Q. I need to lose weight, and I’m trying to be more active. I’m thinking about getting a fitness tracker or a smartphone app to track my steps. But are they accurate?
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 suggests 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, twice for each step count, for a total of 56 trials. During the trials, the participants wore all of the following:
• On the waistband: one pedometer and two accelerometers
• Wrists: three fitness trackers
• Pants pockets: two smartphones, one running three apps and the other running one
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.
Our advice: If you’re factoring cost into your decision and you already have a smartphone, it’s less expensive to download an app than to invest in a fitness tracker.