title: The fitness of apps: a theory-based examination of mobile fitness app usage over 5 months.
abstract: BACKGROUND
  There are thousands of fitness-related smartphone applications ("apps") available for free and purchase, but there is uncertainty if these apps help individuals achieve and maintain personal fitness. Technology usage attrition is also a concern among research studies on health technologies.
  
  
  METHODS
  Usage of three fitness apps was examined over 5 months to assess adherence and effectiveness. Initially, 64 participants downloaded three free apps available on Android and iOS and 47 remained in the study until posttest. With a one group pre-posttest design and checkpoints at months 1, 3, and 5, exercise and exercise with fitness apps were examined in the framework of the Theory of Planned Behavior (TPB) using a validated survey. Apps were selected based on their function from the Functional Triad. Perceived fitness was also measured.T-tests, sign tests, Fisher's exact tests, and linear and logistic regression were used to compare pre to posttests and users to non-users of the apps.
  
  
  RESULTS
  Forty-seven participants completed both pre and posttests. Individual item scores indicated no significant change pre to posttest except for decreases observed in usefulness of using apps for exercise (attitude) (-0.78, P<0.01), peer influence on exercise (subjective norm) (-0.51, P<0.05), peer influence on exercise with apps (subjective norm) (-1.02, P<0.01), perceived difficulties in exercising with apps (perceived behavioral control) (-1.29, P<0.001), and the expected frequency of exercise with apps over the next 2 weeks (behavioral intention) (P<0.0001 in a sign test). Subscale total scores indicated significant decreases in subjective norm regarding exercise (-0.72, P<0.05), subjective norm regarding exercise with apps (-1.72, P<0.01), and perceived behavioral control over exercising with apps (-2.56, P<0.01) between pre and posttest. When comparing app users (n=32) to non-users (n=15), there was only a significant difference in subscale total scores at posttest for attitude toward exercising using apps, which was significantly more favorable among users than non-users (32.3vs. 27.6, P<0.05). Fitness perception did not change over 5 months regarding cardiovascular fitness, strength, endurance, flexibility, or body composition. Technology usage attrition was desirable at 31.9%.
  
  
  CONCLUSIONS
  App usage and effectiveness appears to have a connection to usefulness (attitude) and to perceived difficulties of exercising using apps (perceived behavioral control). Exercise and exercise using apps are not influenced by peer influence (subjective norm). Intention to exercise using these particular apps decreased (behavioral intention). Those who utilized the apps were more likely to have a positive attitude about the apps. Usefulness and perceived difficulties in particular should be considered with future app development. App usefulness and ease of use may be facilitated by using health behavior theories to guide development.
authors.affiliation: School of Health Studies, Northern Illinois University, DeKalb, IL, USA.
authors.forename: Lynn Katherine
authors.initials: LK
authors.lastname: Herrmann
authors.affiliation: School of Health Studies, Northern Illinois University, DeKalb, IL, USA.
authors.forename: Jinsook
authors.initials: J
authors.lastname: Kim
keywords: Physical fitness; behavior; mobile apps; technology; theory