Q. I’m trying to be more active. Which are more accurate at tracking steps: Fitness trackers or smartphone apps?
A. Overall, wearable fitness trackers as well as smartphone applications do a good job of tracking physical activity, though a 2015 research letter in JAMA suggested that smartphones may have a slight edge. This small study examined the accuracy of 10 top-selling smartphone apps and devices by comparing their readings with those made by an observer who counted steps using a tally counter.
For the study, 14 healthy adults (mostly female) walked on a treadmill for 500 and 1,500 steps, repeating the exercise several times. During the trials, the participants wore all of the following:
• On the waistband: one pedometer and two accelerometers
• On the wrists: three fitness trackers
• In one pants pocket: a smartphone (Apple iPhone 5s) simultaneously running three step-tracking applications (Fitbit, Health Mate, and Moves)
• In the other pants pocket: a smartphone (Samsung Galaxy S4) running one step-tracking application (Moves)
At the end of each trial, step counts from the devices were recorded. The investigators found that smartphone readings were only slightly different—either higher or lower—from observed step counts, while fitness trackers differed more from observed counts.