Accuracy of commercially available heart rate monitors in athletes: a prospective study

Wearable fitness tracking devices are a billion-dollar industry (1). Endurance athletes, particularly competitive runners, increasingly rely on wrist worn devices to guide their training (2,3). Distance, pace, performance zones and heart rate (HR) are just a few of the many aspects of physical activity that can be tracked through these optically based commercially available devices. In particular, the HR feature is employed by many distance runners as a marker of their fitness progress (4). Given that long distance runs, interval workouts, and even hill sprints are all part of training plans for competitive runners, the accuracy of HR monitoring becomes extremely important so that a balance is achieved across these different training loads. Convenience and comfort of the wrist-based devices has enabled them to largely replace chest straps that employ electrodes that measure cardiac electrical activity