Youth Baseball Pitching Stride Length: Normal Values and Correlation With Field Testing

Measuring the Average Peak Timing of Kinematic Variables in Youth and Adolescent Baseball Pitchers

Background

Previous studies have examined the timing of peak kinematic variables during the pitching cycle in high school, collegiate, and professional pitchers. These same variables have been studied less in younger populations.

Purpose

To determine whether youth and adolescent baseball pitchers will experience peaks in certain kinematic variables at different times throughout the pitching cycle compared to professional/collegiate pitchers.

Study Design

Cross-sectional, descriptive study.

Methods

Twenty-four participants were recruited for testing consisting of five recorded pitches using 3-Dimensional VICON® motion analysis system. The maximum values and timing of the peak kinematic variables were averaged across all trials using VICON Polygon® data analysis software. These values were recorded as percentages of the pitching cycle, defined from foot contact (0%) to ball release (100%). The following variables were examined: shoulder external rotation range of motion, shoulder internal rotation velocity, trunk rotation range of motion, trunk rotation velocity, pelvic rotation velocity, and stride length. Descriptive outcomes were calculated and results were compared to previous studies examining the same variables in collegiate and professional pitchers.

Results

Twenty-four male participants (mean age 12.75 years, SD ± 2.02) were included in the study. Mean and standard deviations were identified for peak kinematic variables of shoulder external rotation ROM (158.71°, ±9.32), shoulder internal rotation velocity (92.26 rad/sec, ±19.29), trunk rotation velocity (15.94 rad/sec, ±1.68), trunk rotation ROM (23.57°, ±8.14), and average stride length (81.97% height ±4.57). Additionally, mean and standard deviations of peak kinematic variables were expressed as percentages to reflect when they occurred in the pitching cycle and included trunk rotation ROM (8.45%, ±12.72), pelvic rotation velocity (33.26%, ±16.42), trunk rotation velocity (41.59%, ±9.27), shoulder external rotation ROM (71.34%, ±6.61), and shoulder internal rotation velocity (86.93%, ±6.45).

Conclusion

The sequential order of each variable was similar in youth and adolescents in comparison to collegiate and professional pitchers. However, the timing of each variable within the pitching cycle occurred approximately 10% earlier in the younger pitchers. The findings suggest differences in pitching mechanics exist between younger and more experienced populations.

Level of Evidence

Level 3.

Stride Length and Torso Biomechanics As They Relate To Medial Elbow Injuries In Adolescent Aged Baseball pitchers: A Clinical Commentary

There is a limited amount of literature examining torso biomechanics and stride length while addressing their relationship to medial elbow injuries in the adolescent baseball pitcher. Anatomical changes, growth, early sport specialization, multiple team participation, mound distance, mound height, and high pitch counts place adolescent pitchers at an exceptionally higher risk for medial elbow injuries. Existing evidence indicates that decreased stride length and altered trunk rotation is correlated with increased medial elbow loading for the adolescent overhead athlete. Further research is required to quantify adequate parameters for torso kinematics, control, and their correlation to stride length, in order to positively affect the biomechanical transfer of energy and potentially prevent injuries during the overhead throwing motion. The purpose of this clinical commentary is to examine and summarize the role of torso biomechanics and stride length in relation to medial elbow injuries in adolescent baseball pitchers.

Level of Evidence

5.

Disabled Throwing Shoulder 2021 Update: Part 1-Anatomy and Mechanics

The purpose of this article is to provide updated information for sports health care specialists regarding the Disabled Throwing Shoulder (DTS). A panel of experts, recognized for their experience and expertise in this field, was assembled to address and provide updated information on several topics that have been identified as key areas in creating the DTS spectrum. Each panel member submitted a concise presentation on one of the topics within these areas, each of which were then edited and sent back to the group for their comments and consensus agreement in each area. Part 1 presents the following consensus conclusions and summary findings regarding anatomy and mechanics, including: 1) The current understanding of the DTS identifies internal impingement, resulting from a combination of causative factors, as the final common pathway for the great majority of the labral pathoanatomy; 2) intact labral anatomy is pivotal for glenohumeral stability, but its structure does not control or adapt well to shear or translational loads; 3) the biceps plays an active role in dynamic glenohumeral stability by potentiating "concavity compression" of the glenohumeral joint; 4) the ultimate function of the kinetic chain is to optimize the launch window, the precise biomechanical time, and position for ball release to most effectively allow the ball to be thrown with maximum speed and accuracy, and kinetic chain function is most efficient when stride length is optimized; 5) overhead throwing athletes demonstrate adaptive bony, capsular, and muscular changes in the shoulder with repetitive throwing, and precise measurement of shoulder range of motion in internal rotation, external rotation, and external rotation with forearm pronation is essential to identify harmful and/or progressive deficits. LEVEL OF EVIDENCE: Level V, expert opinion.

Relationships between Hip Flexibility and Pitching Biomechanics in Adolescent Baseball Pitchers

CONTEXT

Inadequate hip active range of motion (AROM) may stifle the energy flow through the kinematic chain and decrease pitching performance while increasing the risk for pitcher injury.

OBJECTIVE

To examine the relationship of hip AROM and pitching biomechanics during a fastball pitch in adolescent baseball pitchers.

DESIGN

Cross-Sectional study.

SETTING

Biomechanics laboratory.

PARTICIPANTS

A voluntary sample of 21 adolescent baseball pitchers (16.1 ± 0.8 yrs.; 183.9 ± 5.2 cm; 77.9 ± 8.3 kg). Main Outcome Measure (s): Bilateral hip internal rotation (IR), external rotation (ER), flexion, extension, and abduction AROM were measured. Three-dimensional biomechanics were assessed as participants threw from an indoor pitching mound to a strike zone net at regulation distance. Pearson correlation coefficients were used to determine correlations between hip AROM and biomechanical metrics.

RESULTS

Statistically significant negative correlations were found at foot contact between back hip ER AROM and back hip abduction angle (p=0.030, r=-0.474), back hip ER AROM and torso rotation angle (p=0.032, r=-0.468),and back hip abduction AROM and lead hip abduction angle (p=0.037, r=-0.458). Back hip extension AROM was positively correlated with increased stride length (p=0.043, r=0.446). Lead hip abduction AROM was also positively correlated with normalized elbow varus torque (p=0.034, r=0.464).

CONCLUSIONS

There were several relationships between hip AROM and biomechanical variables during the pitching motion. The findings support the influence hip AROM can have on pitching biomechanics. Overall, greater movement at the hips allows for the kinematic chain to work at its maximal efficiency, increasing pitch velocity potential.

Lumbopelvic Control and the Development of Upper Extremity Injury in Professional Baseball Pitchers

BACKGROUND

The baseball-throwing motion requires a sequential order of motions and forces initiating in the lower limbs and transferring through the trunk and ultimately to the upper extremity. Any disruption in this sequence can increase the forces placed on subsequent segments. No research has examined if baseball pitchers with less lumbopelvic control are more likely to develop upper extremity injury than pitchers with more control.

PURPOSE

To determine if baseball pitchers who sustain a chronic upper extremity injury have less lumbopelvic control before their injury compared with a group of pitchers who do not sustain an injury.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 49 asymptomatic, professional baseball pitchers from a single Major League Baseball organization participated. Lumbopelvic control was measured using an iPod-based digital level secured to a Velcro belt around each player's waist to measure anteroposterior (AP) and mediolateral (ML) deviations (degrees) during single-leg balance with movement and static bridge maneuvers. During a competitive season, 22 of these pitchers developed upper extremity injuries, while the remaining 27 sustained no injuries. Separate 2-tailed t-tests were run to determine if there were significant differences in lumbopelvic control between groups (P < .05).

RESULTS

There were no significant between-group differences for the stride leg (nondominant) during the bridge test in either the AP (P = .79) or the ML (P = .42) directions, or either direction during the drive leg bridge test (P > .68). However, the injured group had significantly less lumbopelvic control than the noninjured group during stride leg balance in both the AP (P = .03) and the ML (P = .001) directions and for drive leg balance in both the AP (P = .01) and the ML (P = .04) directions.

CONCLUSION

These results demonstrate that baseball pitchers with diminished lumbopelvic control, particularly during stride leg and drive leg single-leg balance with movement, had more upper extremity injuries than those with more control. Clinicians should consider evaluating lumbopelvic control in injury prevention protocols and provide appropriate exercises for restoring lumbopelvic control before returning athletes to competition after injury. Specific attention should be given to testing and exercises that mimic a single-limb balance task.

Relationship between stride length and maximal ball velocity in collegiate baseball pitchers

[Purpose] To evaluate the relationship between stride length during a pitch and maximal ball velocity and define the determinants of stride length in collegiate baseball pitchers. [Participants and Methods] Eighteen collegiate baseball pitchers participated in this study. Using a standard tape measure, the distance between each participant's legs was measured after maximal abduction of both hip joints in a standing position. The pitchers threw fastballs on an indoor pitching mound at an official pitching distance. The throwing motion was recorded with four high-speed video cameras (240 Hz), while the ball velocity was measured using a radar gun. The stride length at foot contact was calculated at the maximal ball velocity using a three-dimensional motion analysis system. [Results] The maximal ball velocity (mean 129.8 km/h) had a significant positive correlation with the absolute stride length during a pitch (r=0.55), but no correlation with the relative stride length (% body height, % lower extremity length, and % maximal open legs' width). Stride length during a pitch did not significantly correlate with the pitcher's body height, lower extremity length, and maximal open legs' width. [Conclusion] A longer stride length contributes to a higher ball velocity in collegiate baseball pitchers.

Changes in lower extremity function and pitching performance with increasing numbers of pitches in baseball pitchers

Compared to upper extremity function, the changes in lower extremity function with increasing numbers of pitches have not fully been investigated in baseball pitchers. In addition, little is known about the correlation between lower extremity function and pitching performance. The purpose of this study was to evaluate the effect of fatigue on lower extremity function and pitching performance in a simulated baseball game. Eighteen collegiate baseball pitchers threw 117 pitches in 9 innings (13 pitches per inning) with 5-min rest between innings at an official pitching distance in a simulated game. Isometric hip muscle strength (abduction and adduction) and squat jump performance (height, mean/peak power, and mean/peak velocity) were measured before and after the game. The mean ball velocity and pitching accuracy were assessed per inning. Ball velocity significantly decreased in the 7th (P=0.026) and 9th (P=0.001) innings compared to the 1st inning, but pitching accuracy did not change significantly. Hip abduction (P=0.009) and adduction (P=0.001) strength significantly decreased after the game, but squat jump performance did not significantly change before and after the game. A significant correlation between decreased ball velocity in the 9th inning and decreased hip adduction strength was found (P=0.011, r=0.583). Our findings suggest that hip abduction and adduction strength are susceptible to fatigue owing to repetitive throwing motions and that hip adduction strength, especially, is an important physical fitness factor for maintaining ball velocity during a game in baseball pitchers.

Youth Baseball Pitching Mechanics: A Systematic Review

Context:

Pitching injuries in youth baseball are increasing in incidence. Poor pitching mechanics in young throwers have not been sufficiently evaluated due to the lack of a basic biomechanical understanding of the “normal” youth pitching motion.

Objective:

To provide a greater understanding of the kinetics and kinematics of the youth baseball pitching motion.

Data Sources:

PubMed, MEDLINE, and SPORTDiscus databases were searched from database inception through February 2017.

Study Selection:

A total of 10 biomechanical studies describing youth pitching mechanics were included.

Study Design:

Systematic review.

Level of Evidence:

Level 3.

Data Extraction:

Manual extraction and compilation of demographic, methodology, kinetic, and kinematic variables from the included studies were completed.

Results:

In studies of healthy youth baseball pitchers, progressive external rotation of the shoulder occurs throughout the start of the pitching motion, reaching a maximum of 166° to 178.2°, before internally rotating throughout the remainder of the cycle, reaching a minimum of 13.2° to 17°. Elbow valgus torque reaches the highest level (18 ± 4 N·m) just prior to maximum shoulder external rotation and decreases throughout the remainder of the pitch cycle. Stride length is 66% to 85% of pitcher height. In comparison with a fastball, a curveball demonstrates less elbow varus torque (31.6 ± 15.3 vs 34.8 ± 15.4 N·m).

Conclusion:

Multiple studies show that maximum elbow valgus torque occurs just prior to maximum shoulder external rotation. Forces on the elbow and shoulder are greater for the fastball than the curveball.