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The Best Way to Measure Your Heart Rate While Exercising

Tim Boyer's picture
Fitness trackers tested for heart rate accuracy

Did you buy a fitness tracker because it has a heart rate monitor? A new study says that fitness trackers are not so accurate after all, and reveals the truly best way to measure your heart while exercising.


According to researchers at the Cleveland Clinic, those popular fitness trackers people buy to keep tabs on their heart rate while exercising may not be as accurate as marketing would have them believe. The problem with this is that users who have a cardiac condition may be relying on the accuracy of their fitness tracker to stay within physician-recommended, safe heart rate thresholds during rehabilitation and exercise.

Here's how an Apple Watch heart rate monitor saved a life

This problem led to a study that focused on testing the heartrate measurement accuracy of 4 popular brands of fitness trackers under varying levels of activity while exercising.

Here’s a brief Fox News video that discusses the study:

Why Chest Monitors are More Accurate than Wrist Worn Fitness Trackers

Chest monitors that yield more accurate heart rate measurements basically work by detecting an electrical impulse through the skin each time the heart beats. The chest-worn heart monitor consists of a transmitter attached to a strap worn around the chest, and a receiver worn on the wrist like a watch. When the transmitter picks up the electric signal from the heart, an electromagnetic signal containing heartrate data is sent to the wrist receiver, which then displays the heart rate.

In the case of typical fitness trackers, however, optical sensors are used to detect the blood coursing through your veins, and then relays that information to an algorithm which then interprets the data and displays it as your heart rate. One of the inaccuracies of this is that the optical sensors are reading your blood flow when it’s relatively far from your heart. In addition, the accuracy of the tracker can also be reduced by light hitting the sensor as you move your arm while exercising.

How the Trackers Did in the Study

What the researchers found when comparing an accurate chest strap monitor against 4 different fitness trackers, was not only variability in accuracy between the different brands of fitness trackers, but also variability dependent on the level of exercise.

For measuring heart rates at different times with activities that caused the heartrates to range between 49 to 200 beats per minute, they found:

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• Apple Watch—91% accurate.
• Mio Fuse—91% accurate.
• Fitbit Charge HR—84% accurate and underrated heartrate during vigorous activity.
• Basis Peak—83% accurate and overrated heartrate during moderate activity.

Conclusions of the Study

The researchers concluded that none of the commercial fitness trackers tested possessed the accuracy of a chest strap type monitor and that wrist worn fitness trackers were at their most accurate at measuring resting heart rates, with diminishing accuracy during exercise.

Their analysis confirmed that wrist-worn monitors are fine for recreational use, but that chest strap style monitors are needed for people when maintaining safe heart rate thresholds during rehabilitation and exercise is imperative due to their medical condition.

For more about Fitness Trackers, here are two selected articles about their usefulness:

Is Your Brand of Activity Tracker Really Accurate?

Wearable Fitness Tracker Update You Need to Know Before Buying One


The Cleveland Clinic Health Essentials― “Your Fitness Tracker Isn’t the Best Way to Measure Heart Rate

Accuracy of Wrist-Worn Heart Rate Monitors JAMA Cardiology (Published online October 12, 2016); Robert Wang, MD et al.

Fox News “Accurate wearables, when not to exercise, new salt warning

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