COROS is a sports technology company best known for GPS watches used by runners, cyclists, climbers and outdoor athletes. Its range also includes an optical heart rate armband. The devices are worn on the wrist or upper arm and focus on training, navigation, recovery and long battery life.

How it works
Lights measure changes in blood flow to estimate heart rate and blood oxygen, while motion sensors track movement and sleep. Satellite receivers map pace, distance and routes outdoors. Some watches add elevation and temperature sensors. The COROS app combines these signals into workouts, training load, recovery estimates, sleep stages and route data.

Key considerations
Features vary between models, and wrist based heart rate can become less reliable during rapid or irregular movement. COROS prioritises sport and navigation over broader smartwatch functions.