It's more like, their prana's forced out, so that their actions are always more powerful than they'd usually be. Open the tap to let out some water, but the water blasts out instead cos of high pressure in the tank.
Saber couldn't, for example, fight Diarmuid at Mach whatever like she did in F/Z, cos her dexterity's been reduced thanks to the equivalent of having a jetpack strapped to her that blasts off at full force every time she swings, but thanks to that she'd knock him through a couple buildings with her first swing instead.