IF you’ve got your fitness tracker ready to chart your victory at the London Marathon on Sunday, you could be in for a bit of a shocker.
New analysis from Which? has found that some of the most popular trackers are wildly inaccurate.
In fact, one tracker underestimated the distance of a full marathon by 11 miles.
Researchers have been looking into 118 fitness trackers from big brands including Apple, Fitbit and Garmin.
Surprisingly, the worst offender was runners’ favourite Garmin, whose Vivosmart 4 underestimated a full marathon by 41.5 per cent.
That means that if you were to run the London Marathon (26.2 miles) wearing a Vivosmart 4, you’d actually have run an extra 11 miles by the time the watch had told you that you’d run 26.2 miles.
To illustrate the difference in distance covered using the London Marathon route, runners relying on this model would cross the finish line at Buckingham Palace, carry on running south and continue all the way to South Croydon.
At the other end of the spectrum, anyone wearing a Huawei Watch 2 Sport could find themselves finishing a whole seven miles short of the finish line – underestimating the distance by 28 per cent.
It was the most inaccurate watch reviewed.
Apple fared relatively well in the Which? tests, with the smallest difference between its most and least accurate models.
Least reliable trackers for running
These were all tested on a marathon course. At the end, each should have registered 26.2 miles.
Here’s what they actually showed:
Garmin Vivosmart 4: 37 miles (-41.5 per cent)
Samsung Gear S2: 36.2 miles (-38 per cent)
Misfit Ray: 34.6 miles (-32 per cent)
Xiaomi Amazfit Bip: 34 miles (-30 per cent)
Fitbit Zip: 30.9 miles (-18 per cent)
Polar A370: 30.9 miles (-18 per cent)
Apple Watch Series 3 (GPS): 22.8 miles (+13 per cent)
Huawei Watch 2 Sport: 18.9 miles (+28 per cent)
The best Apple model – the Apple Watch Series 1 – only overestimated distance by 1 per cent.
Which? testing has also shown considerable variations for tracking running distance within brands too, suggesting that buying a fitness tracker from a well-known or reliable brand doesn’t guarantee accuracy.
Garmin, for example, produced several good models, including the Vivoactive 3 which was 100 per cent accurate.
But the Garmin Vivosmart 4 underestimated distance by 41.5 per cent, and the Garmin Vivosmart HP overestimated by 30 per cent.
Natalie Hitchins, Which? head of home products and services, said: “Running a marathon is no mean feat, so runners who are putting in the months of training beforehand will want to know their fitness tracker is trustworthy, and not jeopardising their finish times.
“Our tests have found a number of models from big-name brands that can’t be trusted when it comes to measuring distance, so before you buy, make sure you do your research to find a model that you can rely on.”
A spokesperson from Garmin said that the Vivosmart 4 is an “all-round smart fitness activity tracker used to monitor wellness, health and fitness for a range of activities”.
“As the Vivosmart 4 does not incorporate GPS, our recommendation for someone who is running long distances such as a marathon, would be to choose a tracking device such as our Forerunner range which is dedicated to running and incorporates GPS.”
A Huawei spokesperson told The Sun: “The test results may vary depending on testing conditions such as indoor and outdoor environments and individual runner variances.
“With regards to running indoors, as this particular test was carried out on a treadmill, the algorithm of Huawei Watch 2 Sport calculates the user’s stride length from the acceleration sensor data while running at different speed.
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“Watch 2 Sport tracks the distance by evaluating the data of user’s stride length and steps.
“The results may deviate owing to individual runner variances.”
“Huawei is fully committed to providing accurate and better running experience for users, and we will continuously work to optimise our existing and new generation products.”
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