Evaluating the Implementation Fidelity of the REJOIN (Using Exercise to Relieve Joint Pain and Improve Aromatase Inhibitor Adherence in Older Breast Cancer Survivors) Pilot Trial

Implementation fidelity (IF), the extent to which interventions are delivered as intended, is essential for assessing program integrity and informing future dissemination/scalability. The REJOIN pilot trial adapted Fit & Strong! ( F&S! ) to deliver an education/exercise intervention targeting aromatase inhibitor-associated joint pain among older breast cancer survivors (BCS) at two institutions. An independent reviewer analyzed video-recorded sessions to assess IF domains (content, dose/exposure, delivery quality, participant responsiveness, contextual factors) using a 5-point Likert scale (1-low, 5-high). Overall, IF was high (mean 4.5/5.0), indicating successful implementation of the adapted F&S! curriculum. Content (mean = 4.4) showed minor curriculum deviations, dose/exposure (mean = 3.6) varied by session lengths, delivery quality (mean = 5.0) reflected enthusiastic ACSM and F&S! certified instructors, participant responsiveness (mean = 4.4) was evident through compliance/engagement, contextual factors (mean = 4.8) included additions of breast cancer specific content and adaptations and mitigating technical issues of remote delivery. Monitoring IF ensures program integrity and informs future intervention design/dissemination.