SMS reminders to increase accelerometer wear-time: a within-trial RCT comparing persuasive messages

Abstract

Background: Increasing accelerometer wear-time enhances the reliability of outcomes in physical activity research. Literature on persuasion suggests increased compliance with requests supplemented by a rationale. This study tested whether providing a rationale raises accelerometer wear-time. Methods: A within-trial RCT was conducted during baseline data collection in a school-based physical activity intervention trial. Of 186 total participants (mean age=18.6), 97 (52%) opted to receive daily SMS reminders to wear their accelerometers. These 97 participants were then randomised to receive either succinct reminders or reminders that additionally included a rationale. Findings: No significant difference in wear days was observed between those receiving SMS reminders (M=4.9, SD=2.2) and those not (M=4.4, SD=2.5) (p=0.67). Mean wear days did not significantly differ between the succinct reminder group (M=4.8, SD=2.3) and the rationale group (M=5.0, SD=2.0) (p=0.82). Discussion: Additional reasons may be unnecessary for participants already motivated to wear an accelerometer. Selection bias might explain why receiving reminders was not associated with increased wear time.