The Aging^PLUS trial: Design of a randomized controlled trial to increase physical activity in middle-aged and older adults

Background: Negative views of aging (NVOA), low self-efficacy beliefs, and poor goal planning skills represent risk factors that undermine adults' motivation to engage in physical activity (PA). Targeting these three risk factors may motivate adults to become physically active. Objective: To assess the efficacy of Aging^PLUS, a 4-week educational program that explicitly targets NVOA, low self-efficacy beliefs, and poor goal planning skills compared to a 4-week health education program. The study also examines the role of NVOA, self-efficacy beliefs, and goal planning as the mechanisms underlying change in PA. Design: This randomized controlled trial (RCT) utilizes the experimental medicine approach to assess change in PA as a function of modifying three risk factors. The RCT recruitment target includes 288 mostly sedentary adults ranging in age from 45 to 75 years. Methods: Eligible middle-aged and older adults are recruited through community sources. Participants are randomized to either the Aging^PLUS or the control group. Participants in both groups are enrolled in the trial for 8 months total, with four assessment points: Baseline (pre-test), Week 4 (immediate post-test), Week 8 (delayed post-test), and Month 6 (long-term follow-up). The intervention takes place over 4 consecutive weeks with 2-h sessions each week. PA engagement is the primary outcome variable. Positive changes in NVOA, self-efficacy beliefs, and goal planning are the intervention targets and hypothesized mediators of increases in PA. By utilizing a multi-component approach and targeting a cluster of psychological mechanisms, the Aging^PLUS program implements the experimental medicine approach to health behavior change.