HEART-RATE MONITORS WE LOVE

The heart-rate data your watch is gathering for you is not always correct. A study in

JAMA Cardiology found wrist-worn, optically based monitors such as those used in Garmin, Apple and Fitbit devices were most accurate at rest. That, and because variables such as skin tone, activity, heat, humidity, altitude and pregnancy can also affect your heart rate, means it can be tough to get a consistently accurate reading. Still, wrist-worn devices are becoming increasingly accurate, especially the ones you see here.