There are a seemingly endless merry-go-round of myths, half-truths, and fallacies that abound in the health and fitness space.
We’ve covered several of them previously on the blog, and today we key in on yet another -- the belief that evening workouts negatively impact sleep.
You’ve likely heard this a time or two before, but is there any merit to the belief, or is it just another in a long line of malarkey you’ve been fed by gurus?
Let’s discuss.
Do Late Workouts Affect Sleep?
2019 Meta-Analysis: The Set-Up
The good news is that we don’t have to wildly speculate or take the advice of a guru concerning evening workouts and sleep quality.
There’s actually a fair amount of actual research conducted in humans to help us answer this common question.
Most recently, a meta-analysis was published in 2019 titled Effects of Evening Exercise on Sleep in Healthy Participants: A Systematic Review and Meta-Analysis.[1]
Beginning with a data pool of 11,000+ references, researchers whittled it down using a diverse range of inclusion/exclusion criteria, which included:[1]
After removing the studies that did not fit the selection criteria, they ended up with 23 studies examining the effects of evening exercise vs a no-exercise control on a variety of sleep metrics.[1]
“Evening exercise” for the purposes of this meta-analysis were any bouts of exercise that occurred between 7.2 minutes to FOUR hours prior to bedtime, which (if we’re being honest) is a fairly wide berth.
Also, of import is the fact that researchers only included studies which involved healthy adults who did not present at the time of their respective study with any known sleep disorders or severe medical conditions.
2019 Meta-Analysis: The Findings
After pooling the data and running that stats, the team of researchers found that individuals who did evening workouts experienced significantly greater rapid eye movement (REM) and slow-wave (“deep”) sleep, while spending less time in stage 1 sleep, compared to individuals that did not exercise within 4 hours of bedtime.[1]
As we’ve covered previously on the blog, your body goes through several sleep cycles each night, with each averaging around 90 minutes or so. Each sleep cycle is divided into two major phases:
- Non-REM sleep, and
- REM Sleep
Non-REM sleep can further be divided into 3 or 4 stages (depending on which source you’re consulting), with each successive stage going deeper into sleep, meaning stage 3 is deeper than stage 2 and stage 2 is deeper than stage 1.
For more information on the various stages of sleep, click here.
Based on the researcher’s findings from the collected body of research, it appears that evening workouts help individuals spend more time in deep sleep and less time in light sleep stages.
This is particularly intriguing when you factor in the fact that sleep researchers believe slow wave sleep (deep sleep) to be paramount for cerebral restoration and recovery (i.e. long-term brain health and function).[2]
Other noteworthy findings published in the meta-analysis were that individuals who went to bed with a relatively higher body temperature were linked with poorer sleep efficiency, and they were also more likely to wake after the onset of sleep.[1]
If you didn’t know, “sleep efficiency” is the ratio of total sleep time vs total time spent in bed expressed as a percentage.
Researchers also found no significant difference in total sleep time between subjects who exercised in the morning and those who exercised in the evening.
However, they did find that individuals who engaged in exercise daily tended to have greater total sleep time than individuals who did not exercise during the day.[1]
This is all the more noteworthy when you consider that previous sleep research shows that total sleep time has a direct impact on daytime sleepiness (meaning the more total sleep you have, the more likely you are to feel alert and energized).[3]
Interestingly, researchers did note that evening workouts did adversely impact sleep metrics (reduced sleep efficiency and slightly increased onset of sleep) when individuals exercised intensely within 60 minutes of bedtime.[1]
Researchers theorize that this could be due to incomplete cardiovascular recovery, which led to an increased heart rate and reduced parasympathetic activity at bedtime.[1]
The paper concludes by stating:
“Overall, the studies reviewed here do not support the hypothesis that evening exercise negatively affects sleep, in fact rather the opposite. However, sleep-onset latency, total sleep time, and SE might be impaired after vigorous exercise ending ≤ 1 h before bedtime.”[1]
In other words, according to this meta-analysis, evening workouts do NOT negatively impact sleep. If anything they IMPROVE sleep.
The caveat is that if you are doing evening workouts, sleep efficiency might be impaired if performing some sort of high-intensity workout with 60 minutes of bedtime.
But, there’s more!
Newer Findings on Evening Workouts and Sleep Quality
On the heels of the recent meta-analysis, a new study was published in the journal Experimental Physiology examining the effects of high-intensity exercise a few hours prior to bed on sleep quality.[4]
11 inactive, non-smoking middle-aged men (avg. age 49 ± 5 years) took part in the study.
“Inactive” was classified as regularly completing <150 minutes of moderate-intensity exercise per week.
Similar to the meta-analysis, subjects were not eligible for the study if they presented with serious medical conditions or used medications which impacted sleep quantity or quality.[4]
Prior to completing any exercise tests, researchers tracked the subjects' regular sleep habits for two nights to account for any possible sleep apnea as well as to document each male’s regular sleep stages and arousals.
After the initial assessments were completed, the men then completed three separate exercise trials in randomized, crossover fashion, with each one lasting three days a piece.
Each subject performed 30 minutes of high-intensity interval training (HIIT) alternating between 60 seconds (1 minute) of maximum effort and 240 seconds (4 minutes) of 50% VO2 Max active recovery at one of the following times of day:
- Morning (6 a.m. to 7 a.m.)
- Afternoon (2 p.m. to 4 p.m.)
- Evening (7 p.m. to 9 p.m.)
Each 3-day exercise bout was separated by a minimum of 5 days to allow for adequate recovery and avoid any confounding factors with the other exercise modalities.
In addition to tracking sleep quality and quantity, researchers also measured feelings of perceived appetite as well as post-exercise calorie intake following the exercise bouts. They even tracked plasma concentrations of appetite-related hormones, such as ghrelin (the major “hunger” hormone in the body).[4]
After all the exercise conditions were completed and data analyzed, researchers found that there were no significant differences between the time of day the men exercised and its impact on the following sleep parameters[4]:
- Sleep onset latency (how soon you fall asleep after laying in bed)
- Wake after sleep onset
- Sleep efficiency
- Stage 1 or Stage 2 sleep
- Total sleep time
- Time in bed
- Arousal index
Interestingly, researchers found that when the men exercised in the morning, they spent more time in stage 3 (“deep”) sleep than before the trial started when they weren’t exercising. This backs up the findings we noted above stating that exercise (regardless of time of day) improves deep sleep).
Regarding the impact of HIIT on perceived feelings of hunger/appetite and ghrelin, researchers noted a reduction in ghrelin concentrations[4].
But, the men did NOT report any significant changes in their perceived feelings of hunger, nor did the researchers note any substantial differences in energy intake. This is particularly intriguing given that lower ghrelin concentrations would lead to less feelings of hunger.
Researchers theorized that the men may have needed to exercise more regularly to notice a tangible change in appetite.[4]
The researchers concluded:
“In summary, this study does not support the recommendation of avoidance of early evening HIIE due to its effect on sleep. Rather this study shows HIIE can be safely performed in the early evening without subsequent detriment to sleep duration or arousal index. Also, HIIE performed in the afternoon and early evening are likely to be associated with greater performance output; therefore, greater reductions in orexigenic signals. As such, collectively these observations support the early evening as a viable time-of-day for individuals to engage in HIIE should this be a preferential time-of- day.”[4]
Again, we see that evening workouts (even high intensity ones) DO NOT adversely affect sleep quality.
The Bottom Line on Evening Workouts and Sleep
Based on the current body of evidence, we can pretty much put to bed the notion that evening workouts negatively impact sleep quality.
If anything, evening workouts (and exercise in general any time of day) improve sleep quality and quantity.
There is a small amount of evidence indicating that high-intensity training within 60 minutes of bedtime could negatively impact sleep quality, but more research is needed to back up these preliminary findings.
The primary takeaway here is that exercise (at any time of day) benefits sleep quality and quantity.
Workouts any time of day are better than no workouts at all (regarding health AND sleep).
If you can only train late at night, then go for it (just watch the caffeine intake).
Training late at night will not harm your sleep, but if you find it does, then try to squeeze in your workout at some other time of day.
References
- Stutz, J., Eiholzer, R., & Spengler, C. M. (2019). Effects of Evening Exercise on Sleep in Healthy Participants: A Systematic Review and Meta-Analysis. Sports Medicine, 49(2), 269–287.https://doi.org/10.1007/s40279-018-1015-0
- Roth T. Slow wave sleep: does it matter?. J Clin Sleep Med. 2009;5(2 Suppl):S4‐S5.
- Carskadon MA, Dement WC. Nocturnal determinants of daytime sleepiness. Sleep. 1982;5(Suppl 2):S73–81
- Larsen, P. , Marino, F. , Melehan, K. , Guelfi, K. J., Duffield, R. and Skein, M. (2019), Evening high‐intensity interval exercise does not disrupt sleep or alter energy intake despite changes in acylated ghrelin in middle‐aged men. Exp Physiol. Accepted Author Manuscript. doi:10.1113/EP087455
