The Effect of Pitch Type on Elbow Biomechanics in High School Pitchers

Abstract

Background:

Pitch type, ball velocity, and spin rate have been previously hypothesized to influence elbow varus torque and subsequent risk of injury; however, existing research is inconclusive, especially in high school pitchers.

Purpose:

To examine elbow varus torque, cumulative elbow torque, and loading rate within high school pitchers throwing fastball, changeup, and breaking ball pitches. Additionally, to quantify the potential relationship between ball spin and elbow kinetics.

Study Design:

Descriptive laboratory study.

Methods:

A total of 31 high school pitchers (age, 16.9 ± 0.9 years, height, 183.4 ± 6.3 cm; weight, 77.7 ± 8.5 kg) were analyzed using 3-dimensional motion capture (480 Hz) and TrackMan while throwing a full bullpen of pitches consisting of fastball, curveball, changeup, and sliders. Elbow varus torque, torque loading rate, and cumulative torque were calculated and, in combination with ball velocity and spin rate, were analyzed using mixed-effects to establish within-player differences between pitch types. To investigate variability within each pitch type, standard deviations for each variable were compared using analysis of variance.

Results:

Fastball pitches had significantly faster ball velocity and higher elbow varus torque (35 ± 0.5 m/s; 67.8 ± 2.7 N·m) (P < .001) compared with breaking balls (29.9 ± 0.6 m/s; 62.3 ± 3.5 N·m) and changeups (31.6 ± 0.6 m/s; 59 ± 3.2 N·m). Fastball pitches had significantly greater cumulative elbow varus torque and loading rate compared with all pitch types (P < .001). There was no significant difference in cumulative elbow varus torque between changeup and breaking balls. Fastball pitches had significantly higher loading rates compared with changeup and breaking balls (P < .001). Fastball and breaking ball pitches had higher spin rates compared with the changeup pitch (P < .001); however, no difference was found between fastball and breaking ball spin rates (P = .102). There was no difference in variability between pitch types for all variables assessed. There was no significant relationship between spin rate and elbow varus torque, within or across pitch type groups (P > .01).

Conclusion:

Fastballs were associated with the greatest ball velocity, peak elbow varus torque, cumulative torque, and loading rate among the 3 pitch types analyzed. Although spin rate was highest in fastballs and breaking balls, it did not correlate with elbow torque and thus indicates limited relevance to injury or performance in this population. Injury prevention efforts should focus on workload management and physical development, rather than pitch type or spin rate, in high school pitcher injury prevention efforts.

Clinical Relevance:

Increasing velocity and fastball pitch types should be considered when assessing the risk of elbow injuries in high school pitchers.