Is your fitness tracker lying to you?


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SALT LAKE CITY — It's a very common phrase in the office, at the gym, even in your neighborhood: "Gotta get my steps today!"

But is your fitness tracker counting correctly? The KSL Investigators decided to test three of the most popular brands — the Fitbit Charge 2, the Samsung Gear Fit2 and the Garmin Vivosmart HR. All three retail for under $200.

The next step was to recruit 10 KSL employees and take them and the fitness bands to the experts at The Orthopedic Specialty Hospital, or TOSH, where they have the equipment to measure just how accurate the trackers really are.

The test

TOSH has the team and the equipment that can analyze distance, calories, heart rate and steps. After getting their height and weight, each of the "subjects" strapped a heart rate monitor to their chest, hopped on a research treadmill that measures steps and distance, and put on a breathing tube that monitors oxygen consumption.

"Nobody told me about a face contraption," said KSL TV reporter Debbie Dujanovic. "That was not in the memo."

With testing equipment in place, each person took turns strapping on all three fitness bands and walking or running on the treadmill for 10 minutes.

After everyone went through the test, it was time for Dr. Jim Walker, Sports Science director at TOSH, and his team to crunch the numbers. What they found results that varied depending on the measurement they were using.

Results

1. Steps

With one subject, the Fitbit counted 1061 steps while the lab counted 1061 steps. It was 100 percent accurate. But with another subject, Fitbit counted 1101 steps while the lab counted 1319 steps. That's more than 200 steps off in just 10 minutes.

"It depends on the person, on how they wore it, how they moved, on how accurate the individual device was," Walker explained.

As for steps overall, the Fitbit was 95 percent accurate on average. Sounds pretty good, but not as good as the Samsung, which was 97 percent accurate, or the Garmin, which came out on top with 98-percent accuracy.

When it comes to counting steps, a KSL TV investigation showed the Garmin Vivosmart HR generated the most accurate results. (Photo: KSL TV)
When it comes to counting steps, a KSL TV investigation showed the Garmin Vivosmart HR generated the most accurate results. (Photo: KSL TV)

2. Distance

With all three trackers, distance was less accurate than steps. Both the Fitbit and the Garmin measured one subject running almost 1.2 miles while the lab clocked him at 1 mile even.

"It's a 20 percent difference," Walker said. "You go 5 miles and it's going to tell you that you went 6 miles. So that's a pretty large error rate."

This time, it was the Garmin in third with 87 percent, the Fitbit in second with 88 percent, and the Samsung with the best accuracy on average, but only at 89 percent.

When it comes to measuring distance, a KSL TV investigation showed the Samsung Gear Fit2 generated the most accurate results. (Photo: KSL TV)
When it comes to measuring distance, a KSL TV investigation showed the Samsung Gear Fit2 generated the most accurate results. (Photo: KSL TV)

3. Heart rate

"I want to get out and get sweaty and get my heart rate up for 30 to 45 minutes," KSL Newsradio host Alex Kirry said. "That's what I want out of my workout."

All three devices tended to overestimate maximum heart rate, but the Fitbit was the most off. The lab showed one subject peaked at 93 beats per minute (BPM); the Fitbit had him at 135.

"If the heart rate device that you're using to measure it is that far off, then you're not achieving the training effect that you're looking for during that workout," Walker said.

For heart rate measurements, the Fitbit came in third with 89 percent accuracy on average. The Garmin and the Samsung were a very close first and second, with the Garmin at 93-percent accuracy and the Samsung with 94-percent accuracy.

When it comes to measuring heart rate, a KSL TV investigation showed the Samsung Gear Fit2 generated the most accurate results. (Photo: KSL TV)
When it comes to measuring heart rate, a KSL TV investigation showed the Samsung Gear Fit2 generated the most accurate results. (Photo: KSL TV)

4. Calories

Last but not least, everyone's favorite measurement: calories.

"I want to eat more cupcakes and pizza, so I want to know if I match up to what it says I can eat," said KSL TV reporter Alex Cabrero.

You remember that face contraption? That's how Walker's team measures calories. The fitness bands, however, use a combination of your physical activity, your gender, age, height and weight.

All three bands, according to TOSH technicians, underestimated calories burned on one test subject. But the Samsung was the most off, showing Cabrero burned only 83 calories while the lab said he burned 144. It was third place with only 58-percent accuracy. The Garmin was second with 79-percent accuracy, and the Fitbit fared the best this time around, with 91-percent accuracy.

When it comes to measuring calories burned, a KSL TV investigation showed the Fitbit Charge 2 generated the most accurate results. (Photo: KSL TV)
When it comes to measuring calories burned, a KSL TV investigation showed the Fitbit Charge 2 generated the most accurate results. (Photo: KSL TV)

Conclusion

"Whether they're plus or minus from reality is kind of immaterial for the general fitness exerciser, but it's a way to track," Walker said.

Bottom line: None of the fitness trackers tested were 100 percent accurate — but maybe they don't need to be.

"It keeps me accountable," said KSL TV photographer Mark Wetzel.

"It motivates me to meet my goal every day," said Candice Madsen, special projects producer at KSL TV.

"It reminds me, 'Oh yeah, I've gotta get my steps in today,'" Dujanovic said.

"You feel really guilty at the end of the day when you look down and it's like 3,000 steps, and you're like, 'Ah! I've got to go walk some more,'" Cabrero said.

The bands are just a good reminder to keep counting.

KSL reached out to Fitbit, Garmin and Samsung for comment on this story. Fitbit was the only company that responded, sending this statement:

“Fitbit trackers are designed to provide meaningful data to our users to help them reach their health and fitness goals, and are not intended to be scientific or medical devices. Overall, the success of Fitbit products comes from enabling people to see their overall health and fitness trends over time — it’s these trends that matter most in achieving their goals.”

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