I'll take a stab at it and Jamt can correct me if I'm wrong or if I am missing something (because I'm dumb ). A downward acceleration of the cm refers to it's movement towards the center of the earth, an upward acceleration of the cm refers the it's movement away from the center of the earth...in essence, vaulting. As we move from one side of the skis to the other the cm first begins to accelerate upwards, away from the earth as the 2 paths converge (from the fall line on through the apex), crosses over the bos in transition, then accelerates downwards as the 2 paths begin to diverge.
An up movement of the cm refers to it's rising perpendicularly above the bos and a down movement the opposite (think Ron Lemaster's definitions of up & down) Now, an upward acceleration of the cm doesn't necessarily coincide with an up movement of the cm because we can still be flexing (which is moving the cm downwards towards the skis) as the cm is beginning to accelerate upwards as the paths converge (because it's beginning to vault). A downward acceleration of the cm doesn't necessarily coincide with a downward movement of the cm because we can be extending laterally at the top of the turn, which is an up movement of the cm in relation to the skis, while at the same time the cm is being accelerated downwards, because it is inclining inside.
In order to have an upwardly accelerating cm in the apex (so that we can balance appropriately) it has to have first been accelerated downwards (what goes up must come down and vice-versa ), so a push off type of movement at transition/initiation is not helpful in this regard because it can cause an upward acceleration of the cm which is the opposite of what we want. On a related note, too much angulation too soon can also be bad as it prematurely balances us over the outside ski and essentially halts the downward acceleration, thus limiting further inclination.
All of this is what Jamt means when he says "...you can affect how it is distributed throughout the turn", "it" being the force pushing the skis down into the snow (which in turn is upward acceleration of the cm).
Edited by zentune - 5/13/14 at 10:19pm