The Needle's Full Turn

The popular correction says a marketing department invented the figure in 1965 to sell a pedometer. Yamasa Tokei Keiki tells it the other way round. In 1963, physicians and journalists already promoting a ten thousand steps a day movement asked founder Jiro Kato to build a device that could measure it.

Kato delivered in 1965. The Manpo Meter sold for 2,200 yen, and its name borrowed the movement's slogan. The dial did the rest: its needle completed exactly one full rotation at 10,000 steps. The number stopped being an exhortation and became a lap.

In 2004 Catrine Tudor-Locke and David Bassett traced the target, in Sports Medicine, to Japanese walking clubs and a business slogan. They proposed a graduated index of five zones instead of one magic line. Researchers cited it for two decades. Wristbands kept the single number.

Later data neither crowned it nor buried it. In 2019 I-Min Lee and colleagues followed 16,741 older women and found mortality falling with steps, then levelling off around 7,500. In 2022 Amanda Paluch's meta-analysis of 15 cohorts set the plateau by age, near where the slogan already sat.

Then the country that wrote the slogan set a lower number. In its 2024 third term, Health Japan 21 set the daily target for adults aged 20 to 64 at 8,000 steps. Ten thousand was never wrong so much as never derived, a slogan drawn around a dial.