Feet are particularly effective at releasing heat because they contain special blood vessels that allow warmth to escape quickly. When one foot is exposed to cooler air, it acts like a natural heat vent, helping your body cool down more efficiently without drastic measures like removing blankets or lowering the thermostat.

Sleep researchers also measure something called the distal-to-proximal gradient (DPG), which compares the temperature of your extremities to your core. A higher DPG—meaning warmer hands and feet relative to the body—has been linked to faster sleep onset. Studies show that people who release heat through their feet tend to fall asleep more quickly. That said, the trick doesn’t work for everyone.

People with cold feet, poor circulation, or certain conditions may find it uncomfortable and sleep better by keeping their feet warm instead. Ultimately, the goal is comfort. But if you’re struggling to drift off, slipping one foot out from under the covers might be a surprisingly effective way to help your body settle into sleep naturally.