If there’s a triad for staying healthy, exercise, proper nutrition, and quality sleep would be it. You could also add stress management to the list. If you’re pressed for time, you might tap into the health and fitness benefits of high-intensity interval training, since you can get fitness benefits with a shorter workout if you boost the intensity of your sessions with an interval structure. Vigorous exercise may also offer additional benefits for heart health.
If you can’t fit in that HIIT workout until after dinner, you might wonder whether launching into a vigorous workout will make it harder to sleep. Some studies show that exercising at any time of the day can help you get a better night’s sleep, but most of these studies focused on moderate-intensity exercise. They showed that morning workouts offer the biggest benefits for sleep quality but exercise at any time of day improves sleep quality.
But what about high-intensity exercise? Vigorous exercise takes your training (and heart rate) to a whole new level. It activates your sympathetic nervous system more, specifically the “fight or flight” component that invigorates you. Plus, high-intensity exercise creates an after-burn where your heart rate and metabolism are higher for hours after such a workout.
How a HIIT Workout Later in the Day Affects Sleep
In a study published in the journal Sleep Medicine Reviews, researchers analyzed 15 studies focusing on how vigorous exercise affects sleep. They were particularly interested in how a single high-intensity workout session impacted sleep. They focused on the role of exercise timing, and how the time interval between exercise and sleep affected sleep quality. After looking at data on 15 studies, they reached some interesting conclusions.
Their findings? The timing between exercise and bedtime matters. When subjects engaged in high-intensity exercise two hours or more before bedtime, their sweat sessions improved their sleep quality. In contrast, when they exercised vigorously within two hours of bedtime, sleep quality dropped. It took longer for the participants to fall asleep too.
Other Ways High-Intensity Exercise Affects sleep
Although engaging in high-intensity exercise more than 2 hours before bedtime improved sleep quality, participants showed a modest reduction in rapid-eye-movement (REM) sleep. This is a stage when dreaming occurs, and when, underneath your lids, your eyes dart back and forth. The drop in REM sleep occurred irrespective of when the subjects worked out in the evening. REM sleep plays a role in consolidating memories and problem-solving. Studies show that people who don’t enter REM sleep have problems remembering what they learned before bedtime. In the study, the type of exercise had a small impact on sleep quality too. Subjects got the most sleep improvements from cycling exercises.
It’s not surprising that intense exercise within 2 hours of bedtime worsens sleep quality. Your sympathetic nervous system is still fired up, and it takes longer for your body to enter rest and relaxation mode again.
However, some studies show that a drop in body temperature helps bring on sleep. For example, research shows that taking a hot bath before bedtime and then sleeping in a cooler room shortens the time it takes to fall asleep.
Other Benefits of High-Intensity Exercise in the Evening
There’s another perk of doing an evening HIIT session. Research shows intense exercise in the evening helps reign in the appetite hormone ghrelin, the one that sends you running to the kitchen for a late-night snack. Plus, the evening is the time when most people snack, usually while watching television. Working out after dinner is a way to break the sit and snack cycle.
Time High-Intensity Exercise Right
High-intensity exercise later in the day may improve your sleep quality, but the timing matters. If you do HIIT training in the evening, don’t do your workout within 2 hours of bedtime. Make sure you’re practicing good sleep hygiene too. Keep the temperature of your bedroom between 66 degrees F and 70 degrees F. According to Sleep.org and the results of research, this is the optimal room temperature for quality sleep. Sleeping in a warmer room reduces sleep efficiency.
Other Sleep Hygiene Tips
Be sure you’re sleeping in a pitch-black room too, since even small amounts of light can hinder the release of melatonin, the sleep hormone, a hormone that helps bring on sleep and has powerful antioxidant activity. Don’t use devices that release blue light within a few hours of bedtime either, for the same reason. Make sure you’re getting natural light exposure during the day to set your internal biological clock properly.
Be consistent with when you turn in to bed too. Your body will adapt to that schedule and begin to wind down when bedtime rolls around. If possible, keep your sleep and wake time the same even on the weekend.
The Bottom Line
Make sure you’re getting the sleep your body needs for recovery. It matters! Studies link poor sleep quality with a higher risk of health problems, such as cardiovascular disease, type 2 diabetes, depression, anxiety, and premature mortality. Exercise can boost sleep quality if you time it right. Make sure you’re getting both parts of the equation, exercise and sleep, right.
- “Exercising for Better Sleep | Johns Hopkins Medicine.” https://www.hopkinsmedicine.org/health/wellness-and-prevention/exercising-for-better-sleep.
- “How Exercise Affects Sleep | Sleep.org.” 24 Mar. 2021, https://www.sleep.org/exercise-affects-sleep/.
- Kline CE. The bidirectional relationship between exercise and sleep: Implications for exercise adherence and sleep improvement. Am J Lifestyle Med. 2014 Nov-Dec;8(6):375-379. doi: 10.1177/1559827614544437. PMID: 25729341; PMCID: PMC4341978.
- Blume C, Garbazza C, Spitschan M. Effects of light on human circadian rhythms, sleep and mood. Somnologie (Berl). 2019 Sep;23(3):147-156. doi: 10.1007/s11818-019-00215-x. Epub 2019 Aug 20. PMID: 31534436; PMCID: PMC6751071.
- “The Best Temperature for Sleep: Advice & Tips | Sleep ….” 24 Jun. 2021, https://www.sleepfoundation.org/bedroom-environment/best-temperature-for-sleep.
- Concordia University. “Intense workouts before bedtime won’t guarantee a good night’s rest, new research shows: Evening exercise is better for uninterrupted sleep.” ScienceDaily. ScienceDaily, 28 September 2021. <www.sciencedaily.com/releases/2021/09/210928121330.htm>.
- com. “Dream Deprivation: How Loss of REM Sleep Impacts Health and Learning”
- com. “What is REM sleep?”
- The Physiological Society. “Evening exercise will not ruin sleep and might even reduce appetite.” ScienceDaily. ScienceDaily, 21 February 2019. <www.sciencedaily.com/releases/2019/02/190221083411.htm>.
- “How Room Temperature Affects Sleep | Sleep.org.” 12 Mar. 2021, https://www.sleep.org/temperature-for-sleep/.
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