What’s happening when limbs fall asleep?
The unpleasant sensation of “pins and needles” that occurs when a hand or foot falls asleep is a feeling that most people would probably like to avoid. While a limb is asleep, there is typically no sensation at all, but the moment you change positions, you’re struck with this uncomfortable tingling sensation, which may even be painful. There is a widespread misconception that pins and needles is caused by a surge of blood flowing back into the limb, but that is rarely the case. The culprit behind sleeping limbs and their unpleasant awakening is more likely your nervous system, not your veins and arteries. This article will take a closer look at what exactly happens when your limbs fall asleep and how you might avoid this irritating problem.
Understand your nervous system
Your peripheral nervous system allows all parts of your body to communicate with the brain and spinal cord, which comprise the central nervous system. When a nerve is compressed, its communication with the brain is cut off along with the fresh supply of oxygenated blood to the nerve. For some nerves, there will be no sensation until you move and restore the lines of communication and blood flow, though others might fire off erratic impulses causing a light tingling or numbness. This sensation goes by the scientific name paresthesia, though we tend to refer to it casually as pins and needles.
Keep your body moving
Common sources of nerve compression that can cause nerves to fall asleep are sitting with legs crossed and falling asleep on your arm. Therefore, you can typically avoid letting your limbs fall asleep by maintaining good posture and moving around frequently—particularly if you spend most of your day sitting at a desk. In some cases, nerve compression is not relieved by movement, meaning that numbness and tingling may be persistent sensations. Conditions such as carpal tunnel syndrome or herniated spinal discs are linked with these symptoms, and they may require specialized orthopedic care for relief.