I think you are talking about the Cams, which gives mechanical advantage, eg at the end of the draw cycle you are pulling back (and holding) only 75% (this is adjustable on some cams) of the 40 pounds of draw weight.
Longer stiffer risers are more stable and more accurate. There is also a lot of physics involved with the limb angles etc. to absorb more vibration and shock, for quiter and more stable shots.
I think you are talking about the Cams, which gives mechanical advantage, eg at the end of the draw cycle you are pulling back (and holding) only 75% (this is adjustable on some cams) of the 40 pounds of draw weight.
Longer stiffer risers are more stable and more accurate. There is also a lot of physics involved with the limb angles etc. to absorb more vibration and shock, for quiter and more stable shots.