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

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.