Do upper body mechanics influence force on the ground?

A colleague on another forum mentioned the following:

“An Arm swing can force the body to rotate and generate rotational forces. Knees pointing in or out can come from the hips or feet but the impact is a loss of power. The same can be said with hip swivels. The lack of stiffness in the area will often result in a loss of power. Toes turning in will prevent an athlete from getting to the big toe. Feet turning out can result in the creation of rotational power which will spill out the vertical power needed to run fast.”

These statements certainly caught my interest. Are they accurate? To help answer that question from a physics standpoint, I once again turned to Paul Boardman of Chicago, who has always been a wonderful resource for these more complex issues.

Here is Paul’s take on these matters:

Force can be dissipated in collisions by any form of resultant deformation.  Force of foot contact could indeed be utilized in rotating (torquing) the foot through an inversion or eversion (angular displacement.  Such force would then not be available to store energy in the elastic medium for re-use on reflex.

But what happens to the energy carried into impact with the ground very much depends on the athlete's ability to channel it into temporary elastic storage versus absorbing it internally in the form of a sprained ankle, vibrating bone, detached tendon, etc.  So, could the torque of landing impact be dissipated by rotating the trunk rather than used to generate stored energy in the elastic media of the legs? I think that answer is hypothetically, yes! 

 If the trunk is strong and tensed, this dissipation should be minimal.  Displacement of the trunk and or resultant deformation under impact would be another story.  Core strength is important for this reason.   The greater the inertia (mass) and tension of any media, the less energy that will be transmitted at the interface between it and a source media and the more that will be reflected (returned to sender).  There is an impedance mismatch then between the initial media and the second.  Here I may be oversimplifying by comparing the 'leg' to the 'trunk' as if they were two linked and adjacent media with an energy pulse traveling through the leg and encountering the leg-trunk boundary.  Example: string attached at one end (fixed) to a concrete block.  Any energy traveling down the string toward the block will mostly be reflected back into the string and very little (though not zero) will be transmitted into the block.

I suspect examples of 'unorthodox' styles of running are athletes actually capable of maximizing the stretch reflex energy cycle with inverted or everted feet because they are responsible for the foot set angle prior to impact and the force of impact is NOT responsible for driving the foot into that orientation.  They may even be more 'efficient' at utilizing the stretch reflex cycle when the foot is so positioned despite any increased environmental resistance to forward (rolling) motion of the foot brought about by this orientation. 

Ken Jakalski