Physical inactivity is associated with increased risk of co-morbidity and premature mortality. Given the rapid growth of mobile phone technology and the increasing number of users, the investigators developed an interactive mobile phone-based physical activity intervention for sedentary women. The investigators propose to conduct a randomized, controlled trial to assess the efficacy of the mobile phone-based physical activity intervention on increasing physical activity over a 3-month period. 192 sedentary women will be randomized in a 2-to-1 ratio to a 3-month mobile phone-based physical activity intervention group or to a control group. To provide insight into how best to maximize the potential for sustained physical activity after completion of the 3-month program, women in the intervention group who complete the physical activity program will be further randomized into a 6-month maintenance intervention-PLUS program (pedometer plus mobile phone diary) or to a 6-month maintenance intervention-REGULAR program (pedometer only). Unlike a conventional maintenance follow-up in which all subjects continue in their respective randomization arms, re-randomizing subjects into either a maintenance intervention-REGULAR group or a maintenance intervention-PLUS group will allow us to examine the dose-response of the maintenance methods if the intervention is effective.
The primary purpose of this study is to assess the efficacy of the mobile phone-based physical activity intervention on increasing physical activity compared to the control group.