Inclusion Criteria:  Pain around the antero-lateral (deltoid area) region of the proximal shoulder during active movements in abduction and/or external rotation. 3/5 positive impingement tests: Neer, Hawkins-Kennedy, empty can, painful arc, and resisted external rotation or abduction. Pain at rest less than 3cm in a visual analogue scale (VAS).  Exclusion Criteria:  Previous shoulder surgery. Being treated with physical therapy or pharmacogical therapy for shoulder pain. External rotation range of motion less than 45º or 50% compared to the contralateral side. Suspected shoulder instability (previous dislocation/subluxation, sulcus sign, anterior drawer test, anterior/posterior aprehension test, relocation test). Suspected cervical radiculopathy (distraction, spurling, ULNT1, squeeze test, ipsilateral rotation less than 60º) Presence of neck pain. Suspected rotator cuff tears (drop arm test, external rotation lag sign, diagnostic imaging). Contraindications to blood flow restriction therapy.