Ever wonder why overhead athletes don’t have massively muscled shoulders? Think baseball pitchers, tennis players, volleyballers and other court sports and more often than not they will be toned but relatively slender, especially considering the amount of force they are able to impart upon the ball or racket. They throw or hit hard, so where do they get all that speed?
The answer is that the force generated doesn’t actually originate in the shoulder, but rather is transferred through it. Big shoulder muscles are for hitting things.
It’s all about what’s called the kinetic chain, which refers to successive movement of multiple joints to perform a complex or skilled task. Large muscle groups are good for generating lots of force. If you can transfer this through progressively smaller or distant body parts (ie further up or down the chain), the effect is like cracking a whip.
The main force generators for overhead athletes, therefore, are the legs and pelvis, where the largest muscle groups are located. Their size makes for good movement and force initiators. From there on in, only small additions to force production are made by successive body parts.
Muscle groups like the rotator cuff and the scapular stabilizers have a critical role in this model, not as force producers, but as force transmitters. Your shoulder and arm require stability to allow the forces generated to pass through the limb and onto the racket or ball, without losing any efficiency. The length of the lever, as in racket sports, or the sheer velocity required, as in a baseball pitch, require that these stabilizing muscles, as well as others controlling other body parts, must be strong enough to withstand these forces. Exercises to develop stability in these areas must be tailored specifically to meet these needs, particularly when you remember that endurance is a factor.
↑ Notice in the above sequence that the pitcher’s weight transfers not only from back foot to front but from high to low, and that the dynamic forward step from cocking to acceleration precedes the arm coming forward. Power generated by the legs and hips thus transfers through the trunk (hence the need for good core stability here) and into the shoulder and elbow, and ultimately transferred to the ball at release.
Poor technique and overuse are factors commonly taken into account by PT’s when treating the overhead athletic shoulder. A skilled therapist will also take into consideration the possibility that these factors may the result of compensation for inadequate force generation lower down the chain. A thorough assessment of the overhead athlete should therefore require an appraisal of the entire kinetic chain, so don’t be surprised if your PT wants to look at your legs and hips if you’re a thrower with a sore shoulder.