A new study from the University of British Columbia finds that the iPhone’s built-in pedometer can miss a tonne of your daily steps — especially when you forget to take it with you.
Researchers equipped 33 participants with iPhones and tested accuracy both under lab conditions and over three days of daily activity. The phone apps performed pretty well while participants were on treadmills in the lab, underestimating steps by between five and 9.4 per cent, which is said to be acceptable for pedometers.
But in the field, when compared to the readings produced by pedometers fixed to participants’ waists, the phone apps way off, missing an average of 1,340 steps per day or
21.5 per cent of steps.
The reason for the disparity? Participants forgot to carry their phones with them to the bathroom.
“The free-living test demonstrated large differences between the accelerometer and the iPhone step counts,” say the study’s authors, whose research was published in the Journal of Sports Sciences. “Many participants in this study reported not taking their iPhones to the washroom or other short walking breaks –as such, steps taken during these breaks would further add to the error between the iPhone and accelerometer.”
The researchers found that on the treadmill, the iPhone pedometer did better at counting steps at faster speeds, underestimating by 9.4 per cent at a pace of 2.5 km/h but only being off by less than five per cent at higher speeds.
The results show that, from a scientific perspective, at least, data coming from smartphone activity apps should be treated with caution, even if the readings are reasonably accurate overall.
“The accelerometer in the iPhone actually does a pretty good job when tested under lab conditions,” said senior author Guy Faulkner of UBC’s School of Kinesiology, in a press release. “You just have to have it on you at all times.”
Part of fitness culture everywhere, wearable fitness trackers such as the Fitbit have themselves been compared in study conditions to smartphone apps, with the smartphones producing comparable results. One 2015 study concluded that more important than the type of device, where on the body it’s worn can make a difference, with waist-worn devices producing more accurate results than wrist- or arm-worn ones.
At the same time, users may be disappointed to hear that fitness trackers won’t necessarily make you fitter. A number of studies have drawn the conclusion, including a 2016 study conducted by researchers at the University of Pittsburgh which found that the wearable devices were actually a hindrance to weight loss.
The two-year study involved 470 obese or overweight participants who were put on low- calorie diets and asked to exercise more. After six months, all participants had lost weight, at which time, half the group were given fitness trackers to monitor their progress. At the two-year mark, both groups were found to be similarly active, but where participants without fitness trackers lost an average of 5.9 kg, those in the fitness tracking group had lost an average of 3.5 kg.
The reason? Researchers surmised that viewing the readouts of their activity likely gave participants license to be less stingy with their calories. "These technologies are focused on physical activity, like taking steps and getting your heart rate up," said John Jakicic, health researcher at the University of Pittsburgh and study lead author, to NPR. "People would say, 'Oh, I exercised a lot today, now I can eat more.' And they might eat more than they otherwise would have."