Ground Reaction Forces and Peak Throwing Shoulder Forces in Softball High School Pitchers

Abstract

To optimize pitching performance, pitchers must generate substantial ground reaction forces to aid pitch velocity while minimizing the forces experienced in their throwing shoulder. Extremely high shoulder forces are generally thought to be injurious for softball pitchers. Therefore, this study aimed to identify the relationship between ground reaction forces during the propulsion phase of the pitch and peak shoulder forces during the pitch. Thirty-two high school softball pitchers (1.70±0.06 m, 76.09±17.50 kg, and 15±1 y) pitched fastballs for strikes. Kinematic and kinetic data from the three fastest pitches were averaged for analysis. The relationships between ground reaction forces during pitch propulsion and peak shoulder kinetics during the propulsion and acceleration phases were examined via multiple regressions and correlations. A vertical ground reaction force was significantly associated with a peak resultant shoulder force (t=–3.176 and p=0.003). The rate of ground reaction force development was correlated with the peak shoulder distraction force (r=–0.367 and p=0.033) and the resultant force during propulsion (r=–0.439 and p=0.009). These observations underscore the potential significance of lower body contributions and kinetic chain sequencing in reducing shoulder forces during the early stages of the pitch, which may have implications for injury risk as ground reaction forces during pitch propulsion may decline with fatigue.

Keywords

biomechanics - softball - windmill pitching - kinetics - kinematics

Publication History

Received: 10 July 2025

Accepted after revision: 09 October 2025

Article published online:
14 November 2025

• References

• 1 Barrentine SW, Fleisig GS, Whiteside JA, Escamilla RF, Andrews JR. Biomechanics of windmill softball pitching with implications about injury mechanisms at the shoulder and elbow. J Orthop Sports Phys Ther 1998; 28: 405-414
• 2 Hill JL, Humphries B, Weidner T, Newton RU. Female collegiate windmill pitchers: influences to injury incidence. J Strength Cond Res 2004; 18: 426-431
• 3 Oliver GD, Saper MG, Drogosz M. et al. Epidemiology of shoulder and elbow injuries among US high school softball players, 2005-2006 through 2016-2017. Orthop J Sports Med 2019; 7 2325967119867428
• 4 Holtz KA, Zaremski JL, Janosky J, Friesen K.B, Oliver GD. A model for causality of pitching-related overuse injuries in women’s fastpitch softball. Int J Sports Med 2024; 45: 804-809
• 5 Como M, Fatora G, Boden SA. et al. Shoulder Injury Incidence and Epidemiology in Youth, High School, and Collegiate Fastpitch Softball Players: A Systematic Review and Future Research Perspectives. Sports Health 2025; 17(4): 759-765
• 6 Oliver GD, Gilmer GG, Anz AW. et al. Upper Extremity Pain and Pitching Mechanics in National Collegiate Athletic Association (NCAA) Division I Softball. Int J Sports Med 2018; 39: 929-935
• 7 Oliver G, Friesen K, Barfield JW. et al. Association of Upper Extremity Pain With Softball Pitching Kinematics and Kinetics. Orthop J Sports Med 2019; 7 2325967119865171
• 8 Friesen KB, Butler LS, Bordelon NM. et al. Biomechanics of Fastpitch Softball Pitching: A Practitioner’s Guide. Sports Health 2025; 17(6): 1200-1213
• 9 Luera MJ, Dowling B, Magrini MA, Muddle TW, Colquhoun RJ, Jenkins ND. Role of rotational kinematics in minimizing elbow varus torques for professional versus high school pitchers. Orthop J Sports Med 2018; 6 2325967118760780
• 10 Scarborough DM, Linderman SE, Sanchez JE, Berkson EM. Kinematic Sequence Classification and the Relationship to Pitching Limb Torques. Med Sci Sports Exerc 53: 351-359
• 11 Aguinaldo AL, Escamilla RF. Induced power analysis of sequential body motion and elbow valgus load during baseball pitching. Sports Biomech 2022; 21: 824-836
• 12 Nimphius S, McGuigan MR, Suchomel TJ, Newton RU. Variability of a “force signature” during windmill softball pitching and relationship between discrete force variables and pitch velocity. 2016; Hum Mov Sci 47: 151-158
• 13 de Swart AF, van Trigt B, Wasserberger K, Hoozemans MJ, Veeger DH, Oliver GD. Energy flow through the lower extremities in high school baseball pitching. Sports Biomech 2022; 13: 1-15 Online ahead of print
• 14 Howenstein J, Kipp K, Sabick M. Peak horizontal ground reaction forces and impulse correlate with segmental energy flow in youth baseball pitchers. J Biomech 2020; 108: 109909
• 15 Friesen KB, Saper MG, Oliver GD. Biomechanics Related to Increased Softball Pitcher Shoulder Stress: Implications for Injury Prevention. Am J Sports Med 2022; 50(1): 216-223
• 16 Friesen K. The Effects of Body Composition on Female Softball Pitching Biomechanics. School of Kinesiology, Auburn University 2020
• 17 Wu G, Siegler S, Allard P. et al. ISB recommendation on definitions of joint coordinate system of various joints for the reporting of human joint motion—part I: ankle, hip, and spine. J Biomech 2002; 35: 543-548
• 18 Wu G, Van der Helm FC, Veeger HD. et al. ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion—Part II: shoulder, elbow, wrist and hand. J Biomech 2005; 38: 981-992
• 19 Veeger H. The position of the rotation center of the glenohumeral joint. J Biomech 2000; 33: 1711-1715
• 20 Bell AL, Brand RA, Pedersen DR. Prediction of hip joint centre location from external landmarks. Hum Mov Sci 1989; 8: 3-16
• 21 Escamilla RF, Fleisig GS, Barrentine SW, Zheng N, Andrews JR. Kinematic comparisons of throwing different types of baseball pitches. J Appl Biomech 1998; 14: 1-23
• 22 Darke JD, Dandekar EM, Aguinaldo AL, Hazelwood SJ, Klisch SM. Effects of game pitch count and body mass index on pitching biomechanics in 9-to 10-year-old baseball athletes. Orthop J Sports Med 2018; 6 2325967118765655
• 23 Fleisig G, Chu Y, Weber A, Andrews J. Variability in baseball pitching biomechanics among various levels of competition. Sports Biomech 2009; 8: 10-21
• 24 Pataky TC, Robinson MA, Vanrenterghem J. Vector field statistical analysis of kinematic and force trajectories. J Biomech 2013; 46: 2394-2401
• 25 Nicholson KF, Hulburt TC, Kimura BM, Aguinaldo AL. Relationship between ground reaction force and throwing arm kinetics in high school and collegiate pitchers. J Sports Med Phys Fit 2021; 62: 1179-1183