitive function after a disturbed night. “Poor sleep is a risk factor for poor health and exercise can help to alleviate some of these problems - but only up to a point,” notes Dr Lederle.

“If you continue to shorten your sleep there will be a point at which exercise can’t make all the damage go away. Because exercise comes with a sense of doing or achieving something, we tend to value it higher than sleep. But if it involves cutting short the best stress relief and most natural performance maintenance supplement ever – sleep – it’s a bit of a fallacy.”

So while swapping a snooze for a 5am workout might keep you alert some of the time, it’s best not to rely on training as a long-term strategy for beating fatigue. Instead, move regularly - ideally in the morning - and prioritize calm evenings to support better sleep.

Words: Chloe Gray