Planning implementation and scale-up of physical activity interventions for people with walking difficulties: study protocol for the process evaluation of the ComeBACK trial

BACKGROUND: There is currently little evidence of planning for real-world implementation of physical activity interventions. We are undertaking the ComeBACK (Coaching and Exercise for Better Walking) study, a 3-arm hybrid Type 1 randomised controlled trial evaluating a health coaching intervention and a text messaging intervention. We used an implementation planning framework, the PRACTical planning for Implementation and Scale-up (PRACTIS), to guide the process evaluation for the trial. The aim of this paper is to describe the protocol for the process evaluation of the ComeBACK trial using the framework of the PRACTIS guide. METHODS: A mixed methods process evaluation protocol was developed informed by the Medical Research Council (MRC) guidance on process evaluations for complex interventions and the PRACTIS guide. Quantitative data, including participant questionnaires, health coach and administrative logbooks, and website and text message usage data, is being collected over the trial period. Semi-structured interviews and focus groups with trial participants, health coaches and health service stakeholders will explore expectations, factors influencing the delivery of the ComeBACK interventions and potential scalability within existing health services. These data will be mapped against the steps of the PRACTIS guide, with reporting at the level of the individual, provider, organisational and community/systems. Quantitative and qualitative data will elicit potential contextual barriers and facilitators to implementation and scale-up. Quantitative data will be reported descriptively, and qualitative data analysed thematically. DISCUSSION: This process evaluation integrates an evaluation of prospective implementation and scale-up. It is envisaged this will inform barriers and enablers to future delivery, implementation and scale-up of physical activity interventions. To our knowledge, this is the first paper to describe the application of PRACTIS to guide the process evaluation of physical activity interventions. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials Registry (ANZCTR) Registration date: 10/12/2018. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13063-021-05990-3.