Why do we have a “reflex” that shakes the leg/knee when sitting?

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If you sit in a chair, keeping the heel a couple inches over and then start moving the knee up and down a bit rapidly, after a second or two the leg will just “keep doing it”, for whoever long, quite fast. You can stop ofc, but I takes no effort or thinking at all to just let the leg “do what it does”… Ive asked other people and they all can/do the same. What is the reason for this “involuntary spasm” or what I can call it?

Edit: keeping the toes on the floor, and heel a bit over..

In: Biology

2 Answers

Anonymous 0 Comments

First, note that it is not a reflex. A reflex is an involuntary response reaction due to some kind of stimulus. The classic example is when the doctor hits your knee cap with that small hammer and your leg kicks in response. Another would be how seeing a bright light can sometimes cause people to sneeze. Behavior like the one you describe is more accurately described as fidgeting.

There are many potential causes for fidgeting behavior. Boredom or stress can cause it. Some medications can cause it. Tic disorders like Tourette’s can cause it. Neurological disorders can cause it. Basically it varies from person to person. Toe tapping, finger drumming, pen clicking, hair twirling, etc. are all fidgeting behaviors that people can engage in. Most of the time they are harmless (if perhaps annoying to other people around you).

Anonymous 0 Comments

This type of leg shaking is often an involuntary muscle contraction and can be referred to as a tremor. It’s not always a cause for concern and can happen for various reasons, such as restless leg syndrome, anxiety, or even just out of habit or boredom.