Identifying the most effective components of a physical activity intervention for adults with knee replacement: the MOST Energized! study protocol

Abstract Background Despite improvements in pain and function following total knee replacement (TKR), most patients do not achieve recommended levels of moderate-vigorous physical activity (MVPA), putting them at increased risk of chronic disease and mortality. Thus, there is a need for effective and scalable physical activity programs for adults with TKR. This trial aims to identify which supplemental, non-automated intervention components, when added to a fully-automated online physical activity program, contribute to the greatest increases in physical activity at 6 and 12 months. Methods This study is a randomized trial with a factorial design using the multiphase optimization strategy (MOST) framework. Adults (N = 336) who underwent a TKR at least 12 months ago receive a fully-automated, 6-month online exercise program (Energize! ) and are randomized to receive between 0 and 4 non-automated supplemental intervention components (phone calls, progress reports to healthcare providers, videos highlighting stories from others with TKR, and/or individualized human feedback sent via email). Remote assessments occur at baseline, 3 months (mid-intervention), 6 months (post-intervention), and 12 months (following a 6-month no intervention period). The primary outcome is change in accelerometer-assessed MVPA (total minutes and percentage of participants meeting the MVPA guideline of ≥ 150 min/week. Secondary outcomes include change in pain intensity and physical function. Additionally, cost-effectiveness and intervention engagement will be evaluated. Discussion This protocol paper describes a robust and innovative approach to determine the most effective intervention components to increase MVPA after TKR. Based on study findings, an optimized, remotely delivered physical activity program will be developed for this population. Trial registration ClinicalTrials.gov, ID: NCT06768762. Registered on 2025-01-06.