Fitness trackers ‘wildly inaccurate’ speaking of counting calories burnt during exercise

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Woman jogging in park

A study has claimed fitness trackers are wildly inaccurate

A study found brands such as Fitbit and Jawbone were up to 40 per cent wrong during strenuous work-outs. Fitness trackers are wildly inaccurate when it comes to counting calories burnt off during exercise , according to new research.

Three fitness trackers significantly underestimated the calorie burn for household tasks and all four overestimated calorie burn during energetic exercise.

Some 115 million wearable trackers and smart watches were sold worldwide last year, according to research firm Gartner.

Fitbit, the most popular brand sold 21.4 million devices and Apple about 12 million of its watches which count calories burnt off during exercise.

Fitbit One
Fitbit is the most popular fitness tracker and has sold 21.4million devices

Fitbit is currently fighting a class action in the US over claims that two of its trackers misreported heart rates, potentially putting people’s lives at risk.

Read more: 10 best fitness trackers and bands for under £50

US researchers from Ball State University in Indiana tested two wrist-worn trackers, the Fitbit Flex and the Jawbone UP24 and two hip-worn trackers, the Fitbit Zip and Fitbit One, on 30 adults taking part in a variety of fitness classes.

The Apple watch also counts calories burnt off during exercise

Volunteers were hooked up to a metabolic analyser to measure their calorific outputs.

All the trackers were accurate to within eight per cent of the calorie count while doing light exercises.

For exercise designed to mimic household activity, all the trackers except the Fitbit Flex significantly underestimated energy expenditure by between 27 per cent and 34 per cent.

Fitbit is one of the must-have items this Christmas

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None of the trackers accurately measured calories burn off during energetic exercise, with some out by up to 40 per cent.

Researcher Alexander Montoye said: “Fitness trackers began to take off in popularity in 2013, but we didn’t really know how well they worked.

“We found irregularities in several areas, but still for a lot of people they can be a good motivational tool.

The study does say fitness trackers can still be a good motivational tool

“There are benefits to constantly tracking what you do.”

A spokesman for Fitbit said: “Fitbit trackers are designed to provide meaningful data to users to help them reach their health and fitness goals and are not designed to be scientific or medical devices.”

A spokesman for Jawbone said the UP24 was a “relatively old product” which used older technology.

It said the UP platform was designed to “engage, motivate and change people’s behaviour to improve well being”.

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