Three-dimensional kinematic analysis of glenohumeral, scapular, and thoracic angles at maximum shoulder external rotation associated with baseball shadow pitching: comparison with normal pitching

Comparison of glenohumeral and scapulothoracic kinematics between fastballs and curveballs during baseball pitching

Shoulder injuries are common in baseball pitchers and primarily involve the glenohumeral joint. Past analyses have examined shoulder biomechanics during different pitch types simply as the motion of the upper arm relative to the thorax. In this study, glenohumeral and scapulothoracic kinematics were compared between fastballs and curveballs at key timepoints throughout a pitch. Upper extremity kinematics of thirteen collegiate pitchers were collected during fastball and curveball pitches with motion capture. A linear model approach was utilised to estimate scapular kinematics based on measurable humerothoracic motion. Glenohumeral kinematics were computed from the scapular and humeral motion data. Comparisons of scapulothoracic and glenohumeral kinematic variables at times of maximum glenohumeral external rotation, ball release, and maximum glenohumeral internal rotation between pitch types were made using paired t-tests with Benjamini-Hochberg corrections. There were no significant differences in glenohumeral kinematics. Fastballs elicited significantly less scapulothoracic internal rotation and more posterior tilt at maximum glenohumeral external rotation. Fastballs produced significantly less scapulothoracic internal rotation and anterior tilt at maximum glenohumeral internal rotation. This study provides further evidence that risk of injury to the glenohumeral joint may be consistent between fastballs and curveballs and offers insights into subtle differences in scapular kinematics between pitch types.

Evaluation of approaches to estimate scapular kinematics during baseball pitching

Biomechanical analyses of pitching possess limitations in accurately measuring dynamic scapular orientation and are thus unable to distinguish between glenohumeral and scapulothoracic contributions to global shoulder motion. In lieu of direct measurement, several methods to estimate scapular kinematics have been developed. This study evaluated the ability of the linear model and the double calibration acromion marker cluster (D-AMC) approaches to estimate scapular kinematics throughout a full-speed pitching motion. Each approach's estimates were compared against scapulothoracic range of motion limits established in a non-pitching biplane fluoroscopy study involving various functional arm movements that approximate physiological limits of scapular motion. Fourteen healthy collegiate pitchers participated. Motion capture measured upper extremity joint kinematics during full-speed fastball pitches. Linear model and D-AMC approaches estimated scapulothoracic kinematics during each pitch. Linear model estimates of scapulothoracic kinematics were largely within established physiological limits on each scapular axis of motion while D-AMC estimates exceeded fluoroscopy-established bounds for more subjects and by larger, less physiologically plausible amounts. These findings demonstrate that the linear model outperforms the D-AMC and suggest that it is a viable approach to estimate scapular kinematics during pitching. Finally, these results offer additional evidence to support the accepted pattern of scapular kinematics during pitching.

Relationship between Standing Trunk Extension Angle and Medial Elbow Injuries in Young Baseball Pitchers

Purpose: The purpose of this study was to investigate the relationship between the standing trunk extension angle and medial elbow injuries. Subjects and methods: The study participants were 90 male baseball pitchers (10−12 years) belonging to youth baseball teams. Pitching elbow injuries were evaluated by an orthopedic surgeon using ultrasound scans and physical examination findings. A single optical three-dimensional motion analysis system was used for the trunk extension measurements, with three-dimensional coordinates captured. The overall, upper, and lower trunk angles were then analyzed. Results: Trunk extension angle during standing trunk extension was significantly smaller among participants who were positive for medial elbow injuries on ultrasound scans (positive: 71.4° ± 10.3°; negative: 75.7° ± 9.2°; t = 2.05, p < 0.05). The upper trunk extension angle was significantly smaller than the lower trunk extension angle among participants who were positive for medial elbow injuries on physical examination (upper: 33.0° ± 6.9°; lower: 41.2° ± 8.2°; t = −2.42, p < 0.05). Conclusions: Trunk extension angle during standing trunk extension is associated with medial elbow injuries. Evaluating the trunk extension angle as multiple segments rather than a single rigid body is valuable.

Shadow pitching deviates ball release position: kinematic analysis in high school baseball pitchers

Background

Although shadow pitching, commonly called “towel drill,” is recommended to improve the throwing motion for the rehabilitation of pitching disorders before the initiation of a throwing program aimed at returning to throwing using a ball, the motion differs from that of normal throwing. Learning improper motion during ball release (BR) may increase shoulder joint forces. Abnormal throwing biomechanics leads to injures. However, there has been no study of shadow pitching focusing on the BR position. The purpose of the present study was to evaluate the BR position and kinematic differences between shadow pitching and normal throwing. In addition, the effect of setting a target guide for BR position on throwing motion was examined in shadow pitching.

Methods

The participants included in this study were 20 healthy male students who were overhand right-handed pitchers with no pain induced by a throwing motion. Participants performed normal throwing (task 1), shadow pitching using a hand towel (task 2), and shadow pitching by setting a target of the BR position (task 3). A motion capture system was used to evaluate kinematic differences in throwing motions, respectively. Examination items comprised joint angles and the differences in BR position.

Results

BR position of task 2 shifted significantly toward the anterior, leftward, and downward directions compared with task 1. The distance of BR position between tasks 1 and 2 was 24 ± 10%. However, task 3 had decreased BR deviation compared with task 2 (the distance between 3 and 1 was 14 ± 7%). Kinematic differences were observed among groups at BR. For shoulder joint, task 2 showed the highest value in abduction and horizontal adduction among groups. In spine flexion, left rotation and thorax flexion, task 2 was significantly higher than task 1. Task 3 showed small differences compared with task 1.

Conclusions

The BR position of shadow pitching deviated significantly in the anterior, leftward, and downward directions compared with normal throwing. Furthermore, we demonstrated that the setting of BR target reduces this deviation. Thus, the target of BR position should be set accurately during shadow pitching exercises in the process of rehabilitation.

An individualized linear model approach for estimating scapular kinematics during baseball pitching

Assessment of scapulothoracic and glenohumeral contributions to shoulder function during baseball pitching are limited by challenges in accurately measuring dynamic scapular orientation. A recently validated individualized linear model approach that estimates scapular orientation based on measurable humerothoracic orientation has yet to be adapted for pitching and may improve upon currently recommended methods such as the acromion marker cluster (AMC). This study evaluates the ability of a pitching-specific individualized linear model to estimate scapular orientation in static positions throughout a throwing motion by comparing against palpation and an AMC. Individualized linear models were created for 14 collegiate pitchers by determining scapulothoracic and humerothoracic orientations at static arm postures throughout their individual dynamic throwing motions. Linear model and AMC estimates were compared against palpation at intermediate test positions within the throwing motion that were excluded from model creation. Linear model estimates were similar to palpation at all test positions and on all scapulothoracic axes while AMC estimates differed on internal/external rotation and anterior/posterior tilt during cocking (p = 0.001, p = 0.018) and follow-through (p = 0.003, p = 0.006). Linear model root mean square error (RMSE) values were smaller than AMC values for all positions/axes. Linear model RMSE values (2.8-6.3°) were within a range of published values previously deemed acceptable, while AMC values (5.1-15.8°) went beyond this range. The linear model approach accurately estimates static scapular orientation throughout a pitching motion and improves upon current methods. Future applications to dynamic pitching may facilitate understanding of how scapulothoracic and glenohumeral joint function relate to injury risks, rehabilitation, and performance.

Analysis of lower extremity side-reaching motion in junior high school baseball players

[Purpose] The aim of this study was to clarify the movement pattern of the pelvis and trunk of junior high school baseball players based on the lateral reach motion of the lower limb, which is related to poor pitching movement. [Participants and Methods] Twenty-five male students belonging to a baseball club participated in this study. Each participant performed the lower limb side reach movement in the standing position, during which the movements of the knee joint, hip joint, pelvis, and trunk were analyzed. [Results] A significant correlation was found between reach distance and reach leg hip abduction, supporting leg hip abduction, trunk side bending, and trunk tilt. We found a significant correlation between reach leg hip abduction and pelvic tilt and trunk side bending and between supporting leg hip abduction and pelvic tilt, knee valgus, and trunk side bending. Furthermore, we found a significant correlation between knee valgus and lower leg tilt and trunk tilt and between trunk side bending and pelvic tilt. [Conclusion] This study suggests that in the standing position movement at this age, the hip and trunk movements are related to and affect performance.

Effect of different trunk postures on scapular muscle activities and kinematics during shoulder external rotation

BACKGROUND

Shoulder external rotation at abduction (ER) is a notable motion in overhead sports because it could cause strong stress to the elbow and shoulder joint. However, no study has comprehensively investigated the effect of different trunk postures during ER. This study aimed to investigate the effect of different trunk postures on scapular kinematics and muscle activities during ER.

METHODS

Fourteen healthy men performed active shoulder external rotation at 90° of abduction with the dominant arm in 15 trunk postures. At maximum shoulder external rotation in 15 trunk postures, including 4 flexion-extension, 6 trunk rotation, and 4 trunk side-bending postures, as well as upright posture as a control, scapular muscle activities and kinematics were recorded using surface electromyography and an electromagnetic tracking device, respectively. The data obtained in the flexion-extension, trunk rotation, and trunk side-bending postures were compared with those obtained in the upright posture.

RESULTS

In the flexion-extension condition, scapular posterior tilt and external rotation significantly decreased, but the muscle activities of the lower trapezius and infraspinatus significantly increased in maximum trunk flexion. Moreover, scapular upward rotation and the activity of the serratus anterior significantly increased in maximum trunk extension. In the rotation condition, scapular posterior tilt and external rotation significantly decreased, but the activity of the serratus anterior significantly increased in the maximum contralateral trunk rotation posture. In the trunk side-bending condition, scapular posterior tilt and the external rotation angle significantly decreased.

CONCLUSION

Trunk postures affected scapular kinematics and muscle activities during ER. Our results suggest that different trunk postures activate the lower trapezius and serratus anterior, which induce scapular posterior tilt.