Do fitness trackers really work?

By Joel Werner and Tegan Osborne.

Fitness trackers are the accessory of the moment for the aspirationally active — you can see them dangling from wrists and pinned to belts everywhere.

Figures suggest about one in five of us use some form of wearable technology.

These devices claim to track everything from steps to sleep. But does the science stack up?

Market research shows that up to 50 per cent of people stop using their wearable device within 12 months.

According to Dr Mitesh Patel, an Assistant Professor of Medicine and Healthcare Management at the University of Pennsylvania, the people who are mostly likely to see benefits from using a fitness tracker are those who are already motivated and engaged in their health.

“Those individuals tend to be able to take this data and literally run with it,” he said.

“Whereas the people who have chronic conditions or are obese or have diabetes, for those folks giving a device is often not enough.”

But if you’re not one of those people who already enjoys running at the crack of dawn and eating salad, there is still hope.

Dr Patel said technology needed to be paired with “effective behaviour change strategies” in order for people to improve their health.

So he took people who were overweight or obese and examined the effect of a financial incentive on their motivation to achieve a daily goal of 7,000 steps.

Group support and personal accountability key

Those in the control group, who were given no financial incentive, achieved their goal about 30 per cent of the time.

The next two groups — one which received $1.40 incentive each day the goal was reached and the other which could win up to $50 each time in a lottery — both achieved their goal 35 to 36 per cent of the time.

But a fourth group, who stood to lose $1.40 each time a target was missed, achieved their goals 45 per cent of the time.

Dr Patel said this was because we tended to respond to losses more than gains.

“We are often engaged based on our emotions, so we hate the feeling of regret, not being able to collect a reward that we could have gotten had only we tried a little bit harder,” he said.

In another study, Dr Patel also found there were benefits to working with a group — synching your device with friends or family and getting competitive.

“You need some kind of individual reinforcement, but you also need someone there to support you, you need to feel accountable to a team-mate, a family member or a friend,” he said.

“That combination of social structure and reward incentives can really help us to achieve better outcomes than just using the device alone.”

How accurate are they?

Robert Furberg, a clinical informaticist at RTI International in North Carolina, said fitness trackers perform best when measuring steps.

“Because that’s really what this device was intended to measure,” he said.

But many of these devices then extrapolate that data, to provide figures like distance, activity intensity and calories burned.

“I tend to have this data model in my head of a series of concentric circles,” Dr Furberg said.

“At the centre you have this unit of step that is measured … So we might say, ‘Great job, you took 10,000 steps last night, because we are estimating your stride length, you have run 4 kilometres’.

“But then beyond that it’s not just you’ve taken 10,000 steps and run 4 kilometres, but that in doing so you have burned 1,500 calories.”

The problem is, the further you get away from the actual measurement of steps, the greater the likelihood of introducing some mathematical error.

You can however increase the accuracy, by putting in personal data like height, weight and calories consumed.

A University of Pennsylvania study found wearable fitness trackers were not quite as accurate at tracking steps as pedometers and accelerometers, and could be up to 22 per cent off.

Another key finding was that for the most part, smartphones with fitness apps were just as reliable as a fitness tracker.

Kelly Evenson, from the University of North Carolina, recently spent time examining key research studies into fitness trackers.

“Overall we had 22 studies… we found that most studies — both in the lab and in the field — found that steps were quite accurate from the trackers,” she said.

“We only found one study that explored distance, and distance was overestimated at slower speeds and underestimated when you are going faster, like running.”

Conversely, the studies showed that fitness trackers usually underestimated the number of calories burned.

In terms of tracking sleep, she said the devices were prone to overestimation.

But when compared to polysomnography, which is the gold standard measure of sleep, the trackers did “quite a good job”.

This post originally appeared ABC Health & Wellbeing.

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