Smartphone pedometers underestimate steps, but valuable health tool, study says

A recent study looking at iPhone’s built-in pedometers is a step toward using the tool as a clinical intervention in improving people’s health, a University of B.C. researcher said.

Smartphones pose an opportunity for researchers to gather objective data on the public’s health and physical activity but before they can be used, the accuracy of the devices need to be tested, lead author Mark Duncan said in an interview Saturday.

“This was very much a first step to make sure that we understand what the data looks like and how well it represents the actual behaviour,” he said.

The study involved 33 participants testing the phones in regular living conditions and in a lab.

Comparing users’ step count on the iPhone pedometer with an accelerometer worn on their waists in their day-to-day life, the study found the iPhone was underestimating the number of steps by 21.5 per cent or 1,340 steps.

The phones fared better in lab tests where accuracy was within five per cent when users walked at a normal pace.

At a slow pace of only 2.5 kilometres an hour, the accuracy of the phones dropped between 7.6 and 9.4 per cent.

Duncan said the discrepancy is likely due to people forgetting to carry their phones at all times.

“If someone goes off to the washroom or to the kitchen and leaves their phone on their desk, obviously it’s not going to count those steps,” he said.

While the accuracy of the device isn’t strong enough to be a primary research tool, Duncan said the information is valuable for the average user interested in improving their health.