The Impact of Drive Leg Impulse and Slope on Throwing Velocity and Kinematics in the Competitive Throwing Athlete.

Abstract

Background: Multiple studies have analyzed pitching kinematics using motion analysis technology, but lower extremity drive leg impulse (DLI) and drive leg slope (DLS) are not as well characterized. The purpose of this study was to investigate associations between DLI and DLS and pitch velocity as well as angular velocity of the pelvis, trunk, and humerus.

Hypothesis: Increased DLI and DLS will be correlated positively with pitch velocity and associated with increased angular velocities in the humerus, trunk, and pelvis.

Study design: Retrospective case series.

Level of evidence: Level 4.

Methods: Three-dimensional motion analyses data from 174 pitchers (age, 17.0 ± 1.0 years; height, 1.82 ± 0.07 m; weight, 80.0 ± 11.3 kg) throwing combined 613 fastball pitches were included. Pitchers threw 2 to 5 pitches, and the variables collected between pitches were averaged and recorded. Statistical analysis was performed using linear regressions to determine the association between DLS as well as DLI and pitch velocity and angular velocities of the pelvis, trunk, and humerus.

Results: Pitchers with higher DLI were associated with lower pitch velocities (β = -22.32; 95% CI, -32.75 to -11.88, P < 0.01). There were no significant associations for DLS and velocity (β = -0.60; 95% CI, -1.48 to 0.29, P = 0.18) or DLS and DLI with rotational velocities except for DLI and trunk kinematics (β = -0.60; 95% CI, -1.48 to 0.29, P = 0.18).

Conclusion: In the combined cohort, DLI correlated negatively with pitch velocity, although this relationship does not exist in the subgroup analysis. Higher DLS was found in pitchers with slower pitch velocities in the elite, high school, and youth groups, although not statistically significant. No associations were found with DLS and any angular velocities between any level of play analyzed in this study, suggesting no consistent association regardless of playing level.