Concept
Cadence lock
A wrist optical sensor error where the displayed heart rate follows running cadence rather than the runner's pulse.
Why it happens
Repetitive arm movement and weak optical contact can create a signal that the watch interprets as pulse. Cold skin, loose fit, vibration, and sweat can increase the chance.
How to recognize it
The trace may jump suddenly and settle near a familiar cadence value, often around the same number of beats and steps per minute, while breathing and effort do not match.
How to reduce it
Wear the watch snugly above the wrist bone, warm up, clean the sensor, and compare with a chest strap when accurate rapid changes matter.
When a surprising reading closely matches cadence, check effort and sensor fit before changing the workout.
Every high wrist reading is not cadence lock; real effort, heat, hills, stress, and illness can also raise heart rate.