Background: Remote monitoring of physical activity in patients with chronic conditions could be useful to offer care professionals real-time assessment of their patient's daily activity pattern to adjust appropriate treatment. However, the validity of commercially available activity trackers that can be used for telemonitoring purposes is limited.Objective: The purpose of this study was to test usability and to determine the validity of four consumer-level activity trackers as a measure of free-living activity.
Methods:A usability evaluation (study 1) and validation study (study 2) were conducted. In study 1, ten individuals each wore one activity tracker for a period of 30 days and filled in a questionnaire on ease of use and wearability. In study 2, we validated four selected activity trackers (Apple Watch, Misfit Shine, iHealth Edge and Yamax Digiwalker) against the reference standard (Actigraph GT3X) in 30 healthy participants for 72 hours. Outcome measures were 95% limits of agreement (LoA) and bias (Bland-Altman analysis).Furthermore, median absolute differences (MAD) were calculated. Correction for bias was estimated and validated using leave-one-out cross validation.