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Wearable technology

Christmas calories – should you trust your fitness tracker?

The average Briton will consume more than 5,000 calories on Christmas day alone, according to research by Wren Kitchens. So when you’re trying to burn off that festive excess, you’ll want to know that your fitness watch or tracker is giving you the right information. The research by Wren Kitchens surveyed 2,000 people about their typical Christmas dinner, and found that the average person eats as many as 5,240 calories in just one day.

With such indulgence, it’s understandable that some people want to begin a health kick to start the new year – and a fitness watch or tracker could provide the perfect motivational tool to help you get fit.

If you want to keep an eye on how many calories you’ve burned, which a lot of people do after the festive period, then most trackers will provide you with this information. Or if distance is the way you’d like to track your fitness, there are plenty of trackers that can do that, too. But we’ve found some fitness watches and activity trackers that greatly overstate or understate your data.

Here we reveal the dramatic differences between actual calories burned and what your tracker tells you. And we’ve worked this out based on your favourite festive treats. Best Buy fitness watches and activity trackers[1] – find out which models aced our accuracy tests

Calories burned – what we’ve found

Some trackers simply aren’t accurate enough when it comes to tracking calories burned.

One device overstated this by a whopping 105% during our testing, so you’ll think you’ve burned more than twice the number of calories that you actually have. This means that instead of killing enough calories for four glasses of Christmas prosecco[2], you’d only have burned off enough for two.

Another device understated calories burned by 28%, which means you’re actually burning off more than it says you have. If you want to indulge in our Best Buy mince pies[3], this tracker would tell you that you’d worked off enough for less than three, when you could actually scoff four (it is Christmas, after all).

It’s not all bad news, though, as we’ve found some trackers that measured calories burned with almost no error.

To find out more about the way we test fitness watches and trackers for accuracy, head over to the how we test page[4].

Distance tracking – what we’ve found

According to the Wren Kitchens research, you’d need to run two marathons to burn off that 5,000-calorie festive feast, but we’ve found trackers that failed to track distance accurately, too.

While we don’t recommend running two marathons, and certainly won’t be trying this ourselves, the graph below shows how far you would have run before the most inaccurate trackers from our tests tell you that you’ve reached the two-marathon mark.

If you want to track distance while out running, then built-in GPS is a good feature to look for, as it means you can leave your phone at home and still track your route.

See our pick of the top five fitness watches and activity trackers with built-in GPS[5].


  1. ^ Best Buy fitness watches and activity trackers (
  2. ^ Christmas prosecco (
  3. ^ Best Buy mince pies (
  4. ^ how we test page (
  5. ^ top five fitness watches and activity trackers with built-in GPS (

New Apple Watch band can predict heart problems

The Apple Watch’s latest band isn’t luxury leather or a Milanese loop, it’s unassuming plastic, but the sensors inside it could save your life. The KardiaBand, made by AliveCor, works together with the tracker already built into the Apple Watch 3[1] to detect dangerous arrhythmia, such as atrial fibrillation, which can lead to a stroke. Built-in sensors constantly monitor the rhythm of your heart and will notify you with an electrocardiogram, or ECG, reading when they detect anything unusual.

Pressing your thumb or finger to the metal panel on the band will give you an on-the-spot ECG reading. Already FDA approved in the US, the KardiaBand is now available to buy in the UK from AliveCor’s website for GBP199. There is also the KardiaMobile, which works the same way as the band, but doesn’t require an Apple Watch.

It loses a few features in the process, but it’s half the price at GBP99. Best Buy fitness watches[2] – track your exercise and heart rate with a top-rated fitness watch.

What else can the KardiaBand do?


The KardiaBand has a range of other features, but whether you can access them depends on your subscription level. There are basic and premium subscriptions.

Basic is free and premium is GBP10 per month or GBP100 for the year. When buying the KardiaBand you get a free 30-day trial for the premium subscription and you can cancel at any time. Interestingly, in the US, a premium subscription is required.

The table below shows the difference between the two.

Feature Basic Premium Records heart rhythm anytime Yes Yes Instant ECG analysis Yes Yes Detect normal heart rhythm of atrial fibrilation Yes Yes Email and print ECG recordings Yes Yes Monthly reports for your doctor No Yes Blood-pressure tracking No Yes Weight and medication tracking No Yes Unlimited cloud storage No Yes SmartRhythm monitoring for Apple Watch No Yes

Unfortunately, in the UK blood-pressure tracking isn’t set up, but all of the other features are there. SmartRhythm combines the data collected by the band and the Apple Watch to predict your heart-rate pattern. If the prediction differs from your heart rate then SmartRhythm will recommend you do an ECG.

AliveCor says that ECGs captured during these irregular rhythms can help better manage your heart health.

Send your data to a doctor

The monthly reports can be forwarded to your doctor free of charge, or you can pay GBP5 to have your data sent to a cardiologist for analysis. This charge is separate from the subscription, and you don’t need to be a premium member to have an expert take a look at your ECGs. You will receive a response within 24 hours.

Should anyone not use it?

Not quite – you shouldn’t use the KardiaBand if you have an ICD or a pacemaker, and the band isn’t designed for kids.

Torn between wearables?

Find out whether to buy a smartwatch or a fitness tracker[3].


  1. ^ Apple Watch 3 (
  2. ^ Best Buy fitness watches (
  3. ^ smartwatch or a fitness tracker (

Apple Watch Series 3 versus Samsung Gear Sport

The Apple Watch Series 3 GPS and Samsung Gear Sport are two of the latest devices from smartwatch giants Apple and Samsung but, in this battle of the heavyweights, who comes out victorious? The results are in, and we can tell you the top smartwatch contender. This pair of smartwatches enter the metaphorical boxing ring with similar prices – there’s only GBP30 between them.

The Apple Watch Series 3 GPS[1] (38mm) is the pricier of the two and costs GBP329, while the Samsung Gear Sport[2] is GBP299. If you want the larger-faced 42mm Apple Watch Series 3 GPS, you’ll need to spend GBP359 – GBP60 more than the Samsung. They’re both health and fitness focused, but have a full range of smart features too.

In terms of key specs, how do they match up – and is there anything that sets these two apart? Below we take a look at exactly what each has to offer. Best Buy smartwatches[3] – find out which models beat the competition in our tough tests.

Apple Watch Series 3 GPS (38mm) Samsung Gear Sport OS compatibility iOS Android & iOS Display size (mm) 36 30.5 Display resolution (pixels) 340 x 272 360 x 360 Weight (g) 50.24 66 Dimensions (mm) 38.6 x 33.3 x 11.4 44.6 x 42.9 x 11.6 Battery life claim 18 hours Four days


They could barely be more different to each other in terms of looks.

The Apple Watch Series 3 has the rectangular bezel that the range has become known for, while the Samsung Gear Sport has a round watch face sat on a rounded-square surround, plus a rotating bezel. When it comes to the size of the case of each watch (including the bezel and measured diagonally), there’s very little in it. The Samsung Gear Sport feels a little bulkier, mainly due to the rounded-square surround of the face, and the fact that it’s heavier than the Apple Watch: the Gear Sport tips the scales at 66g, against the 50g Apple Watch Series 3.

You’ll be wearing these devices every day, so you want to be able to customise the look to suit you. The Apple Watch Series 3 GPS is only available with an aluminium bezel, unlike the Cellular version which can also be bought in stainless steel, with variation in silver, black or rose gold. It comes with a silicone sports band as standard, which comes in silver, pink, grey or black.

You can then choose from a range of bands, including woven nylon, leather or stainless steel, although these cost extra. The Samsung Gear Sport is only available with a blue or black silicone band.

Smart features

These are both advanced devices, and will let you receive and respond to texts, calls, emails, social media notifications and calendar alerts straight on your wrist. Neither have built-in LTE connectivity, unlike the Apple Watch Series 3 GPS + Cellular and the Samsung Gear S3.

When it comes to on-board storage for storing apps and music, the Watch is the winner with 8GB versus the Gear Sport’s 4GB. While they both have a raft of smart features, what’s important is how they deal with them. One of these smartwatches scored five stars for the smooth way it manages smart notifications, and the ease with which you can deal with these.

Health and fitness tracking

Both devices have plenty of on-board sensors for health and fitness tracking, including built-in GPS and a heart-rate monitor, plus a water resistance rating of up to 50 metres.

They will both track steps, distance covered and calories burned, as well as a wide range of exercises. Using the Gear Sport, you can set goals for steps taken, floors climbed, calorie consumption, and even water or caffeine intake. The Watch only lets you set a move goal, which is based on the number or calories burned through an activity.

Both watches will notify you when a goal is met, and you’ll get an encouraging message such as ‘good work’ too. You can add third-party apps for particular fitness tracking functionality, such as Strava or MapMyRun. The App Store has the advantage over Samsung’s Tizen when it comes to the fitness apps available – there’s still a lot of choice and you’ll find most of the well-known health and fitness apps, but Apple has far more.

One health metric that the Apple Watch doesn’t track is your sleep. Given the battery life claims, you may well be charging your device overnight anyway, but this feels like a bit of an oversight considering even basic fitness trackers can capture sleep data. We know that the accuracy of health and fitness tracking data is important, as it helps you to track your improvements.

But how did these devices perform in our tough fitness tracking accuracy tests? We reveal all in our full reviews. More interested in fitness?

Find out whether to buy a smartwatch or a fitness tracker.[4]

Battery life

In this contest, the Samsung Gear Sport delivers a knockout punch to the Apple Watch Series 3.

Despite the number of features on offer, Samsung claims you’ll get around four days of battery life per charge, while the Series 3 promises just 18 hours – meaning you’ll need to charge it once a day, depending on usage.

To find out how both devices performed in our full testing, you’ll need to check out our full Apple Watch Series 3 GPS[5] and Samsung Gear Sport[6] reviews.


  1. ^ Apple Watch Series 3 GPS (
  2. ^ Samsung Gear Sport (
  3. ^ Best Buy smartwatches (
  4. ^ smartwatch or a fitness tracker. (
  5. ^ Apple Watch Series 3 GPS (
  6. ^ Samsung Gear Sport (