Are fitness trackers really tracking your heart rate?

CLEVELAND, OH (WOIO) - Tracking a workout has become synonymous with hitting the track and lifting weights. However, the technology you use may not track your heart rate like it's supposed to.

Cleveland Clinic conducted a survey with 50 healthy adults with the mean age of 37-years-old. FitBit HR, Polar H7, Mio Fuse, and Apple Watch were all put to the test to see which one accurately tracked your heart rate.

Dr. Gordon Blackburn headed up the study and says the fitness enthusiasts may be shocked.

"The wrist straps are not all that accurate and there's a great discrepancy among them," said Blackburn. "The Apple Watch is the most accurate of the wrist versions. FitBit down the near bottom of the group. The  Mio Fuse was the poorest performing one."

Dr. Blackburn goes on to say the problem with the findings is the wristbands could negatively impact the way you workout.

"Someone could be pushing harder than they need to or they aren't working as hard as they should be," he said.

For fitness bands, Fitbit (FIT, -1.90 percent) continued to dominate, capturing 75 percent of sales. Garmin (GRMN, +9.12 percent) came in second with a 12.5 percent share, according to Fortune.

Some of the companies responded to the study with the following statements.

Mio Fuse said: "Mio has an excellent reputation for providing optical heart rate accuracy, and the introduction of our Personal Activity Intelligence (PAI) ensures that heart rate is accessible and understandable to all. PAI looks at heart rate over a seven-day rolling window to provide unique personalized insights on an activity's impact to your overall health. This defocuses the importance of needing to know the exact heart rate at any one time, and rather puts emphasis on understanding what getting your heart rate up does for your health over time."

FitBit said: "Fitbit is committed to making the best activity trackers on the market for consumers who want information to make informed decisions about their health and fitness, and we stand behind our heart tracking technology. Fitbit trackers are not intended to be medical devices. Unlike chest straps, wrist-based trackers fit comfortably into everyday life, providing continuous heart rate for up to several days without recharging (vs. a couple hours at a time) to give a much more informative picture of overall health and fitness trends. We conducted extensive internal studies with more than 60 subjects, which show that Fitbit's PurePulse technology performs to industry standard expectations for optical heart rate on the wrist with an average absolute error of less than 6 bpm and an average percent error of less than 6%. Fitbit devices were tested against properly calibrated industry standard devices like an EKG chest strap across the most popular activities performed worldwide – including walking, running, biking, elliptical and more. This is accuracy is achieved even while having battery life up to five days. (*Battery life and charge cycles vary with use & other factors; actual results will vary.) We believe optimal heart rate monitoring for those striving to reach their health and fitness goals is best achieved by taking heart rate across an extended time frame, such as during the entire task of interest, to get more reliable and meaningful outcomes. Instantaneous heart rate readings at a pre-determined time point can be more subject to error (e.g., human error and random mechanical disturbances through unwanted movement)."

Fitbit also noted that other studies have had different results. Consumer Reports independently tested the heart rate accuracy of the Fitbit Charge HR and Surge, giving both products an "excellent" rating. The Annals of Emergency Medicine recently cited a case report of a 42-year-old man's Fitbit tracker/smartphone app providing data to inform medical decision making and his treatment for arrhythmia.

An 18-year-old UK woman was studying for her exams when her tracker revealed that her resting heart rate had increased from 84 bpm to 210 bpm. Medics said if the Southport teen hadn't called for help, she could have died. A similar story made national news in Australia, where a gentleman noticed the readings on his Fitbit showed his heart lurching between 47 beats per minute and a staggering 218 beats per minute. He was rushed to the hospital where he was diagnosed with a life-threatening arrhythmia.

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