To complete the throw, the baseball pitcher brings his arm behind him at the top of his head. The arm is then in maximum external rotation, which can potentially cause posterior capsular dislocation of the shoulder. This malposition of the glenohumeral joint limits the movement of the arm in internal rotation when the arm is forward. This deformity will lead to rotator cuff injury.

Summary

In fact, the pitcher provides the ball with an ideal acceleration force to be able to distract the one who is batting. The field of excursion of the throw, i.e. external rotation when the arm is behind and internal rotation when it is in front, is constant. So, if the external rotation increases significantly, the internal rotation will thus be decreased. This will lead to shoulder dysfunction and this discomfort will be its symptom.

Movement of extension (red arrow) and external rotation of the arm during the climb.

The thrower’s shoulder should be loose enough to throw. On the other hand, it must be sufficiently stable to avoid subluxation of the humeral head and to maintain control throughout the throwing movement (acceleration and deceleration phases). The surrounding musculature must be strong enough to help accelerate the arm. However, it must exhibit neuromuscular effectiveness to produce dynamic functional stability.

Ball throwing movement phase


The lower limbs and trunk play a fundamental role as force generators, ensuring optimal energy production and transfer to propel the ball upon release. The harmonious coordination of this “kinetic chain” proves crucial to minimize the need for strong stress on the shoulder.

The throwing motion contributes to the smooth synchronization of this kinetic chain. The scapula occupies a key position in influencing the positioning of the glenoid, thus allowing extreme movements without impact. If the kinetic chain is broken at any level, it places increased stress on the shoulder, necessary to maintain normal throwing speed, control and performance.

A thorough understanding of the components of the kinetic chain and the mechanics of normal throwing is essential. The glenohumeral joint offers a variety of extreme movements. The action of throwing a baseball requires the rotator cuff to support repetitions of contractions and relaxations without dysfunction. The precise role of the cuff is to position and center the humeral head with great precision in the shallow glenoid fossa during the throw. This delicate balance is commonly referred to as the “ pitcher’s paradox .”

Pitcher Paradox

The “pitcher’s paradox” is a phenomenon often observed in throwing sports, such as baseball, softball, or javelin. This paradox refers to a seemingly paradoxical situation where the movement of the thrower’s arm appears to defy certain laws of classical physics, notably those related to the conservation of energy.

The “pitcher paradox” refers to a problem observed among pitchers, particularly in baseball. It is characterized by a complex combination of movements which, although necessary to propel the ball with force and precision, can lead to excessive strain and long-term injury.

In essence, the paradox lies in the fact that the movements required to generate high throwing velocity can simultaneously contribute to excessive stresses on the shoulder structures. Pitchers perform rotations and powerful arm extensions, but these movements can lead to problems such as rotator cuff tears, labrum damage, or other shoulder injuries.

The challenge lies in the need to balance optimal athletic performance with the preservation of long-term joint health. Sports medicine professionals and coaches are constantly looking for ways to optimize throwing mechanics while reducing the risk of injuries associated with pitcher’s paradox. This often includes specific training programs and techniques aimed at strengthening and stabilizing the shoulder structures, while maximizing the effectiveness of the sporting movement.

The pitcher’s paradox can be explained as follows:

  1. Hip Rotation: When a pitcher makes a throw, he begins by rotating his trunk and hips in one direction, often backwards.
  2. Weight Shift: Next, the thrower performs a rapid weight shift from the back leg to the front leg, thereby generating considerable energy.
  3. Arm Rotation: During this weight transfer, the thrower’s arm undergoes significant rotation, creating a centrifugal force.
  4. Elbow Extension: When releasing the ball, the thrower’s elbow is often at maximum extension, creating a linear trajectory for the ball.
  5. Conservation of Kinetic Energy: According to the laws of conservation of kinetic energy, the initial rotation of the pitcher’s trunk and hips should theoretically slow the movement of the arm as it reaches the release of the ball. However, the paradox lies in the fact that in many cases the pitcher’s arm appears to speed up rather than slow down.
  6. Jerky Effect: This phenomenon is often attributed to a jerk effect, where the pitcher’s body skillfully coordinates the different parts of the movement to maximize the release speed of the ball. Certain specific biomechanical aspects, such as sequential muscle activation and effective separation of the trunk and hips, contribute to this apparent acceleration.

The thrower’s shoulder must have enough slack to allow excessive external rotation but stable enough to prevent symptomatic humeral head subluxations, thus requiring a delicate balance between mobility  and functional stability . This balance is often compromised and is thought to result in various types of injuries to surrounding tissues. (Wilk and others)

Immense stabilization must be employed by the tissues of these athletes due to the extreme angular velocities and the large amount of force that is transmitted through the glenohumeral joint and its surrounding structures. Injuries to a pitcher’s shoulder typically present with one or more of the following findings:

  • Increased shoulder external rotation PROM
  • Decreased shoulder external rotator strength
  • Bone adaptations
  • Scapular muscle imbalances
  • Bad posture
  • Change in pitching mechanics and pitching by fatigue.
  • At the extremes of the movement, the forces generated and the speed at which this movement occurs endanger the stabilizing structures of the glenohumeral joint and the scapula.
  • If there is muscular disharmony, the humeral head will press on surrounding structures. This will cause damage that often takes a long time to heal.

Phase you launch

Baseball pitchers experience significant stress on their shoulder due to the repetitive and intensive nature of the throwing motion. Here is some additional information on potential problems associated with rotations and powerful arm extensions in pitchers:

  1. Rotator Cuff Tears: The rotator cuff is a group of muscles and tendons that stabilize the shoulder. Rapid rotations of the arm during throwing can place significant pressure on this region, leading to partial or complete tears of the rotator cuff. These injuries can cause pain, loss of strength, and decreased range of motion.
  2. Labrum Injuries: The labrum is a ring of cartilage that surrounds the glenoid socket of the shoulder, providing increased stability. Throwing movements can cause shearing forces on the labrum, potentially leading to labral tears. Labrum injuries can cause shoulder instability and feelings of “caught” or “stuck” during movements.
  3. Tendinopathies: The shoulder tendons, particularly the biceps tendon and rotator cuff tendons, are under significant stress during throwing movements. This can lead to tendinopathy, inflammation and degenerative damage to the tendons, causing pain and impaired function.
  4. Shoulder Instability: Rapid movements of the arm can contribute to shoulder instability, where the supporting structures fail to keep the humeral head centered in the glenoid fossa during movement. This increases the risk of injury and may require surgical procedures to restore stability.
  5. Treatment and Prevention: Managing throwing problems often involves a combination of rest, rehabilitation, muscle strengthening, and sometimes, surgery. Specific training programs aim to strengthen the shoulder stabilizing muscles, improve throwing biomechanics, and prevent long-term injuries.

At the end of cocking, the arm is in maximum external rotation. This position causes compression of the supraspinatus and infraspinatus muscles as well as their tendons between the posterosuperior glenoid rim, the posterior humeral head and the greater tuberosity.

External impingement occurs with excessive superior translation of the humeral head into the glenoid fossa. This reduced translation of the subacromial space results in impact on the structures occupying this space, including the subacromial bursa and rotator cuff tendons.

In throwers, repetitive hyperextension associated with internal impingement (abnormal positioning of the humeral head) causes the deep layers of the infraspinatus to fray, ultimately resulting in a partial-thickness tear. A similar situation is observed on the articular surface of the supraspinatus.

In the long term, this can lead to external malposition of the glenohumeral joint, leading to a reduction in the glenohumeral rotation field in internal rotation, essential during the last phase of the throw, i.e. when the ball leaves the hand.

The position of extreme abduction and external rotation occurs during the overhead throw compressing the supraspinatus and infraspinatus muscles and their tendons between the posterosuperior glenoid rim, posterior humeral head, and greater tuberosity.

Symptoms

Stage I – Painful Shoulder Syndrome

  • Initially, the athlete reports deep pain in the anterior shoulder when throwing certain pitches (usually sliders and curveballs) or after throwing a few innings.
  • The athlete also reports decreased step speed and accuracy and difficulty with activities of daily living.
  • The situation improves with rest and the athlete can continue throwing.

Stage II – Deep pathological pain

  • At this point, stage I pain and soreness have gradually progressed to pain, primarily located in the posterior shoulder, which prevents full abduction and external rotation (the throwing motion).
  • A rest period is no longer effective.
  • Sleeping on the affected shoulder causes nighttime pain and painkillers are required.

Differential diagnosis

  • Acromioclavicular joint injury
  • Biceps tendinitis
  • Cervical radiculopathy
  • Myocardial infarction

Osteopathic approach

  • Rest is necessary
  • The goal is to control inflammation using cold compress application
  • Do not lie on the injured side (on your back it is better to put a pillow under your arm).
  • Release of the myofascial knots of the supra and infraspinatus muscles.
  • When the swelling is reduced, slowly begin glenohumeral mobilization in internal rotation.
  • Strengthening the pectoral muscles

Reference

  • Wilk et al. Shoulder Injuries in the Overhead Athlet

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