The influence of shoulder abduction and external rotation on throwing arm kinetics in professional baseball pitchers

Professional baseball pitchers produce similar ball velocity and kinematics when pitching from the wind-up and stretch deliveries: a biomechanical analysis

Historically, the wind-up delivery is considered a more biomechanically advantageous pitching motion compared to the stretch. Recently, some pitchers have shifted to pitching exclusively from the stretch regardless of the game situation. The goal of this study was to compare temporal, kinematic and kinetic variables between the wind-up and stretch deliveries. Professional pitchers (n = 52, 189.1 ± 4.8 cm, 92.8 ± 8.4 kg) threw fastballs evaluated by 3D-motion capture (480 Hz) from both the wind-up and stretch deliveries. Within a pitcher, there was no significant difference in ball velocity between the two deliveries (p = 0.15). The stretch delivery was significantly quicker to ball release at toe off 2 (p < 0.001) (the last frame the pitcher's foot contacts the ground before progressing to maximum knee height) and maximum knee height (p < 0.001). The majority of differences occurred prior to foot contact. The wind-up delivery produced greater maximum shoulder external rotation (p < 0.001) and lead knee flexion at ball release (p < 0.001). Pitching from the stretch incurred greater shoulder superior force (p < 0.001). It remains unknown if this is clinically significant as pooled means show only a 2% difference. Therefore, pitching a fastball from either the wind-up or stretch delivery provides comparable mechanics and throwing arm load with likely comparable risk of injury.

Kinematic Modeling of Pitch Velocity in High School and Professional Baseball Pitchers: Comparisons With the Literature

Background

Kinematic parameters predictive of pitch velocity have been evaluated in adolescent and collegiate baseball pitchers; however, they have not been established for high school or professional pitchers.

Purpose

To create multiregression models using anthropometric and kinematics features most predictive for pitch velocity in high school and professional pitchers and compare them with prior multiregression models evaluating other playing levels.

Study Design

Descriptive laboratory study.

Methods

High school (n = 59) and professional (n = 337) baseball pitchers threw 8 to 12 fastballs while being evaluated with 3-dimensional motion capture (480 Hz). Using anthropometric and kinematic variables, multiregression models for pitch velocity were created for each group. A systematic review was conducted to determine previous studies that established kinematic models for ball velocity in youth, high school, and collegiate pitchers.

Results

Leg length was predictive of pitch velocity for high school and professional pitchers (P < .001 for both). When compared with previously established models for pitch velocity, almost all groups were distinct from one another when assessing age (P maximum < .001), weight (P max = .0095), and pitch velocity (P max < .001). Stride length was a significant predictor for the youth/high school pitchers, as well as the current study's high school and professional pitchers (P < .001 for all). Maximal shoulder external rotation (collegiate: P = .001; professional: P < .001) and maximal elbow extension velocity (high school/collegiate: P = .024; collegiate: P < .001; professional: P = .006) were shared predictors for the collegiate and current study's professional group multiregression models. Trunk flexion at ball release was a commonly shared predictor in the youth/high school (P = .04), high school/collegiate (P = .003), collegiate (P < .001), and the current study's professional group (P < .001).

Conclusion

Youth, high school, collegiate, and professional pitchers had unique, predictive kinematic and anthropometric features predictive of pitch velocity. Leg length, stride length, trunk flexion at ball release, and maximal shoulder external rotation were predictive features that were shared between playing levels.

Clinical Relevance

Coaches, clinicians, scouts, and pitchers can consider both the unique and the shared predictive features at each playing level when attempting to maximize pitch velocity.

Feasibility of the pitch efficiency rating: A novel tool for systematic assessment of pitching mechanics in developing throwing athletes

BACKGROUND

Injuries in younger baseball athletes continue to increase despite work characterizing risk factors. Three-dimensional (3D) motion capture may identify suboptimal pitching mechanics that predispose an athlete to injury, but 3D-motion analysis is often inaccessible. Thus, there is a gap between the current biomechanics literature and its practical application in young athletes. The current study aims to assess the reliability of the pitch efficiency rating (PER) as a systematic tool to evaluate throwing mechanics in developing baseball pitchers.

OBJECTIVE

To determine the feasibility of application and reliability of a novel, scientifically informed tool (PER) for the assessment of pitching mechanics.

DESIGN

Reliability study using Bland-Altman methods for assessing agreement between two raters.

SETTING

Academic medical center through community outreach.

PARTICIPANTS

Pitching mechanics were assessed and rated with the PER for 40 athletes (26 high school, 14 Division III), average age 19.0 years old (range 15.3-23.7 years old).

INTERVENTIONS

N/A.

MAIN OUTCOME MEASURES

Interrater and intrarater reliability as calculated by intraclass correlation coefficient (ICC).

RESULTS

For initial readings comparing interrater reliability between Rater 1 and Rater 2, the ICC was calculated at 0.80 (95% confidence interval [CI] 0.66-0.89) and 0.76 (95% CI 0.60-0.86) for the second set of ratings. Regarding intrarater reliability across reads, ICC was found to be 0.63 (95% CI 0.43-0.79) for Rater 1, and 0.91 for Rater 2 (95% CI 0.85-0.95).

CONCLUSIONS

The present study introduces the PER as a potential tool for evaluating pitching mechanics. However, the intrarater reliability of the PER did not meet preestablished criteria in one of the two pilot raters. Further study is needed to continue to assess the reliability of the tool across diverse demographics.

Adaptive pathology: new insights into the physical examination and imaging of the thrower's shoulder and elbow

Throwing with high velocity requires extremes of glenohumeral external rotation of the abducted arm where particularly high forces in the shoulder and elbow are endured. Repeated throwing leads to dominant-arm bony remodeling of the humerus, glenoid, and elbow, and multiple soft tissue changes that would be considered abnormal. Many of these features are thought to be adaptive and protective. The purpose of this work is to (1) define the concept of adaptive pathology; (2) review the mechanics of the throwing motion; (3) review pertinent physical examination and imaging findings seen in asymptomatic throwers' shoulders and elbows and describe how these changes develop and may be adaptive-allowing the thrower to perform at high levels; and then (4) review the principles of surgical treatment in the throwing athletes, which should focus on reducing symptoms, but not necessarily restoring the thrower's anatomy to normal.

Workload Comparison of Contemporary Interval Throwing Programs and a Novel Optimized Program for Baseball Pitchers

Background

In the rehabilitation of injured baseball pitchers, there is lack of consensus on how to guide a player back to pitching. It is unknown how different contemporary interval throwing programs (ITPs) progress in the amount of throwing workload.

Purposes

To 1) evaluate three prominent ITPs commonly employed in baseball pitcher rehabilitation and assess whether these ITPs produce training loads that increase in a controlled, graduated manner and 2) devise an ITP that produced training loads which increased steadily over time.

Study Design

Cross-sectional study.

Methods

Three publicly available ITPs from prominent sports medicine institutions were analyzed. Elbow varus torque per throw was calculated from a 2nd order polynomial regression based upon a relationship between recorded torque measurements and throwing distance measured from a database of 111,196 throws. The relative rate of workload increase was measured as an acute:chronic workload ratio (ACWR). For each ITP, throw counts, daily/acute/chronic workloads, and ACWR were calculated and plotted over time. Finally, an original ITP was devised based upon a computational model that gradually increases ACWR over time and finished with an optimal chronic workload.

Results

Each ITP exhibited a unique progression of throwing distances, quantities, and days to create different workload profiles. The three ITPs had throwing schedules ranging from 136 days to 187 days, ACWR spiked above or fell below a literature-defined "safe" range (i.e. 0.7 - 1.3) 19, 21, and 23 times. A novel ITP, predicated on a 146-day schedule and with a final chronic workload of 14.2, was designed to have no spikes outside of the safe range.

Conclusion

Existing ITPs widely utilized for rehabilitation of baseball pitchers exhibit significantly inconsistent variation in the rate of throwing load progression. Computational modeling may facilitate more incremental workload progression in ITPs, thereby reducing injury during rehabilitation and more efficiently condition a pitcher for return to competition.

Level of Evidence

3b.

Relationship Between Arm Path, Ball Velocity, and Elbow Varus Torque in Professional Baseball Pitchers

Background

Currently, most pitching instructors suggest a shorter arm path-the total distance the arm travels during pitching. Theoretically, this combination allows for better body segment sequencing, a more efficient energy transfer through the kinetic chain, and increased ball velocity, while limiting elbow varus torque.

Hypothesis

Shorter arm paths would be associated with increased ball velocity and decreased elbow varus torque.

Study Design

Descriptive laboratory study.

Methods

A total of 182 professional pitchers threw 8 to 12 fastball pitches while evaluated by 3-dimensional motion capture (480 Hz). The arm path was calculated as the total distance the hand marker traveled during the pitch. The pitch was divided into early, late, and total arm paths. A linear regression model assessed the interpitcher relationship between arm path, elbow varus torque, and ball velocity. A linear mixed-effects model with random intercepts assessed intrapitcher relationships.

Results

Interpitcher comparison showed that total arm path weakly correlated with greater elbow varus torque (P = .025). Strong correlations were found between ball velocity and early (R2 = 0.788; P < .001), late (R2 = 0.787; P = .024), and total arm paths (R2 = 0.792; P < .001). Strong positive intrapitcher correlations were found between elbow varus torque and early (R2 = 0.962; P < .001) and total arm path (R2 = 0.964; P < .001). For individual pitchers, there was a large variation in the early (30.1 ± 15.7 cm) and late (21.4 ± 12.1 cm) arm path. For every 30-cm (11.8-inch) increase in early arm path (the mean range for an individual pitcher), there was a 1.29-N (β = 0.0429) increase in elbow varus torque and a 0.354 m/s (0.79 mph) (β = 0.0118) increase in ball velocity.

Conclusion

A shorter arm path correlated with decreased elbow varus torque and decreased ball velocity in intrapitcher comparisons. Determining the individual mechanics that decrease elbow varus torque may help coaches and trainers correct these patterns.

Clinical Significance

A shorter arm path during the pitch can decrease elbow varus torque, which limits the load on the medial elbow but also has a detrimental effect on ball velocity. An improved understanding of the impact of shortening arm paths on stresses on the throwing arm may help minimize injury risk.

Forearm Pronation at Foot Contact: A Biomechanical Motion-Capture Analysis in High School and Professional Pitchers

Background

It has previously been speculated that baseball pitchers who display excessive forearm pronation at foot contact (FC) have a higher propensity toward ulnar collateral ligament injury and subsequent surgery.

Purpose

To evaluate the association between degree of forearm pronation/supination at FC and throwing arm kinetics in high school and professional pitchers, at both the individual (intrapitcher) and the group (interpitcher) level.

Study Design

Descriptive laboratory study.

Methods

High school (n = 41) and professional (n = 196) pitchers threw 8 to 12 fastballs while being assessed with a 3-dimensional motion-capture system (480 Hz). Pitchers at each playing level were divided into a supination or pronation subgroup depending on degree of forearm pronation at FC. Regression models were built to observe the relationship between forearm pronation at FC and kinetic and kinematic parameters of interest.

Results

At both the individual and the group level of high school and professional pitchers, there was no significant correlation between forearm pronation at FC and elbow varus torque (P _min = .21). For every 10° increase in forearm pronation at FC in the individual high school pitcher, elbow flexion at FC decreased by 5°, whereas maximum elbow extension velocity was achieved 0.6% later in the pitch. In addition, elbow medial force increased by 4.1 N and elbow varus torque increased by 0.8 N·m for every 10° increase in forearm supination at FC. For every 10° increase in forearm supination in the individual professional pitcher, ball velocity increased by 0.5 m/s, shoulder external rotation at FC decreased by 11°, and elbow medial force decreased by 5.5 N.

Conclusion

Supination- or pronation-predominant forearm motion during the pitch did not significantly differ between playing levels. Excessive forearm pronation at FC was not a significant risk factor for increased throwing arm kinetics for high school or professional pitchers. There was a weak positive association between forearm supination at FC and elbow varus torque in the individual high school pitcher. Ultimately, coaches and pitchers may be better served by redirecting their focus to other mechanical aspects of the pitch that may have stronger associations with injury risk implications as well as performance.

A Systematic Review of Lower-Body Kinematic and Strength Factors Associated With Pitch Velocity in Adult Baseball Pitchers

CONTEXT

Ball velocity for baseball pitchers is influenced by a multitude of factors along the kinetic chain. While a vast amount of data currently exist exploring lower-extremity kinematic and strength factors in baseball pitchers, no previous study has systematically reviewed the available literature.

OBJECTIVE

The aim of this systematic review was to perform a comprehensive assessment of the available literature investigating the association between lower-extremity kinematic and strength parameters and pitch velocity in adult pitchers.

EVIDENCE ACQUISITION

Cross-sectional studies that investigated the association between lower-body kinematic and strength factors and ball velocity in adult pitchers were selected. A methodological index for nonrandomized studies checklist was used to evaluate the quality of all included studies.

EVIDENCE SYNTHESIS

Seventeen studies met the inclusion criteria comprising a total of 909 pitchers (65%, professional, 33% college, and 3% recreational). The most studied elements were hip strength and stride length. The mean methodological index for nonrandomized studies score was 11.75 of 16 (range = 10-14). Pitch velocity was found to be influenced by several lower-body kinematic and strength factors including the following: (1) hip range of motion and strength of muscles around the hip and pelvis, (2) alterations in stride length, (3) alterations in lead knee flexion/extension, and (4) several pelvic and trunk spatial relationships throughout the throwing phase.

CONCLUSIONS

Based on this review, we conclude that hip strength is a well-established predictor of increased pitch velocity in adult pitchers. Further studies in adult pitchers are needed to elucidate the effect of stride length on pitch velocity given mixed results across multiple studies. This study can provide a basis for trainers and coaches to consider the importance of lower-extremity muscle strengthening as a means by which adult pitchers can improve pitching performance.