Your body doesn’t always wake up at the same time as your brain. Sometimes this produces horrific episodes of sleep paralysis — haunting sensations that you’re pinned to your mattress and can’t help but play witness to the terror unfolding in front of you. Then there’s your leg falling asleep, which is a teensy bit easier to deal with, but you’ll be damned if it’s not a little bit annoying.
If you ask the Greeks (or any medical doctor worth her salt), the condition of a limb falling asleep and the pins and needles sensation that follows is actually called “paresthesia.” Despite the frigidness of the diagnosis, the condition is pretty mild. When a bundle of nerves or nerve fibers gets pinched, restricting the pathway between the nerve endings and the brain, any feeling sustained in the location goes untransmitted. The result? Your limbs feel empty, heavy perhaps. And so you get up, dead-legged, hobbling around the room like a newborn fawn waiting for feeling to return.
A slumbering arm, a dormant foot — these awful waking sensations after a pleasant night of sleep both arise for the same reason. And luckily, getting rid of them isn’t entirely impossible, though you may have to be somewhat patient while your body realizes it hasn’t actually lost a limb. First off — and it should go without saying — if you haven’t already rolled off the sleeping limb, do that. For any patch of nerves to work properly, the pressure inhibiting their signaling must be lifted. If it isn’t, your overly dramatic brain begins to think your limb’s been chopped off, so it stops sending nutrients as well, especially if nearby arteries are pinched, too.
You’re not totally paralyzed, though. You can still flop your arm around even if the fine motor controls have been sapped overnight. This is because the insulation surrounding the nerve fibers are thicker in some structures than in others. The sheath surrounding the nerves responsible for motor control, for instance, is thinner than it is for touch. So you can move a limb even if you can’t feel it. Pain- and temperature-regulated fibers are fairly thin as well, so little time passes once you move your limbs before your nerves recognize the newly jumpstarted pain signal.
Unfortunately, there’s no good way of getting around this pain signal, known colloquially as “pins and needles.” Some receptors are closer to the surface of your skin, while some are deeper within the limb, producing a burning feeling or an itch that can’t be scratched. However, if you’re somebody who likes to get things over with, consider loosening the muscles in your neck to help open the nerve pathways to your sleeping arms and rocking your hips back and forth to stimulate your lower body’s response.
If neither of those works, the best defense is a good offense: Wait it out, and try to avoid sleeping on your arm next time.