The biomechanics of the pitching motion in American baseball has been studied extensively. This research is in large part motivated by the frequency of injuries to the shoulder and elbow. Excellence does not reduce the likelihood of injury, and it may even increase it. While a large percentage of throwing injuries occur as a result of the follow-through after the ball has been released, the greatest strain on the elbow occurs during the maximum biomechanical load of what most experts refer to as the “late cocking phase” or the “maximum external rotation phase”. During this phase, the elbow is subject to extreme valgus torque, which is offset by muscle contraction, ligament tension, and bone compression.
During the late cocking phase, the non-dominant leg and the lower body are already accelerating forward which creates the maximum load on the soft tissues of the arm. At the Gray Institute, this separation of the lower body and the trunk from the arm is called “proximal acceleration load.” It is an integral component of powerful movements in most sporting activities (batting, golfing, javelin, etc.) The forces that create the velocity of the pitch can, over time, destroy the tissues under certain conditions, particularly when there is dysfunction elsewhere in the body.
Manifestation of Injuries in Adult vs. Adolescent Pitchers
In the adult pitcher, the flexor pronators muscle of the forearm fatigue or become weak, then too much of the load resistance will shift to the ligaments on the inside of the elbow and the bony structures on the outside. The well-publicized tear of the ulna collateral ligament and reconstructive surgery is one common injury that can result.
In adolescent throwers, the torques are the same, but because of the immature musculoskeletal tissues, the most common injuries are different. The ligaments have more laxity. They stretch more but tear less often. The bone growth centers are most susceptible, including the attachment of the flexor-pronator muscle (tension), the growth plate of the humerus (tension and compression), and the proximal end of the radius (compression). Without delving into all the medical aspects, let’s discuss what might be done to prevent these injuries.
Assessing the Kinetic Chain for Injury Prevention
Biomechanics research tells us that as a pitcher becomes more successful (throws harder) there is more stress on the elbow. Preventive measures that have been instituted are pitch limits and delaying throwing a lot of curve balls until greater maturity has been achieved. Improving pitching mechanics and more sophisticated training programs have helped. However, if the entire kinetic chain is not assessed, the cause of poor mechanics will not be discovered, and the training programs will not address these causes.
The Correlation between “Opening Up too Soon” and “Little League Elbow”
Pitching, like many sports movements, requires great skill. This skill is often developed without the requisite foundational physical capabilities that can prevent injuries. Let’s use the problem in throwers called ‘opening up too soon.” This is a mechanical flaw that results in lost velocity and reduced accuracy of the pitch. The pitcher is encouraged to avoid this loss of proper mechanics, but often the problem is based in the body’s inability to produce/maintain the desired sequence. One research study showed that if the pitcher’s trunk started coming forward before the front leg hit the ground, the chances of suffering from “little league elbow” were much higher. Sounds like “opening up too soon” increases the stress on the elbow.
So the challenge for anyone working with young throwers is to find the cause(s) of this flaw. The cause is rarely in the arm, and could be anywhere in the body. At the Gray Institute determining mobility (having the motion) and stability (controlling the motion) is part of every assessment. Both global body movements and sport-specific movements must be analyzed where the body parts change direction (called Transformational Zones). If “little league elbow’ is created by “opening up too soon”, the cause can range from limited motion in the foot, hips, or spine to weakness or lack of endurance in the abdominal muscles or anywhere else in the Chain Reaction of throwing.
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