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How Accurate Are Activity Trackers?

More and more people are deciding to include the use of activity trackers in their daily routines. They let the sleek wristbands monitor nearly their every move and make decisions basing on the data that their devices give them. However, you might still be hesitant to enter this lifestyle.

This could primarily be due to you not knowing the answer to this question: how accurate are these activity trackers? After all, if you are going to make life choices basing on what these bracelets tell you, they better be really accurate. But how accurate are activity trackers truly? And at the end of the day does accuracy really matter for those who want to use activity trackers?

Accuracy of Step Counting and Heart Rate Monitoring

How Accurate Are Activity Trackers?

Of all the functions of activity trackers, studies point to step counting as being the most accurate. This is the primary and most basic function of trackers, after all. The mechanism used to count steps, the accelerometer, is something that has been in use even before activity trackers took the market, what with the former prominence of pedometers.

A study sponsored by the American Council on Exercise found out that activity trackers predicted the correct number of steps within 10% accuracy. The small margin of error is said to be caused by relatively quicker and smaller steps, which are sometimes not detected by the trackers’ sensors.

Another function that experts say is surprisingly accurate is heart-rate monitoring. Several studies have already looked into the accuracy of activity trackers, one of the most notable of which is the one done by the Stanford University School of Medicine in early 2017. The authors of this study looked at two activity tracker functions: heart rate monitoring and calorie counting.

The data gathered from these two functions were compared to data gained from gold-standard tests that doctors use. Heart rate data from activity trackers were compared to findings from an electrocardiogram.

The devices studied were only wrong 5% of the time, which is a pretty impressive rating. The high accuracy of heart-rate monitors is assumed to be due to the very objective nature of this statistic. Trackers do not need complex formulas to compute for heart-rate, all they have to do is measure it directly.

Accuracy of Calorie Counting

While trackers are excellent in measuring step counts and heart-rates, this does not seem to be the case for calorie counting. The aforementioned study compared calorie counts in trackers to a system that measures carbon dioxide and oxygen to determine the rate of metabolism.

The results showed that trackers were off 27 to 93% of the time. Another study, done by the National Institute of Health and Nutrition in Japan, also compared tracker calorie data to a sophisticated metabolic monitoring system that traces isotopes in the subjects’ urine. Some devices overestimated calorie burn while some downplayed the measurement.

Very few devices can count calorie burn accurately, and none are consistently accurate. Even the best trackers are wrong 27% of the time, a surprisingly high rate considering that these are the best in the market. This calorie counting confusion is said to be due to the rather complicated method used to calculate calorie burn.

After all, calorie burn is not as objective as heart-rate; the latter can be directly measured while the former can only be inferred from other data, like steps taken, distance traveled, etc.

Each tracker uses its own algorithm to compute for calorie burn, and most use a specific formula that requires users to input personal data such as height, weight, age, and gender. Experts say that it’s possible that this formula is not applicable to every single individual, and that is why calorie counters could be way off.

Some studies say that waist-based trackers are better at calorie counting compared to wrist-based wearables, but they also say that even these waist-based devices are not consistently accurate. Another study done by University of Arizona researchers found out that fitness trackers are also unable to correctly calculate energy expended on light activities (like simply standing or cleaning). The fitness trackers tested performed best when capturing brisk aerobic activity, such as walking or jogging, as opposed to light activities or resistance exercises.

This shows us the limitations that activity trackers still have; even technology is not perfect after all. Even the best trackers in the market cannot give on-point data all the time. So, should this discourage us from using activity trackers? Should we just throw our wearables away? Experts say that trackers can still fulfill their purpose despite these limits.

Is Accuracy Important?

Though activity trackers could be used by professionals to gather real-time data on the users’ bodies, this is not the primary goal of these devices. Trackers are made to encourage people to be more active and live healthier lives. Trackers achieve this by providing motivation in the form of data that the users can use to set and achieve fitness goals.

If this is the case, then real medical accuracy is not the point in the devices, but instead what trackers can really offer are relative measurements. Comparing your calorie burn rate today to that of yesterday could still tell you how much more effort you poured in today, or how much you slacked off for that matter. You can still use trackers to set short-term, achievable goals, and you can still use the data that it provides for simple referencing at the very

Trackers should not be viewed as all-knowing devices that could tell you every single working of your body, but rather as simply a tool in your effort to become healthier and more active. The motivating power that trackers have is not invalidated by their lack of accuracy in counting calories burned.

These wearables can still help you to overcome bad habits and establish a personal exercise program. You can still use them to tell the world how dedicated you are to be physically fit. They can still turn the arduous task of losing weight into a fun game that you can play with your friends.

Also, the flaw of trackers in counting burnt calories does not erase the fact that it is already doing well in terms of step-counting and heart-rate. These two functions can already help a lot for people who simply want to keep their day-to-day lives in check.

Yes, the technology used to craft activity trackers is still not perfect, but it’s undoubtedly getting better. After all, we already have step counting and heart-rate monitoring right, so who knows how much trackers can progress in the years to come.


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