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The scapular kinematics and muscle activation in high school baseball pitchers with glenohumeral internal rotation deficit
glenohumeral internal rotation deficit,baseball,scapular kinematics,muscle activation,shoulder injuries,
|Publication Year :||2019|
Background: The characteristics of overhead throwing and striking tasks were believed to be related to the mechanism of injury. As a repetitive nature of sports throwing, pitchers' shoulder had developed a range of motion adaptation, including increased external rotation and decreased internal rotation in the glenohumeral joint at 90° of abduction in the throwing shoulder. These adaptations were highly related to injury occurrence. Glenohumeral internal rotation deficit (GIRD) was believed to be one of the risk factors contributing to shoulder injury. Additionally, it’s associated with altered scapular kinematics. However, it was not clear how these alternations related to specific phases of the pitching motion. Objective: The objective of the present study was to compare the scapular kinematics and muscle activity in asymptomatic baseball pitchers without GIRD (AswG), asymptomatic baseball pitchers with GIRD (AsG), and symptomatic baseball pitchers with GIRD (SG) during fast ball pitching. Design: High school pitchers were recruited from high schools in Taipei city and New Taipei city. They were recruited from 3 groups, the AswG group, AsG group, and SG group. Each subject underwent an assessment of the glenohumeral range of motion and capsular tightness. Then, three-dimensional electromagnetic motion analysis and electromyography muscle activity were used to record the scapular kinematics and absolute muscle activation during fast ball pitching. Main outcome measures: Scapular kinematics (upward/downward rotation, anterior/posterior tilt, external/internal rotation) and absolute muscle activation (upper trapezius, lower trapezius, serratus anterior, anterior deltoid, biceps brachii, and triceps brachii) were main outcomes of the study. Results: For the scapular external/internal rotation, there was an interaction effect (p<0.05). The AsG group was significantly decreased external rotation than the AswG group at maximum external rotation and ball release (15.3° and 18.5°, p=0.029 and 0.022, respectively). However, at the time of the lead leg at the highest point, the SG group was significantly increased external rotation than the AsG group (2.9°, p=0.043). For the scapular upward/downward rotation, the AsG group had decreased upward rotation about 14.3° compared with the AswG group (p=0.033). For scapular anterior/posterior tilt, the AsG group had increased anterior tilt than the AswG group in each phase (6.8°, 15.0°, 18.4°, and 17.3°, p=0.002, 0.008, 0.001 and 0.005, respectively). Also, the SG group had increased anterior tilt than the AswG group (4.1°, 12.2°, 14.5°, and 13.7°, p= 0.044, 0.027, 0.009 and 0.022, respectively). For muscle activities, the AsG group had higher muscle activity than the AswG group in anterior deltoid during the acceleration phase (26.4%, p=0.031). In triceps brachii muscle, the SG group had lower muscle activity than the AsG group during early-cocking and acceleration phase (8.8% and 37.8%, p=0.028 and 0.016, respectively). Otherwise, the AsG group had higher triceps brachii muscle activity than the AswG group during early-cocking and acceleration phase (9.9% and 36.8%, p=0.015 and 0.018, respectively). In serratus anterior muscle, the SG group had lower muscle activity than the AsG group during early-cocking and late-cocking phase (4.8% and 30.2%, p=0.004 and 0.007, respectively). Instead, the AsG group had higher serratus anterior muscle activity than the AswG group during early-cocking and late-cocking phase (3.7% and 30.8%, p=0.018 and 0.006, respectively). Conclusions: Subjects with GIRD had scapular kinematics alteration. They tried to compensate for the deficits by muscle activation, but the effect was limited.
|Appears in Collections:||物理治療學系所|
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