Tracking physical activity: problems related to running longitudinal studies with commercial devices

The problems with inactive and sedentary lifestyles are widely recognised. People believe that activity tracking systems, such as the Fitbit, may aid them in meeting recommended levels of physical activity. Similar systems have been the subject of previous research, but many of these studies were conducted over a short-term and some results may be attributable to reactivity or novelty effects. We ran a longitudinal mixed-methods effectiveness study using the Fitbit Zip activity tracker with 50 participants. In this paper we present two main challenges experienced during this study: the unreliability of the device and a lack of engagement by some of the participants. The issues we experienced can help inform the design of future studies.