At lunch one day last week, I realized that almost all the people around me (all men, Silicon Valley types talking about Silicon Valley matters, so far as I could tell) were jiggling their legs, apparently without any realization they were doing so. I’ve long been familiar with the behavior, though never in such a concentrated form; it was like I had fallen into a convention of leg-jigglers. (I am not one.)

Quite a number of variants: some one-legged (mostly the left, in this small accidental sample), some two-legged; and some subtle, a light bouncing off the ball of the foot, and others more vigorous, up to one guy who was pumping his left leg extravagantly.

Unfortunately, not a whole lot seems to be known about leg-jiggling / leg jiggling, leg shaking, foot jiggling, or sewing-machine leg, as it is variously known.

A YouTube video from one leg-jiggler can be viewed here. And there’s an xkcd cartoon (“Resonance” of 2/26/07) on the subject:

(Mouseover text: It’s really hard to control the frequency, actually.)

An arresting posting on the Japan Talk site: “Why You Should Never Shake Your Legs in Japan” by John Spacey on 6/20/12:

Bimbo yusuri (貧乏ゆすり) is the Japanese term for shaking of the legs or knees while seated. The term can be literally translated “poor person shake” [for reasons that are not clear].

Shaking the leg while seated is often an unconscious habit. It’s far more common amongst men. There are several theories why people do it. These include that it improves your circulation when seated, burns calories or releases nervous energy. [From the guy in the YouTube video: “Explain what you mean by ‘nervous energy’.”]

It’s highly recommended to avoid shaking your legs in Japan. According to Japanese manners leg shaking is extremely rude. It indicates that you’re impatient or nervous about something and lack self control.

A habit of shaking your legs may seem innocent enough. However, in Japan it can seriously damage your professional and/or social life. Shaking your legs in front of a customer or a date indicates that you’re an impatient person of low manners (according to local customs).

Some deck-clearing. Ordinary leg-jiggling is distinct from Restless leg(s) syndrome. From Wikipedia:

Restless legs syndrome (RLS) also known as Willis-Ekbom disease (WED) or Wittmaack-Ekbom syndrome, is a neurological disorder characterized by an irresistible urge to move one’s body to stop uncomfortable or odd sensations. It most commonly affects the legs, but can affect the arms, torso, head, and even phantom limbs. Moving the affected body part modulates the sensations, providing temporary relief.

RLS sensations range from pain or an aching in the muscles, to “an itch you can’t scratch”, an unpleasant “tickle that won’t stop”, or even a “crawling” feeling. The sensations typically begin or intensify during quiet wakefulness, such as when relaxing, reading, studying, or trying to sleep. Additionally, most individuals with RLS suffer from periodic limb movement disorder (limbs jerking during sleep), which is an objective physiologic marker of the disorder and is associated with sleep disruption.

Ordinary jigglers are typically unaware of their actions and experience no trigger for them, but RLS is set off by unpleasant sensations.

Some sites on jiggling connect it to ADD (attention deficit disorder) or OCD (obsessive-compulsive disorder), but I’ve found no careful studies along these lines. But again and again, people talk about the behavior in terms of releasing “nervous energy”, appealing to a metaphorical concept of folk medicine that is hard to make objective.

(A note: I’ve known a small number of people who, as children and young adults, had a very high need for physical exertion; they “couldn’t sit still”, had to be in motion. So they were sometimes said to have a lot of “nervous energy”. But in my experience, these people, as children and as adults, were not jigglers.)

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