Unpacking Stress: How Smartwatches Gauge Your Mental Strain

Smartwatches typically measure stress by monitoring Heart Rate Variability (HRV), which is the variation in time between heartbeats. A higher HRV generally indicates a more relaxed state, while a lower, more consistent HRV can suggest stress or a 'fight or flight' response. The watch uses its optical heart rate sensor to detect these tiny variations and then applies algorithms, often combined with accelerometry data (movement), to provide a stress score. It's an interesting topic for anyone with modern tech who wonders how these features actually work.