Influence of Lead Knee Extension on Ball Velocity and Elbow Varus Torque in Professional and High School Baseball Pitchers.

Background: When the lead leg of a pitcher contacts the ground, the knee braces and then rapidly extends, initiating energy transfer to begin pelvis and trunk rotation. Purpose: To investigate the relationship of lead knee extension during the pitching delivery with peak lead knee extension velocity, ball velocity, and elbow varus torque in high school and professional pitchers. Study Design: Descriptive laboratory study. Methods: Data from 50 professional (PRO) and 50 high school (HS) pitcher groups were retrospectively analyzed. Pitchers threw 8 to 12 fastballs under 3-dimensional motion analysis (480 Hz). The groups were divided according to high or low lead knee extension: PRO-high (n = 18), PRO-low (n = 16), HS-high (n = 16), and HS-low (n = 17). Lead knee flexion, lead knee extension velocity, ball velocity, and elbow varus torque were analyzed between groups. Regression analyses were performed to quantify associations between lead knee extension and ball velocity and elbow varus torque for all pitchers. Results: At foot contact, all pitchers landed with similar knee flexion. PRO-high and HS-high pitchers had significantly greater lead knee extension through remaining pitching time points compared with the PRO-low and HS-low pitchers. PRO-high pitchers had faster ball velocity than PRO-low pitchers (39.8 ± 1.1 vs 39.3 ± 1.3 m/s, respectively), and HS-high pitchers had faster ball velocity than HS-low pitchers (34.1 ± 2.6 vs 31.2 ± 1.8 m/s, respectively) (P < .05). PRO-high pitchers had decreased elbow varus torque compared with PRO-low pitchers (85.3 ± 10.7 vs 95.4 ± 13.3 N·m, respectively); conversely, HS-high pitchers had greater elbow varus torque than HS-low pitchers (64.2 ± 14.7 vs 56.3 ± 12.2 N·m, respectively). For every 1° increase in lead knee extension, ball velocity increased by 0.47 m/s (P < .001) and elbow varus torque increased by 0.27 N·m (P = .025). Conclusion: Proper lead knee extension allowed efficient energy transfer through the kinetic chain to produce optimal ball velocity and minimize elbow varus torque in professional pitchers. Conversely, while proper lead knee extension improved ball velocity among high school pitchers, this did not minimize elbow varus torque. Clinical Relevance: Professional pitchers can extend their lead knee with minimal impact at the elbow. In high school pitchers, cognizance of proper full-body pitching mechanics remains a priority over increased velocity.

Ground reaction forces in baseball pitching: temporal associations with pitch velocity among high-velocity pitchers.

How baseball pitchers interact with the ground is an important aspect of pitching technique and performance. Previous studies on ground reaction forces in baseball pitching have largely been limited to pitchers at the youth or adolescent level, with only a few studies examining higher velocity pitchers. Additionally, previous studies have limited their analyses to only peak kinetic values, neglecting any temporal importance of when these peak values occur. Therefore, our purpose was to provide normative ground reaction force values and examine the associations between pitch velocity and ground reaction forces in high-velocity pitchers. We retrospectively extracted pitch velocities as well as rear and lead leg ground reaction force data from internal databases for 105 high-velocity pitchers. We analysed the associations between the full ground reaction force time series and pitch velocity using statistical parametric mapping regression. Regression analysis revealed pitch velocity significantly predicted lead leg braking ground reaction force from approximately 27% to 35% of the period between front foot contact and ball release. These data reinforce the importance of effective braking forces for achieving maximal pitch velocities. Additionally, our observed peak ground reaction force values were considerably higher than those previously reported.

Lower extremity kinematic and kinetic factors associated with bat speed at ball contact during the baseball swing.

The purpose of this study was to determine which biomechanical variables measured during the baseball swing are associated with linear bat speed at ball contact (bat speed). Twenty collegiate baseball players hit a baseball from a tee into a net. Kinematics were recorded with a motion capture system sampling at 500 Hz and kinetics were measured by force plates under each foot sampling at 1000 Hz. Associations between bat speed, individual joint and segment kinematics, joint moments and ground reaction forces (GRF) were assessed using Pearson correlations and stepwise linear regression. Average bat speed was 30 ± 2 m/s. Lead foot peak vertical (159 ± 29% BW, r = 0.622, P = 0.001), posterior (-57 ± 12% BW, r = -0.574, P = 0.008) and resultant (170 ± 30% BW, r = 0.662, P = 0.001) GRF were all correlated with bat speed. No combination of factors strengthened the relationship to bat speed beyond these individual variables. These results illustrate the role of the lead leg in generating and transferring ground reaction forces through the kinetic chain in order to accelerate the bat. Training to improve bat speed should include both general lower extremity strengthening exercises and sport-specific hitting drills to improve lower extremity force production following lead foot contact.