Functional Electrical Stimulation Combined With Exercise for Rotator Cuff-Related Shoulder Pain in Older Adults

The goal of this clinical trial is to learn whether adding functional electrical stimulation (FES) to a shoulder exercise program improves how the shoulder muscles work together in older adults with rotator cuff-related shoulder pain. FES uses small electrical currents delivered through pads on the skin to help muscles contract. The main questions it aims to answer are: 1. Does exercise combined with FES improve coordination between the rotator cuff and deltoid muscles more than exercise alone? 2. Does exercise combined with FES increase the space between the top of the upper arm bone and the shoulder blade (acromiohumeral distance), which may reduce pinching of the shoulder tendons? Researchers will compare a group that receives resistance exercise with FES to a group that receives the same resistance exercise without FES. Participants will: 1. Attend exercise sessions 3 times per week for 4 weeks (12 sessions) 2. Complete 4 testing visits: before training, after 2 weeks, after 4 weeks, and 4 weeks after training ends 3. At each testing visit, perform shoulder strength tasks while muscle activity is recorded with sensors on the skin and thin wire sensors placed in the muscle, have an ultrasound of the shoulder, and complete questionnaires about shoulder pain and function

Inclusion Criteria: * Having pain more than 2 weeks in the anterolateral shoulder region * A painful arc of movement (60°-120°) * Having shown positive impingement signs, including positive Neer, Hawkins, and Empty Can tests Exclusion Criteria: * Acute diagnosed rotator cuff tears * Osteoarthritis-induced shoulder pain * Currently receiving treatment or physical therapy for shoulder pain * Previous shoulder surgery * Taking medications that affect the central nervous system * Metabolic or cardiovascular disease * Metal Implants or pacemakers * Skin lesions on the shoulder * Aversion to needles