Re: A simple mechanical model of body use.
Unless I'm interpreting it incorrectly, Sigman's balloon man model doesn't really care about the joints... so for all intents and purposes, in the IS model there is no fulcrum... only control unit(s) which is/are the dantien(s). The absence/elimination of fulcrums in the IS models is what enables "jin everywhere all the time" (what you're calling groundpath in all directions). This is presumably also why posture and alignment ultimately don't actually matter in the forming and maintaining of groundpath, since a balloon man by definition has nothing to align.
In fact, one might argue that the purpose of relaxation is exactly this -- to eliminate the presence/effect of these "fulcrums" in the body and to create a body that is wholly connected. Local tension at any point creates a fulcrum (and thus a point of weakness/reliance as illustrated in your diagram), regardless of whether it occurs at a joint or not.
Last edited by tanthalas : 01-24-2013 at 03:48 PM.