The SEXSI trial is a pragmatic, assessor and participant blinded, randomized, controlled, superiority trial, with a two-group parallel design. Patients with subacromial impingement syndrome will be randomized to either usual care or a home-based intervention consisting of progressive high volume resistance training in addition to usual care using a 1:1 allocation. The primary end-point will be change in the Shoulder Pain and Disability Index (SPADI) 16 weeks after baseline.