title: Exploring the usability of a mobile app for adolescent obesity management.
abstract: BACKGROUND
  Obesity is a global epidemic. Behavioral change approaches towards improving nutrition, increasing physical activity level, improving sleep, and reducing sitting time are recommended as best practices in adolescent obesity management. However, access to evidence-based treatment is limited and portable technologies such as mobile apps may provide a useful platform to deliver such lifestyle interventions. No evidence-based validated app exists for obesity intervention; therefore, a novel mobile app (Reactivate) was developed for use in the Temple Street W82GO Healthy Lifestyles Program (W82GO).
  
  
  OBJECTIVE
  This study aimed to test the usability (technical effectiveness, efficiency, and user satisfaction) of the Reactivate mobile app in obese adolescents.
  
  
  METHODS
  Ten adolescents (7 males and 3 females, aged 12-17 years) who had been treated for obesity (>98th percentile for body mass index) at the Temple Street Children's University Hospital were recruited. Participants were given 8 tasks to complete in order to test the technical effectiveness of the app. A research assistant timed the user while completing each task in order to test the relative user efficiency of the app (time-on-task). The tasks fell into 5 categories and required the user to enter personal settings, find and answer surveys, create a message, use the goal setting feature, and enter details regarding their weight and height. In exploration of user satisfaction, each participant completed the standardized software usability measurement inventory (SUMI), which measures 5 aspects of user satisfaction: efficiency, effect, helpfulness, controllability, and learnability. Descriptive statistics were used to explore the mean relative user efficiency and SUMI scores.
  
  
  RESULTS
  Mean age was 14.26 (SD 1.58) years. All adolescents completed each of the tasks successfully. The mean relative user efficiency scores were two to three times that of an expert user. Users responded that they would use Reactivate to monitor their growth over time, for motivation, and for goal setting. All users described Reactivate as an important mobile app.
  
  
  CONCLUSIONS
  Our study describes the usability of a mobile app used in adolescent obesity management. Adolescents found Reactivate easy to use and their SUMI results indicated that the app scored high on user satisfaction. Usability testing is an important step towards refining the development of the Reactivate app, which can be used in the treatment of obesity. The study on the clinical efficacy of the Reactivate app is currently underway.
authors.affiliation: Department of Physiotherapy, Temple Street Children's University Hospital, Dublin, Ireland. omalleyg@tcd.ie.
authors.forename: Grace
authors.initials: G
authors.lastname: O'Malley
authors.forename: Grainne
authors.initials: G
authors.lastname: Dowdall
authors.forename: Amanda
authors.initials: A
authors.lastname: Burls
authors.forename: Ivan J
authors.initials: IJ
authors.lastname: Perry
authors.forename: Noirin
authors.initials: N
authors.lastname: Curran
keywords: adolescent; mobile health; obesity; participatory health care; usability testing
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