Footfrontier: The One Foot That Guards the Edge of the Duvet

Footfrontier (n.): the single bare foot sent out from under the duvet on a warm night to patrol the cool air at the edge of the bed. The rest of you stays tucked in, warm and safe. The foot goes alone, like an explorer at the border of a quiet, dark country, and somewhere around the moment it settles, sleep finally arrives.

Footfrontier is a delicate negotiation. Two feet out is too cold, and you might as well be sleeping on a balcony. No feet out is too hot, and you lie there flipping the pillow and counting the tiny sounds of the house. One foot out, however, is perfect. Most people have a favourite foot for the job, and very few could tell you why it is always the left.

The foot on footfrontier duty must never go too far. A few centimetres past the edge of the mattress is fine. Dangling right over the side is a different matter, because everyone knows, in a part of the brain that stopped growing up at the age of seven, that a foot hanging into the dark is a foot on its own. The border is patrolled, but it is never crossed.

Couples share footfrontier the way they share a duvet, which is to say with some tension. One sleeper's foot sticks out on the left, the other's on the right, and the duvet is slowly pulled towards the middle until both feet are out and neither person is sure how it happened. Cats, meanwhile, regard the foot on patrol as a small, warm, twitching visitor that has come to play.

The real idea behind it

The strange thing is that footfrontier works, and there is a reason. To fall asleep, your body needs to cool its core by a little, and it does much of that through its hands and feet. As bedtime approaches, tiny vessels in the skin of your feet open wider, and warmth from deep inside travels out to them and escapes into the room. Your feet are, in effect, radiators with a switch you never knew you had.

In a study published in the journal Nature in 1999, researchers in Switzerland found that how warm people's hands and feet were, compared with the skin nearer the middle of the body, was the best predictor of how quickly they fell asleep. The warmer the feet, the faster sleep came, because warm feet are feet that are busy giving heat away.

So a foot sent out from under the duvet on a warm night is simply helping that job along, handing a little extra warmth to the cool air. It is also why a pair of soft socks can help on a cold night: they warm the feet so they can start the same work. The foot on the border knows exactly what it is doing, even if you are fast asleep.