GY just wandered on here, slaming a medicine ball against the stomach can do 2 things damage muscle and whats underneath Liver , Kidneys, Splean repreduction organsif you bruise or damage them theyve got enough on repairing themselves and not doing what they are there for purifying and regenerating blood so the bruising in the body is slower to repair the system wont work as well. There are more damaged fighters about because of this practice than you think Im one the idea is not to get hit because of the damage it does, so it doesnt sound a good idea to do it on a purpose. Plus there are better ways to do it