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Troy M. Purdom, PhD – Assistant Professor, Longwood University

Adams Hope – Student, Longwood University

Atkins Taylor – Student, Longwood University

Handley Rachel – Student, Longwood University

Trebour Madison – Student, Longwood University


Repetitive overhead movements performed at high intensities can cause musculature imbalances specific to overtraining such as scapular dyskinesis. Athletes with scapular dyskinesis often exhibit limited range of motion with a predisposition to injury. PURPOSE: To examine the effects of repetitive overhead sport-specific movements on scapular position and muscle activation in overhead athletes compared to the general population. METHODS:  Subjects included both male and females and consisted of two groups: Division I tennis players (AP) (n=12), and recreationally fit college students (n=15) as the general population (GP). The AP group was evaluated after a two week break from competition. Bioelectrical impedance was used to measure body composition; the obese subclass two and three were excluded due to altering shoulder anthropometrics. Participants performed a shoulder objective (OT) and functionality test (FT) designed to access scapular positioning and functionality, respectively. The OT included subjects laying on a firm surface in a supine position with knees elevated. The height of the shoulder was measured from the table surface relevant to the anterior aspect of the acromion. The FT utilized a goniometer to measure glenohumeral joint angle and rotation. Subjects laid prone with 45° of shoulder abduction and 90° of elbow flexion. The subjects then externally rotated their shoulder perpendicular to the table indicating the start position. Subjects then internally rotated their shoulder where their hand moved toward their umbilicus. If scapular protraction occurred prior to reaching 40° of internal rotation, this indicated a positive test. Multiple independent and dependent t-tests were conducted to evaluate OT and FT for within-group (dominant and non-dominant arm comparisons) and between-group variance. Data are presented as mean ± SD; alpha level was set to (p< 0.05). RESULTS:  Independent t-test indicate that shoulder protraction of the athletes’ dominant arm compared to the general population occurred sooner (AP: 44.7 ± 11.3; GP: 54.7 ± 8.6 deg; p = 0.02). No significance (p > 0.05) was observed with AP dominant/non-dominant FT comparisons despite the dominant arm activating 14.5% sooner compared with the non-dominant arm (dom: 44.7 + 11.3; nondom: 52.3 + 8.3 deg). No significant differences (p > 0.05) were observed for within-group or between-group OT tests. CONCLUSION: The FT show that the athletic population had hyperactivation of the anterior shoulder girdle and therefore altered kinetics (scapular dyskinesis) was present compared to the general population. Despite resting position of the shoulder was unchanged compared to the general population, repetitive overhead training may affect shoulder mobility due to muscular activation imbalances. Complications from dyskinesis have been shown to create micro-trauma, subluxations, dislocations, impingements, and other related musculoskeletal injuries.  PRACTICAL APPLICATIONS:  The FT is a low cost and quick evaluation tool to monitor shoulder muscle kinetic abnormalities within athletes. The FT can be used to monitor prevalence of dyskinesis as a preventative strategy to maintain performance and prevent injury. The OT however does not seem to be sensitive enough to evaluate dyskinesis in athletic and general populations.


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