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T.S. Huang1, Y.H. Weng1, C.C. Chang2, Y.S. Tsai2, J.J. Lin1,3
1National Taiwan University, School and Graduate Institute of Physical Therapy, Taipei, Taiwan, 2University of Taipei, Graduate Institute of Sports Sciences, Taipei, Taiwan, 3National Taiwan University Hospital, Division of Physical Therapy, Department of Physical Medicine and Rehabilitation, Taipei, Taiwan
Background: Scapular dyskinesis is defined as altered scapular position and movement. The impact of scapular dyskinesis on shoulder dysfunction and athletic performance remains unclear. No study has investigated the influence of scapular dyskinesis on scapular kinematics, muscle activation, shoulder function and athletic performance in high school baseball pitchers.
Purpose: We aimed to investigate
(1) differences in clinical measurements of shoulder characteristics as well as scapular kinematics, muscle activation, shoulder function and performance in high school pitchers with and without scapular dyskinesis, and
(2) the related factors associated with shoulder function and performance, including clinical measurements of shoulder characteristics, scapular dyskinesis, scapular kinematics and muscle activation.
(1) differences in clinical measurements of shoulder characteristics as well as scapular kinematics, muscle activation, shoulder function and performance in high school pitchers with and without scapular dyskinesis, and
(2) the related factors associated with shoulder function and performance, including clinical measurements of shoulder characteristics, scapular dyskinesis, scapular kinematics and muscle activation.
Methods: Thirty-eight high school baseball pitchers were recruited and classified into two groups based on dyskinesis (n=26) or no dyskinesis (n=12) in this cross-sectional study. They were assessed with the Kerlan–Jobe Orthopaedic Clinic shoulder and elbow (KJOC) scale and clinical measurements of shoulder characteristics including the glenohumeral range of motion, scapular muscle strength, pectoralis minor index and posterior displacement of scapular inferior angle and medial border, as well as the assessment of scapular kinematics, muscle activation and ball speed during fastball pitching.
Results: Less scapular external rotation (6.3–14.4 degrees, p = 0.012), more inferior angle displacement (1.9 cm, p = 0.036) and decreased upper trapezius (UT) activation (7.1–12.5%, p = 0.019-0.035) were found in pitchers with scapular dyskinesis than in those without dyskinesis. Additionally, more scapular external rotation at ball release and increased lower trapezius (LT) activation during the acceleration phase were significantly associated with higher KJOC scores in the regression model (total R2 = 0.231). No variables were related to ball speed.
Conclusion(s): More inferior angle displacement as well as less scapular external rotation and decreased UT activation during fastball pitching were found in high school pitchers with scapular dyskinesis. A higher functional score was related to increased external rotation of the scapula and LT muscle activation during pitching.
Implications: For high school pitchers with scapular dyskinesis, increased external rotation of the scapula and LT muscle activation during pitching, which are related to KJOC functional scores, should be the focus of rehabilitation. On the other hand, scapular dyskinesis is not related to ball speed in high school pitchers.
Funding, acknowledgements: Ministry of Science and Technology, 107-2314-B-002 -033-MY3, Taiwan
Keywords: Scapular dyskinesis, Baseball, Performance
Topic: Musculoskeletal: upper limb
Did this work require ethics approval? Yes
Institution: National Taiwan University Hospital
Committee: Human Subject Research Ethics Committee
Ethics number: 201712089RINC
All authors, affiliations and abstracts have been published as submitted.
