Elbow Flexion Excursion: Intra– and Inter–Throwing Arm Kinetic Evaluations in High School and Professional Baseball Pitchers

Abstract

Background:

Elbow flexion at stagnant time points of the pitch has been associated with increased elbow varus torque (EVT) and elbow injury history.

Purpose:

To determine how elbow flexion angle throughout the pitch (excursion) between individual pitchers and a cohort of pitchers influences throwing arm kinetics in high school (HS) and professional (PRO) pitchers.

Study Design:

Descriptive laboratory study.

Methods:

HS (n = 59) and PRO (n = 288) pitchers were instructed to throw 8 to 12 fastball pitches evaluated with 3-dimensional motion capture system (480 Hz). Linear regression models were developed to examine the association between elbow flexion excursion with ball velocity and throwing arm kinetics. An intrapitcher analysis utilizing a linear mixed model was also used, introducing pitchers as a random effect.

Results:

The mean elbow flexion excursion was significantly greater for HS (70° ± 22°) compared with PRO (63° ± 21°) pitchers (P < .001), while the mean normalized EVT was significantly less for HS pitchers (3.9% ± 0.7% vs 4.8% ± 0.8% body weight [BW] × body height; P < .001). For every 1 SD increase in elbow excursion, ball velocity increased by 0.8 to 1.0 m/s (approximately 2 mph) for intra- and interanalyses (P _max = 0.006; β = 0.31-0.39) for HS pitchers, while it increased by only 0.2 to 0.4 m/s (<1 mph) for PRO pitchers (P _max = 0.016; β = 0.10-0.17). EVT increased by 0.34 to 0.40 SD for every 1 SD increase in elbow excursion for intra- and interanalyses for HS pitchers and by 0.13 to 0.22 SD for PRO pitchers. Elbow medial force increased by 1.9% to 2.3% BW for every 1 SD increase in elbow excursion for intra- and interanalyses of HS pitchers (β = 0.35-0.44) and by 1.4% to 1.7% BW increase for PRO pitchers (β = 0.23-0.27).

Conclusion:

PRO pitchers have decreased elbow flexion excursion compared with HS pitchers. This may be an advantageous mechanism by which to minimize throwing arm kinetics, including EVT and elbow medial force, supported by both intra- and interpitcher analyses. Ball velocity benefits with increased elbow excursion were marginal for both cohorts.

Clinical Relevance:

In support of previous literature suggesting that increased elbow flexion at later portions of the pitch is associated with increased EVT and injury history, this study further substantiates that this may be deleterious kinematics to baseball pitchers.