Exercising helps to improve your health and wellbeing in so many ways—and having better quality sleep is one of them. Research shows that lack of physical activity can interfere with the body’s natural circadian rhythm and sleep patterns by suppressing melatonin production, a must-have for inducing drowsiness before bed. Plus, movement has the potential to help you fall asleep faster and stay asleep throughout the night.
Just as exercise supports quality Zzzz’s, solid sleep ultimately supports your workout routine and fitness goals. “Sleep is one of the most critical elements in any fitness program,” says researcher Jacob Wilson, Ph.D., C.S.C.S., CEO of the Applied Science and Performance Institute and member of The Vitamin Shoppe Wellness Council. According to one 2022 study published in Nutrients, disturbed sleeping patterns can lead to increased snacking, hunger, and muscle loss.
The key here is timing. Exercising too late at night or too early in the morning could backfire if squeezing in that sweat impacts your sleep. Though everyone’s schedule is different, it can be helpful to have cut-off times around how early or late to exercise in order to avoid sleep disruptions and deficits. Here’s the earliest in the morning you should wake up to work out, as well as the latest you should wrap up your workout in order to keep your circadian rhythm intact, doze off without issue, and clock enough total hours of shut-eye.
The Earliest Time Of Day You Should Work Out
If you wake up at an ungodly hour to squeeze in a workout before starting the day, think twice. “To me, early morning workouts are much more worrisome than nighttime workouts,” Wilson says. “When you get up at extreme times (think four or five in the morning), you tend to lose sleep, which is generally awful for body composition.”
Research shows that when you skimp on sleep, you’re more likely to eat unhealthy foods, have increased appetite and be more susceptible to weight gain. Plus, since sleep plays such a crucial role in recovery, missing out can sabotage whatever strength and performance goals you may have. (Worth noting: Lack of sleep can also affect cognition and mood.)
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Unless you get into bed around eight or nine at night and fall asleep swiftly, it’s hard to secure enough sleep (seven to nine hours per night) when you’re getting out of bed long before the sun rises, Wilson says.
If those early bedtimes just aren’t realistic for you, you’re better off sleeping for another hour or two and letting your body rest without the excess pressure, Wilson says. Set your alarm for a 6 a.m. workout at the earliest.
The Latest Time Of Day You Should Work Out
Not everyone likes starting their morning with a workout—and sometimes it feels just plain amazing to sweat off a long, stressful day later on. However, you don’t want that energy boost to backfire and keep you up at night. Luckily, as long as you choose your workout wisely, evening exercise can actually help you sleep.
“Over 23 studies show that moderate-intensity exercising (like cycling or jogging) at night generally does not hurt sleep patterns, and may do the opposite,” Wilson says. “However, very high-intensity exercise, such as interval training or a leg workout, may decrease REM sleep.”
If you stick to something moderate-intensity, nighttime workouts shouldn’t mess with sleep. Just give yourself 90 minutes before bed to power down and cool off. This ensures your core body temperature has returned to its neutral state so that you feel cool, comfortable, and ready to snooze. And, no sweat, no problem: Low-intensity exercise, such as pilates, walking, and yoga, shouldn’t cause enough of a stir in your body to keep you up at night, even if you do them closer to bedtime.
Read More: Why You May Want To Skip HIIT When You’re Feeling Extra Stressed
On the flip side, “it seems that, though it doesn’t impact total sleep, HIIT training within a four-hour window of bedtime can decrease REM,” Wilson says. REM sleep is important for cognitive thinking, memory, learning and brain development, so it’s best to wrap any HIIT exercise at least four hours before hitting the hay to be safe, he suggests. If your bedtime is 10 p.m., that means finishing up HIIT workouts by 6 p.m., latest.
The Bottom Line
“Research shows that the harder you train, the more you should be conscious of evening workouts,” says Wilson, “However, people who sleep great likely have little to worry about.” So, while these guidelines may be helpful, your body and natural rhythm is ultimately your best guide. For example, some might find that they sleep best when they reserve HIIT for days when they can exercise in the morning or afternoon. Others, meanwhile, might have no trouble passing out within a couple of hours post-HIIT. Everyone is different, so pay attention to how your workout timing impacts your sleep, energy levels, and progress, and adjust your routine accordingly from there.