Role of Rotational Kinematics in Minimizing Elbow Varus Torques for Professional Versus High School Pitchers

Abstract

Background:Elbow injury rates among baseball pitchers are rapidly rising. However, this increase has been most dramatic among high school (HS) pitchers.Purpose:To examine pitch velocity and the kinetic and kinematic characteristics of HS versus professional (PRO) pitchers to identify potential differences that may play a role in the increased risk of ulnar collateral ligament injury in youth pitchers.Study Design:Controlled laboratory study.Methods:A total of 37 HS (mean ± SD: age, 16 ± 1 years) and 40 PRO (age, 21 ± 2 years) baseball pitchers completed maximal-effort baseball pitches during a single testing session, from which pitch velocity (PV), absolute and normalized elbow varus torque (EVTA and EVTN, respectively) during arm cocking and at maximum shoulder external rotation (MER), and 8 other elbow and shoulder torques or forces and rotational kinematics of the pelvis and trunk were analyzed, recorded, and compared.Results:PV was greater in PRO than HS athletes; EVTA was greater in PRO than HS athletes during arm cocking and at MER; but EVTN was similar during arm cocking and greater in HS than PRO athletes at MER. In PRO athletes, PV was not related to EVTA during arm cocking or MER (r = 0.01-0.05). Furthermore, in PRO athletes, EVTA during arm cocking and at MER were inversely related to upper trunk rotation at hand separation and foot contact and to pelvis rotation at elbow extension (r = –0.30 to –0.33). In contrast, in HS athletes, PV was strongly related to EVTA during arm cocking and MER (r = 0.76-0.77). Furthermore, in HS athletes, PV and EVTA during arm cocking and at MER were moderately or strongly related to the other elbow and shoulder torques and forces (r = 0.424-0.991), and EVTA was not related to upper trunk rotation or pelvis rotation throughout the throwing motion (r = –0.16 to 0.15).Conclusion:The kinetic and rotational kinematic differences observed between PRO and HS pitchers in this study may help explain the greater performance of PRO pitchers while allowing them to minimize EVT during pitching. HS pitchers, however, do not appear to be as capable of utilizing the forces generated by rotation of their trunk and pelvis to aid in pitching, and those who throw the hardest generate the greatest forces at the shoulder and elbow. As a result, they experience higher EVTs relative to their body size, which may place them at an increased risk of injury.Clinical Relevance:HS pitchers throw harder primarily by generating larger forces in the arm and shoulder. Thus, owing to the relative physical immaturity of HS versus PRO pitchers, these factors may place them at an increased risk of injury. Coaches may first wish to focus on improving the rotational kinematics of HS pitchers rather than first focusing on achieving greater pitch velocities.

Segmental Power Analysis of Sequential Body Motion and Elbow Valgus Loading During Baseball Pitching: Comparison Between Professional and High School Baseball Players

“…However, elbow valgus torque at MER was a different value than MEV, which was defined as the peak elbow valgus torque during the arm-cocking phase in their analysis. 27 In the present study, MEV did in fact occur at MER, and therefore, it was the only elbow valgus torque extracted for analysis, which when normalized was also found to be similar between professional (0.04 ± 0.01 bw-h) and high school pitchers (0.04 ± 0.01 bw-h). Therefore, the exposure of elbow valgus torque relative to body size appears to be comparable between professional and high school pitchers.…”

“…Thus, the difference in absolute MEV was offset by the differences in height and weight, both of which were significantly different between professional and high school pitchers, and resulted in similar loads at the elbow relative to their respective body size. Conversely, in a recent study, 27 high school pitchers exhibited higher normalized elbow valgus torque at MER than did professional pitchers. However, elbow valgus torque at MER was a different value than MEV, which was defined as the peak elbow valgus torque during the arm-cocking phase in their analysis.…”

A Clinician’s Guide to Analysis of the Pitching Motion

“…Youth at 66% of height [24]. Longer strides can increase pitching velocity without affecting accuracy [8•, 22, 25].…”

“…The study suggested that experience played a greater role in pitching mechanics than age. Luera et al [24] compared professional and high school pitchers' rotational kinematics and elbow varus torque. They found pitch velocity and absolute elbow varus torque during the cocking stages and at maximum external rotation to be greater in professional pitchers.…”

“…They showed an increase in elbow varus torque from 13 to 15 years old. It has been reported that youth pitchers have three times greater activation of the rotator cuff and biceps muscles compared to professional pitchers [24]. This puts adolescents at a higher risk for overuse injury and suggests protection measures need to be established early.…”