It’s no secret that exercise can improve your sleep. According to the National Sleep Foundation, moving more throughout your day can not only boost your sleep quality, but also boost how long you snooze for. However, one question remains: Does when you work out matter? Here, we break down whether working out before bed improves or sabotages your sleep.
How Exercise Supports Sleep
Why does breaking a sweat help you sleep like a baby?
“It helps you reach deep sleep and REM sleep, so it’s very critical,” says Michael J. Breus, PhD, board-certified sleep specialist and author of The Power of When. These deepest stages of sleep (known as stage three and REM) are crucial for your body's recovery processes; without enough of them, you wake up still feeling tired. Unsurprisingly, they're also key for your body's ability to adapt to exercise, Breus says.
(Lucky for our middle-aged Spartans out there: Some research suggests they see the most significant sleep benefits from regular exercise, no matter what type.)
Timing Is Everything—Or Is It?
Though lacing up your sneakers, no matter the time of day, may seem like a sure-fire way to sleep better, that's not necessarily the case. In fact, many of us have wondered whether working out before bed will actually keep us up.
Some research suggests that evening exercise can still help you reach deep sleep and spend more time in it—eventually. However, doing certain workouts too close to bedtime can make falling asleep difficult.
“It’s all about temperature,” says Breus. “Our sleep cycle follows our core body temperature. In the evening, our temperature rises until about 10:30, and then it begins to fall. When this happens, it signals our bodies to release [the hormone] melatonin—the key to sleep.”
If you break a serious sweat that sky-rockets your core body temperature past eight or nine at night, though, you risk delaying your body's melatonin release until later than you care to stay up.
How To Make Working Out Before Bed, Well, Work
Although different bodies need different lengths of time to get body temperature back down after exercise, most people should expect to need somewhere around two-and-a-half to three hours, says Breus. To play it safe, schedule any hardcore training for at least four hours before you plan to hit the hay.
Of course, if you only have time to hit the gym after dark, you can certainly still train; just keep it lighter and less intense.
In this case, Breus recommends weight training or yoga. If you just have to slip in some cardio, do it at the beginning of your session, so you have as much time as possible to cool down after. Another option: Split your daily training between a quick bout of cardio in the morning and a shorter strength session in the evening. This way, you still get both in, without affecting your ability to fall asleep too much.
If you do go hard after dark, you can always take a cold shower post-sweat to help your body cool down and prep for shut-eye more quickly, Breus says.
The Bottom Line
Ultimately, your ideal exercise time depends on your body and your chronotype (your individual biological clock). For early birds, morning workouts truly feel best, while night owls may prefer to sweat after work. Other people may do their best training around lunch. (To figure what works best for you, check out his chronotype quiz).
If you’re not sure how your workouts affect your sleep, Breus recommends keeping a diary for a week or two. Compare how you sleep after morning workouts, evening workouts, and off-days, and schedule your sweats accordingly. After all, if you want to grow stronger, faster, and fitter, you need solid shut-eye to recover and adapt.