What are the five phases of a pitching cycle, and which two phases are identified as critical in terms of potential injury to the UCL (ulnar collateral ligament)?
The five phases of the pitching cycle are as follows:
1. Windup: Initiates with the pitcher's initial movement, going into a single-leg stance, and ends when the pitcher's hands break apart.
2. Early Cocking: Begins when the pitcher's hands break apart and the ball is removed from the glove. The shoulder goes into abduction and external rotation, ending when the pitcher's foot hits the ground.
3. Late Cocking: Starts when the pitcher's foot hits the ground, with the shoulder continuing into abduction and external rotation, and the elbow flexing between 90 and 120 degrees. This phase concludes at max external rotation.
4. Acceleration: Begins when max external rotation is achieved, and the shoulder starts to come forward. The shoulder goes into abduction and internal rotation, while the elbow starts to go into extension. This phase ends at ball release.
5. Deceleration or Follow-Through: Begins at ball release, and the shoulder completes its move, going through abduction and internal rotation. The key here is the elbow's rapid extension, terminating with the termination of movement.
The two critical phases identified for potential UCL (ulnar collateral ligament) injury are:
1. Late Cocking Phase: Large valgus forces are experienced on the UCL during this phase, especially when the shoulders are at max external rotation, and the elbow is flexed between 90 and 120 degrees.
2. Deceleration Phase: High forces on the elbow, particularly compression forces on the medial elbow, occur during rapid extension of the elbow. This phase is crucial and can lead to valgus extension overload.
Despite the protection provided by the flexor-pronator mass, which absorbs about half of the forces, the UCL still bears a significant load, and cumulative microtrauma during repetitive pitching can lead to UCL injuries, including insufficiency, partial tearing, or complete tearing. The mechanism of injury differs between adults and adolescents, with adolescents more prone to avulsion injuries due to the weaker growth plates compared to the UCL. In adults, the UCL is weaker than mature bone, so you will see more mid-substance UCL tears.