British Columbia

Study finds iPhone health app miscounts your daily steps

UBC study finds smartphones health apps often underestimate the amount of physical activity exerted by users.

UBC study finds smartphones health apps often underestimates total physical activity

The iPhone's health app often undershoots the amount of steps a person takes in a day. (ubcpublicaffairs/YouTube)

Ever find yourself a few steps shy of hitting the 10,000 mark? Turns out your smartphone might be holding you back.

The popular iPhone health app isn't the most reliable personal trainer, according to a new study from the University of British Columbia.

Researchers found that the iPhone app can underestimate the number of steps taken in a day by as much as 20 per cent.

"Any time you're measuring something, there's going to be a little bit of error," said Mark Duncan, PhD candidate at UBC's School of Kinesiology and lead author of the study.

But sometimes, it's not the technology itself that's entirely to blame.

Two separate tests

Duncan's study used 33 participants and was divided into two parts: a lab test, and a test in ordinary living conditions.

In the lab, participants walked on a treadmill. Their steps were both manually counted and tracked using two iPhones — a personal phone, and a lab phone.

"At lower speeds, [the iPhones] were less accurate, missing about nine to ten per cent of steps," said Duncan.

However, the gap narrowed at speeds above five kilometres per hour, missing less than five per cent of steps, a figure that Duncan says is more in line with traditional pedometers.

iPhones tend to be more accurate at counting steps when users walk faster than five kilometres per hour — the same standard walking speeds utilized by Google and Apple maps apps. (Toru Hanai/Reuters)

A 20 per cent gap

But the greater discrepancy occurred in the second phase of the study, when participants tracked steps outside the lab.

In addition to keeping their phones on while they went about their daily routine, they also wore fixed accelerometers around their waists for three days, which tracked how fast and how far they moved.

According to the study, the iPhone underestimated the accelerometer data by an average of 21.5 per cent, or 1,340 steps per day.

Duncan says the gap is significant — but the iPhone might not be entirely to blame.

"A lot of that could be attributed to people not necessarily bringing their phones with them, or carrying them in their [backpacks] instead of on their persons — like in their hands, or in their pockets."

Leaving your phone behind when you make a trip to the bathroom, or run out to grab a coffee at work, seems to be where the error stems from, Duncan says.