Garmin is a large American navigation and electronics company that has become one of the biggest names in fitness wearables. Its range runs from plain activity bands to multisport watches and dive computers, and extends to chest straps, bike sensors, smart scales and a blood pressure cuff.

How it works

The watches shine green and red light into the skin at the wrist and measure what comes back. Blood absorbs light differently as it pulses, so the returning pattern gives heart rate and, on many models, an estimate of blood oxygen. Motion sensors, a skin thermometer and satellite positioning fill in the rest. It all lands in Garmin Connect as a long record of training, sleep, stress and recovery.

Key considerations

Optical heart rate at the wrist drifts during hard interval work, where a chest strap still reads more accurately.