Biomechanical Analysis of Weighted-Ball Throwing

Fleisig GS, Diffendaffer AZ, Aune KT, Ivey B. Biomechanical analysis of weighted-ball exercises for baseball pitchers. Sport Heal A Multidiscip Approach. 2017;9(3):210-215. doi:10.1177/1941738116679816.

Background

Weighted ball throwing programs are becoming increasingly popular across all ages of baseball.  These training programs are based on the idea that throwing lighter balls will build arm speed and throwing heavier balls will build arm strength.  It is unclear how throwing with lighter or heavier balls changes kinematics and kinetics compared with standard baseball pitching.

Purpose

The purpose of this study was to compare biomechanics among common weighted-ball exercises and with standard pitching in high school and collegiate baseball pitchers.

Study Population

  •  Experienced high school (n=18) or collegiate (n=7) pitchers who were experienced with weighted ball training.
  • Pitchers with an injury in the previous 12 months were excluded.

Methods

Thirty-eight reflective markers were placed on the body of research participants as they performed 3 repetitions of 10 different exercises.  All throws were randomly ordered and performed with maximal effort.  The exercises were fastball pitching with 4-oz, 5-oz, 6-oz, and 7-oz baseballs from a pitching mound to home plate 18.4 m away. Throwing 4-, 5-, 6-, and 7-oz baseballs from flat ground to home plate 18.4 m away were made utilizing a “crow hop”.  “Holds” were performed from flat ground with a 14 oz and 32 oz rubber balls. For holds, the participant performed his full pitching motion on flat ground but without releasing the ball.

For each trial (except for the holds), ball velocity was measured by a radar gun. For all trials, the 3-dimensional motions of the reflective markers were tracked with a 12-camera automated motion capture system.

Key Findings

  •  As ball mass increased, ball velocity decreased.
  • Velocities of the ball, pelvis, and shoulder were greater for flat-ground throws than for pitching from the mound.
  • Angular velocities for the pelvis, upper trunk, shoulder, and elbow were significantly lower for the flat-ground holds than during standard pitching.
  • As ball mass increased, elbow and shoulder joint torques and forces decreased.
  • Angular velocities and joint kinematics were not significantly different between 4- and 5-oz balls.
  • Compared with pitching from a mound, throwing on flat ground produced greater elbow varus torque and less elbow flexion torque.

Study Limitations

  • Youth, professional, and non-pitching positional players were not investigated.
  • Pitching with lighter 2-oz and 3-oz balls were not performed.
  • Kinematics and kinetics were based on skin markers, which do not precisely mimic bone movement, which may create motion artifact.

Practical Implications & Closing Thoughts

The findings from this study do not support the belief that throwing with weighted balls increases torque at the shoulder and elbow joint.  The decreased forces and torques displayed with throwing heavier balls implies decreased acceleration compared to standard baseballs.  Throwing with weighted balls does not appear to significantly alter pitching mechanics. There were little differences in body positions between varying ball masses.  Therefore, it appears that pitchers can train with their normal mechanics when pitching 4- to 7-oz baseballs from a mound.

Pitching from a mound results in a longer stride and greater shoulder external rotation and pelvis rotation at front foot contact.  Because of the kinematic differences between pitching from the mound and crow hop throws from flat ground, flat-ground exercises may not be appropriate for practicing proper pitching mechanics.  Flat-ground throws also produce increased shoulder internal rotation velocity and elbow varus torque.  This suggests these exercises may be beneficial for improving arm velocity but may also be stressful to the elbow joint.

The results of this study and previous research1 with youth baseball players show throwing with lighter balls decreases kinetics.  Also, compared with throwing standard-mass balls, elbow and shoulder velocities increase with lightweight balls for youth baseball players and decrease with overweight balls for adult baseball players.   Based on this research, throwing with light-weight balls appears to be a reasonable approach to training in all baseball pitchers.  However, future studies should seek to investigate trends in pitching injuries for those involved in any weighted ball training program.

References

  1. Fleisig GS, Phillips R, Shatley A, et al. Kinematics and kinetics of youth baseball pitching with standard and lightweight balls. Sport Eng. 2006;9:155-163.

 

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