Standard chest-strap heart rate monitors more accurate than wrist-worn monitors
WASHINGTON — When popular wrist-worn fitness trackers were tested for accuracy to gauge heart rate across several types of exercise and intensity, standard chest-strap monitors had the greatest accuracy, researchers reported at the American College of Cardiology Scientific Session.
“As physiologic monitoring via wearables becomes more popular, we should ensure that we ascertain the accuracy of each one of these monitors before we employ them in any sort of decision making,” Marc Gillinov, MD, the Judith Dion Pyle chair in heart valve research, thoracic and cardiovascular surgery at Cleveland Clinic, told Cardiology Today.
The single-center study included 50 healthy volunteers (mean age, 38 years; 43% women). Each participant received a continuous four-lead ECG and was fitted with a chest monitor (Polar H7), an armband monitor (Scosche Rhythm+) and two randomly assigned wrist-worn monitors: Apple Watch, Fitbit Blaze, Garmin Forerunner 235 and/or TomTom Spark Cardio.
Heart rate was recorded at rest and after light, moderate and vigorous exercise across three types of activities, including the treadmill, stationary bike and elliptical (with and without hand levers). The researchers compared measurements via the wearable devices with readings from the chest strap and ECG. Participants exercised for 18 minutes.
According to the results, the chest-strap monitor most closely matched readings from the ECG.
Although the watch-style heart rate monitors may accurately report heart rate at rest, and most were acceptable on the treadmill, except for Fitbit Blaze, the researchers noted inaccuracy during biking and elliptical training. The Apple Watch and Garmin Forerunner 235 wrist-worn devices and the arm band were acceptable during biking. Apple Watch was the only wrist-worn monitor to provide accurate heart rate readings when participants switched to the elliptical trainer without arm levers. No wrist-worn device provided accurate measurements when participants used the elliptical trainer with arm levers. With the exception of the Apple Watch, the wrist and arm monitors studied became less accurate with increasing levels of exercise.
“Even though all these wrist-worn monitors work by the same general principles, there is considerable variation among them,” Gillinov said in a press release. “Overall, they were most accurate when someone was using the treadmill at low intensity and worst when exercising on the elliptical at high intensity.”
The researchers noted several limitations of the study. One limitation is that not every available fitness tracker was studied. Moreover, these types of heart rate monitors may introduce more variables that can result in incorrect readings, such as insufficient contact with the skin due to sweating or poor fit. This study is also limited due to its small size.
The researchers concluded that “electrode-containing chest monitors should be used when accurate heart rate measurement is imperative.”
The devices studied were chosen based on their popularity and sales figures, Gillinov told Cardiology Today.
Fitness trackers continue to grow in popularity.
“A fair number of cardiac patients are reporting that they are using a heart rate monitor,” he said. However, some patients report being concerned by heart rate readings that appear to be spurious, he said.
“We are just at the beginning of a revolution in personal management of health by virtue of wearable physiological monitoring,” Gillinov stated in the release. “As people take more control of their health and record their own physiological data, they need to know how accurate it is; this is especially concerning for people with heart conditions that can be exacerbated [with activity].”
These data build upon earlier research by Cleveland Clinic researchers that assessed a different set of heart rate monitors and was limited only to walking or jogging on the treadmill. The researchers called for larger studies of various fitness trackers in special populations, such as those with diabetes, HF or obesity and in the post-MI setting. Gillinov told Cardiology Today that the next step is a study of fitness trackers in patients undergoing cardiac rehabilitation.
Until more data are available, “if a physician thinks it’s important for a patient to monitor his or her heart rate, use these data to tell them which devices are more likely to be accurate and agree with [ECG],” Gillinov said. – by Katie Kalvaitis
Gillinov AM, et al. Poster 1315M-03. Presented at: American College of Cardiology Scientific Session; March 17-19, 2017; Washington, D.C.
Disclosure: Gillinov reports no relevant financial disclosures.