Exploring the usability of a smartphone application to monitor fatigue and activity for people with acquired brain injury.

Background: Fatigue after acquired brain injury (ABI) leads to detrimental changes in ABI survivors' daily activities and participation. There is a need to capture individual's experience of fatigue as it happens, to better support self-management of fatigue. Study aims: To investigate the usability of a real-time tracker of fatigue and activity (using ecological momentary assessment delivered by a smartphone application) and the feasibility of capturing activity and environmental factors using phone sensors. Methods: Participants wore an activity monitor and completed up to eight surveys a day on a smartphone app, for 6 days, completed the system usability scale (SUS) and were interviewed on their views of using the app. Interview transcripts were analysed using qualitative content analysis. Agreement between data from the phone's sensors and the activity monitor was analysed using Kappa statistics. Results: Seven participants completed between 11 and 58 surveys. Mean score on the SUS indicated good perceived usability of the app. Phone sensors did not reliably capture physical activity or background noise. Participants found the app easy to use and perceived self-monitoring to help their understanding of fatigue. A fatigue-tracking app may be acceptable to ABI survivors and has potential to aid self-management of fatigue.