Table 1.

Summary of commonly used metrics obtained from wearables.

Metric	Technology
Physiological
Heart rate – resting	PPG
Heart rate – reactive (e.g., during a logged exercise)	PPG
Heart rate variability (typically overnight)	PPG
Blood pressure	PPG
Respiration rate	PPG
Blood oxygen saturation (SpO2)	PPG
ECG	Electrical heart sensor
Skin temperature	Temperature sensor
EDA/galvanic skin response/skin conductance	EDA
Behavioral – Physical Activity
Step count	Gyroscope, accelerometer
Physical activity types	PPG, gyroscope, accelerometer, GPS
Physical activity duration	PPG, gyroscope, accelerometer
Metabolic equivalent for the task or minutes spent in “heart rate zones”	PPG
Sedentary behavior (e.g., total time spent sitting, sitting events, number of periods of prolonged sitting time)	Gyroscope, accelerometer
Behavioral – Sleep
Total sleep time	PPG, gyroscope, accelerometer
Sleep efficiency	PPG, gyroscope, accelerometer
Sleep onset latency	PPG, gyroscope, accelerometer
Wake after sleep onset	PPG, gyroscope, accelerometer
Sleep stages	PPG, gyroscope, accelerometer
Time in bed	Gyroscope, accelerometer
Behavioral – Location
Location variability	GPS
Distance traveled	GPS
Time spent at home and/or work	GPS

Note. PPG = photoplethysmography; ECG = electrocardiogram; EDA = electrodermal activity; GPS = global positioning system.