May 22, 2020 21:00:00

Are fitness trackers really accurate in steps, heart rate and calorie consumption?

While fitness trackers are gaining in popularity due to their usefulness, some people may be wondering, 'Is this really true?' About the exercise records that fitness trackers show. The non-profit news site '

The Markup ' reports the results of previous studies on the accuracy of commercially available fitness trackers.

How Accurate Is Your Commercial Fitness Tracker? – The Markup
https://themarkup.org/ask-the-markup/2020/05/21/how-accurate-is-your-commercial-fitness-tracker

◆ Accuracy of steps

Fitness trackers have the ability to show steps, but the device does not actually measure 'steps'. Many devices have an embedded accelerometer, which translates the user's movements detected by the accelerometer into steps using a pretrained algorithm. Therefore, the user can increase the accuracy of the number of steps by adding information such as height, weight and age.

However, in

a study examining the accuracy of the fitness tracker Fitbit, Lean Feihan, associate professor of physical therapy at the University of British Columbia, pointed out that the device algorithm is based on 'university male'. For this reason, if the gait is 'standard' or 'intentional walking' is measured correctly, cases such as 'walking in a small step in the kitchen' and 'walking with a stroller' are not reliable. It will be.

In an experiment conducted by Mr. Feihan, when jogging or walking in the lab, only 1/3 to 1/2 of the actual moving time was counted, and the number of steps was underestimated to about 50%. .. Meanwhile, experiments outside the lab have shown that Fitbit overestimates 35% compared to other pedometers and accelerometers.

It also reduces the reliability of the steps taken by the elderly and children. A 2019 study showed that when the elderly wore a tracker on a treadmill, they couldn't record accurate steps because they were slow and did not trigger the sensor. Similar findings have been shown for people with stroke alterations and for patients with Parkinson's disease . Feihan also points out that Fitbit underestimates the steps taken by older people by 25% compared to other devices.

◆ Heart rate accuracy

Most fitness trackers use a technique called

photoplethysmography (PPG) to measure heart rate. This involves illuminating the wrist with a green LED light, measuring the blood volume from the amount of LED light absorbed by the blood, and estimating the heartbeat. However, previous studies have shown that green LED lights can be absorbed by melanin in the skin. In other words, accurate measurement may not be possible depending on the skin color.

In this regard, Fitbit said, 'In order to achieve consistent performance suitable for users of all skin tones, we have designed an optical system that emits green light with sufficient intensity even for dark skin tones and The device is also sensitive enough to detect heartbeat signals. '

However, the Fitbit community has also been complaining by users with actually dark skin that 'If you wear Fitbit on your wrist, your heart rate will not be read correctly.'

◆ Accuracy of consumed calories

Most fitness trackers show you how much calories you burn by exercising information such as movement, heart rate, and height, age, weight, and gender. However, the calorie consumption shown by the fitness tracker is one of the most unreliable.

Michael Mattson, a researcher at the Karolinska Institute in Sweden, investigated the accuracy of the calorie consumption shown by the fitness tracker, and found that there is no device with an error rate of 20% or less in the calorie consumption calculation Did.

According to Mattson, the biggest cause of calorie consumption not being shown correctly is the algorithm. Since the data used as the basis of algorithm training are mostly 'white men in their thirties', the problem is that the farther from the standard data the user is, the lower the accuracy becomes. In order to show more accurate information, it is necessary to train the algorithm based on research data examined on subjects of various ages, body shapes, and exercise levels.

Fitness trackers are convenient and fun, but if you want to count calories accurately, you shouldn't rely on them. 'It's important for everyone to be aware of and be aware of all technology errors,' said Helena Mentis, head of the Body Motion Labs at the University of Maryland at Baltimore County. I will.