Either i'm made of steel or the risk is rather limited and perhaps different from person to person. It is true that hits on bones make darker bruises and are more painful but i consider such hits as unavoidable if one exposes his/her body to whipping. So far i never got awareness of any damage, but the reaction and strong warning made me a bit uncomfortable. Trying to hit specific area's isn't easy and it is even more difficult to avoid some spots.