Smartwatches Give Rough Health Estimates, Not Exact Readouts
A Conversation explainer says six common smartwatch health metrics—calories burned, steps, heart rate, sleep, recovery, and VO2max—are estimates, not direct measurements. Calorie estimates can be off by over 20%, steps undercount by about 10%, heart-rate accuracy decreases at higher intensities, sleep stages are unreliable, and recovery metrics (based on HRV and sleep) and VO2max readings are biased. Treat daily numbers as rough trends, and rely on how you feel, how you perform, and your actual recovery to guide training.