Don't have my book handy (eating lunch at Atlanta Bread) but I seem to remember the downward motion being the result of 1) axis tilt and 2) uncocking lead wrist.
6-B-2-0: When the Left Wrist is Cocked it forms the Second Power Accumulator.
while:
2-N-1-B The Downward Force results from the action of Axis Tilt (Hip Slide) and/or the Uncocking Left Wrist if there is any of either. Otherwise the Lever assemblies are dropped, pulled or pushed downward from their fulcrums.