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Background: The SMART design allows for changes in the intervention during the randomized controlled trial period. Despite its potential and feasibility for defining the best sequence of interventions, so far, it has never been utilized in a smartphone/gamified intervention for physical activity.
Objectives: To investigate the feasibility of a SMART design for assessing the effects of a smartphone app intervention to improve physical activity in adults. We also aimed to describe the participants’ perception regarding the protocol and the use of the app for physical activity qualitatively. Secondarily, we aimed to analyze the participants’ response to the intervention.
Methods: We conducted a feasibility 24-week/2-stage SMART [ReBEC #RBR-8xtc9c] in which 18 insufficiently active participants (< 10,000 steps per day) were first randomized to Group 1 (smartphone app only), Group 2 (smartphone app + tailored messages) and a Control Group. Participants were motivated to increase at least 2,000 steps/day on average each week. Based on the 12-week intermediate outcome, responders kept their interventions and non-responders were re-randomized to subsequent treatment, including a new group 3 (Smartphone app + gamification) in which participants were instructed to form groups to use several game elements available in the chosen application (Pacer®). Participants in the Control group were instructed to maintain their usual routine during all protocol. We fit linear regressions for each participant with the relationship between weeks and steps per day. We considered responders those with any positive slope at the end of the 1st stage intervention. We compared the accelerometer-based steps per day before and after the intervention as well as the slopes of the app-based steps per day between the first and second stages of treatment.
Results: Twelve participants, including five controls, finished the intervention. We identified two responders in Group 1. We did not observe significant changes in the steps per day, neither throughout the intervention nor compared to the control Group. However, the re-randomization of the five non-responders led to a change in the slope of the steps per day of a median, -198 steps per day (interquartile range, -279 to -103) to 20 steps/day (-204 to 145), P = .079. Finally, we observed in three participants in the Group 2 an increase in the number of steps per day up to the sixth week followed by an inflection to baseline values or even lower (i.e., a quadratic relationship). The qualitative analysis showed that participants’ reports could be classified into three categories: (1) difficulty in managing the app and technology or problems with the device, (2) suitable response to the app, and (3) difficulties to achieve the goals.
Conclusions: The SMART design was feasible and changed the behavior of the steps per day after re-randomization. Our results suggest that the re-randomization should be implemented earlier to take advantage of the tailored messages. Also, difficulties with technology and a realistic and individualized goal should be considered in interventions for physical activity using smartphones. Brazilian Clinical Trials Registry (ReBEC #RBR-8xtc9c)