Empowered Relief and Exercise Rehabilitation for People With Subacromial Shoulder Pain

The goal of this clinical trial is to learn whether a single 2-hour online pain skills session called Empowered Relief can help adults with subacromial shoulder pain who are taking part in a 12-week exercise program. The main questions it aims to answer are: * Does Empowered Relief lower unhelpful thoughts and beliefs about pain? * Does Empowered Relief help participants complete more of their prescribed exercises? All participants will receive the same 12-week exercise program and the Empowered Relief session. The timing of the Empowered Relief session will be randomly assigned between day 10 and day 26 after starting the exercise program. This allows researchers to compare each participant's responses before and after the session. Participants will: * Follow a 12-week home exercise program for their shoulder. * Take part in one 2-hour online Empowered Relief session. * Answer brief daily questions for 12 weeks about their thoughts about pain, what they expect to feel during exercise, what they actually feel after exercise, and how much of their exercise program they complete. * Answer brief weekly questions after their Empowered Relief session about their use of the strategies taught in the session. * Complete longer questionnaires at the start of the study and after 4, 8, and 12 weeks.

Inclusion Criteria: * Age 18 to 65 years, inclusive. * Shoulder pain for at least 3 months. * Sufficient Danish language proficiency to understand study information, follow instructions, and complete questionnaires. * Diagnosis of subacromial pain syndrome (SAPS), confirmed by either: * an existing clinical diagnosis provided by a referring clinician, or * a standardized study-based clinical examination with at least 3 of the following 5 tests positive: Painful Arc test, Empty Can (Jobe's) test, Neer's test, Hawkins-Kennedy test, and External Rotation Resistance test. * Pain Catastrophizing Scale (PCS) score greater than 16. Exclusion Criteria: * Current regular use of strong analgesic medication, excluding over-the-counter medication. * Pregnancy. * Referral for postoperative shoulder rehabilitation. * Corticosteroid injection in the affected shoulder within the past 2 months. * Current fracture of the affected shoulder, radiographically verified. * Glenohumeral osteoarthritis in the affected shoulder, radiographically verified. * History of shoulder dislocation or subluxation in the affected shoulder. * Suspected labral lesion of the affected shoulder. * Suspected full-thickness rotator cuff tear. * Suspected frozen shoulder (adhesive capsulitis). * Presence of competing conditions that may explain the shoulder pain or interfere with participation, including but not limited to cancer, inflammatory rheumatic disease, neurological disorders, fibromyalgia, or severe psychiatric disease.