AM or PM? Breaking Down the Effect of Workout Time on Your Sleep Cycle

Rise and shine or wind down with a workout? The key to unlocking better sleep might just lie in the timing of your exercise routine. 

What the research says

Participating in moderate-intensity exercise improves sleep quality no matter your age, according to a review of 14 studies published in the European Journal of Physiotherapy. The study authors use “sleep quality” to mean falling asleep in a reasonable time, not waking up for long periods throughout the night, and spending most of your time in bed actually sleeping.

Being physically active throughout the day is a boon for snooze time. “Exercise helps regulate your body’s internal clock, balance hormones, and release endorphins, which promotes relaxation,” says Shelby Harris, PsyD, a licensed clinical psychologist specializing in behavioral sleep medicine and director of sleep health at Sleepopolis. And while you should aim to get the recommended seven-plus hours of sleep advised by the Centers for Disease Control and Prevention, recent research has shown that regular physical activity can even counteract some of the unhealthy long-term effects of sleep deprivation. (Win-win!)

When it comes to exercise, certain factors impact your sleep, including the time that you work out. Because a sweat session affects your alertness and body temperature, it can influence your sleep later on in the day, especially if you’re a nighttime exerciser, says Harris. And sometimes, this can work against you. 

Whether you’re someone who sets their alarm to head to the gym early or saves it for after work or dinner, read on to learn more about how your preferred exercise time changes your sleep -- and what to do about it.

If you’re an AM exerciser

The sun is up and so are you, heading out for a run or to the gym. Exercise can be a great way to wake up. Fitting in activity in the morning ensures that you get it done without your to-dos getting in the way. 

One common problem, however, is if you have to wake up earlier -- and consequently get less sleep than needed because of it. “Sleep is foundational. You’re chasing your tail if you don’t get adequate sleep,” says Shane Creado, MD, a double board-certified psychiatrist and sleep medicine doctor who works with athletes. Levels of cortisol are naturally elevated in the morning when you wake up. Working out without adequate sleep will fuel a higher rise of this hormone, he says, which can affect your appetite, hormones, and mood later. 

A tip from Hatch: All of Hatch’s devices have options for using light to help you rise in the morning. A sunrise alarm can help support wakefulness by supporting your natural circadian rhythm.

In short, whether you’re exercising for the positive impact on your mind and mood or to improve sports performance, “your goals are contingent upon adequate sleep,” he says. Choose your wakeup time and then back up by at least the CDC-recommended 7 hours, which will give you your proper bedtime. 

If you’re a PM exerciser

Ideally, finish up a moderate-to-vigorous workout two to three before bed, says Harris, which optimizes the benefits of exercise without cutting into your sleep. You may find that your individual needs are different, so it’s important to know what works for you. (More on this below.) 

Exercise releases chemicals like dopamine and adrenaline that make your body feel more alert and activated. “What allows us to fall asleep more effectively is a lower body temperature and heart rate,” Creado says. And what does exercise do? It raises your body temp and heart rate. That’s why it’s important to allow your nervous system adequate time to come back down to baseline so you can be mentally and physically prepared to sleep, he says.

There can be some exceptions to this rule. “For certain people, exercising closer to bedtime might be beneficial,” says Creado. If you have trouble falling asleep at night because your mind is running a ticker tape of anxious thoughts, then the endorphins released during exercise can help ease that anxiety and prepare you to relax, he explains. 

There’s also exercise that promotes relaxation and a sound night of sleep, such as gentle forms of yoga and stretching. “These practices calm down your nervous system,” says Creado. 

Factors like genetics, age, and personal preferences can affect how easily affected you are by exercise timing, explains Harris. “Some people might be more sensitive to late-day workouts impacting their sleep, while others might not experience any disturbance at all,” she says. Don’t hesitate to play around with the timing and intensity of your workouts and take note of how you react, figuring out what’s best for both your schedule and sleep based on your goals. Sweet dreams.