To compare the effects of low-load resistance training with and without blood flow restriction on thickness, strength and pain of shoulder girdle muscles in individuals with shoulder impingement syndrome

Investigating the effects of low-load resistance training combined with blood flow restriction on the thickness and strength of the supraspinatus, infraspinatus, middle trapezius, and biceps muscles and its pain-reducing effects in individuals with shoulder impingement syndrome

a pragmatic, parallel-group, single-blind (with blinded outcome assessment), randomized controlled trial (RCT)

This single-blind trial at Amir Alam Hospital randomly allocates patients with shoulder impingement to receive 12 sessions of low-load resistance training, either with real BFR or with a sham BFR cuff. Participants and outcome assessors are blinded to the allocation, while the treating therapist is not. All patients also receive standard passive physiotherapy in each session consisting of TENS, US and hotpack.

Inclusion Criteria Age range of 40 to 60 years Literacy in Persian Shoulder pain with a maximum duration of 3 months since onset Nighttime shoulder pain or pain during overhead activities with a VAS score ≥ 3 Positive Painful arc test and at least three of the following tests: • Neer • Hawkins-Kennedy • Empty can • Infraspinatus Exclusion Criteria Contraindications to the use of BFR Simultaneous pain in both shoulders Diagnosis of frozen shoulder Positive drop arm test indicating a complete rotator cuff tear History of surgery, fracture, or dislocation in the shoulder region Use of anti-inflammatory drugs during the daytime while undergoing the physiotherapy course

Group 1: Low-load resistance training (at 20-40% of 1RM) with BFR (LLRT+BFR group) Group 2: Low-load resistance training (at 20-40% of 1RM) without BFR (LLRT group)

muscles thickness muscles strength pain (NRPS ) pain pressure threshold SPADI questionnaire

The method used is balanced block randomization with a block size of 4. The unit of randomization is the individual participant. The study did not employ stratified randomization, meaning no specific stratification variables (such as age or disease severity) were used to create subgroups before randomization. The primary tool for implementing randomization was sequentially numbered, sealed, opaque envelopes. The random sequence was built by an independent researcher prior to the study's commencement. This was done by listing all possible combinations that would result in 2 allocations to Group A (LLRT) and 2 allocations to Group B (LLRT+BFR) within each block of 4 participants. This sequence was transcribed and placed into the sealed envelopes.

This trial implements a structured blinding protocol where participants are blinded to their group assignment through allocation concealment using sequentially numbered, sealed, opaque envelopes, coupled with a sham procedure for the control group to mimic the sensory experience of the BFR cuff. The treating physiotherapist administering the interventions cannot be blinded due to the necessary application of the BFR technique. The principal investigator overseeing the trial remains blinded to group allocation during active data collection and analysis to prevent bias. Crucially, all outcome assessors are blinded: a clinical assessor, separate from the treating therapist, conducts all physical and questionnaire-based evaluations without knowledge of the assignment, and a radiologist performs all ultrasound measurements independently with no information on the participant's group.