I have repeatedly had similar results. Opening the front foot into plant WILL artificially cause the hips to start rotating.
I say artificilly, because although the hip rotation begins, it does not do so forcefully.
As Mankin says, in disagreement with Epstein, it "uses up the hips." (without creating any power)
Good a way to put it as any.
Certainly, some elite hitters DO plant to a fairly open front foot. But it is caused by the hips rotating into foot plant as well. At least, that is my belief.
Whch doesn't matter much. If the MEASURED force is greater when hitting from a closed foot, then there you have it. Certainly, the bio-mechanics literature supports this, in that it indicates that keeping the foot closed (relatively) more actively brings the pelvic muscles into play, better initiating the Serape Effect.
This where learning to throw OH using step behinds or shuffle steps will help out getting the rotation part down in hitting. The player needs to figure out rotate around the front hip joint and I see the similarities in a good OH throw.
I am not talking about pitching, IF work will do just fine.
