Upper Extremity Pain and Pitching Mechanics in National Collegiate Athletic Association (NCAA) Division I Softball

A Model for Causality of Pitching-related Overuse Injuries in Women's Fastpitch Softball

Fastpitch softball is a popular women's sport, and athletes, particularly pitchers, are at high risk for overuse injury. Softball-related injury rates are low; however, the prevalence of overuse injuries is high. Injuries at the high school and collegiate levels occur early in the season, and approximately 50% of shoulder and elbow injuries in softball are attributable to overuse. Survey research showed 77% of high school pitchers pitch with pain, and 73% of collegiate pitchers reported an overuse injury in the previous season. Modifiable and non-modifiable intrinsic and extrinsic risk factors contribute to injury risk in a model that can be used in history taking, clinical examination, and management of softball-related injuries. In this manuscript, we present a scoping review of fastpitch softball injury research by competitive levels from 1990 to present. We also introduce a model for overuse injury causality in this athlete population. With this information, clinicians will be able to identify risk factors related to injury in softball pitchers. More research is needed to make evidence-based recommendations for injury prevention in this athlete population.

Understanding Shoulder and Elbow Injuries in the Windmill Softball Pitcher

Although pitching-related injuries in the overhead athlete have been studied extensively, injuries associated with windmill pitching are not as clearly elucidated. Windmill pitching produces high forces and torques in the upper extremity, and studies have shown it creates similar shoulder and elbow joint loads to those reported in baseball pitchers. Studies have shown that the windmill pitching motion generates high levels of biceps activation with an eccentric load, placing the biceps at increased risk for overuse injuries. Although the American Orthopaedic Society for Sports Medicine published prevention guidelines including recommendations for maximum pitch counts in softball, these recommendations have not been adopted by most United States softball governing bodies. The repetitive windmill motion in conjunction with high pitch count demands in competitive softball creates notable challenges for the sports medicine physician. As with overhead throwing athletes, identifying and preventing overuse is crucial in preventing injuries in the windmill pitcher, and prevention and rehabilitation should focus on optimizing mechanics and kinematics, core, hip, and lower body strength, and recognition of muscle fatigue. With more than two million fastpitch softball participants in the United States, it is essential to better understand the etiology, evaluation, and prevention of injuries in the windmill pitching athlete.

Effects of Increasing Pitch Count on Pitch Type Ball Metrics and Release Height in High School Softball Pitchers

BACKGROUND

Softball research has investigated changes in physical characteristics, mechanics, and ball speed as elements of fatigue. However, the influence of pitch volume on ball metrics is unclear. The purpose of this study was to investigate the influence of pitch volume on ball performance and release metrics in softball pitchers across different pitch types.

HYPOTHESIS

As pitch volume increased, there would be a decrease in ball metrics of the fastball and changes in breaking pitches would be observed earlier than the fastball or changeup.

STUDY DESIGN

Descriptive laboratory study.

LEVEL OF EVIDENCE

Level 5.

METHODS

A total of 21 (15.4 ± 1.6 years; 1.6 ± 0.2 m; 76.0 ± 17.2 kg) softball pitchers participated. Procedures consisted of participants pitching a simulated game consisting of 100 pitches, taking a 30-minute break, and then throwing 12 pitches to simulate the first inning of a doubleheader. Participants randomly threw each pitch type (fastball, changeup, curveball, or dropball). Ball performance and release metrics were measured using a Rapsodo portable pitch tracker.

RESULTS

A 3 (time) by 4 (pitch type) multivariate analysis of variance revealed that pitch speed was significantly higher in the first inning compared with the last inning and the doubleheader inning. The fastball, curveball, and dropball revealed a significant difference in pitch speed between timepoints. Specifically, the curveball and dropball first-inning pitch speed was significantly greater than the last and doubleheader inning. Alternatively, the fastball had a significant increase in pitch speed from the last inning to the doubleheader inning.

CONCLUSION

The typical 30-minute break given between games for doubleheaders may be sufficient recovery time for the fastball but not for the curveball and dropball.

CLINICAL RELEVANCE

The Rapsodo device is an accessible method of tracking ball performance and pitch release metrics and could be helpful in identifying when a pitcher may be experiencing performance detriments in response to increasing pitch count.

Evaluating Risk Factors for Biceps Tendon Injuries in Softball Players: A Systematic Review

OBJECTIVE

Softball players commonly suffer overuse injuries due to the demands of repetitive throwing. The biceps tendon plays an important role in stabilizing the shoulder during the windmill pitch. The purpose of this study was to evaluate the measures used to identify and study biceps tendon pathology in softball players.

DESIGN

This was a systematic review.

SETTING

PubMed MEDLINE, Ovid MEDLINE, and EMBASE were searched.

PARTICIPANTS

Studies that investigated biceps tendon injuries in softball players.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Range of motion (ROM), strength, and visual analog scale data were collected.

RESULTS

Of 152 search results, 18 were included. A total of 536 of 705 athletes (76%) were softball players (average age 14-25 years). Five of 18 articles (27.7%) studied changes in external rotation with the shoulder at 90 degrees of abduction, and 4 of 18 (22.2%) studied internal rotation. Two of 18 studies (11.1%) examined ROM or strength changes in forward flexion.

CONCLUSIONS

While researchers agree that the windmill pitch places significant stress on the biceps tendon, our study finds that the metrics used to evaluate shoulder pathology in these players primarily evaluate the rotator cuff without isolating the biceps tendon. Future studies should include clinical tests and biomechanical metrics more specific to identifying biceps and labral pathology (eg, strength, fatigue, and ROM in glenohumeral forward flexion, elbow flexion, and forearm supination) and attempt to clarify differences in pathology between pitchers and position players to better characterize the frequency and severity of biceps tendon pathology in softball players.

Softball Pitchers' Body Segment Girths Are Associated with Varied Biomechanics at Ball Release of the Pitch

PURPOSE

The purpose of this study was to examine the relationships between pitcher trunk and throwing arm girth with kinematics at ball release of the softball pitch. Softball pitchers can be of various shapes and sizes; however, it is unknown if segment girth might influence pitch biomechanics. Because of the importance of body positioning at ball release of the windmill pitch, this study examined the relationship between segment girth and pitch biomechanics at ball release.

METHODS

Forty-two pitchers volunteered to participate (1.706 ± 0.061 m, 74.98 ± 15.94 kg, 15.5 ± 1.7 yr). Participants' throwing upper arm, chest, waist, and hip girth were measured. Participants then pitched fastballs to a catcher (43 ft) while an electromagnetic motion capture system synced with a force plate and motion analysis software collected kinematic data (sampled at 240 Hz).

RESULTS

Linear regressions revealed that upper arm, chest, and waist girth were associated with throwing arm shoulder horizontal abduction. Greater segment girth was associated with less horizontal abduction at ball release of the pitch.

CONCLUSIONS

Segment girth is related to pitch biomechanics and may influence body positions at crucial softball pitch events such as ball release.

CLINICAL RELEVANCE

Understanding biomechanical differences according to body segment girth is important for safe and optimal player development and performance.

Comparison of Peak Shoulder Distraction Forces Between Pain and Pain-Free Youth Baseball Pitchers

Background

Increased shoulder distraction force during a baseball pitch may make a pitcher susceptible to rotator cuff or glenohumeral labral injuries. A precursor to a pitching injury may be pain experienced in the throwing arm.

Purpose

To (1) compare peak shoulder distraction (PSD) forces in youth baseball pitchers with and without upper extremity pain when throwing a fastball and (2) assess if PSD forces across trials differ between pain and pain-free groups.

Study Design

Controlled laboratory study.

Methods

A total of 38 male baseball pitchers aged 11 to 18 years were separated into a pain-free group (n = 19; mean age, 13.2 ± 1.7 years; mean height, 163.9 ± 13.5 cm; mean weight, 57.4 ± 13.5 kg) and a pain group (n = 19; mean age, 13.3 ± 1.8 years; mean height, 164.9 ± 12.5 cm; mean weight, 56.7 ± 14.0 kg). Pitchers in the pain group indicated that they experienced pain in their upper extremity while throwing a baseball. Pitching mechanical data from 3 fastballs per pitcher were recorded with an electromagnetic tracking system and motion capture software. The mean PSD (mPSD) was calculated as the mean PSD of 3 pitches per pitcher, the trial with the highest recorded PSD was determined as the maximum-effort PSD (PSDmax), and the PSD range (rPSD) was defined as the difference of the PSD force of the trial with the highest PSD and the lowest PSD for each pitcher. The PSD force was normalized to the pitcher's body weight (%BW). Pitch velocity was also recorded.

Results

The mPSD force was 114%BW ± 36%BW for the pain group and 89%BW ± 21%BW for the pain-free group. Pitchers in the pain group exhibited a significantly higher PSDmax force (t_30.548 = 2.894; P = .007) and mPSD force (t_29.231 = 2.709; P = .009) compared with those in the pain-free group. There were no significant between-group differences in the rPSD force or pitch velocity.

Conclusion

The normalized PSDmax force was higher in pitchers who experienced pain while throwing fastballs compared with pitchers who were pain-free while throwing.

Clinical Relevance

Baseball pitchers who experience pain in their throwing arm are likely to have higher shoulder distraction forces. Improvement in pitching biomechanics and corrective exercises may assist in the mitigation of pain while pitching.

Sports-Related Shoulder Injuries Among Female Athletes

PURPOSE OF REVIEW

The objectives of this review are to explore the recent literature evaluating sports-related shoulder injuries among female athletes.

RECENT FINDINGS

Recent literature has highlighted sex-related differences in injury trends and patterns among athletes. Increased participation of women in both recreational and professional sports has resulted in increased exposure to injury. While men experience greater rates of shoulder injury overall, women tend to experience more overuse-related injuries. Evidence also suggests women are more susceptible to shoulder laxity and rotator cuff tears. In comparison to their male counterparts, women note poorer function, increased pain, and decreased activity level following shoulder injuries. Women may also be more likely to experience worse outcomes following surgical intervention. Sex-related differences in injury patterns and outcomes results from a combination of molecular and environmental influences, including hormone pathways, shoulder morphology, and differing rates of participation in, and athletic regulations among, certain sports. Sex-related differences occur in how athletes sustain, experience, and recover from sports-related injuries. A comprehensive understanding of sex-related injuries enhances clinical decision making, treatment, and recovery. Further research is needed to clarify sex as an independent variable when evaluating sports-related shoulder injuries.

Pelvis and Trunk Energy Flow in Collegiate Softball Pitchers With and Without Upper Extremity Pain

BACKGROUND

The softball pitch is a full-body motion, where efficient proximal to distal energy flow through the kinetic chain is said to reduce stress at the upper extremity. Although altered trunk kinematic parameters are associated with upper extremity pain in softball pitchers, further research is needed to determine whether differences exist in proximal energy flow between softball pitchers with and without pain.

HYPOTHESIS/PURPOSE

To examine pelvis and trunk energy flow during the acceleration phase of the pitch in collegiate softball pitchers with and without upper extremity pain. It was hypothesized that those with upper extremity pain would have less energy flowing into the proximal ends of the pelvis and trunk as well as less energy flowing out of the distal ends of the pelvis and trunk during the acceleration phase when compared with pitchers who did not have upper extremity pain.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 54 female National Collegiate Athletic Association Division I softball pitchers (age, 20.2 ± 2.0 years; height, 173.5 ± 6.9 cm; weight, 78.5 ± 11.5 kg) were assigned to pain (n = 17) and pain-free (n = 38) groups. Participants pitched 3 maximal effort rise-balls for a strike, and the average of the 3 trials was used for analysis. Kinematic data were collected at 100 Hz using an electromagnetic tracking system. A segment power analysis was performed to quantify energy flow for the pelvis and trunk. The Mann-Whitney U test was used to compare pelvis and trunk energy flow during the acceleration phase of the pitch as well as pitch velocity between collegiate softball pitchers with and without upper extremity pain.

RESULTS

No significant differences were found between pelvis and trunk energy flow during the acceleration phase or pitch velocity between collegiate softball pitchers with and without upper extremity pain (all P values >.057).

CONCLUSION

Previous research determined that kinematic parameters differ between collegiate pitchers with and without upper extremity pain. However, the current study found no difference in pelvis and trunk energy flow or pitch velocity. Although altered kinematics in collegiate pitchers with upper extremity pain may serve as compensation patterns to maintain pitch velocity and proximal energy flow, future research is needed to confirm this postulation.

CLINICAL RELEVANCE

The lack of energy flow differences between upper extremity pain groups suggests that pitchers may adapt their biomechanics to maintain trunk and pelvis energy flow patterns. Coaches, athletes, and clinicians should know that movement adaptations can allow for maintained performance levels but may result in the presence of pain that may manifest in other deleterious and injury-susceptible biomechanics.

An Investigation of Bilateral Symmetry in Softball Pitchers According to Body Composition

Introduction

High body fat percentage (bf%) is considered a potential injury risk factor for softball pitchers amidst the already high rates of pitching-related injury. Similarly, research points out that large bilateral asymmetries are another risk factor for softball pitchers. As softball pitching is a highly asymmetric sport and the repetitive nature of the windmill pitch places high stress on the body while pitchers are in unbalanced and asymmetric positions, research examining body composition and asymmetry is necessary.

Purpose

The purpose of this study was to compare functional characteristics of softball pitchers with a healthy and a high bf%. Bilateral symmetry was assessed for pitchers' hip and shoulder isometric strength (ISO) and range of motion (ROM) between the following two groups of softball pitchers: (1) those with a high bf% (≥32%) and (2) those with a healthy bf% (<32%).

Methods

A total of 41 high school female softball pitchers from the southern United States agreed to participate (1.69 ± 0.07 m, 76.14 ± 17.08 kg, 15.1 ± 1.1 years). Pitchers completed a dual-energy X-ray absorptiometry (DEXA) scan and were grouped into one of the following two categories based on their bf%: healthy (<32 bf%) and high (≥32 bf%). Bilateral symmetry was assessed for pitchers' hip and shoulder ISO and ROM using a handheld dynamometer and inclinometer, respectively. Bilateral arm bone and lean mass was also measured via the DEXA.

Results

Mixed analyses of variance revealed a significant interaction between bf% groups and side dominance for internal rotation shoulder ROM, F_{(1, 39)} = 14.383, p < 0.001, η²_p = 0.269. Main effects for side dominance were also observed for shoulder external rotation ISO, F_{(1, 39)} = 8.133, p = 0.007, η²_p = 0.173, hip internal rotation ISO, F_{(1, 39)} = 4.635, p = 0.038, η²_p = 0.106, arm bone mass, F_{(1, 39)} = 38.620, p < 0.001, η²_p = 0.498, and arm lean mass, F_{(1, 39)} = 101.869, p < 0.001, η²_p = 0.723.

Conclusion

Asymmetries and slight differences in functional characteristics exist between bf% groups. Altered functional characteristics may influence pitchers' windmill pitch movement and should be acknowledged by support staff to improve softball pitchers' health and longevity.

Implications

Insight into asymmetries can help researchers and clinicians understand the implication of excess body fat and further theorize mechanisms of injury among this athlete population.

The 100 Most-Cited and Influential Articles in Collegiate Athletics

Background

Bibliometric citation analyses have been widely used in medicine to help researchers gain foundational knowledge about a topic and identify subtopics of popular interest for further investigations. There is a lack of similar research in collegiate athletics.

Purpose

To identify the 100 most-cited research publications related to collegiate athletics.

Study Design

Cross-sectional study.

Methods

The Clarivate Analytics Web of Knowledge database was used to generate a list of articles relating to collegiate athletics on January 24, 2022. Articles were filtered by the total number of citations, and the 100 most-cited articles were selected. For each article, we identified and analyzed the following: author name, publication year, country of origin, journal name, article type, main research topic area, competitive level, sex of study population, and level of evidence.

Results

Of the top 100 most-cited articles, 63 were related to medicine. In total, 96% of articles were published in the United States, and 80% were published in the year 2000 or later. Of the top 100 articles, 85 were observational; only 5 were experimental. The sport most represented was soccer, followed by football, baseball, and basketball. Of the top 100 articles, 21 were published in a single journal, the American Journal of Sports Medicine. Ten authors published ≥5 of the top 100 most-cited studies.

Conclusion

The majority of top 100 articles were published in the United States after 1999 and primarily focused on medicine-related topics. Soccer was studied by more articles than football, baseball, and basketball. An author's prestige may have influenced the likelihood of citation. The top 100 most-cited studies provide researchers, medical students, residents, and fellows with a foundational list of the most important and influential academic contributions to the literature on collegiate athletics.

Athlete body composition influences movement during sporting tasks: an analysis of softball pitchers' joint angular velocities

Softball pitchers are often above-average size and frequently injured; therefore, it is necessary to understand how biomechanics can change according to pitcher body composition. The purpose of this study was to examine the relationship between joint peak angular velocities and pitch velocity, as well as examine how pitchers' joint angular velocities differ between high and healthy body-fat percentage (BF%) groups. Forty high-school and college softball pitchers (170.6 ± 6.3 cm, 75.5 ± 16.1 kg, 16 ± 2 years, 34.6 ± 7.4 BF%) completed body composition testing and were placed in one of two groups: 1) high-fat% (≥32%) or 2) healthy-fat% (<32%). Pitchers completed fastball trials. Kinematic data were tracked using an electromagnetic system synced with motion analysis software. Peak and times-series joint angular velocities were tracked over the final 101 frames of the pitch. Pitch velocity was significantly correlated with peak elbow flexion (r = .380, p = .016) and wrist flexion (r = .621, p < .001) angular velocity. A small difference in elbow joint angular velocity was found between body fat percentage groups between ball release and follow-through (SPM(t)1,38 = 3.296, p = .003). Peak joint angular velocities are related to pitch velocity and slight differences in movement patterns exist according to pitcher body fat percentage.

Peak Elbow Flexion Does Not Influence Peak Shoulder Distraction Force or Ball Velocity in NCAA Division I Softball Pitchers

Background:

High shoulder distraction force has been observed in softball pitchers during the acceleration phase (top of the pitch to ball release) of a pitch. Increasing elbow flexion may reduce shoulder forces and the susceptibility to pain by shortening the lever arm of the throwing arm.

Purpose:

To determine the association of peak elbow flexion during the acceleration phase of the pitch with peak shoulder distraction force and ball velocity.

Study Design:

Descriptive laboratory study.

Methods:

A total of 61 female collegiate softball pitchers (mean age, 19.9 ± 1.9 years; mean height, 175.7 ± 5.7 cm; mean weight, 83.6 ± 12.7 kg; 49 right-handed) volunteered for this study. Biomechanical data were collected with a 3-dimensional electromagnetic tracking system while the pitchers threw 3 maximal-effort fastballs at a regulation distance. Peak elbow flexion and peak shoulder distraction force were calculated for the acceleration phase and averaged across the 3 trials. Ball velocity was assessed with a radar gun.

Results:

Simple linear regression analyses indicated that peak elbow flexion did not influence peak shoulder distraction force during the acceleration phase of the pitch (F(1,59) = 2.412; P = .126), with R² = 0.023. Additionally, peak elbow flexion during the acceleration phase of the pitch did not influence ball velocity (F(1,59) = 2.435; P = .124), with R² = 0.023. A bivariate correlation analysis showed a significant association between ball velocity and shoulder distraction force (R² = 0.343; P = .007) in which ball velocity constituted approximately 34% of the variance in shoulder distraction force.

Conclusion:

Peak elbow flexion did not influence ball velocity or peak shoulder distraction force during the acceleration phase of a windmill softball pitch. However, there was a significant and positive relationship between ball velocity and peak shoulder distraction force. These results may indicate that ball velocity and other kinematic variables may be more related to shoulder distraction force than elbow flexion.

Clinical Relevance:

Increasing elbow flexion can shorten the lever arm, but it did not reduce shoulder distraction force or increase ball velocity. Therefore, elbow flexion may be more useful as a description of the pitching style rather than a single measure related to increased performance or the risk of injuries. Future research should continue to examine the relationship between other kinematic parameters with shoulder distraction force.

Biomechanics Related to Increased Softball Pitcher Shoulder Stress: Implications for Injury Prevention

BACKGROUND

Softball pitchers exhibit high throwing shoulder distraction force, which is a theorized mechanism of throwing shoulder overuse injury. Windmill pitching involves a variety of highly individualistic pitching styles, and certain kinematics preceding ball release likely influence the amount of shoulder stress that a pitcher accrues.

PURPOSE

To examine the association of trunk and throwing arm kinematics, kinetics, and timing variables with peak throwing shoulder distraction force in high school softball pitchers.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 37 high school pitchers (mean ± SD; height, 1.71 ± 0.06 m; weight, 75.53 ± 16.12 kg; age, 16 ± 2 years) threw 10 fastball pitches at regulation distance (43 ft [13.1 m]) and with maximum effort. Kinematic data were collected at 240 Hz using an electromagnetic motion capture system synced with motion analysis software. The 3 fastest pitches were averaged and analyzed. Kinematic, kinetic, and timing variables were entered into a stepwise linear regression analysis.

RESULTS

Four variables were included in the significant model (F_4,39 = 147.51; P < .001) and explained peak shoulder distraction force (R² = 0.944; adjusted R² = 0.938; SE = 0.036): increased peak elbow distraction force (t = 19.90; P < .001) and extension moment (t = 3.63; P = .001), as well as decreased elbow flexion velocity (t = -2.37; P = .023) and trunk flexion at foot contact of the pitch (t = -3.00; P = .005).

CONCLUSION

Elbow kinetics and angular velocity, as well as trunk positioning at foot contact, are associated with peak throwing shoulder distraction force in high school softball pitchers.

CLINICAL RELEVANCE

Variables associated with peak throwing shoulder distraction force provide information regarding injury mechanism and coachable cues that might reduce shoulder injury risk among pitchers.

Segment power analysis of collegiate softball hitting

The primary aim of this investigation was to describe the energy flow through the kinetic chain during softball hitting using a segmental power analysis. Twenty-three NCAA Division I collegiate softball athletes (20.4 ± 1.7 yr; 166.7 ± 22.0 cm; 74.9 ± 15.9 kg) performed three maximum effort swings off a stationary tee placed in the middle of the strike zone. Pelvis, trunk, humerus, forearm and hand segment powers were integrated across four phases of the softball swing (load, stride, acceleration, and follow-through). The load and stride phases had low segment energy inflow and outflow values as well as net segment energy flow for all body segments compared to subsequent phases of the swing. The acceleration phase showed large trunk inflow values relative to the pelvis. There was also descriptively larger front compared to back-side upper extremity inflow. Finally, the follow-through phase showed primarily energy outflow for the upper extremity segments likely attributed to slowing down rotation.

Shoulder and Hip Range of Motion and Strength Changes Throughout a Season in College Softball Players

BACKGROUND

Many studies have been done on the strength and mobility of the shoulder and hip in baseball players, but fewer studies have examined these metrics in softball players.

PURPOSE

The purpose of this study was to observe and analyze changes in range of motion (ROM) and strength at the hip and shoulder that occur over the course of a competitive season, to describe preseason ROM and strength at the hip and shoulder in healthy college softball players through side-to-side comparison, and to compare measurements between pitchers and position players.

STUDY DESIGN

Descriptive Cohort Study.

METHODS

Data was collected over the course of six seasons, and a total of fifty-four healthy softball athletes (including pitchers and postiion players) who completed at least one set of preseason and postseason measurements were included. Subjects underwent passive ROM (External rotation [ER], internal rotation [IR], total arc of motion [TAM]) and strength (ER/IR at the shoulder, abduction/extension at the hip) measurements at preseason and postseason timepoints.

RESULTS

Over a season, position players demonstrated an increase in all ROM metrics in both shoulders, except dominant IR, and a decrease in ER strength at the shoulder bilaterally (p<0.05). They also showed decreased ROM in all metrics across both hips (p<0.05). Pitchers had increased IR and TAM ROM in the dominant shoulder, decreased strength in both shoulders (ER throwing; ER and IR non-throwing), decreased ROM in both hips, and decreased abduction strength in the non-dominant hip (p<0.05). Position players showed less preseason IR in the dominant shoulder compared to non-dominant IR (Dominant: 31.7 ± 1.6°, Non-dominant: 37.0 ± 2.3°; p<0.05).

CONCLUSION

Softball pitchers and position players both show increased ROM at the shoulder and decreased ROM at the hip over the course of a season. Position players demonstrated side-to-side discrepancies and seasonal changes at the throwing shoulder similar to those seen in baseball players. The preseason mobility of the dominant shoulder of pitchers increased over the season while strength of hip abduction in the non-dominant side was reduced.

LEVEL OF EVIDENCE

3.

Predicting Shoulder Force to Prevent Injury: Body Fat Mass Increases Shoulder Stress among Pitchers

PURPOSE

The purpose of this study was to examine the relationship between whole body and throwing arm composition and length with throwing shoulder distraction and anterior force. While literature shows a relationship between shoulder force and pain, as well as between body mass and pain, it was hypothesized that pitchers with greater body fat mass would display increased throwing shoulder force during the acceleration phase of the softball pitch.

METHODS

Thirty-eight high school softball pitchers from southern United States agreed to participate (1.69 ± .07 m, 74.71 ± 16.36 kg, 15.2 ± 1.1 years). All procedures were completed within one visit. Pitchers underwent a dual-energy x-ray absorptiometry scan then threw fastballs at regulation distance while motion was measured using an electromagnetic motion capture system. Data from the three fastest pitches were averaged and analyzed. Peak shoulder distraction and anterior force during the acceleration phase of the softball pitch were extracted and used as dependent variables in two separate regression analyses. Whole body and throwing arm fat mass and lean mass, as well as throwing arm length were entered as independent variables into both regression equations.

RESULTS

The first regression equation was statistically significant, F(5,37) = 13.28, p < .001 and explained approximately 62% of the variance in peak shoulder distraction force (R2 = .675, Adj. R2 = .624). Increased whole body fat mass (B = 13.76, SE = 5.39, Beta = .91, t = 2.553, p = .016) significantly predicted peak throwing shoulder distraction force. The second regression equation predicting peak anterior force was not significant.

CONCLUSION

Increased fat mass may exacerbate the high force observed at the throwing shoulder and further increase injury susceptibility to pitchers.

Decreased Shoulder and Elbow Joint Loads During the Changeup Compared With the Fastball and Curveball in NCAA Division I Collegiate Softball Pitchers

BACKGROUND

Baseball leagues have implemented pitch count and pitch type restrictions based on biomechanical concepts associated with pitch type. Softball has not yet adopted these practices, although softball pitchers continue to pitch at a high volume and learn multiple pitches at a young age.

PURPOSE

To examine shoulder and elbow kinetics between the fastball, curveball, and changeup, as well as to provide descriptive upper extremity pain data in National Collegiate Athletic Association (NCAA) softball pitchers.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Study participants consisted of 27 female NCAA Division I softball pitchers (age, 20.2 ± 1.9 years; height, 175.7 ± 5.7 cm; weight, 83.6 ± 12.7 kg). The participants pitched 3 balls of each pitch type, and kinetic data were recorded. A one-way within-participants repeated-measures multivariate analysis of variance was used to determine significant differences in kinetics and pitch speed between pitch types.

RESULTS

Results revealed a statistically significant main effect for pitch type (Wilks λ = .087; F = 36.523; P < .001). Post hoc testing showed that the changeup produced less anterior elbow force compared with the fastball (P < .001) and the curveball (P = .012). In addition, the changeup produced less shoulder distraction force compared with the fastball (P < .001) and the curveball (P = .001). Additionally, there was a significant difference in pitch speed between all 3 pitch types (P = .006). The curveball revealed no statistically significant kinetic differences compared with the fastball.

CONCLUSION

The fastball and curveball placed similar stress on the upper extremity in collegiate softball pitchers. However, in comparison with the changeup, the fastball and curveball placed increased stress on the upper extremity. More research is needed to fully explain the differences seen between pitch type and injury risk.

CLINICAL RELEVANCE

Sports medicine professionals, coaches, and athletes should use the current study results to note these differences in shoulder distraction and elbow anterior forces between softball pitch types. The study results can be used as a reference and basis for future research investigating kinetic differences across varying pitch types.

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.

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-Šidák 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.

The influence of a simulated game on muscular strength in female high-school and collegiate softball pitchers

Softball pitchers often pitch several games within a day and over consecutive days during a competitive season. High volumes of pitches thrown can decrease muscular strength, resulting in less proximal force generation and upper extremity compensation to maintain performance. Therefore, the purpose of this study was to assess upper and lower extremity muscular strength after pitching in a simulated game. Fourteen softball pitchers (17.9 ± 2.3 years, 166.4 ± 8.7 cm, 72.2 ± 12.6 kg) completed baseline isokinetic strength assessment for knee, hip, trunk and pitching elbow flexion and extension as well as trunk rotation. Seven days later, participants pitched a simulated game consisting of 105 fastballs prior to repeating all strength assessments. Changes in muscular strength were assessed using paired samples t-tests, with significance set a priori as p ≤ 0.05. Normalised (%BW) stride leg knee extension peak torque was significantly higher (p = 0.020) post-simulated game (75.1 ± 24.6%BW) as compared to baseline (64.0 ± 19.5%BW) and trunk flexion peak torque was significantly higher (p = 0.009) post-simulated game (84.8 ± 47.0%BW) as compared to baseline (63.5 ± 47.1%BW). This study showed an increase in knee extension and trunk flexion strength after an acute bout of pitching. The findings give insight into muscular changes following pitching which can assist in appropriate softball training and recovery.

Single-Leg Squat Compensations Are Associated With Softball Pitching Pathomechanics in Adolescent Softball Pitchers

Background:

A lack of lumbopelvic-hip complex (LPHC) stability is often associated with altered pitching mechanics, thus increasing pain and injury susceptibility. The single-leg squat (SLS) is a simple diagnostic tool used to examine LPHC stability.

Purpose:

To examine the relationship between trunk compensatory kinematics during the SLS and kinematics at foot contact during the windmill pitch.

Study Design:

Descriptive laboratory study.

Methods:

Participants included 55 youth and high school softball pitchers (mean age, 12.6 ± 2.2 years; height, 160.0 ± 11.0 cm; weight, 60.8 ± 15.5 kg). Kinematic data were collected at 100 Hz using an electromagnetic tracking device. Participants were asked to complete an SLS on each leg, then throw 3 fastballs at maximal effort. Values of trunk flexion, trunk lateral flexion, and trunk rotation at peak depth of the SLS were used as the dependent variables in 3 separate backward-elimination regression analyses. Independent variables examined at foot contact of the pitch were as follows: trunk flexion, trunk lateral flexion, trunk rotation, center of mass, stride length, and stride knee valgus.

Results:

The SLS trunk rotation regression (F(1,56) = 4.980, P = .030) revealed that trunk flexion predicted SLS trunk rotation (SE = 0.068, t = 2.232, P = .030) and explained approximately 7% of the variance in SLS trunk rotation (R² = 0.083, adjusted R² = 0.066). The SLS trunk flexion regression (F(1,56) = 5.755, P = 0.020) revealed that stride knee valgus significantly predicted SLS trunk flexion (SE = 0.256, t = 2.399, P = .020) and explained approximately 8% of variance in SLS trunk flexion (R² = 0.095, adjusted R² = 0.078).

Conclusion:

Additional trunk rotation and trunk flexion at peak depth of the SLS showed increased knee valgus and trunk flexion at foot contact of the pitch, both of which indicate poor LPHC stability during the softball pitch and may increase the potential for injury.

Clinical Relevance:

Players and coaches should implement SLS analyses to determine their players’ risk for injury and compensation due to poor core stability.

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.

Hip Range of Motion and Strength and Energy Flow During Windmill Softball Pitching

CONTEXT

Inadequate hip range of motion (ROM) and isometric strength (ISO) may interfere with energy flow through the kinetic chain and result in increased injury susceptibility.

OBJECTIVE

To examine the relationship of hip ROM and ISO with energy flow through the trunk and pitching-arm segments during the windmill softball pitch in youth athletes. A subsequent purpose was to examine the relationship between energy flow and pitch speed.

DESIGN

Descriptive laboratory study.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A sample of 29 youth softball pitchers (age = 11.2 ± 1.3 years, height = 155.0 ± 10.4 cm, mass = 53.2 ± 12.6 kg).

MAIN OUTCOME MEASURE(S)

Bilateral hip internal-rotation and external-rotation (ER) ROM and ISO were measured. Net energy outflow and peak rates of energy outflow from the distal ends of the trunk, humerus, and forearm were calculated for the acceleration phase of the windmill softball pitch, and pitch speed was measured.

RESULTS

Regression analysis revealed an effect of drive-hip ER ISO on the net energy flow out of the distal ends of the trunk (P = .045) and humerus (P = .002). Specifically, increased drive-hip ER ISO was associated with increased net energy outflow from the trunk to the humerus and from the humerus to the forearm. No significant effects of hip ROM or other hip ISO measures were observed. Additionally, pitchers who achieved higher peak rates of distal outflow tended to achieve higher pitch speeds.

CONCLUSIONS

An association was present between drive-hip ER ISO and the net energy flow out of the distal ends of the trunk and humerus during the acceleration phase of the windmill softball pitch, emphasizing the importance of hip and lower body strength in executing the whole-body windmill pitch. Overall, energy-flow analysis is an interesting new way to analyze pitching mechanics and will aid in furthering our understanding of performance and injury risk in windmill softball pitching.

Lower Extremity Pain and Pitching Kinematics and Kinetics in Collegiate Softball Pitchers

The primary aims of the study were (1) to examine kinematics and kinetics of those pitching with and without lower extremity pain in collegiate softball pitchers, and (2) to determine if there was an association between the lower extremity pain and lower extremity kinematics, trunk kinematics, and shoulder kinetics in collegiate softball pitchers. Thirty-seven NCAA Division I female collegiate softball pitchers (19.8±1.3 yrs,173.7±7.7 cm, 79.0±12.4 kg) participated. Participants were divided into two groups, those who were currently experiencing lower extremity pain and those who were not. Participants threw three rise ball pitches. Kinematic data were collected at 100 Hz using an electromagnetic tracking system. Mann-Whitney U tests revealed no significant kinematic or kinetic differences between pitchers with and without lower extremity pain. Additionally, there were no significant correlations between pain and recorded kinematic and kinetic variables. Considering there were no biomechanical differences observed between pitchers, coaches and athletic trainers should take caution with athlete assessment since athletes may not display altered biomechanics. Further examination into the duration and degree of pain is needed in an attempt to fully understand the implication of pain and pitching mechanics.

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.

Softball pitching mechanics and shoulder injuries: a narrative review

Softball is the third most popular women's collegiate sport in the United States, with 19,680 total athletes as of the 2015-2016 season. Despite its popularity and growth in recent years, research focusing on the biomechanics of the windmill pitch and its associated shoulder injuries is relatively scarce. The incidence of shoulder injury is highest during the preseason and the beginning of the regular season. The windmill pitch can be divided into distinct phases, with the shoulder experiencing the greatest force during the delivery phase. Significant demands placed on the shoulder during the windmill pitch put pitchers at a higher risk of developing shoulder injuries than position players. Maximum shoulder compression/distraction forces during the windmill pitch have been shown to be comparable to those experienced during the baseball overhand throw, dispelling the myth that the windmill pitch is not taxing on the shoulder. Injuries associated with the high compression/distraction forces include lesions to the rotator cuff, glenoid labrum, and biceps brachii. Pitcher-specific training, cross-training, and whole-body conditioning should be incorporated into current training regimens to decrease the risk of shoulder injuries.

Association of Upper Extremity Pain With Softball Pitching Kinematics and Kinetics

Background:

There is a paucity of research regarding the relationship between fastpitch softball pitching mechanics and reported pain. Thus, understanding the pitching mechanics of athletes pitching with upper extremity pain and those pain free is paramount.

Purpose:

To examine lower extremity pitching mechanics, upper extremity kinetics, and upper extremity pain in National Collegiate Athletic Association (NCAA) Division I female softball pitchers.

Study Design:

Descriptive laboratory study.

Methods:

A total of 37 NCAA Division I female softball pitchers (mean age, 19.84 ± 1.28 years; mean height, 173.67 ± 7.77 cm; mean weight, 78.98 ± 12.40 kg) from across the United States were recruited to participate. Participants were divided into 2 groups: upper extremity pain (n = 13; mean age, 19.69 ± 1.18 years; mean height, 172.60 ± 11.49 cm; mean weight, 86.75 ± 13.02 kg) and pain free (n = 24; mean age, 19.91 ± 1.35 years; mean height, 174.26 ± 4.96 cm; mean weight, 74.78 ± 9.97 kg). An electromagnetic tracking system was used to obtain kinematic and kinetic data during the riseball softball pitch.

Results:

At foot contact (F_3,33 = 7.01, P = .001), backward elimination regression revealed that stride length, trunk rotation, and center of mass (COM) significantly explained about 33% of variance with softball pitchers experiencing upper extremity pain (adjusted R² = 0.33).

Conclusion:

At foot contact, the kinematic variables of increased trunk rotation toward the pitching arm side, increased stride length, and a posteriorly shifted COM were associated with upper extremity pain in collegiate softball pitchers. Variables early in the pitching motion that do not set a working and constructive proximal kinetic chain foundation for the rest of the pitch to follow could be associated with breakdowns more distal in the kinetic chain, possibly increasing the susceptibility to upper extremity pain.

Clinical Relevance:

The identification of pitching mechanics associated with pain allows clinicians to develop exercises to avoid such mechanics. Avoiding mechanics associated with pain may help reduce the prevalence of pain in windmill softball pitchers as well as help coaches incorporate quantitative biomechanics into their instruction.

The Association of Upper-Body Kinematics and Earned Run Average of National Collegiate Athletic Association Division I Softball Pitchers

Friesen, KB, Barfield, JW, Murrah, WM, Dugas, JR, Andrews, JR, and Oliver, GD. The association of upper-body kinematics and earned run average of national collegiate athletic association Division I softball pitchers. J Strength Cond Res XX(X): 000-000, 2019-Although recent literature has increased examination of the association of injury and biomechanics, there remains a lack of evidence supporting optimal windmill pitch mechanics. Therefore, the purpose of this study was to investigate trunk and pitching arm kinematics and their association with performance outcome: earned run average (ERA), in collegiate softball pitchers. Twenty-three NCAA Division I collegiate softball pitchers (20.14 ± 1.07 years; 173.93 ± 6.68 cm; and 85.79 ± 11.06 kg) performed 3 maximal effort rise ball pitches to a catcher located at a distance of 43 ft. (13.11 m). Kinematic data of the trunk and pitching arm were collected using an electromagnetic tracking system. A multiple regression analysis was performed at each pitch event: top of backswing, foot contact, ball release, and follow-through. The multiple regression at foot contact showed an overall statistically significant regression equation (F6, 16 = 3.7, p = 0.017) and explained approximately 42% of the variance in ERA (R = 0.579, Adj. R = 0.421). Results revealed that those pitchers who had greater trunk (SE = 0.018, t = -2.5, p = 0.023) and elbow flexion (SE = 0.006, t = -4.2, p = 0.001) at the event of foot contact had lower ERAs. This study supported previous research on the importance of trunk and elbow angle at front foot contact on rise ball pitch performance. These key technique points and the importance of elbow flexors should be explored in future research and potentially visually attended to by coaches and strength professionals.

Functional differences in softball pitchers with and without upper extremity pain

OBJECTIVES

Though pitchers often throw during multiple games in a day, there are currently no pitch count restrictions in softball. The accumulation of high pitch counts over time may contribute to the development of upper extremity pain. The purpose of our study was to examine functional characteristics of shoulder and hip range of motion (ROM), isometric strength (ISO), and ball speed in softball pitchers with and without upper extremity (UE) pain.

DESIGN

Controlled laboratory design.

METHODS

Fifty-three NCAA Division I softball pitchers (20.0±1.4 years; 173.3±8.3cm; 80.9±12.3kg) participated and were divided into two groups: pain-free (n=30) and pain in the UE (n=23). Bilateral shoulder and hip external rotation (ER) and internal rotation (IR) ROM and ISO were measured prior to pitching to a catcher located 13.1m (43ft) away.

RESULTS

Independent samples t-tests revealed significantly greater throwing side (TS) hip ER ROM (p=0.012), TS hip IR ISO (p=0.038), glove side (GS) hip ER ISO (p=0.025), TS shoulder ER ISO (p=0.002), GS shoulder IR (p=0.006) and ER (p=0.004) ISO in the pain free group versus the UE pain group.

CONCLUSIONS

Differences in shoulder and hip ROM and ISO exist between those who have upper extremity pain and those who do not. Therefore, findings suggest that both the upper and lower extremities should be considered when treating softball pitchers with UE pain.

Differences in trunk and upper extremity kinematics and segmental velocities during the offside forehand polo swing between male and female athletes

Although polo is a well-known equestrian sport, it is fundamentally misunderstood. The purpose of this study was to examine trunk and upper extremity kinematics and segmental velocities during the offside forehand polo swing between male and female athletes. Ten female and 17 male professional polo athletes volunteered. An electromagnetic tracking system collected kinematic data at 100 Hz while participants performed three offside forehand polo swings from a stationary wooden horse. One-way ANOVAs revealed statistically significant differences (p<0.05) in all kinematic variables and segmental velocities. Specifically, males exhibited a greater mean difference (MD=23°) of trunk flexion at take away (TA) and top of backswing (TOB)(MD=29°) trunk lateral flexion at ball contact (BC)(MD=23°), trunk rotation at TA(MD=97°) and TOB(MD=118°), shoulder abduction at TOB(MD=64°), and shoulder elevation at TOB(MD=13°) and BC(MD=40°). Females displayed greater trunk rotation at BC(MD=91°), shoulder elevation at TA(MD=19°), and elbow flexion at TA(MD=90°). Additionally, females generated greater segmental velocities early in the swing, while the males generated velocity later. The movement patterns observed amongst the males suggest energy is being transferred more efficiently along the kinetic chain, thus more efficient swing mechanics, but further investigation into the role of the trunk and lumbopelvic-hip complex in reference to the polo swing is warranted.

What Do We Know About Youth Softball Pitching and Injury?

Participation rates in fastpitch softball are continually on the rise, especially in youth. With the increased participation also comes the increased injury susceptibility. Unfortunately, the common misconception about the dynamic 360° windmill softball pitch, that it is a natural motion and thus does not cause stress on the shoulder, deterred investigation into pitching mechanics until recently. As pitching injuries in softball are on the rise, more attention is needed into the mechanics of the windmill softball pitch and injury implications. Therefore, it was the purpose of this current opinion paper to shed light on what is known about youth softball pitching and injury susceptibility.