Smartphone tracking of physical activity is now more accurate

An interdisciplinary team of scientists at Northwestern University is making it easier for physicians to collect data and design treatment plans for people who have difficulty with physical activity and movement, such as those with Parkinson's disease.

Physical activity tracking apps on a smartphone can detect a person's moment-to-moment physical activity such as walking, sitting or standing. But studies have shown that where a person carries their smartphone can affect the accuracy of the tracker.

Using data from a new Northwestern Medicine study, researchers developed an algorithm that when used with an activity tracking app can predict the location of the phone at any time. "While it remains true that smart phone activity trackers are the most accurate when the phone is placed in the pocket or on a belt, with this algorithm we can provide an estimate of error associated with other locations where the phone is carried," said Konrad Kording, PhD, associate professor of physical medicine and rehabilitation and principal investigator of the study.

Most women, for example, carry their cell phones in a purse, while most men carry theirs in a pocket or on a belt. And during the day many people often change how and where they carry their phones. The new algorithm takes all that into consideration to keep the tracker as accurate as possible.