Thanks Keen,

Regarding the hip/shoulder mobility question, you are correct in your thought process. I must note, however, that I am not the originator of discussing this correlation.

The correlation is one that was brought to our attention by one of our team orthopedic surgeons; though it must be stated that reality of it is quite obvious.

The kinematic sequence of events associated with terrestrial based team sport athletes colliding with one another, fully airborne collisions excepted, begins from the ground up. Thus, a linkage of dynamic considerations is formed from ground support to the body part that makes contact. In the case of shoulder traumas it goes without saying the shoulder and or arm is one of the final points of contact and, therefore, the end of the kinematic sequence.

If the sequence is initiated from the ground and finalized at an upper appendage then we know that the hips serve as a primary force transducer.

Knowing that the biodynamics of a collision are complicated and multi-dimensional it goes without saying that any lack of mobility at the hips will overload the force transmitting joint structures between the hips and the point of contact. In the case of collisions involving the arms, it is the shoulder that becomes overloaded as a result of limited mobility at the hip.

My own insight is not required to convey this point, however.

Stand in front of a door way, walk quickly through the doorway and grab one side of the door frame, with the same side arm, in an effort to stop yourself. Notice the rotation that occurs at the hip/trunk and how this lessens the stress experienced at the shoulder.

Now do it again, and this time keep your hips/trunk a rigid as possible; thereby, limiting hip/trunk rotation as you stop your self with the arm. Notice the increased stress experienced at the shoulder.

There you have it.

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