The impact of E-diaries and accelerometers on young adults' perceived and objectively assessed physical activity

Objective E-diaries and accelerometers promise more objective, real-time measurements of health behavior. However, social-psychological theory suggests that using electronic behavioral monitoring may influence rather than just record physical activity (PA), especially when a device is novel. Design Participants (n = 146) were randomly assigned to either an accelerometer-only, e-diary-only, accelerometer + e-diary, or a no-technology control group for one week to assess how these technologies influenced PA, both perceived and actual, in young adults. Method Participants reported their PA, overall and number of discrete exercise sessions (DES) at baseline and follow-up; accelerometers provided daily step counts and e-diaries captured daily reports of PA for the active week of the study. Results Average daily steps in the accelerometer-only and accelerometer + e-diary groups did not differ nor did daily reports of PA via e-diary compared to accelerometer + e-diary group, showing that neither technology affected actual PA. ANCOVAS tested group differences in perceived PA; The accelerometer-only group had increased perceived overall PA but not DES compared to no-technology control. Conclusions Accelerometers may increase perceived overall PA, but the tested technologies did not increase DES or actual PA, suggesting that they may be viable unbiased measures of PA.