Skip to main content
NCBI home page
International Journal of Sports Physical Therapy logoLink to International Journal of Sports Physical Therapy
. 2022 Jun 1;17(4):732–737. doi: 10.26603/001c.35258

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

Zachary Dietz 1, Dylan DeWeese 1, Neil Shaw 1, Cody Huth 1, Jacob Ball 1, Victoria Reeves 1, Ryan Monti 1,✉, Ryan Bitzel 1
PMCID: PMC9159723  PMID: 35693855

Abstract

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

Keywords: collateral ligaments, pitcher, injury, baseball, adolescent

INTRODUCTION

As competitiveness increases from youth to high school baseball, so do external pressures, expectations, and physical demands. Adolescent pitchers in particular experience a tremendous increase in volume of overhead throwing as age and level of play increase. Zaremski et al. suggest that adolescent pitchers throw an average of 119 pitches per game, including the warm-up, bullpen activity, and in-game pitches.1 Additionally, improving velocity and throwing a variety of different pitches normally become a higher priority in adolescence and beyond. These factors, along with anatomical changes, growth, early sport specialization, participation on multiple teams, mound distance, mound height, and high pitch counts place adolescent pitchers at an exceptionally higher risk for medial elbow injuries. Utilizing proper throwing mechanics, specifically torso rotation and stride length, is one way to minimize this risk without compromising performance. 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. Currently, there is a limited amount of literature connecting torso biomechanics and stride length while addressing their relationship to medial elbow injuries in the adolescent baseball pitcher population.

Elbow Forces with Overhead Pitching

A valgus moment at the elbow consists of a medially directed load, which is greatest during the cocking phase of the pitching motion when the shoulder is abducted and externally rotated. This valgus moment is counteracted by the muscle-tendon units crossing the medial elbow, creating a varus moment during the late cocking phase. As the arm internally rotates through the late cocking phase, at velocities up to 7,500 degrees per second, torque is produced, which places tension on the ulnar collateral ligament and compression at the radiocapitellar joint.2 Pitchers with upper extremity range of motion deficits may compensate from other areas of the body, which could lead to injury. Current literature regarding biomechanical analysis of torso rotation also states that a decrease in synergistic control of torso musculature during the pitch leads to an increased varus moment on the elbow, placing higher torque upon the upper extremity.3–7 Therefore, prior literature has shown how optimizing torso biokinematic control through hip and shoulder separation can aid in increasing pitch velocity.8 In the author’s opinion, this information could be extrapolated to lower the probability of medial elbow injuries.

Overview of the Pitch Cycle

To best describe and evaluate biomechanical control, the process of throwing a pitch needs to be broken down and defined. The baseball pitch utilizes all aspects of the kinetic chain where each segment receives elastic potential energy from the previous segment. The segments follow the summation principle, in which energy is transferred when the subsequent segment begins rotating as the prior segment has reached maximal angular velocity. Stability and neuromuscular control from the lower extremities, lumbopelvic structures, and core musculature are essential to optimize the effects of the summation principle.9 This stability establishes a platform for the upper extremities to receive energy and generate velocity.9 The overhead pitch is routinely broken down into sequential phases related to the generation and transfer of potential and kinetic energy.

After initiation of the pitch cycle, the conversion of potential energy into kinetic energy occurs during the stride phase as the pitcher steps toward home plate.10 The completion of the stride phase is seen as the lead foot makes contact with the ground, the throwing arm reaches its initial point of cocking, and is followed by the initiation of pelvic rotation towards the batter.11–13 As the hips rotate towards home plate, the upper quarter continues into its cocking phase producing lower quarter and upper torso dissociation.3,14,15 This separation aids with achieving maximal shoulder external rotation during the later portion of the cocking phase and creating a pre-stretch to abdominal musculature to eventually aid with energy transfer. Improper timing, lack of segment separation, or loss of energy transfer into the acceleration phase could be a critical point for the necessity of compensatory upper extremity energy generation.10 The acceleration phase follows, as the summation of energy is transferred into shoulder internal rotation and to the point of ball release.

As baseball players age, there are natural changes in pitching mechanics that occur due to a combination of experience, confidence, coaching, and growth. As pitchers mature, there are consistent adaptive changes that occur related to natural physical development as well as related to throwing. These changes include throwing shoulder internal and external rotation range of motion, increased segmental trunk separation, increased stride length, and a decrease in stride forefoot angle.8,15–17 Additionally, this natural physical development is accompanied by kinetic changes producing a resultant increase in velocity and elbow torque.8,12 All of these changes could pose a risk for elbow associated injuries for the developing athlete.

Influence of Trunk Rotation on Risk of Injury

Chaudhari et al. have suggested that inappropriate trunk rotational timing when pitching has been associated with injury.9 Error in timing of trunk rotation correlates with increased demand on the upper extremity, which could lead to a medial elbow injury.10,18,19 The lack of synchronization between trunk rotational timing and stride limits the amount of energy transfer from the trunk to the upper extremity. Loss of rotational range of motion could be the main factor of injury. Previous authors indicate that fatigue and pitching velocity are the best predictive factors of medial elbow injury, which was the driving factor for USA Baseball and Little League Baseball, Inc to implement age-based guidelines for pitch-count maximums and required rest times.4,6,20–22 The question remains: Are pitch-count regulations enough to prevent throwing related injuries in the adolescent population? Other modifiable factors could further aid in reducing overuse injuries. Pitch-counts do not consider the individual kinematics of the pitcher, the transfer of energy through the kinetic chain, the volume a pitcher throws per year, or how fatigue influences the biomechanics of the pitch. Olsen et al. suggest the following modifiable risk factors and suggest that they are related to the predisposition of adolescent pitchers to medial elbow injury: inadequate pitch counts, pitch velocity greater than 85 miles per hour, throwing more than eight months in the year, and throwing through fatigue all exponentially increase risk of injury (Table 1).23 In addition, this clinical commentary presents considerations regarding the kinematic chain that predispose the baseball pitcher to medial elbow injury. Optimizing safe kinematics could ultimately aid with injury prevention and provide a positive effect towards an athlete’s baseball career.

Table 1. Risk Factors and Likelihood of Upper Extremity Injury23.

Risk Factors Likelihood of Significant Upper Extremity Injury
Pitching faster than 85 mph 2.5x
Throwing >80 pitches/game 3.8x
Throwing >8 months/year 5x
Pitching fatigued 36x
Open in a new tab

Mph= miles per hour

Although several factors change from adolescence to young adulthood, studies aiming to identify how pitching mechanics affect elbow loading and velocity are consistent across various ages. As one would expect, velocity, demands, and torque continue to increase with age, but these variables’ relationship with mechanics does not fluctuate.24 For this reason, the biomechanics regarding the pitch cycle are often applied across different age demographics. Previous research has displayed a link between trunk rotation and internal elbow varus moment in college-aged athletes.25 Cohen et al. have shown that increased trunk rotation away from the throwing hand correlates with a more significant increase in varus force than in velocity.25 Furthermore, early rotation of the trunk has been found to cause alterations in shoulder positioning for pitchers between the ages of 9 through 18.26 There is no evidence to support an ideal amount of rotation to balance the risk and benefit, but there is support for excess trunk rotation being harmful.

Influences of Stride Length on Risk of Injury

Previous authors have utilized a focused approach to pelvic and torso rotation as a power generator for the overhead athlete.25,27 Research falls short when comparing stride length abnormalities to upper extremity injuries in the adolescent population. Stride length, as defined by Ramsey et al. is the horizontal distance between the location of the drive-foot calcaneus at peak knee-height and the calcaneus of the contralateral foot at ground contact.28 This is a highly modifiable aspect of pitching mechanics that has been found to impact various body segments along the kinetic chain during the pitching motion, including forces experienced at the shoulder and elbow.29 Prior authors have reported a desired stride length (DSL) among highly skilled and proficient pitchers aged 17-21, ranging from 80-87% of body height, but DSL has been reported to be as low as 66% of body height in less experienced middle school and adolescent aged athletes. Pitchers that exhibit a shorter stride length decrease potential force development throughout the kinetic chain due to a reduced trunk rotation moment.19 Exceeding stride length norms can cause increased physiologic demands on the body; however, are associated with decreased stress to the upper extremity, potentially due to the increased total body momentum towards the plate that occurs with overstriding.28 Current evidence indicates that exceeding or failing to meet an optimal stride length can potentially lead to increased fatigue, kinematic compensations, and upper extremity injuries.28–30 Finally, it is important to note that Sgori et al. have determined that a 10% increase in stride length and its relationship to increased pitch velocity are a natural sign of physical growth and development.8

The pitch cycle is a sequence of events where multiple segments of the body are interconnected through the kinetic chain.18 Efficiency of movement is based on their interdependence to transfer momentum from the ground to the upper body.18 As stride length nears foot contact, highly efficient pitchers will demonstrate a closed foot angle. Closed foot angle is defined as the forefoot being angled toward the thrower’s arm (Figure 1). Overhead athletes who demonstrate excessive closed foot angle upon stride foot contact cause their arm to be ahead of the rotating shoulder during the late cocking phase, leading to a closed front hip, throwing across their body, and lack of efficient force transfer from the pelvis to the upper extremity.22 If the forefoot angle becomes more open toward the glove side, undesirable anterior translational stress can be produced at the shoulder.22 This could be due to early pelvic rotation or altered trunk separation from the upper extremity.10,24 Anterior translated force at the shoulder combined with maximal external rotation range of motion during the late-cocking phase produces increased valgus loading at the elbow, increasing the risk for elbow injuries.22 In contrast, pitchers that demonstrated more of a closed angle at stride foot contact did not present with increased valgus loading at the elbow.22

Figure 1. Stride Leg Positioning.

Figure 1.

Open in a new tab

C = stride foot offset, θ = forefoot angle, - - - = neutral/neither open nor closed

Figure 2. Internal Trunk Rotation Angle at Ball Release.

Figure 2.

Open in a new tab

Adapted from Cohen et al25

Another aspect related to stride foot angle is stride foot offset, the horizontal distance between the center of the lead ankle and center of the trailing ankle (Figure 1). An excessive stride foot offset angle, known as “opening up” (Figure 1), can disrupt the timing and efficiency of torso rotation, transfer of energy up the kinetic chain, causing increased humeral internal rotation torque, and as a consequence could lead to valgus load at the medial elbow.10,18,22,24 Stride foot offset, a component that has not been widely researched, plays a pivotal role in force generation for the overhead athlete.

Examination and Evaluation of the Pitch Cycle

Examination and evaluation can be used to quantify the range of motion, balance, and physical performance capabilities needed to complete the pitch cycle and provide further insight into clinical judgement for correction. This can be accomplished through standard anthropometric measurements and biomechanical analysis. A current concept being explored includes the impact of drive leg hip internal rotation range of motion and its impact on trunk rotation.31,32 Further research is needed to quantify the optimal range of hip internal rotation that is specifically needed for the adolescent baseball player. However, some evidence supports the examination of bilateral hip flexion and internal rotation range of motion due to its resultant influence on elbow injury.31 Prior authors have described a relationship between pitching skill level and lower extremity function as it is related to lower extremity power and single-limb balance.33 Additional physical performance metrics for lower extremity power, such as the double-leg vertical jump, have shown a moderate correlation to stride length in the younger baseball athlete.33 To provide thorough analysis of the pitch cycle, it is advisable to utilize video analysis software that can reduce body motion velocity and capture segmental change.6,34 Additionally, various kinematic values based on age can be utilized to capture lower extremity and trunk positioning (Table 2). Correction of any deficits found can be addressed using therapeutic exercise and education, such as stretching and balance training.35 This could also include methods of motor learning, such as constraints led approach or differential learning, to coordinate patterns of movement and explore solutions for movement error.36

Table 2. Pitch Cycle Biomechanical Nodes for the Adolescent Baseball Pitcher.

Biomechanical 
Node 		Normative Mechanical Values
Forefoot Position Slightly closed
9 y/o 23 º (+3) as one ages to 15 y/o 14 º (+ 4) 15
Stride Length 66% of body height (SD 7.1%) pitchers 9-14 y/o 33
Each year of age associated with a 10% increase in stride length8
Stride Foot Offset 9 y/o 2 +2 cm open as one ages to 15 y/o 18 +3 cm closed 15
Trunk Separation
(Axial rotation of upper trunk relative to the pelvis) 		9 y/o 23 º (+2) as one ages to 15 y/o 42 º (+3) 15
Internal Trunk Rotation at BR
(Throwing arm side towards home plate; Figure 2) 		8-13.5 y/o 25 º (+9)13
(Compared to 18-24.8 y/o 23 º (+8); for every additional 10º increased elbow stress)25
Single-Limb Support
(Dominant leg = same side as throwing arm) 		10.2 sec (SD 5.9)33
Open in a new tab

y/o = years old, SD = standard deviation, BR = ball release, sec = seconds

CONCLUSION

Existing evidence indicates that altered stride foot positioning and trunk rotation is correlated with increased demand on the upper extremity.8,10,18,24,33 Inefficiency throughout the kinetic chain leads to compensation from the upper extremity and increases the tensile forces at the medial elbow. The forces traveling through the kinetic chain lose momentum, leading to the increased demand of the upper extremity to maintain adequate force production. Over time, the increased forces placed upon the throwing arm may lead to overuse injuries in the medial elbow.

Current evidence also indicates that optimal stride length changes according to the age and growth/maturation of the pitcher.8 Optimal torso rotation has not yet been quantified, but problems with early and late rotation have been identified. Both biomechanical components likely impede the transfer of energy throughout the kinetic chain, and compensatory motion transpires. Additional research should be conducted to specifically evaluate the correlation between torso biomechanics and stride length, quantify adequate torso kinematic parameters, as well as their collective effects on elbow injuries in the adolescent population

Conflict of Interest

There are no conflicts of interest to disclose.

References

  1. Unaccounted workload factor: game-day pitch counts in high school baseball pitchers-an observational study. Zaremski J. L., Zeppieri G., Jr., Jones D. L., Tripp B. L., Bruner M., Vincent H. K., Horodyski M. 2018Orthop J Sports Med. 6(4):2325967118765255. doi: 10.1177/2325967118765255. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Deficits in glenohumeral passive range of motion increase risk of elbow injury in professional baseball pitchers: a prospective study. Wilk K. E., Macrina L. C., Fleisig G. S., Aune K. T., Porterfield R. A., Harker P., Evans T. J., Andrews J. R. 2014Am J Sports Med. 42(9):2075–81. doi: 10.1177/0363546514538391. [DOI] [PubMed] [Google Scholar]
  3. Effects of upper trunk rotation on shoulder joint torque among baseball pitchers of various levels. Aguinaldo A. L., Buttermore J., Chambers H. 2007J Appl Biomech. 23(1):42–51. doi: 10.1123/jab.23.1.42. [DOI] [PubMed] [Google Scholar]
  4. The relationship between pitching mechanics and injury: a review of current concepts. Chalmers P. N., Wimmer M. A., Verma N. N., Cole B. J., Romeo A. A., Cvetanovich G. L., Pearl M. L. 2017Sports Health. 9(3):216–221. doi: 10.1177/1941738116686545. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Trunk muscle function deficit in youth baseball pitchers with excessive contralateral trunk tilt during pitching. Oyama S., Waldhelm A. G., Sosa A. R., Patel R. R., Kalinowski D. L. 2017Clin J Sport Med. 27(5):475–480. doi: 10.1097/jsm.0000000000000396. [DOI] [PubMed] [Google Scholar]
  6. Improper trunk rotation sequence is associated with increased maximal shoulder external rotation angle and shoulder joint force in high school baseball pitchers. Oyama S., Yu B., Blackburn J. T., Padua D. A., Li L., Myers J. B. 2014Am J Sports Med. 42(9):2089–94. doi: 10.1177/0363546514536871. [DOI] [PubMed] [Google Scholar]
  7. Associations between timing in the baseball pitch and shoulder kinetics, elbow kinetics, and ball speed. Urbin M. A., Fleisig G. S., Abebe A., Andrews J. R. 2013Am J Sports Med. 41(2):336–42. doi: 10.1177/0363546512467952. [DOI] [PubMed] [Google Scholar]
  8. Predictors of throwing velocity in youth and adolescent pitchers. Sgroi Terrance, Chalmers Peter N, Riff Andrew J, Lesniak Matthew, Sayegh Eli T, Wimmer Markus A, Verma Nikhil N, Cole Brian J, Romeo Anthony A. 2015Journal of shoulder elbow surgery. 24(9):1339–1345. doi: 10.1016/j.jse.2015.02.015. [DOI] [PubMed] [Google Scholar]
  9. Lumbopelvic control and days missed because of injury in professional baseball pitchers. Chaudhari A. M., McKenzie C. S., Pan X., Oñate J. A. 2014Am J Sports Med. 42(11):2734–40. doi: 10.1177/0363546514545861. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Kibler W Ben, Sciascia Aaron D. Mechanics, Pathomechanics and Injury in the Overhead Athlete: A Case-Based Approach to Evaluation, Diagnosis and Management. Springer Publishing; [Google Scholar]
  11. Biomechanics of baseball pitching: a preliminary report. Pappas A. M., Zawacki R. M., Sullivan T. J. 1985Am J Sports Med. 13(4):216–22. doi: 10.1177/036354658501300402. [DOI] [PubMed] [Google Scholar]
  12. Kinematic and kinetic comparison of baseball pitching among various levels of development. Fleisig G. S., Barrentine S. W., Zheng N., Escamilla R. F., Andrews J. R. 1999J Biomech. 32(12):1371–5. doi: 10.1016/s0021-9290(99)00127-x. [DOI] [PubMed] [Google Scholar]
  13. Adolescent baseball pitching technique: a detailed three-dimensional biomechanical analysis. Nissen C. W., Westwell M., Ounpuu S., Patel M., Tate J. P., Pierz K., Burns J. P., Bicos J. 2007Med Sci Sports Exerc. 39(8):1347–57. doi: 10.1249/mss.0b013e318064c88e. [DOI] [PubMed] [Google Scholar]
  14. Trunk axial rotation in baseball pitching and batting. Fleisig G. S., Hsu W. K., Fortenbaugh D., Cordover A., Press J. M. 2013Sports Biomech. 12(4):324–33. doi: 10.1080/14763141.2013.838693. [DOI] [PubMed] [Google Scholar]
  15. Changes in youth baseball pitching biomechanics: a 7-year longitudinal study. Fleisig G. S., Diffendaffer A. Z., Ivey B., Aune K. T., Laughlin T., Fortenbaugh D., Bolt B., Lucas W., Moore K. D., Dugas J. R. 2018Am J Sports Med. 46(1):44–51. doi: 10.1177/0363546517732034. [DOI] [PubMed] [Google Scholar]
  16. Rotational motion changes in the glenohumeral joint of the adolescent/little league baseball player. Meister Keith, Day Timothy, Horodyski Marybeth, Kaminski Thomas W, Wasik Michael P, Tillman Susan. 2005Am J Sports Med. 33(5):693–698. doi: 10.1177/0363546504269936. [DOI] [PubMed] [Google Scholar]
  17. Rotational motion changes in the glenohumeral joint of the adolescent/Little League baseball player. Meister K., Day T., Horodyski M., Kaminski T. W., Wasik M. P., Tillman S. 2005Am J Sports Med. 33(5):693–8. doi: 10.1177/0363546504269936. [DOI] [PubMed] [Google Scholar]
  18. The kinetic chain revisited: new concepts on throwing mechanics and injury. Chu S. K., Jayabalan P., Kibler W. B., Press J. 2016PM R. 8(3 Suppl):S69–77. doi: 10.1016/j.pmrj.2015.11.015. [DOI] [PubMed] [Google Scholar]
  19. Pitching mechanics, revisited. Calabrese G. J. 2013Int J Sports Phys Ther. 8(5):652–60. [PMC free article] [PubMed] [Google Scholar]
  20. Risk factors for elbow and shoulder injuries in adolescent baseball players: a systematic review. Norton R., Honstad C., Joshi R., Silvis M., Chinchilli V., Dhawan A. 2019Am J Sports Med. 47(4):982–990. doi: 10.1177/0363546518760573. [DOI] [PubMed] [Google Scholar]
  21. The effect of stride length and lateral pelvic tilt on Elbow torque in youth baseball pitchers. Tocci N. X., Howell D. R., Sugimoto D., Dawkins C., Whited A., Bae D. 2017J Appl Biomech. 33(5):339–346. doi: 10.1123/jab.2016-0305. [DOI] [PubMed] [Google Scholar]
  22. Baseball throwing mechanics as they relate to pathology and performance - a review. Whiteley R. 2007J Sports Sci Med. 6(1):1–20. [PMC free article] [PubMed] [Google Scholar]
  23. Risk factors for shoulder and elbow injuries in adolescent baseball pitchers. Olsen S. J., II, Fleisig G. S., Dun S., Loftice J., Andrews J. R. 2006Am J Sports Med. 34(6):905–12. doi: 10.1177/0363546505284188. [DOI] [PubMed] [Google Scholar]
  24. Baseball pitching biomechanics in relation to injury risk and performance. Fortenbaugh D., Fleisig G. S., Andrews J. R. 2009Sports Health. 1(4):314–20. doi: 10.1177/1941738109338546. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. The association among trunk rotation, ball velocity, and the elbow varus moment in collegiate-level baseball pitchers. Cohen A. D., Garibay E. J., Solomito M. J. 2019Am J Sports Med. 47(12):2816–2820. doi: 10.1177/0363546519867934. [DOI] [PubMed] [Google Scholar]
  26. The effect of pitching biomechanics on the upper extremity in youth and adolescent baseball pitchers. Davis JT, Limpisvasti Orr, Fluhme Derrick, Mohr Karen J, Yocum Lewis A, ElAttrache Neal S, Jobe Frank W. 2009The American journal of sports medicine. 37(8):1484–1491. doi: 10.1177/0363546509340226. [DOI] [PubMed] [Google Scholar]
  27. Segmental power analysis of sequential body motion and elbow valgus loading during baseball pitching: comparison between professional and high school baseball players. Aguinaldo A., Escamilla R. 2019Orthop J Sports Med. 7(2):2325967119827924. doi: 10.1177/2325967119827924. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Effect of stride length on overarm throwing delivery: a linear momentum response. Ramsey D. K., Crotin R. L., White S. 2014Hum Mov Sci. 38:185–96. doi: 10.1016/j.humov.2014.08.012. [DOI] [PubMed] [Google Scholar]
  29. An inferential investigation into how stride length influences temporal parameters within the baseball pitching delivery. Crotin R. L., Bhan S., Ramsey D. K. 2015Hum Mov Sci. 41:127–35. doi: 10.1016/j.humov.2015.03.005. [DOI] [PubMed] [Google Scholar]
  30. Altered stride length in response to increasing exertion among baseball pitchers. Crotin R. L., Kozlowski K., Horvath P., Ramsey D. K. 2014Med Sci Sports Exerc. 46(3):565–71. doi: 10.1249/MSS.0b013e3182a79cd9. [DOI] [PubMed] [Google Scholar]
  31. Relationship between tightness of the hip joint and elbow pain in adolescent baseball players. Saito M., Kenmoku T., Kameyama K., Murata R., Yusa T., Ochiai N., Kijima T., Takahira N., Fukushima K., Ishige N., Takaso M. 2014Orthop J Sports Med. 2(5):2325967114532424. doi: 10.1177/2325967114532424. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Association between passive hip range of motion and pitching kinematics in high school baseball pitchers. Plummer Hillary A., Bordelon Nicole M., Wasserberger Kyle W., Opitz Tyler J., Anz Adam W., Oliver Gretchen D. Oct 2;2021 International Journal of Sports Physical Therapy. 16(5):1323–1329. doi: 10.26603/001c.27625. https://doi.org/10.26603/001c.27625 [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Youth baseball pitching stride length: Normal values and correlation with field testing. Fry K. E., Pipkin A., Wittman K., Hetzel S., Sherry M. 2017Sports Health. 9(3):205–209. doi: 10.1177/1941738116679815. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Two-dimensional video analysis of youth and adolescent pitching biomechanics: A tool for the common athlete. DeFroda S. F., Thigpen C. A., Kriz P. K. 2016Curr Sports Med Rep. 15(5):350–8. doi: 10.1249/jsr.0000000000000295. [DOI] [PubMed] [Google Scholar]
  35. Rehabilitation of the overhead throwing athlete: there is more to it than just external rotation/internal rotation strengthening. Wilk Kevin E, Arrigo Christopher A, Hooks Todd R, Andrews James R. 2016PM & R: The Journal of Injury, Function and Rehabilitation. 8:S78–S90. doi: 10.1016/j.pmrj.2015.12.005. [DOI] [PubMed] [Google Scholar]
  36. Comparing the constraints led approach, differential learning and prescriptive instruction for training opposite-field hitting in baseball. Gray Rob. 2020Psychology of Sport and Exercise. 51:101797. [Google Scholar]

Articles from International Journal of Sports Physical Therapy are provided here courtesy of North American Sports Medicine Institute

RESOURCES