Comparison of Pelvis and Trunk Kinematics Between Youth and Collegiate Windmill Softball Pitchers.

BACKGROUND: The windmill softball pitch is a dynamic sporting movement that places softball pitchers at high risk of injury. Unlike baseball, there is limited research into the mechanical differences between softball pitchers of varying skill levels. PURPOSE/HYPOTHESIS: The purpose of this study was to compare pelvis and trunk kinematics between youth and collegiate softball pitchers. It was hypothesized that there would be significant differences in pelvis and trunk kinematics between these 2 groups. STUDY DESIGN: Descriptive laboratory study. METHODS: The pelvic and trunk kinematics of 90 softball pitchers were collected during full-effort pitching using a 3-dimensional motion capture system. Participants were grouped based on their age at the time of data collection (35 youth [mean age, 11 ± 1 years]; 55 collegiate [mean age, 20 ± 2 years]). We compared between-group differences in pelvic posterior tilt, lateral tilt, axial rotation, and axial rotation velocity as well as trunk extension, lateral flexion, axial rotation, and axial rotation velocity during the pitching phase between start of pitch and ball release (BR) using 1-dimensional statistical parametric mapping. Statistical significance was determined using Holmes-Sidák stepdown correction-adjusted P values (P '). RESULTS: Compared with youth pitchers, collegiate pitchers exhibited a more posteriorly tilted pelvis from the moment of start of pitch until 94% of the way between start of pitch and BR (P ' = .002) and a more laterally flexed trunk toward the glove side from the moment of start of pitch until 71% of the way between start of pitch and BR (P ' = .010). CONCLUSION: Collegiate pitchers displayed a more posteriorly tilted pelvis and more laterally flexed trunk toward the glove side during the windmill pitching motion when compared with youth pitchers. CLINICAL RELEVANCE: These findings add to the growing body of softball research and help elucidate mechanical differences between youth and collegiate softball pitchers.

Increased Upper Arm Length and Loading Rate Identified as Potential Risk Factors for Injury in Youth Baseball Pitchers.

BACKGROUND: In the throwing elbow, increased elbow torque has been correlated with increased injury risk. Additional insight into the relationships between anthropometric factors and elbow joint loading is warranted. PURPOSE: To investigate the relationship among physical limb length characteristics, elbow kinetics, and elbow kinematics in youth baseball pitchers and to examine the relationship between elbow varus loading rate and elbow kinetics. DESIGN: Descriptive laboratory study. METHODS: A total of 27 male youth baseball pitchers participated (mean ± SD: age, 15.8 ± 2.7 years; height, 176.3 ± 13.0 cm; weight, 71.7 ± 16.4 kg). Upper arm (UA) and forearm (FA) lengths were measured using a moveable sensor to digitize bony landmarks. Kinematic data were collected at 240 Hz using an electromagnetic tracking system. Participants threw 3 fastballs to a catcher at a regulation distance (60 ft 6 in), and the fastest velocity trial was used for analysis. Linear regression was used to determine the relationship among limb length characteristics, elbow kinetics, and elbow kinematics after accounting for the effects of body weight and height. RESULTS: Pitchers with longer UA length experienced increased maximum elbow varus torque (P = .005) and maximum net elbow force (P = .001). Pitchers with an increased forearm to UA ratio had decreased elbow compression force (P < .001) and exhibited a more flexed elbow at foot contact (P = .001). Pitchers with greater maximum loading rates experienced greater elbow varus torque (P = .002). CONCLUSION: In youth baseball pitchers, longer UA length and greater loading rate increase varus torque about the elbow during a fastball pitch. CLINICAL RELEVANCE: Longer UA length and greater loading rate may place pitchers at risk of injury because of their relationship with kinetic values.

Kinematic Differences Exist Between the Fastball, Changeup, Curveball, and Dropball Pitch Types in Collegiate Softball Pitchers.

BACKGROUND: A majority of softball literature focuses on the mechanics associated with pain and injury within a single pitch type per study; however, the generalizability of these findings is unknown since a kinematic comparison has yet to be performed between pitch types. Understanding kinematic differences between pitch types can be used to identify risk factors for injury, improve safety guidelines, and improve performance by linking specific mechanics with desired pitch outcomes. HYPOTHESIS/PURPOSE: The purpose of this study was to compare kinematics between the fastball, changeup, curveball, and dropball pitch types in collegiate softball pitchers. It was hypothesized that there would be significant kinematic differences between pitch types. STUDY DESIGN: Descriptive laboratory study. METHODS: A total of 28 female collegiate softball pitchers pitched 3 trials of each pitch type to a catcher at regulation distance. Pitch speed, stride length, trunk extension, trunk rotation, trunk lateral flexion, elbow flexion, and center of mass for each trial were calculated using an electromagnetic motion capture system and were averaged for analysis. A 1-way analysis of variance (ANOVA) was used to investigate pitch speed differences between the 4 pitch types. A 4 (pitch type) × 5 (event) within-athlete multivariate ANOVA was also used to determine kinematic differences. RESULTS: The results revealed a significant difference in pitch speed between pitch types; a pitch type main effect for trunk extension, trunk rotation, trunk lateral flexion, and center of mass; and an event main effect for all variables except stride length. The results also revealed a pitch type by event interaction for trunk flexion, trunk lateral flexion, and center of mass. Specifically, the dropball type had less trunk extension than the fastball at all pitching events. Similarly, the curveball type had a more posteriorly shifted center of mass than the dropball at the last 3 pitching events of foot contact, ball release and follow-through. CONCLUSION: Significant kinematic differences exist between pitch types, but these differences may be necessary to execute desired pitch outcomes. CLINICAL RELEVANCE: This is the first study to analyze kinematic differences between pitch types in softball pitchers. Understanding the effects of different pitch types on kinematic parameters may enhance injury prevention and performance strategies for softball pitchers.

Biceps Tendon Changes and Pitching Mechanics in Youth Softball Pitchers.

With the lack of pitch count regulation, youth softball pitchers are experiencing unremitting high stresses on the anterior shoulder. The purpose of this study was to examine the association of acute changes in the long head of the biceps tendon with pitching kinematics and kinetics in youth softball pitchers following an acute bout of pitching. Twenty-three softball pitchers (12.17±1.50 yrs.; 160.32±9.41 cm; 60.40±15.97 kg) participated. To investigate the association between biceps tendon changes and kinematic and kinetic changes from pre- to post-simulated game, each biceps tendon measure was split into those whose biceps tendon thickness, width, and/or area increased pre- to post-simulated game, and those whose did not. There were significant differences in biceps tendon longitudinal thickness (Z=- 2.739, p=0.006) and pitch speed; as well as a difference between groups in biceps tendon transverse thickness and the amount of change in trunk rotation at the start of the pitching motion (p=0.017) and the amount of change in trunk flexion at ball release (p=0.030). This study illustrates the association of trunk and lower extremity kinematics and shoulder kinetics with morphologic changes in the biceps tendon with an acute bout of windmill softball pitching.

DESCRIPTIVE PROFILE OF SHOULDER RANGE OF MOTION AND STRENGTH IN YOUTH ATHLETES PARTICIPATING IN OVERHEAD SPORTS.

BACKGROUND: The unilateral and repetitive nature of overhead sports, often result in a biomechanical overload of the upper extremity. Understanding the musculoskeletal shoulder range of motion (ROM) and strength patterns in the youth sports of baseball, softball, and tennis could assist injury prevention screening and further the development of conditioning and rehabilitation programs. PURPOSE: To generate a descriptive profile of shoulder musculoskeletal characteristics and determine whether bilateral differences in shoulder ROM exist in youth baseball, softball, and tennis athletes. A secondary aim was to determine whether shoulder rotational adaptations are correlated with playing position, sport, or years of experience. STUDY DESIGN: Descriptive Laboratory. METHODS: A total of 136 competitive youth overhead athletes (baseball: n = 51,12.8 ± 0.9yrs; softball: n = 63,12.3 ± 1.1yrs; and tennis: n = 22,12.5 ± 0.9yrs) participated. Bilateral shoulder internal (IR) and external (ER) passive ROM and external rotation strength were measured using an inclinometer and handheld dynamometer. RESULTS: Significant differences (p<.001) in bilateral shoulder ROM and ER strength were found between the athletes in the three sports. Post-hoc test revealed tennis athletes had greater bilateral shoulder ROM than both baseball and softball athletes, but baseball and softball athletes had greater bilateral ER strength than tennis athletes. There were no differences between baseball and softball athletes. Additionally, tennis athletes had greater bilateral internal rotation and total ROM but less ER strength than baseball pitchers, baseball positional athletes, softball pitchers, and softball positional athletes. There were no significant differences between positions and baseball and softball athletes. There were no significant correlations between playing position, sport, or years of experience. CONCLUSION: The results of this study showed differences in shoulder passive ROM and strength adaptations between youth tennis, baseball, and softball athletes. The descriptive nature of this study is impactful as it presents specific ROM adaptions seen in this population. Future research is needed to further evaluate if the "at risk" ROM identified in older populations holds true in the youth population. LEVEL OF EVIDENCE: Diagnosis, Level 3b.

Glenohumeral external rotation weakness partially accounts for increased humeral rotation torque in youth baseball pitchers.

OBJECTIVES: To examine differences in shoulder internal rotation (IR) torque among youth pitchers of above and below average relative glenohumeral (GH) rotation strength levels. It was hypothesized that differences in IR torque during the pitching motion would could be explained by differences in relative IR and external rotation (ER) strength. DESIGN: Descriptive laboratory study. METHODS: Isometric GH rotation strength and upper extremity pitching mechanics were assessed in 78 male youth baseball pitchers (12.7±2.0yrs; 1.63±14.0m; 56.9±12.4kg). Shoulder IR torque during the pitch was examined at maximum humeral external rotation (MER) and throughout the arm acceleration phase (ACC). Multivariate analysis of covariance (MANCOVA) was used to examine the differences in pitching IR torque between GH strength groups. RESULTS: A significant main effect of ER strength on the dependent variables was present after controlling for fastball velocity (λ=0.855, F2,72=6.13, p=0.003, ηp2=0.145). Follow up univariate tests indicated significant differences in IR torque between strength groups at MER (F1,73=12.36, p<0.001, ηp2=0.145) and during ACC (F1,73=6.65, p= 0.012, ηp2=0.083). Participants who displayed ER strength at or below the group mean experienced greater IR torque at MER and greater average IR torque during ACC than participants who displayed ER strength above the group mean. CONCLUSIONS: Weakness of the GH ER musculature partially accounts for increased shoulder IR torque during pitching.

Lumbopelvic-Hip Complex and Scapular Stabilizing Muscle Activations During Full-Body Exercises With and Without Resistance Bands.

Wasserberger, KW, Downs, JL, Barfield, JW, Williams, TK, and Oliver, GD. Lumbopelvic-hip complex and scapular stabilizing muscle activations during full-body exercises with and without resistance bands. J Strength Cond Res 34(10): 2840-2848, 2020-Inefficient sequencing in the kinetic chain has been linked to decreased performance and increased injury risk. Resistance band usage is very common in baseball/softball due to accessibility and low cost. However, resistance band use has primarily focused on the rotator cuff and surrounding shoulder musculature, thereby ignoring the rest of the kinetic chain. Currently, it is unclear whether resistance bands are effective tools for training musculature outside the throwing extremity. Thus, the purpose of this study was to examine muscle activations of the lumbopelvic-hip complex (LPHC) and scapular stabilizing musculature during 4 full-body exercises with and without the use of a resistance band. Twenty healthy, active individuals (174.39 ± 1.58 cm; 74.10 ± 1.75 kg; 21.85 ± 1.13 years) participated. Data were collected through surface electromyography for the LPHC and scapular stabilizing musculature during 4 full-body exercises with and without a resistance band. Statistical analyses were used to determine significant differences in activation levels between exercises and within exercises between conditions. Data showed a significant difference on muscle activation based on the interaction between resistance band usage and exercise choice (Λ = 0.276, F24, 136.92 = 3.19, p < 0.001). Adding a resistance band was effective in increasing muscle activation within the scapular stabilizing musculature. Conversely, the use of a resistance band was not as effective in increasing the activation of LPHC musculature. Future studies should investigate exercises that increase LPHC musculature activation. Coaches and clinicians can use these results to make more informed decisions when prescribing exercises to athletes for performance enhancement and rehabilitation.