OBJECTIVE: 'Better By Moving' is a multifaceted intervention developed and implemented in collaboration with patients and healthcare professionals to improve physical activity in hospitalized adults. This study aimed to understand if, how and why 'Better By Moving' resulted in higher levels of physical activity by evaluating both outcomes and implementation process.

DESIGN: Mixed-methods study informed by the Medical Research Council guidance.

SETTING: Tertiary hospital.

PARTICIPANTS: Adult patients admitted to surgery, haematology, infectious diseases and cardiology wards, and healthcare professionals.

MEASURES: Physical activity was evaluated before and after implementation using the Physical Activity Monitor AM400 on one random day during hospital stay between 8 am and 8 pm. Furthermore, the time spent lying on bed, length of stay and discharge destination was investigated. The implementation process was evaluated using an audit trail, surveys and interviews.

RESULTS: There was no significant difference observed in physical activity (median [IQR] 23 [12-51] vs 27 [17-55] minutes, P = 0.107) and secondary outcomes before-after implementation. The intervention components' reach was moderate and adoption was low among patients and healthcare professionals. Patients indicated they perceived more encouragement from the environment and performed exercises more frequently, and healthcare professionals signalled increased awareness and confidence among colleagues. Support (priority, resources and involvement) was perceived a key contextual factor influencing the implementation and outcomes.

CONCLUSION: Although implementing 'Better By Moving' did not result in significant improvements in outcomes at our centre, the process evaluation yielded important insights that may improve the effectiveness of implementing multifaceted interventions aiming to improve physical activity during hospital stay.