Dangers of Inaccurate Fitness Trackers

A woman adjusting her fitness tracker wrist band A recent study by Cleveland Clinic confirms that the Apple Watch is the most accurate wearable fitness tracker. However, when it comes to measuring heart rate, a chest strap has the most comparable results to an Electrocardiogram (EKG) at 99% accuracy.

Data Collection

The research, published in the October issue of JAMA Cardiology, was gathered from 50 healthy individuals who tested four popular fitness trackers while resting, walking and jogging. Heart rate was monitored by the Apple Watch, Mio Fuse, Fitbit Charge HR and Basic Peak as the individuals exercised on a treadmill from two up to six miles per hour. Compared to an EKG, the results were:

  • Apple Watch: About 91% accurate and most consistent
  • Mio Fuse: About 91% accurate, but less consistent
  • Fitbit Charge HR: About 84% accurate
  • Basic Peak: About 83% accurate

The Fitbit Charge HR was found to underestimate the participants’ heart rates, while the Basic Peak overestimated. The researchers also noted that accuracy began to fall at about 100 beats per minute (bpm). Heart-rate monitoring became increasingly inconsistent around 130 – 140 bpm.

Interpreting the Results

Fitbit is currently facing a class action lawsuit for inaccurate heart-rate monitoring. The company argues that fitness trackers are not medical devices.

These gadgets can monitor your heart rate with sensors that detect pulse through the skin or optical light that measures changes in blood volume with each heartbeat. The numbers can be impacted by movement, like the swinging of your arms as you work out. Unfortunately, an inaccurate reading can pose serious health dangers for individuals, including:

  • Those with a heart problem: Someone with a medical condition cannot take the risk of an under- or overestimated heart rate. If physical activity is only permitted up to a certain heart rate, inaccuracy could result in serious complications.
  • Those training for a fitness event: Committed athletes take their training very seriously. These individuals could end up pushing themselves too hard or performing poorly if heart rate is being reported inaccurately.
  • Those struggling to lose weight: An inaccurate heart rate reading can either give someone false hope or cause them to give up when they don’t appear to be meeting their goals.

The results of this study are limited; a small group of healthy individuals were tested on the treadmill only. Researchers at Cleveland Clinic are looking to further develop results for elliptical workouts and biking to provide more definitive results.

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