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RELATIONSHIP BETWEEN KINETICS OF COUNTERMOVEMENT JUMP AND PROXIMAL MECHANICS OF COLLEGIATE BASEBALL PITCHING �Motoki Sakurai, Mu Qiao, David J. Szymanski, & Ryan L. Crotin

Department of Kinesiology, Louisiana Tech University, Ruston, LA

INTRODUCTION

METHODS

RESULTS

Nineteen collegiate baseball pitchers (age = 19.9 ± 1.5 yr, height = 186.5 ± 5.9 cm, body mass = 90.7 ± 13.8 kg, % body fat = 14.6 ± 5.2%) volunteered for this study. Signed informed consent was obtained from all participants. The research study was approved by the university’s IRB.

Two data collections took place that included pitching motion capture and recording bilateral CMJ kinetics. Twelve motion capture cameras tracked the whole-body movement and 2 force plates recorded ground reaction force (GRF) from each leg in both tests. In the pitching test, participants were asked to throw 5 fastballs for strikes on a custom-made mound from the stretch position. In the CMJ test, participants performed at least 3 CMJs or until they failed to achieve a greater jump height after the third trial. Jump kinetics and pitching kinematics data were compared based on the differences in throwing velocity and total linear momentum in the anterior-posterior (AP) direction, respectively. The medians for throwing velocity (fast and slow) and AP linear momentum (high and low) of participants were identified to divide them into two groups in each analysis.

CONCLUSIONS

• Pitchers throwing at higher velocity had greater anterior-posterior, mediolateral and transverse momentum profiles and greater peak GRF and power demonstrated by their CMJ. However, significant differences were not found in proximal angular velocities for pitching.
• Pitchers with higher AP linear momentum had greater transverse angular momentum in the pitching delivery and produced greater peak GRF and concentric impulse in their CMJ. Significant differences were not found in proximal angular velocities for pitching between momentum groups.
• Pitchers with higher throwing velocity and AP linear momentum had heavier body mass and lean body mass compared to the other groups.
• Lower body power seen in CMJ impacts throwing velocity and momentum profiles for Division 1 collegiate pitchers.
• Bilateral CMJ assessment is highly recommended to understand pitchers’ capacity to throw at high velocity when peak power and GRF are calculated.

Inefficient proximal mechanics (pelvis and trunk) in baseball pitching encourages greater throwing arm effort in achieving high ball velocities where very few studies have evaluated the influence of leg power on pelvis and trunk motion (2). Powerful lower body mechanics may enable more efficient trunk mechanics and momentum transfer to provide optimal force transfer to throw at high velocity. With effective force transfer generated from the legs to the throwing arm via proximal segments, throwing arm effort may be lowered (1, 4). The countermovement jump (CMJ) is a valid and reliable test that assesses an athlete’s ability to develop force and power output from lower body (3, 4). Pitchers who demonstrate powerful CMJ ability may be able to produce greater force in their lower body to provide efficient proximal mechanics and momentum transfer while pitching that encourage high ball velocity outcomes. However, the relationship between force/power output in the CMJ and pitching mechanics remains unclear. The purpose of this study was to identify how CMJ kinetics influence proximal mechanics in the baseball pitching motion with a focus on momentum transfer.

REFERENCES

1. Howenstein, J, Kipp, K, and Sabick, M. Peak horizontal ground reaction forces and impulse correlate with segmental energy flow in youth baseball pitchers. J Biomech 108, 2020.
2. Kibler, WB. The role of the scapula in throwing activities. Am J Sports Med 26: 325-337, 1998.
3. Lehman, G, Drinkwater, EJ, and Behm, DG. Correlation of throwing velocity to the results of lower-body field tests in male college baseball layers. J Strength Cond Res 27(4): 902–908, 2013.
4. Mayberry, J, Mullen, S, and Murayama, S. What can a jump tell us about elbow injuries in professional baseball pitchers? Am J Sports Med 48(5): 1220–1225, 2020.

PRACTICAL APPLICATION

• Strength and conditioning coaches should prescribe explosive training such as multiplanar lower body plyometric exercises with a variety of intensities and equipment.
• Olympic-style lifts may also be effective, yet appropriate teaching progressions should be made to safely train athletes.
• Increased lean body mass may be more effective for pitchers to have greater pitching performance including throwing velocity and momentum profiles. Increased body fat is not advised for performance enhancement.
• Shoulder stabilization exercises should be prescribed for collegiate pitchers because they are likely to achieve higher throwing velocity with greater transverse angular momentum. Excessive rotational movements of trunk may cause excessive stress on the throwing arm due to the possibility of increased hyperangulation of the throwing arm.
• For the assessment of pitchers’ lower body performance using bilateral CMJ, a primary coaching focus should be to improve absolute peak GRF and jumping power.

Table 1. Differences in kinematics and momentum profiles in pitching and kinetics in CMJ across throwing velocity groups.

Table 2. Height, body mass, and lean body mass differences across fast velocity and slow velocity groups.

Table 3. Differences in kinematics and momentum profiles in pitching and kinetics in CMJ across high and low anterior-posterior linear momentum.

Table 4. Height, body mass, and lean body mass differences across high and low anterior-posterior linear momentum (M) related to throwing velocity.

Results are shown in the tables. Significant p-value was set below 0.05 for all the variables examined in this study. Table 1 and 3 presents Cohen’s d effect size calculations.