Monday, 2 February 2015

Is What You're Doing Before Bed Affecting Your Sleep?

Have you ever been sitting at home, at night, thinking of things you could do to make yourself tired enough to sleep?  During these moments, have you ever thought to yourself: “Oh, I know!  I’ll hit the gym! I’ll workout really hard before I go to bed, to make myself super tired!  This will surely make me fall asleep immediately when I get home!”  If you’re like me, (or even like many other people that I’ve talked to), this thought has probably crossed your mind.  Ultimately, though, despite the fact that it is late and we want to go to bed, our go-to solution—making ourselves tired at the gym—fails time and time again.  Finally, I decided, “Enough is enough! There must be a reason for this!”  I turned to the literature for answers.

Research conducted in Japan turned out to be very helpful. Two researchers, Shiro Oda and Kazuki Shirakawa, conducted a study with twelve male university students.  All men spent 4-7 days in either a research center or an apartment.  Everything in their environment for those 4-7 days was monitored, controlled and the same for everyone—temperature, lights, wake-time, sleep-time, activities they did during the day (all seated activities that required minimal energy, if any; e.g., reading), what they ate (same menu, same nutritional breakdown; no caffeine, alcohol), and when they ate.  The only element in the environment that the researchers allowed to differ was the level of exercise that the students got that day.  All students experienced days where they had to either not exercise at all, exercise with moderate intensity, or exercise with high intensity.  When it was an “exercise day,” their task was to run on a treadmill for 40 minutes at either moderate or high intensity (measured by their heart rate), right before bed (9:20-10:00 pm).  

Sleep recordings were taken every night to measure how long it took the students to fall asleep, how long they slept, whether or not they woke up after initially falling asleep (and for how long), and how normal their stages of sleep were.  Every morning, when the students woke up, they also completed a survey on how well they thought they slept.  The researchers predicted that only high intensity exercise before bed would make it harder for the students to fall asleep at night.

In fact, the researchers did find that those students who had high intensity workouts before bed had both a harder time falling and staying asleep (especially due to elevated heart rates).  Also, in the morning, the students themselves reported having a harder time falling asleep.  However, contrary to the researchers’ prediction, since no substantial sleep differences were found between moderate and high intensity exercise (but rather, only between high intensity exercise and not working out at all), this seems to suggest that exercise before bed (moderate or intense) can be potentially harmful for initiation and maintenance of sleep. 

Although this particular research from Japan only examined male students, I can confidently say (from a female perspective) that their findings are applicable to women as well.  Ever since I stopped working out before bed, I began sleeping much better.  This has profound implications for our lives (men and women, alike).  Unless we challenge our assumptions about what works and what doesn’t, we will forever be frustrated and tired.   In the specific case of working out before bed, it may initially seem counterintuitive that pre-sleep exercise will actually keep you awake longer and make your sleep worse (as opposed to tiring you out and preparing you for sleep).  However, we must realize that the
lack of sleep that results may have all sorts of negative consequences in other areas of our life, such as reduced cognitive functioning, mood swings, etc….  One potential solution (maybe the most obvious one) would be to reduce or eliminate arousing activities (especially high-intensity ones) before bedtime.  (Well…okay… I am stressing we should reduce or eliminate most arousing activities before bedtime, except maybe the one that I know you’re all thinking about right now…).  If we can work on this, not only will our next workout be improved (because sleep = recovery = stronger muscles = better workout), but also our overall functioning (e.g., ability to complete daily cognitive tasks such as making competent decisions at work) will be improved.  Therefore, at the end of the day, all of this amounts to being mindful about what we are doing before bed.  

Oda, S., & Shirakawa, K. (2014). Sleep onset is disrupted following pre-sleep exercise that causes large physiological excitement at bedtime. European Journal of Applied Physiology, 114, 1789-1799.  

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