Jenna had been coloring for almost 25 minutes, sitting with one leg tucked under her. When the bell rang, she jumped up and her leg felt funny. It was asleep!

If this has happened to you, you know that for a short while you might have lost feeling in your foot, it might have felt heavy, or you might have felt "pins and needles." But why would your foot fall asleep?

Many people say this is because you've cut off the blood supply to your foot, but your nerves are more to blame. Nerves are like tiny threads or wires that run through your whole body, and they carry messages back and forth between your brain and body.

When you sit on your foot, you temporarily compress, or squash, the nerves in that area. These nerves can't send messages back to the brain normally, and so for the moment, the connection is cut off and you don't feel anything. It's kind of like a phone call where your friend hangs up and you haven't yet: Your brain is saying "hello," but your foot isn't able to answer.

After you stand up or uncross your legs and the nerves are no longer compressed, the feeling in your foot soon comes back. It might feel a bit tingly as this happens, like pins and needles or even a bit painful. But it only lasts a few seconds as the connection returns to normal, and it won't hurt your body.

Worried about your sleepy feet? You don't need to be — everyone has a foot fall asleep once in a while, and it's rare for it to mean there is something wrong in a kid's body. If you want to keep your feet awake and kicking, don't sit on them or put them in other positions where you're squashing the nerves.