Int J Sports Med
DOI: 10.1055/a-1667-6080
Orthopedics & Biomechanics

Glenohumeral Internal Rotation Deficit on Pitching Biomechanics and Muscle Activity

Yi-Hsuan Weng
1   School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan
,
Tsun-Shun Huang
2   Department of Physical Therapy and Assistive Technology, National Yang Ming Chiao Tung University, Taipei, Taiwan
,
Cheng-Ya Huang
1   School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan
,
Hsing-Yu Chen
3   Division of Physical Therapy, Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan
,
Yung-Shen Tsai
4   Graduate Institute of Sports Sciences, University of Taipei, Taipei, Taiwan
,
Jiu-Jenq Lin
1   School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan
3   Division of Physical Therapy, Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan
› Author Affiliations
Funding This study was supported by Ministry of Science and Technology in Taiwan, MOST 110-2314-B-002 -054 -MY3 and 107-2314-B-002 -033 -MY3.

Abstract

To characterize the scapular pitching biomechanics in symptomatic GIRD pitchers (SG) compared to asymptomatic GIRD (ASG) and healthy pitchers. The scapular kinematics and associated muscle activities during pitching were recorded in 33 high school pitchers. Compared to healthy, GIRD pitchers had less scapular posterior tilt in each pitching event (average difference, AD=14.4°, p<0.01) and ASG demonstrated less scapular upward rotation at ball release (AD=12.8°, p<0.01) and greater muscle activity in the triceps brachii in the early-cocking phase (AD=9.9%, p=0.015) and in the serratus anterior in the late-cocking phase (AD=30.8%, p<0.01). Additionally, SG had less muscular activity on triceps brachii in the acceleration phase and serratus anterior in the cocking phase (AD=37.8%, p=0.016; AD=15.5%, p<0.01, respectively) compared to ASG. GIRD pitchers exhibited less scapular posterior tilt during pitching, which may cause impingement. Since tightness of the anterior shoulder is a common cause of inadequacy of posterior tilt during arm elevation, stretching exercise of the anterior shoulder is recommended. Given the inadequate recruitment during pitching in the GIRD pitchers, symptoms may develop following potential impingement.



Publication History

Received: 15 June 2021

Accepted: 05 October 2021

Accepted Manuscript online:
12 October 2021

Article published online:
06 December 2021

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