Interprofessional development of a behaviour change resource for physiotherapists promoting physical activity during and beyond breast cancer treatment

Introduction Physical activity can reduce side effects and improve quality of life during and after breast cancer treatment. Although interventions can increase activity, gains are often not maintained once support ends. Embedding behaviour change theory may improve maintenance, but applying it is challenging.Aim To develop a resource helping physiotherapists apply behaviour change techniques within a physical activity intervention during breast cancer treatment.Materials and methods Development drew on literature and observation of 22 exercise sessions delivered by three physiotherapists to 15 participants during the trial’s early phase to identify barriers to physical activity, and behaviour change techniques used in comparable interventions and routine practice. Barriers were mapped to the COM-B model and Behaviour Change Wheel, and techniques selected for relevance and feasibility. Feedback from physiotherapists and the trial team informed refinement.Results Barriers included treatment-related symptoms, time constraints, and reduced motivation or confidence. Physiotherapists were observed using less frequently reported techniques. These findings informed the SMART Trial Behaviour Change Guide, structured around COM-B domains with plain-language explanations and clinician-oriented examples.Conclusions Used in the SMART Trial, the guide supports applying behaviour change theory within physiotherapy-led physical activity interventions and may facilitate integration of these strategies in oncological physiotherapy practice.