RESUMO
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.
RESUMO
Background: Interval throwing programs are used in rehabilitation of throwing injuries, especially ulnar collateral ligament injuries. Athletes who are rehabilitating begin by throwing on flat ground progressing through increasing distances, number of throws, and intensity of throwing. If the athlete is a baseball pitcher, the flat-ground throwing phase is followed by pitching on a mound at progressively increased effort. The goal is to build back arm strength and capacity with an emphasis on proper mechanics. Purpose: To determine whether interval throwing progressively builds joint kinetics (specifically, elbow varus torque) to the level required during full-effort baseball pitching. A secondary purpose was to examine the kinematics produced during interval throwing compared to those seen during baseball pitching. Study Design: Systematic Review. Methods: Following PRISMA guidelines, PubMed, Embase, Web of Science, SPORTDiscus, and Google Scholar were systematically searched for biomechanical studies of flat-ground throwing and partial-effort pitching in baseball between 1987 and 2023. Studies that reported the biomechanics of either flat-ground throwing, or partial-effort pitching were included in this review. The AXIS tool was used to assess study quality. Results: Thirteen articles met the inclusion criteria. Ten studies were determined to be of moderate quality, while three studies were deemed high quality. Elbow varus torque during partial-effort pitching was less than during full-effort pitching. Elbow varus torque for most flat-ground throws did not exceed full-effort pitching torque. While most studies showed increased elbow varus torque with increased flat-ground throwing distance, the distance at which elbow varus torque matched or exceeded full-effort pitching elbow varus torque was not consistent.As flat-ground throwing distance increased, shoulder external rotation angle and shoulder internal rotation velocity increased. Arm slot (forearm angle above horizontal) decreased as flat-ground throwing distance increased. For varied effort pitching, shoulder external rotation angle, shoulder internal rotation velocity, elbow extension velocity, and ball velocity increased as effort increased. While the front knee extended slightly from foot contact to ball release in full-effort pitching, the front knee flexed slightly during partial-effort pitching. Conclusions: An interval throwing program progressively builds elbow varus torque up to levels produced in full-effort baseball pitching. While differences exist between interval throwing kinematics and pitching kinematics, the patterns are similar in general. Level of Evidence: 2.
RESUMO
The purpose of this study was to compare human static pose estimation data measured with a single-view image-based system and a multi-camera marker-based system. Thirty participants (20 male/10 female, mean ± standard deviation 29.1 ± 10.0 years old, 1.75 ± 0.10 m tall, 79.1 ± 18.0 kg) performed six repetitions each of static holds of arm-raises and squats, in a different orientation for each repetition. These trials were captured simultaneously with a 120-Hz 12-camera marker-based system and a variable-frequency single-view image-based system. Data for each trial were time-synchronized between the two systems using a near-infrared LED-light that was visible to both systems. Discrete measurements of bilateral shoulder angles during arm-raises and bilateral knee angles during squats were compared between the systems using Bland-Altman plots and descriptive statistics. Pearson correlation coefficients were calculated, comparing the participant trial mean values across systems. Finally, a two-way ANOVA was used to examine whether participant orientation in the capture volume significantly affected either system. Biases for discrete measurements ranged in magnitude from 1.3 to 1.9°, and standard deviations of the differences between systems ranged from 2.4 to 4.7°. Pearson correlation coefficients were all above 0.97, and the ANOVA was unable to find a statistically significant orientation effect for either system. Thus, the marker-based and image-based systems produced similar measurements of static shoulder and knee angles. Future work should examine more complex measurements using volumetric scan-based models and also investigate the ability of single-view image-based systems to measure dynamic movements.
