Activity trackers are all the rage at the moment. You may have friends and family that have one, or perhaps you’ve been tempted to pick one up yourself. They come in lots of different forms, ranging from standalone movement trackers, to more comprehensive gadgets that also track your heart rate and sleep patterns while functioning as a watch. There are smartwatch and smartphone apps that also perform some of these functions. Some are devices that are marketed to people wanting to make sure they’re doing the minimum amount of exercise necessary to meet their health and weight loss goals, while others claim to be designed with more serious athletes in mind. Are any of them worth the money, or would you be better off saving it for your next pair of running shoes?

There are two questions we need to explore here. The first is to do with the technology itself. Does it do what it claims? If your Fitbit tells you that you’ve walked 9587 steps, how accurate is that? Do the heart rate trackers give you accurate information that you can use when you’re writing your next training plan? Or are they just giving you a false sense of certainty?

The second question is more about how you use the technology. Even if we’re recording accurate data, does tracking all these things really help you to be more active, keep up with your fitness goals, or monitor your training better? Will it give you better results, or is it just a distraction from more important things you could be focusing on?

Let’s look at these in turn.

Accuracy

I like to focus mostly on careful scientific studies in these articles, but when I was researching this one I came across several nice, simple (though unscientific) tests that journalists have done to compare different brands of fitness tracker. One simply wore ten different trackers at the same time, and then compared the numbers they gave him. As you can see, there’s a lot of variation there – and interestingly, when challenged about this, representatives from the manufacturers in question admit freely that the measurements their devices give should be taken with a pinch of salt. They claim that the useful thing is having a “relative” measure of activity: if you’re doing more today than yesterday, that’s a good thing – even if you may not actually be achieving the 10,000 steps your device claims you did. I’ll leave it to the reader to decide whether that position is consistent with the impression given by their advertising material.

Scientific reviews come to similar conclusions: the results you get from these devices have a reasonable correlation with those measured to a clinically accurate standard, but shouldn’t be taken as gospel. Looking a bit more closely, some devices are more accurate than others, and your activity tracker is rather better at counting steps than telling you how many calories you’ve burned.  

How about the devices that track your heart rate? Heart rate monitors worn on the wrist simply don’t perform as accurately as those that use a chest strap. In general, they don’t do too badly when you’re at rest, or at a steady state, but when you’re using them to monitor your heart rate for a workout, the inaccuracy can really start to matter. If you’re thinking of using your activity tracker to give you accurate data for your HIIT workout, for example, then you’re likely to be disappointed.

Usefulness

Although not perfect, the accuracy level of commercially available fitness trackers may be high enough to be worthwhile. But is all that data really useful? Do they help people to get fitter and lose weight?
So far, the evidence seems to suggest not. In one recent study, activity trackers proved less useful for sustaining weight loss than simply telling participants to monitor their level of activity themselves. Another showed that participants using a fitness tracker showed a small increase in their weekly activity while they were being paid a bonus for it, but quickly returned to baseline levels once the bonus ended. What’s more, the small increase in activity levels didn’t translate to any meaningful change in any of the health outcomes being measured by researchers.

Of course, when it comes to using the information from these devices, individual mileage will vary. Even if most users don’t get much benefit in practice, it might still work as a handy motivational tool for others. (Bear in mind, though, that we’re less likely to be an exception to the rule than we think we are.)
What about for more serious athletes? Perhaps you want your fitness tracker not to check you’re achieving a minimum number of steps each day, but to keep tabs on your exercise data and help plan your training better. For runners and cyclists, there are GPS trackers which can measure the distance you’ve travelled and calculate speed. That’s undeniably a handy thing. If that’s what you’re looking for then there are dedicated devices that will do this, but the basic function can also be performed by a cheap smartphone app.

Maybe you’re trying to avoid doing too much, rather than too little. Here’s where we run into the limitations of available research. It’s possible that the extra data might be useful to some – but equally, the gadget might prove yet another technological distraction from the simple but effective training methods that we know to be effective. It seems likely that low tech monitoring of training loads – such as the good, old fashioned “rated perceived exertion” (RPE), requiring nothing more than a pen and paper – are perfectly adequate for most of us.

The verdict: mostly FALSE. If you love shiny new gadgets, and you have money burning a hole in your pocket, then it’s just possible that you might be able to find a use for one of these devices. For most of us, though, it’s probably just an unnecessary distraction.