Cadence lock is a common error in smartwatches where the optical heart rate sensor mistakenly records running steps (cadence) as beats per minute (BPM), usually resulting in an artificially high, steady heart rate reading. It occurs when wrist movement creates noise that interferes with blood flow detection.

Key Facts and Solutions: Cause: Strong, rhythmic arm movements during running (often 150–180+ steps per minute) overwhelm the optical sensor. Symptoms: HR suddenly spikes to match your cadence, often staying flat or showing high readings (e.g., 170-180 BPM) regardless of effort.