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Pitcher’s Elbow: How Valgus Force Puts You at Risk


The risk for pitcher’s elbow injury is linked to high repetition and high stress at the joint. The stress on the medial elbow is known as valgus or abduction load. This is a force that is pushing the joint into an abducted position.  The muscles and ligaments (ulnar collateral ligament) that try to prevent this motion to keep the elbow stable become overworked, and can no longer handle the stress. Athletes are particularly susceptible to injury when they are fatigued. High pitch count, not enough rest, too many curve ball or breaking pitches, and improper technique are major contributing factors in surpassing the load capacity of the elbow.

baseball player pitching


Proper mechanics have a significant impact on how forces are transferred and absorbed through your body.  Kinematic strategies at each body segment in the movement chain has a crucial impact on performance and injury risk.  The speed of a baseball pitch makes it very difficult to see and assess body mechanics accurately (see our article: Amplify Your Coach’s Eye), but with Gears 3D motion capture and force plate technology, we provide the most complete analysis available.


  • Front-foot position at contact
    • When the front foot is externally rotated when planted (or slips into external rotation during the pitch), it leads to higher torso lateral tilt away from the pitching arm. This results in a more sidearm slot, thereby increasing the load at the elbow.
  • TIP: work on hip strength and stability while performing high velocity rotations (eccentric loading during hip internal rotation)


  • Early trunk rotation (initiated before front-foot contact)
    • Ties in with the ideal kinematic sequence – early initiation of trunk rotation is associated with improper sequencing and a subsequent increase in elbow strain
  • Peak rotational velocity of the trunk should occur after the peak rotational velocity of the pelvis (ideal kinematic sequence!)
    • This sequence decreases shoulder external rotation angle and subsequent associated injury risks
    • When the forces from the ground are transferred properly through the body via a good kinematic sequence, it puts less strain on the upper body as the shoulder and elbow won’t have to compensate for poor lower body and trunk mechanics
  • Excessive lateral tilt or sidearm delivery
    • increases elbow extension and valgus load
  • TIP: core stability and rotational strength! Work on creating an ideal kinematic sequence by slowing down your movement first


  • Peak shoulder external rotation (higher rotation angle = more valgus load)
    • This mechanism is typically the result of poor movement elsewhere
  • TIP: shoulder stability strength – this should be a constant part of your training


  • Elbow flexion at peak valgus torque (less flexion = more valgus load)
    • Although less elbow flexion decreases the moment arm about the long axis of the humerus, the longer moment arm about the trunk’s axis of rotation is what increases the valgus load at the elbow – the straighter elbow as the arm lags during early acceleration increases the bending moment at the elbow (particularly when the shoulder is abducted to 90 degrees)
  • Elbow valgus loading rate
    • How fast the load is put onto the elbow
  • Timing of maximum elbow flexion
  • Elbow flexion at ball release (less flexion = more valgus load)
    • These mechanisms are typically the result of poor movement elsewhere
  • TIP: core and shoulder stability


The research is clear on the likely movements that cause injury.  Gears Sports offers research-grade technology to provide the ultimate visual and analytical tool that gives coaches key pieces of information to significantly strengthen their training.  By understanding what is happening under the hood of the athlete engine, coaches and trainers are able to direct their focus to maximize efficiency in the gym and on the field.

Aduinaldo and Chambers. (2009). Correlation of throwing mechanics with elbow valgus load in adult baseball pitchers. American Journal of Sports Science, 37(10). 2043-2048.
Oyama et al. (2014).  Improper trunk rotation sequence is associated with increase maximal shoulder external rotation angle and shoulder joint force in high school baseball pitchers. American Journal of Sports Medicine, 42(9), 2089-2094.

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