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Fitness trackers and smartwatches to avoid if training for a marathon

You might want to choose your fitness tracker or smartwatch carefully if you’re training for a marathon. Research published ahead of tomorrow’s London marathon finds some wearables can be wildly inaccurate at clocking the 26.2 mile distance.

Essential readingTop fitness trackers and health gadgets

Which? tested 118 fitness trackers, sports watches and smartwatches across 8 brands for accuracy. The tests were conducted between May 2016 and February 2018 so do not include the newest devices. The results showed marked differences not only across brands, but also across devices belonging to the same brand.

Topping the list of wearables you might want to avoid if you’re training for the marathon is the Garmin Vivosmart 4. The popular device might be great at tracking basic activity and sleep, but it will have you running 37 miles before saying you’re at the finish line. That’s 41.5% more than the actual marathon distance or an extra 11 miles!

The Samsung Gear S2, Misfit Ray and Amazfit Bip did not fare much better. All three overestimated the distance by more than 30%. The only real surprise on this list is Amazfit Bip considering it has a built-in GPS chip which should help with accuracy.

The eight Apple watches tested performed relatively well, but the Series 3 watch was widest off the mark clocking the full marathon distance at just 22.8 miles. Oddly enough, the Series 1 watch was only 1% off the target! Go figure.

Here are the rankings of the least accurate wearables for each brand.

Wearable Marathon distance (26.2 miles) % inaccuracy
Garmin Vivosmart 4 37.0 -41.5%
Samsung Gear S2 36.2 -38%
Misfit Ray 34.6 -32%
Amazfit Bip 34.0 -30%
Fitbit Zip 30.9 -18%
Polar A370 30.9 -18%
Apple Watch Series 3 (GPS) 22.9 +13%
Huawei Watch 2 Sport 18.9 +28%
*Source: Which? – table shows most inaccurate device by brand based on distance while running

Inaccuracy may not present a problem over short distances, but it could leave marathon runners gasping for breath miles away from the finish line. If they don’t choose their wearable carefully, some athletes would not cross the finish line while others would end up running much further than they need to.

It might look something like this in an actual race!

fitness trackers and smartwatches to avoid if training for a marathon - Fitness trackers and smartwatches to avoid if training for a marathon
Image source: Which?

While the Vivosmart 4 performed worst of the lot, Garmin does have several models which are very accurate. For example, the Vivoactive 3 was 100% on the mark when calculating the marathon distance.

“The Vivosmart 4 is an all-round smart fitness activity tracker used to monitor wellness, health and fitness for a range of activities,” a Garmin spokesman said in response to the research.

“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.”

As Garmin quite rightly suggests, the best way to resolve this is to purchase a quality running watch with built in GPS. This adds bucks to the purchase price, but it helps quite a bit when it comes to accuracy.

“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,” said Natalie Hitchins, Which? Head of Home Products and Services.

“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.”

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