Accuracy of Commercially Available Heart Rate Monitors in Athletes: A Prospective, Randomized Study

In 2018, worldwide sales of wearable fitness monitors are anticipated to exceed 110 million. Millions of consumers purchase fitness trackers that include heart rate monitors in order to help them to maintain their health and wellness. As popularity of these fitness devices grows, assessment and awareness of the accuracy of heart rate measurements becomes increasingly important.

In previous trials, the investigators assessed the accuracy of 4 wrist-worn HR monitors (Apple Watch, Fitbit Blaze, Garmin Forerunner 235, TomTom Spark Cardio) in healthy adult volunteers during various types of exercise. The investigators discovered that the accuracy varied with exercise type. With the treadmill, all devices were acceptable (rc =.88-.93) except the Fitbit Blaze (rc=.76). While biking, the Garmin and Apple Watch were acceptable (rc >.8). On the elliptical trainer without arm levers, only the Apple Watch provided accurate readings (rc=.94). None of the devices gave accurate readings for the elliptical trainer with arm levers (rc <.8). That study is now published.

Reviewers of the investigator's previous work raised an important question: how do commercial optical heart rate monitors perform when measuring heart rate in athletes performing at a high level of exertion? This study addresses that question.

The objective of this study is to evaluate the accuracy of four heart rate monitors in accomplished athletes (i.e. runners) performing at various levels of exertion, including a high level of exertion.