Subacromial impingement syndrome (SAIS) is the most common cause of shoulder pain, accounting for a large proportion of musculoskeletal complaints. It is characterized by narrowing of the subacromial space, leading to pain, weakness, limited range of motion, and impaired shoulder function. Muscle weakness, especially of the rotator cuff and scapular stabilizers, plays a major role in its pathomechanics.

Although conventional strengthening exercises are effective, they are often delayed until pain subsides, which may prolong recovery. Blood Flow Restriction (BFR) training and Pilates exercises have recently emerged as promising approaches that may enhance strength and function during earlier, painful stages of rehabilitation. However, limited research has compared both interventions in patients with SAIS. Therefore, this study aims to compare the effectiveness of BFR training versus Pilates exercises, in addition to conventional therapy, on pain, function, range of motion, muscle strength, and proprioception in patients with painful SAIS.

Shoulder pain is one of the most prevalent musculoskeletal complaints, ranking as the third most common condition encountered in primary care settings. Among the various causes of shoulder pain, subacromial impingement syndrome (SAIS) represents the most frequent diagnosis, accounting for nearly half to two-thirds of reported shoulder pain cases. SAIS is characterized by narrowing of the subacromial space, resulting in compression and irritation of soft tissues such as the supraspinatus tendon, long head of biceps tendon, subacromial bursa, and joint capsule.

Clinically, patients with SAIS present with pain during overhead activities, muscle weakness, and a painful arc of motion, particularly between 60° and 120° of shoulder elevation. Weakness of the rotator cuff and scapular stabilizing muscles contributes significantly to altered scapulohumeral rhythm and compromised glenohumeral stability. Consequently, muscle strengthening is considered a cornerstone in rehabilitation programs.

Traditional resistance training typically requires moderate to high loads (around 60% of one-repetition maximum) to achieve strength gains. However, during the painful phases of SAIS, patients may not tolerate heavy loading, leading to delayed initiation of strengthening exercises and prolonged recovery time. Therefore, alternative strengthening strategies that minimize mechanical stress while promoting muscle adaptation are needed.

Blood Flow Restriction (BFR) training is a technique that applies controlled external pressure to partially restrict arterial inflow and venous outflow, enabling strength gains with low-load resistance (approximately 20-30% of 1RM). It stimulates metabolic stress and anabolic pathways, enhancing muscle hypertrophy and strength while reducing joint stress.

Pilates exercises, on the other hand, are mind-body exercises based on principles of control, concentration, centering, precision, breathing, and flow. They emphasize neuromuscular control, core stability, scapular alignment, and coordinated movement patterns. Previous studies have demonstrated beneficial effects of Pilates in improving pain, function, and muscle strength in various musculoskeletal disorders, including shoulder conditions.

Despite the promising effects of both BFR and Pilates, limited evidence directly compares their effectiveness in shoulder rehabilitation, particularly in patients with SAIS. To the author's knowledge, no previous study has directly compared these two interventions in managing painful subacromial impingement syndrome. Therefore, this study aims to evaluate and compare the effects of BFR training and Pilates exercises, in addition to conventional therapy, on pain intensity, functional disability, shoulder range of motion, muscle strength, and proprioception in patients with SAIS.

Inclusion Criteria:

1 - Age ranging from 18 to 55 years of both genders, with BMI ranging 18.5 to 29.9 Kg/m2 2. Clinically diagnosed with SIS, based on having ≥ 3 positive results of the following; pain during shoulder elevation and overhead activities, the painful arc, Neer impingement, Hawkins-Kennedy impingement, external rotation resistance, or empty can tests 3. Symptoms duration between 4 to 12 weeks (subacute and chronic phases)

4. pain level should be ranged from 3 to 8 on the VAS .

Exclusion Criteria:

1 - History of shoulder surgery, traumatic injury or systematic diseases 2. Any cervical problems as cervical disc & any patient with radioculopathy. 3. Pregnancy. 4. Acute stage of subacromial impingement syndrome 5. Full thickness tear confirmed by the orthopaedist. 6. subjects shouldn't receive any physical therapy sessions in the past 3 months to minimize any confounders to treatment.