Does exercising at night disrupt sleep? 

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Although exercising late at night used to be seen as a sleep killer, it’s now considered an okay practice, with one caveat: you should let a reasonable amount of time pass between leaving the gym and hitting the sack. That’s right, vigorous exercise immediately before bedtime is generally discouraged. 

After reviewing a number of related studies, Harvard Medical School offered the following conclusions: 

  • Evening exercise can help you fall asleep faster with deeper levels of sleep. 
  • If you go to bed too soon after an intense workout, sleep tends to be disrupted. 

How soon is too soon? Turns out anything less than 1 hour is considered too soon. Interestingly, the National Institutes of Health offered a similar review with similar conclusions.

How soon can we really get to bed?

Interesting set of conclusions, but I wanted to test it out for myself. I generally exercise late at night, and I’ve found that an intense workout can result in deep, knock-me-out, restful sleep. No need to test that part; I can attest to the sleep-benefit of late exercise.

But I wasn’t convinced about the one-hour-wait requirement. Seems like I’ve never had a problem with hopping in bed shortly after exercising. Having never really put myself on the clock, I needed to test it out, “scientifically,” to be sure.

Why exercise so late? Simple… while I’ve always been a consistent exerciser, I hate exercising. I know it’s good for me, important to do, but it’s not pleasant. Because of that, despite all best intentions for getting it done early, I tend to put it off. Then, finally, at the end of the day when there’s no more time for excuses, I’ll drag myself over to my home gym to get the job done.

Testing the theory.

So… with that backdrop, I set out to see if I could falsify the wait-an-hour-before-bed theory. Here’s what happened:

I did what was for me a brutal, 20-minute HIIT session, including: 

  • heavy dumbbell curls
  • explosive chain presses
  • deep squats (with a safety bar, dropping well below parallel, then rising explosively)
  • a round of shadow boxing with resistance bands

I did all those exercises successively, as a circuit, one exercise following the other with no rest in between. Then, after each circuit I did about one minute of calisthenics to ensure that my biceps, shoulders, lower-back and hamstrings, were ready to take on the next circuit. 

I did four circuits in all, while maintaining a heart rate of 160+ BPM, and as noted, the whole ordeal lasted 20 minutes. After all of that, for good measure I threw in a set of 20 dead-hang chin-ups, followed immediately (no rest) by a set of 40 pushups, followed immediately (no rest) by a final set of 20 dead-hang chin-ups. 

After that exercise session, feeling totally spent, I dragged my exhausted shell to the shower, set the water somewhere between cold and warm, freshened up, and then hit the sack. There I was, within 20 minutes of a brutal workout, lying in bed, trying to sleep. 

Post-exercise sleep: Round 1

I climbed into bed at exactly 11:30 PM. I knew I could sleep in until 8:00 AM the following morning, so I had 8.5 hours to work with. With no recollection of drifting off, I very suddenly felt myself wake up. I could tell that I had fallen asleep quickly and I felt very much awake (like wide awake) and was sure that I had spent a good many hours in deep restful slumber.

Feeling thirsty, I got up for a glass of water. “It’s got to be just about time to get up and face the day,” I thought. Checking the clock, I was stunned to find it was only 12:30 AM. “WHAT?!!…,” I thought, “how could that be?” That workout must have really whacked me. The approximate hour of sleep was deep and refreshing. (Approximate because I’m not sure how long it took me to nod off; but I am sure it was pretty darn quick.)

Post-exercise sleep: Round 2

So back to bed, wondering what would happen. Feeling wide awake, I was sure the rest of my night would be derailed. Then, just like before, with no recollection of drifting off, I very suddenly felt myself wake up. And just like before, I could tell that I had fallen asleep quickly, but unlike the last time around, I was feeling a bit groggy.

I grabbed the clock to check my progress and found that it was 5:30 AM. Even in my groggy state, I could do the mental math: “At most, that’s only 6 hours of sleep,” I thought. I usually need more sleep than that to feel my best, so I was a bit concerned. I didn’t feel ready to face the day, and at that hour, I wasn’t the least bit confident I would fall asleep again. 

After hitting that 5:30 AM mark, I tossed and turned for what seemed like a couple of long, sleepless hours. Finally, feeling like the alarm had to be within minutes of sounding, I grabbed the clock for another look. It was 7:45 AM. I had blown it. That just wasn’t enough restful sleep to get me comfortably through the day.

“What a lousy night,” I thought. But with 15 minutes to think it over (I wanted to be up by 8:00 AM), I came to some calming realizations. Over the previous 2+ hours I hadn’t engaged in any of the following activities, regardless of how real they seemed and how vividly I was able to recall them:

  • Riding my bike all over downtown Albany (N.Y.), just before sunup.
  • Riding that same bike down a flight of stairs and into the lobby of a downtown building.
  • Furiously pedaling the bike out of that building while being chased by security.
  • Cruising a sunlit highway in the blue Oldsmobile Cutlass I owned over 30 years ago.
  • Taking a curve way too fast and almost hitting another motorist with that Cutlass.
  • Crashing an office Christmas party populated with office workers I didn’t know.
  • Then making my way to a table full of Christmas confections and stuffing my face.

“No, absolutely not,” I assured myself. “There’s no way you did any of that… You’ve been sleeping, buddy!” And with that assurance, I got up to face the day, realizing that I actually felt pretty well rested.

The takeaway.

Here’s my theory about my post exercise bedtime experience. It’s likely one of these 3 things allowed for restful sleep despite the short interval from exercise to bed: 

  1.  I’m just unusual and hopping in bed right after vigorous exercise doesn’t bother me.
  2. If the workout intensity is high enough, hurrying to bed is not a problem.
  3. That shower right before bed, with water temp between cool and warm, made the difference.

Whatever the reason, I’m sticking with my late-night workouts.