Adherence
Wrist-worn optical sensors provide accurate heart rate measurements (median error <5%) during controlled laboratory cycling and running, but fail to accurately estimate energy expenditure (median error >20%) across all activities.
Use your wrist-worn device to track heart rate zones for training intensity; it is generally accurate for this purpose. Do not rely on the calorie/energy expenditure numbers for weight loss decisions, as they are frequently off by 20% or more. Focus on effort and duration rather than the specific caloric burn reported.
Six of the devices achieved a median error for HR below 5% during cycling... No device achieved an error in EE below 20 percent.
Why this rating
Large diverse cohort (n=60), rigorous gold-standard comparison (ECG/Indirect Calorimetry), but limited to laboratory settings.
Source
Accuracy in Wrist-Worn, Sensor-Based Measurements of Heart Rate and Energy Expenditure in a Diverse Cohort
Anna Shcherbina et al. · Journal of Personalized Medicine · 2017
DOI 10.3390/jpm7020003
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