The Effect of Scapular-Focused Exercise With or Without Electromyography Biofeedback in High-School Baseball Pitchers With Shoulder Impingement Syndrome: A Randomized Controlled Trial

Abstract

Background:

Exercise therapy using electromyography biofeedback (EB) is applied widely for pitchers with shoulder impingement syndrome (SIS). However, few studies have targeted adolescent athletes and evaluated various functional outcomes.

Hypothesis:

Scapular-focused exercise (SFE) with EB would lead to greater improvements in muscle activity, strength, function, and pain compared with SFE alone.

Study Design:

Randomized controlled trial.

Level of Evidence:

Level 2.

Methods:

A total of 36 high-school baseball pitchers diagnosed with SIS were assigned randomly to either the SFE+EB group (n = 18) or the SFE group (n = 18), while 9 were excluded before analysis. Both groups participated in a 4-week intervention (3 sessions per week, 60 minutes per session). The SFE+EB group received real-time visual feedback using surface electromyography targeting the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA). The SFE group received verbal and tactile feedback from a physical therapist. Pre- and postintervention assessments included muscle activity, strength, Shoulder Pain and Disability Index, and Numeric Pain Rating Scale.

Results:

No significant differences were found in baseline characteristics between groups except for glenohumeral internal rotation deficit. The SFE+EB group showed significantly greater improvements in MT activity at 90° (13.14 ± 7.38) compared with the SFE group (7.48 ± 6.62) (P < 0.05). Within-group analysis demonstrated significant increase in UT activity in the SFE+EB group at 60°, whereas MT, LT, SA activity, and UT:MT, UT:LT, and UT:SA ratios improved in both groups. Furthermore, LT and SA muscle strength, along with function and pain scores showed similar changes across groups after the intervention.

Conclusion:

SFE with EB significantly enhances MT activation and symptom relief in high-school baseball pitchers with SIS. In addition, therapist-guided SFE without EB also yields clinically meaningful improvements.

Clinical Relevance:

EB may optimize scapular muscle activation. However, individualized therapist feedback remains an effective and accessible alternative for injury prevention and rehabilitation in young athletes.