A novel behavioural INTErvention to REduce Sitting Time in older adults undergoing orthopaedic surgery (INTEREST): protocol for a randomised controlled feasibility study.

Background: Osteoarthritis is a highly prevalent condition in older adults, that causes many sufferers to require a hip or knee replacement in order to improve their quality of life and reduce pain. Individuals waiting for hip or knee replacements are often highly sedentary; thus, it is pertinent to assess whether reducing their sedentariness prior to surgery may aid in improving post-operative outcomes.

Methods/design: The study will be a randomised controlled feasibility trial design, with 2:1 randomisation into an intervention and usual care group respectively. A target of 45 patients aged 60 years or older waiting for elective hip and knee replacements will be recruited from Russells Hall Hospital, Dudley, UK, approximately 8-10 weeks before surgery. The intervention, informed by Self-Determination Theory (SDT), will be composed of multiple behaviour change techniques, namely, motivational interviewing, feedback on current objectively measured sedentary behaviour and activity, goal-setting, environmental modification, self-monitoring, and social support. Assessments will occur at baseline, 1 week pre-surgery, and 6 weeks post-surgery. The primary outcome will be the feasibility of intervention delivery and of the trial procedures, assessed quantitatively based on rates of recruitment, retention, measures-completion, and intervention fidelity assessment, and with mixed-methods assessment of acceptability, practicality, adaption, satisfaction, and safety. Exploratory outcomes will include physical function, cardiometabolic biomarkers, measurement of SDT constructs, and both objective and subjective measurement of physical activity and sedentariness. The study will last up to 18 weeks per participant. No formal between-group comparisons are planned, but the variance in within-group changes and differences between groups in outcome measures will be explored and reported with 95% confidence intervals.

Discussion: This is the first study assessing the feasibility of an intervention to reduce sedentary behaviour in older adults with mobility limitations, and the first to assess whether such a reduction could work in a prehabilitative context prior to surgery. The results of this study will help inform the design of a definitive randomised controlled trial.

Trial Registration: This trial is registered on Clinicaltrials.gov. Registration number: NCT03740412. Date of registration: 13/11/2018.