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Introducing a slightly odd but potentially very useful sleep hack: Keep one foot, or both feet, outside of your blanket. It could help you both sleep better and fall asleep faster, a sleep researcher explained to Science of Us.
I started thinking about this recently when I was idly chatting with a buddy about how (relatively) nice and cool it had been recently in New York, and how much nicer it is to sleep when it’s cooler outside. He replied with what is apparently his formula for a perfect night’s sleep: “One foot out from under the blanket and a nice breeze coming from the window.”
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I do the same thing, I realized — keep my foot outside the covers — but I’ve never known why. A slow news day in August seemed as good as a time as any to find out, so I spoke with Natalie Dautovitch, a spokesperson for the National Sleep Foundation and a psychology professor at the University of Alabama. Dautovitch’s research focuses on chronopsychology — that is, how our routines and biological rhythms fluctuate throughout the day and night, and how that affects our health and well-being. And while she said there’s never been any research specifically looking into my question, she was game to offer up a few theories based on her research.
What it comes down to, she thinks, is the connection between sleep and temperature. Sleep researchers know that right before you fall asleep, your body temperature starts to drop; in the deepest stages of sleep, your body is at its coolest, about one or two degrees below normal. Some scientists believe cooler temperatures cause sleepiness, and although the pre-slumber cooling process happens naturally, there are a few things you can do to help it along, like taking a warm bath right before bed, for example. When you leave the tub, your body temperature rapidly cools, triggering that sleepy feeling. A warm beverage works the same way.
Which brings us back to the foot thing. “I think it’s likely in service of trying to cool our bodies down because we’ve gotten too warm to sleep,” Dautovitch said.
But why the foot, specifically? The skin surfaces of both our hands and feet are unique, Dautovitch explained, both in that they’re hairless and because they contain specialized vascular structures that help with heat loss. Specifically, the hands and feet contain blood vessels called the arteriovenous anastomoses, which — coupled with the lack of hair on the bottoms of your feet — are perfectly designed to help dissipate body heat. So combine that with what scientists know about the decrease in body temperature during sleep, and it’s possible that “sticking your toe out or your foot out could bring you to a more restorative sleep,” Dautovitch said.
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In general, people tend to sleep best in colder rooms, between 60 and 67 degrees, she said. So if you’re looking for a more conventional sleepy-time tip, maybe just get an extra fan.