Researchers explain why leaving your feet outside the covers while sleeping can help you sleep better, Yahoo Health reports.

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.

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.