Objective Healthcare-oriented design in hospitals can promote better clinical outcomes. Creating optimal facilities may increase treatment effects. We investigated the influence of the treatment room on effects of exercise therapy.

Methods In a mixed-method randomised controlled double-blind trial, middle-aged individuals reporting knee or hip pain performed 8 weeks of exercise therapy in (1) a newly built physically enhanced environment, (2) a standard environment or (3) were waitlisted, receiving no intervention. Participants and therapists were blind to study aim. Primary outcome was participants’ Global Perceived Effect (GPE; seven-point Likert scale). Six nested focus group interviews with participants (n=25) and individual interviews with therapists (n=2) explored experiences of the environments.

Results 42 people exercised in the physically enhanced environment, 40 in the standard environment, 21 were waitlisted. Contrary to our hypothesis, the treatment response seemed greater in the standard environment for GPE (0.98, 95% CI0.5 to 1.4) than for the physically enhanced environment (0.37, 95% CI −0.2 to 0.9), between-group difference (0.61, 95% CI −0.1 to 1.3) did not reach statistical significance (p=0.07). Waitlist group reported no improvement (−0.05 95% CI −0.5 to 0.4). In interviews, participants from the standard environment expressed greater social cohesion and feeling at home. Qualitative themes identified; reflection, sense of fellowship and transition. Secondary patient-reported outcomes and qualitative findings supported the primary finding, while improvements in muscle strength and aerobic capacity did not differ between exercise groups.

Conclusion Results suggest that the physical environment contributes to treatment response. Matching patients’ preferences to treatment rooms may improve patient-reported outcomes.

Trial registration number ClinicalTrials.gov identifier: NCT02043613.