Why do our legs shake if we lift our heels whilst sitting down?

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Why do our legs shake if we lift our heels whilst sitting down?

In: Biology

Can you clarify?

Just lifting my heels off the ground while sitting, mine do not shake….if you instead are referring to people that “bounce” their legs up and down, that’s completely different. Their legs aren’t shaking they’re bouncing them by pressing their toes into the floor which causes the heel to rise.

Now as to why people do it, there’s a few different reasons. Some do it out of boredom, some do it when extremely focused on something, some do it as a form of nervous tic.

Regardless, their legs don’t “shake” *because* their heel is off the ground, their heel is off the ground because they are “shaking” (more of a bounce IMO) them.

I know what you mean. It’s an involuntary ‘quiver’.

I would guess that it’s because the central nervous system isn’t used to controlling the muscles that keep the muscles and feet still when they don’t have the ground underneath them, or that the muscles themselves aren’t used to it.

But I might be way off, so wait for someone who knows the real reason to jump in and correct me 😀

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You can get cramp in there if it’s over a prolonged period of time. Cramp is a build up of the waste product (lactic acid) produced when you use a muscle.

I had the same issue with sitting up in bed. My whole body would shake before I was in a resting position. I was anorexic at the time. The reason they shake is that you’re weak in those muscles.

Train them and you won’t have this issue.

Only ever happens to me on the toilet. I assumed it was because I was holding that position too long and a muscle was weak and spasming…much like when you try and hold a plank position and your body starts to shake. (Or at least my scrawny body does)

I’ll quote what someone quoted a year ago of what someone said 7 years ago. But if you want to look it up, it’s called the Golgi Tendon Reflex.

https://en.m.wikipedia.org/wiki/Golgi_tendon_reflex

“Physiotherapist here, OP need not worry…
…it is a reflex response,…

…It’s part of the Golgi tendon reflex. Golgi tendons are small receptors located in every muscle that protect them from over stretching damage. They do this by recognising when a muscle is over stretched and then sending a message to your spinal cord- which then sends a message back telling the muscle to contract to prevent it hurting itself.

When OP goes up onto his tiptoes the Golgi tendons sense his calf (gastrocnemius, soleus and to a lesser degree plantar is) is stretching, so the it sends the message to the spinal cord and we get the contraction reflex. So then his leg rises due to plantar flexion at the ankle and the calf muscles relax. After they relax, his leg drops again- we get the stretch- then the stretch reflex and the cycle repeats, carrying on the continual bounce of his leg…

…Hope this makes sense! TL; DR Golgi tendons.”