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Right before you fall asleep, your hands and feet get warmer. That warming is the real trigger that switches your brain into sleep mode. A 1999 Nature paper tested it against melatonin, core body temperature, heart rate, and how sleepy people felt. The hand and foot warming won.
The drawing in the tweet works on this exact trigger. The pose has a name in Japan: Mōkan Undō, or "capillary exercise." Katsuzō Nishi designed it in 1927. He was the chief technical engineer on the Tokyo subway, Japan's first. It became one of six daily exercises in his system, still done in Japan today.
You lie on your back, point your arms and legs straight up, and shake them for thirty seconds. While the limbs are up, gravity drains the blood from them. When you lower them, the blood floods back into your hands and feet, warming them in seconds. Your brain reads that warming as a green light to sleep.
The shaking activates a separate reflex, the kind most mammals use after a scare. Dogs and rabbits shake themselves off after a fright for the same reason. Dr. David Berceli, a trauma therapist, built a whole method around it, with certified instructors now in 40 countries. The shaking flips your nervous system out of "I'm wired" mode and into "I'm safe to sleep" mode.
Nishi got the biology wrong. He believed capillaries, the tiny blood vessels at the ends of your veins, did the pumping. William Harvey, an English doctor, had shown the heart did the work, three centuries earlier, in 1628. The exercise still works, for entirely different reasons than Nishi thought. The drained limbs come back warm. The body reads that as a sleep cue, and the shaking calms the nervous system on top of it.
A drawing on X with millions of views just rediscovered a 100-year-old Japanese sleep exercise. A subway engineer designed it first, decades before sleep scientists figured out why it would work.
黒葉だむ 『外側の人。』水・土夕方更新✒@kuroabam
番組で見た、寝る前に30秒コレやってから三日連続快眠できてる。（手足をパタパタする） 皆試してみて。
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