Acute Effects of Focal Vibration on Posterior Shoulder Tightness and Tissue Stiffness in Overhead Athletes

This study aims to investigate the acute effects of focal vibration on posterior shoulder tightness, posterior shoulder muscle stiffness, and glenohumeral range of motion in overhead athletes. A total of 36 overhead athletes aged 18-25 years who have regularly participated in overhead sports for at least four years will be included. Participants will be randomly allocated to either the focal vibration group or the sham control group using block randomization. All outcome assessments will be performed immediately before and immediately after a single intervention session. The primary outcome measure is posterior shoulder tightness, assessed using the Horizontal Adduction Test. Secondary outcome measures include posterior shoulder muscle stiffness, assessed using the IndentoPRO digital tissue indentometer, and passive glenohumeral internal and external rotation range of motion, measured using the GYKO inertial sensor. The primary research question is whether focal vibration has an acute effect on posterior shoulder tightness, muscle stiffness, and glenohumeral range of motion in overhead athletes. It is hypothesized that participants receiving focal vibration will demonstrate greater reductions in posterior shoulder tightness and muscle stiffness, as well as greater improvements in glenohumeral range of motion, compared with those receiving the sham intervention.

Inclusion Criteria: Aged between 18 and 25 years. Regular participation in an overhead sport for at least 4 years. Participating in regular training at least 4 times per week. Willing to participate voluntarily in the study and able to provide written informed consent. Exclusion Criteria: History of shoulder surgery within the previous 6 months. History of shoulder, neck, or upper extremity injury within the previous 3 months. Participation in intense upper extremity training within the previous 48 hours. Presence of infection, skin lesions, or open wounds around the shoulder region. Diagnosis of a systemic rheumatologic or neurological disease. Unwillingness to participate in the study or refusal to provide written informed consent.