Understanding anatomy is very useful when treating any client population, however, when treating an athletic population, it is imperative to understand the sport in question, as well as the associated movement patterns. As mentioned previously, most studies are conducted on baseball athletes, but an overhead athlete can play a number of sports, and the mechanics of a baseball pitch/throw can be extrapolated to each of these sports with minor changes. To start, we will outline the mechanics of a baseball player’s pitch.
There are 5 distinct phases of a baseball pitch – wind-up, cocking/stride, acceleration, deceleration, and follow-through. The wind-up phase sets up the pitcher to transfer his weight from their hind leg to their front leg, and is essentially a single leg stance, with opposite knee march. In this phase the hands are together; when the hands break, we enter the cocking/stride phase. In the early cocking phase, the scapula is retracted, the humerus is abducted/externally rotated/horizontally extended – placing maximal stress on the anterior joint capsule. At the same time, the stride leg (contralateral to the throwing arm) begins to extend at the knee/hip and internally rotate. The body’s center of gravity also begins to lower due to the support knee and hip flexing and anteriorly rotating – this is accompanied by extension of the lumbar spine to assist in the shoulder’s external rotation. During this phase, the deltoid and RTC sequentially become active. Internal rotators activate during late cocking to decreased external rotation. Tensile forces are increased in the abdominals and spine to stabilize the trunk. This puts the body in the best position to transfer weight from the support leg to the stride leg as well as energy from the hips and core to the ball.
Acceleration takes place from maximal humeral external rotation/abduction/extension and scapular retraction to when the ball leaves the hand, at which point the scapular has protracted and the humeral position is in internal rotation/flexion along with elbow extension. This is also the point at which the energy stored from the cocking phase is transferred to the ball – therefore successful weight shift from support to stride leg as well as trunk rotation (i.e. thoracic rotation) are necessary for a successful pitch. The Lats and subscapularis muscles are highly active during this short period of time to allow for full internal rotation of the humerus. This ties into the final 2 phases of the pitch – deceleration and follow-through. During these phases, all muscles are active to either slow down the arm or bring it into increased internal rotation. The infraspinatus, teres minor, and posterior deltoid are all active eccentrically to slow down the humerus, while the lats and subscapularis continue to bring the humerus into internal rotation. Elbow flexors including the biceps brachii are active to prevent excessive extension of the ulnohumeral joint. To complete the motion, the trunk continues to rotate contralateral to the throwing arm and flexes. By now, the pitcher should have already transferred all of his weight from his support leg to his stride leg, ending in, again, single leg stance.
Given the above phases of a pitch, the same can be applied to other sports. In volleyball the arm swing phase – when the hitter is in the air – is almost identical to a pitcher’s throw. However it is not as extreme in ROM and the weight shift occurs without rotation in preparation for jumping and can be combined with the hitter’s wind-up phase, while the trunk rotation occurs in the same phase as a pitch, acceleration-deceleration. The other distinction between a pitcher’s arm and an outside hitter’s arm is that the volleyball hitter will swing with decreased abduction and increased flexion through the acceleration phase – their hitting arm will attempt to pass over their head rather than to the side and contact the ball (equivalent to ball release in baseball) with full elbow extension.
In track and field, a javelin thrower’s arm goes through very similar motions as a volleyball hitter. There isn’t much of a wind-up, rather, when the thrower pulls the javelin back, they are already in their cocking phase. Due to the demands of the sport, these throwers also have their arm pass through an arc that is less abducted than a baseball pitcher – they need to achieve height on their throw. The key in this sport, however, is in their legs. The javelin thrower begins with the arm at 90-90, holding the javelin, and starts with a straightforward sprint. During the final steps (when the thrower enters the cocking phase), the thrower moves forward with cross over steps, requiring increased activation of the contralateral adductors followed by contralateral trunk rotation and flexion.
During a tennis serve, again, there is a very similar sequence of movements. There is a windup phase that consists of knee flexion and the toss with scapular retraction of the racquet arm (cocking phase). In order to contact the ball, the athlete must generate power through their lower extremities and core and accompany it with trunk rotation. From here, the movement sequence is similar to the above sequences of acceleration, deceleration, and follow-through.
While a softball pitch presents with different mechanics, the throwing of a softball for positional players is the same. A more thorough breakdown of softball pitching mechanics will be addressed in the future.
By now, hopefully I’ve convinced you how important hip and core stability are in an overhead athlete – it is not enough to only address the shoulder, many times if you solve the deficits in the hips and core, their shoulder impairments will also resolve or reduce in severity. If you don’t believe me, here’s a good article that also discusses hip stability and it’s role in the pitching motion: http://lermagazine.com/cover_story/the-throw-from-below Understanding movement patterns inherent to the athlete’s sport can help direct your manual therapy and neuromuscular re-education, addressed in Part 4: Treatment interventions.