Does Working Out at Night Mess With Your Sleep?
Fast Facts
- High-intensity exercise is not recommended 0 to 4 hours before bed, because your core body temperature becomes too high for deep sleep.
- Low- and moderate-intensity exercise finished one or more hours before bed improves almost all measurements of sleep quality.
It’s no mystery why the gym is quietest at opening and closing—waking up early kind of sucks, and working out late makes it hard to fall asleep, right? Not so fast. Turns out, the late-night workout isn’t as detrimental to the quality of sleep as we all think, as long as you’re smart about it. We’ve evaluated some of the most recent and significant studies on the subject, and put together some tips from a fitness pro to help you tackle the evening workout without compromising on your sleep.
Workout Intensity Matters
A 2019 meta-analysis of 23 different sleep/workout studies measured how working out before bed impacted several sleep quality metrics: rapid-eye movement (REM), sleep after wake onset (also known as WASO, which is how often one wakes after initially falling asleep), and sleep efficiency (also known as SE, which is the ratio of time actually asleep compared to the total time in bed) (1). Big news—the study found that low- and moderate-intensity workouts actually improved every measurement of sleep quality.
But what about high-intensity exercise? The aforementioned study found that while sleep quality was either unchanged or improved for low- to moderate-intensity workouts, high-intensity workouts did in fact result in both an increase in WASO and SE, especially if the workout was done less than one hour before bedtime.
Core Body Temperature Matters, Too
Why the difference? An important factor in overall sleep quality is core body temperature, which has to be low (about one to two degrees below your normal body temperature, driven by the release of the sleep hormone, melatonin) for good-quality sleep to occur. The 2019 meta-analysis found that core body temperature at bedtime was low enough following a 30-60 minute low- or moderate-intensity workout to have zero negative impact on overall sleep quality and even found an improvement in most of the sleep quality metrics. This was true as long as the workout was finished an hour or more before bedtime.
On the other hand, high-intensity exercise (HIE), like HIIT, intense weight training, or hard cardio efforts dramatically increase core body temperature more than lower-intensity workouts, and, naturally, take the body longer to cool down. This bigger increase in core body temperature, combined with the fact that high-intensity training stimulates the nervous system, are the primary reasons why high-intensity training decreases some sleep quality metrics.
High-Intensity Exercise Before Bed
So does that mean absolutely no high-intensity workouts before bed, ever? Not necessarily. Another study published in 2021 (2) conducted a systematic review and meta-analysis of 15 different studies focused specifically on the effects of HIE on healthy, young, and middle-aged adults in the hours before bedtime (0 to 4 hours before bed). Overall, it found that there are quite a few variables at play when considering the effects of HIE on sleep, including workout timing, fitness level, and regularity of timing.
One consistency that the study found was that if HIE finished more than two hours before bedtime, there was an improvement in some (not all) sleep quality factors, notably sleep onset and sleep duration. It also found that if a bout of HIE was finished less than two hours before bedtime, there was a drop in several sleep quality factors. One other notable finding: any amount of HIE done in the hours before bedtime, regardless of timing, led to a decrease in REM sleep.
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How to Get the Most Out of Evening Workouts
So what does all of this mean for you? We talked to Jim O’Brien, CPT, PN1, and Regional Fitness Director at Orangetheory Fitness about best practices to help you get the most out of your evening workout, without compromising on sleep.
Work Out as Early as You Can
“First of all, I typically recommend getting in your workout as early as possible, before outside influences of the day (like work, kids, life in general) get in the way,” says O’Brien. “That being said, we have to do what fits into our lives. So the first thing I’d do is look at doing what you can to optimize your sleep.”
Keep the Intensity Low
However, life happens, and sometimes an evening workout is all you can do. For that, O’Brien recommends keeping the intensity low in order to keep body temperature low enough to make falling and staying asleep easier. “Doing a lower intensity, more traditional weight training would be fine to do in the evenings,” he says. “Moderate and lower intensity cardio [like walking] could also be good to add at the end of one of these sessions.”
Maximize Your Time
Keep end-of-day workouts short. A shorter workout can help extend that window between the end of the workout and bedtime. “If you’re looking to maximize your time in the gym, try supersets, or decrease your rest periods,” O’Brien advises. “If you’re looking for that fatigued feeling, you don’t necessarily have to do a 30-minute HIIT workout. You can instead throw in a finisher at the end of your lifting session, throw in some drop sets, or some cluster sets. I also like bodyweight burnouts to close out a lifting session.”
Find What Works for You
The most important thing for any workout routine is just that—establishing a routine. Not only does this help keep you accountable, but it also helps with sleep quality. Bodies crave routine, and figuring out a consistent time to work out helps everything stay happy and regular. “Most importantly, figure out what’s not going to impact your sleep, and find a style of workout that’s fun for you,” says O’Brien.
The Bottom Line
Overall, the evening workout isn’t as terrible for sleep as it’s made out to be. It’s more about understanding how things like timing and intensity play a role, and making small adjustments to your routine to maximize your sleep quality. Get your routine established (including the all-important bedtime ritual), and stick to it as best as you can.
References
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Stutz, Jan et al. (2019). “Effects of Evening Exercise on Sleep in Healthy Participants: A Systematic Review and Meta-Analysis.”
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Frimpong, Emmanuel et al. (2021). “The effects of evening high-intensity exercise on sleep in healthy adults: A systematic review and meta-analysis.”
