1. Step-detection algorithms are not standardised
Every tracker converts wrist movement into a step count using its own proprietary algorithm. Fitbit, Garmin, Apple Watch, and Mi Band each define a "step" differently at the code level, the minimum acceleration threshold, the cadence window, the filter that separates walking from hand gestures. A 2021 study published in the Journal of Medical Internet Research tested seven consumer wearables on the same participants and found step-count variation of up to 22% between devices on identical walks. One device counted a vigorous hand gesture as four steps. Another ignored slow shuffling entirely. The number on your screen is an interpretation, not a measurement.
