A mixed methods approach to investigating physical activity in people with obesity participating in a chronic care programme awaiting total knee or hip arthroplasty.

Aims: To describe patient-reported physical activity and step count trajectory and explore perceived barriers and enablers to physical activity amongst people with obesity participating in a chronic care programme whilst awaiting arthroplasty.

Design: Convergent parallel mixed-method study.

Method: A patient cohort derived from a longitudinal sample of adults with end-stage osteoarthritis and obesity from a chronic care programme whilst awaiting primary total knee or hip arthroplasty (n = 97) was studied. Physical activity was measured at baseline (entry to the wait list) and before surgery (9-12 months waiting time) using the Lower Extremity Activity Scale (LEAS) and activity monitors (activPAL™). A subset of participants completed in-depth semi-structured interviews 6 months after being waitlisted to explore perceived barriers and enablers to physical activity. Themes were inductively derived and then interpreted through the COM-B model.

Results: Baseline LEAS and activPAL™ data were available from 97 and 63 participants, respectively. The proportion of community ambulant individuals reduced from 43% (95% CI 33%-53%) at baseline to 17% (95% CI 9%-28%) pre-surgery. Paired activPAL™ data (n = 31) for step count, upright time, and stepping time remained unchanged. Twenty-five participants were interviewed. Five themes underpinning physical activity were mapped to the COM-B model components of capability (physical capability), opportunity (accessibility and social norms), and motivation (self-efficacy and beliefs and physical activity).

Conclusions: Participation in a chronic care programme did not improve physical activity levels for people with obesity awaiting arthroplasty. Programs cognisant of the COM-B model components may be required to address the natural trajectory of declining physical activity levels while awaiting arthroplasty.