SEP 24, 2016 7:27 AM PDT

On Pins and Needles: What

WRITTEN BY: Xuan Pham

If you're like me, you like to sit cross-legged or tuck your legs underneath you. But while this is comfortable for the first 5 to 10 minutes, inevitably my legs will start going numb. Then just as I'm readjusting and straightening my legs, the prickly "pins and needles" sensation sets in. The pain is uniquely exquisite and quite strange. What causes these prickly sensations?

While most people may think the lack of blood flow is to blame, that's not the whole story. Furthermore, there aren't any pain receptors associated with blood, so the sensation is all in your head. In particular, putting weight on the legs or sitting cross-legged actually pinches the nerves in the legs. Numbness sets in when brain signals can't get to the foot. Then when you realize it and shift your weight, the signals flow again, but your brain still has to catch up. This uncoordinated process intensifies and numbs the signals simultaneously, creating the telltale tingly or burning sensation. Fortunately, these only last for a few seconds to a few minutes before the brain is acclimated again.
About the Author
  • I am a human geneticist, passionate about telling stories to make science more engaging and approachable. Find more of my writing at the Hopkins BioMedical Odyssey blog and at TheGeneTwist.com.
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