Elbow Varus Torque with Weighted-Ball Throwing in Youth Pitchers

Okoroha KR, Meldau JE, Jildeh TR, Stephens JP, Moutzouros V, Makhni EC. Impact of ball weight on medial elbow torque in youth baseball pitchers. J Shoulder Elb Surg. 2019; Article In Press:1-7. doi:10.1016/j.jse.2019.01.025

Background

Previous research has investigated the relationship between weighted-ball throwing and medial elbow torque in high school and college baseball players.  These studies support the role of weighted-ball throwing to increase velocity in skeletally mature players.  However, further research is needed to show the same benefits in younger baseball players.   Youth athletes have less developed musculature and inconsistent pitching mechanics.  This may predispose them to an increased risk of injury compared with skeletally mature athletes.

Purpose

The primary purpose of this study was to investigate the relationship between ball weight and medial elbow torque in youth baseball pitchers.  A secondary purpose was to identify the impact of ball weight on throwing kinematics.

Study Population

  • Youth players (n = 19) aged 9 to 14 years with previous experience with weighted-ball programs.
  • Exclusion criteria:
    • Players who were not actively participating with a team.
    • Players who were not competitively pitching for their team.
    • Players who were currently experiencing or had a history of injury in the throwing arm.

Research Methods

Players’ throwing arms were fitted for a Motus Compression Sleeve (Motus Global) and worn with the mobile sensor 1.5 inches distal the medial epicondyle.  Players aged 9 to 13 years threw from a distance of 14 m and players aged 14 years threw from a distance of 18.4 m. Participants were instructed to throw 5 maximum-effort fastballs with 3-oz, 4-oz, 5-oz, and 6-oz baseballs, totaling 20 pitches. All throws were from flat ground using a traditional pitching motion.

The mobile sensor application was used to collect the values of medial elbow torque, arm speed, arm slot (the angle of the forearm in relation to the ground at ball release), and shoulder rotation (during the late-cocking phase of throwing).  Players were surveyed to identify the ball they most preferred, least preferred, threw with the highest velocity, threw with the lowest velocity, threw with the most accuracy, and threw with the least accuracy.

Key Results

  •  Medial elbow torque increased 0.92 Nm per 1 oz. increase in ball weight
  • Arm speed decreased by 8.52 RPM per 1 oz. increase in ball weight
  • Ball velocity decreased by 2.0 MPH per 1 oz. increase in ball weight
  • Arm slot and shoulder rotation were not significantly associated with ball weight

Study Limitations

  • This study incorporated a traditional pitching motion but from flat ground.
  • This study may have been underpowered (n = 19) to detect significant associations.

Closing Thoughts & Practical Implications

This study shows elbow varus torque in youth players increases with increasing ball weight.  The dose-response finding suggests caution should be used when integrating heavier weighted-ball throwing in youth players.  Perhaps, lighter weighted-ball throwing is a safer option for most youth athletes and heavier weighted-balls should be incorporated after skeletal maturity.   Further research is needed to substantiate any direct relationship between weight-ball throwing and injury risk in youth athletes.

This study also showed arm speed and pitch velocity is inversely correlated with ball weight.  This is not surprising for players of all ages.  Perhaps, training programs seeking to increase arm speed can be best accomplished using lighter weighted-balls.  On the contrary, building arm strength may be best accomplished with heavier weighted-balls.

The youth athletes in this study preferred throwing with lighter weighted-balls.  They also reported greater perceived velocity with lighter balls.  This is important if we accept the idea that the most important goal for youth athletes is to develop an enjoyment for the game.  Throwing with traditional 5-oz balls or lighter balls may be the best option for youth athletes based on their preference and safety factors.  We should probably delay heavier weighted-ball throwing until skeletal maturity.

 

 

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