I've seen some really intense impact scenes; the main thing to keep in mind when it comes to bloody impact scenes is that once you're bleeding, each subsequent strike is backspattering aerosolized blood into the air. So if the person doing the bleeding has any blood borne illnesses, you've just introduced the whole room to them.
I keep a set of princess bandaids on hand just in case I manage to make someone leak fluid. You can hit acne, or a thin spot in the skin, or a mole or previous scar; and hell, the edge of a toy can hit just right (or wrong) and open someone up. I stop, wipe down the wound, bandaid it, and keep going. lol
People who don't stop, who keep going, with no drop cloths, no care for spatter, no bio-hazard precautions... those give me the willies!