fitness tracker: why portable fitness trackers aren’t as useless as some claim

Wearable fitness trackers will be on many Christmas shopping lists this year, with a huge range of devices (and an ever-growing number of features) hitting the market just in time for the holiday season.

But what does the latest research say about their effectiveness?

Fitness trackers are all the rage

Currently, about one in five people own one of these portable devices, and about a quarter use a mobile app or website to monitor their activity level and health. And sales are expected to increase over the next five years.

The market landscape is changing rapidly. So far, fitness trackers have mostly been used by younger people: about one in four aged 20 to 40 report using one, compared to just one in ten people aged 60 or older.

However, manufacturers are on a mission to change that by adding features that allow users to monitor not only their physical activity, but several other aspects of their health.

For example, recent wearable models from all the major manufacturers claim to measure a multitude of medical parameters, such as blood pressure, body fat levels, the amount of oxygen in your blood, your heart activity, and even identify when you have took a fall (with a function that allows you to call for help).

Wearables have the correct basics

First, a multitude of studies have examined the accuracy of wearable fitness trackers for measurements related to physical activity, including number of steps, heart rate, and number of calories burned. They show that the number of steps is generally very accurate, while the heart rate and calories burned are reasonably accurate.

When study participants wear two different activity trackers at the same time, the number of steps, minutes of activity, and calories burned aren’t exactly the same, but they do correlate.

That is, when one goes up, the other goes up too, and vice versa. This suggests that they generally capture the same information, but with a slightly different sensitivity.

Evidence for sleep tracking is a bit more patchy. Wearable devices are quite good at detecting bedtime, wake-up time, and overall sleep time. But estimates of more technical measures such as “phases” of sleep – such as REM sleep – do not mesh with the medical-grade measurements taken by polysomnography.

Sometimes wearables go beyond the basics

In a 2019 Apple-sponsored study published in the New England Medical Journal, 419,297 participants with no known atrial fibrillation wore an Apple Watch. During the study, 2,161 of them were notified of an irregular heartbeat, of which 84% were subsequently confirmed to have atrial fibrillation (an irregular and rapid heartbeat).

This is a serious medical condition that requires treatment to prevent stroke. The ability to alert users to potential undiagnosed heart disease appears to be very beneficial. Although others have warned that the Apple Watch can also miss cases of undiagnosed atrial fibrillation, which underscores the importance of never relying on wearable measurements for medical purposes.

Another study published in September reaffirmed that the Apple Watch’s EKG function can detect serious heart irregularities. A similar study is currently underway to assess Fitbit’s EKG function, but the results are not yet known.

Build a more advanced tracker

In terms of detecting falls (which would be very useful for the elderly), scientists are developing wrist-worn devices that can do this with precision using accelerometer technology, which is the same underlying technology already. used by wearables. So the technology is there, but at this point it’s not clear whether the promising lab results will translate into accuracy in commercial handheld devices.

Meanwhile, the latest Samsung watch claims to measure blood pressure and body composition (such as body fat, muscle mass, and bone mass). Body composition is measured using a method called bioelectrical impedance analysis.

When the user touches the watch with their opposite hand, it transmits a weak electrical signal through the body and returns to the watch. Body composition is then calculated using algorithms and body weight entered manually.

At this point, there is no data in the scientific literature to support the accuracy of these measurements, so we recommend that you take them with a pinch of salt. Again, only a few years ago, the same criticism was made of EKG measurements from portable devices – and these have subsequently proven to be valid.

The evidence indicates that your efforts will pay off. So it’s all about precision, but do fitness trackers make a difference in people’s lives?

Hundreds of studies have used wearable activity trackers to try to increase physical activity in various general and patient populations. Meta-analyzes (which involve combining the results of several studies) suggest that the devices are effective in helping people become more physically active and lose weight.

A meta-analysis of 35 studies across various chronic disease populations suggested that users added about 2,100 extra steps per day after starting to use a wearable activity tracker. Other meta-analyzes suggested weight loss in the order of 1 to 1.5 kilograms, on average, over the duration of the studies (the duration varying from one study to another).

And studies that specifically look at long-term step tracking suggest that the benefits achieved are still there (albeit smaller) for up to four years after you first wear the device.

Precision and efficiency aside, wearable users generally report being happy with their devices. So, if you happen to have one in your stocking stuffer this year, keep in mind that it might help with those New Years fitness resolutions.

(This article is syndicated by PTI of The Conversation)

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