with the consent of both my cardiologist and surgeon, i started training in muay thai 8 weeks post avr figuring it would be a great way to get back in shape. my cardiologist was a little reluctant given the brutal reputation muay thai has, but in the end, he didn't think it posed any special or dangerous threat to me; or at least not any more than my cycling and rock climbing tendencies. i am not on coumadin nor any other blood thinner (save baby aspririn) though. over the last 4 months, i have been hit in the chest quite hard on several occasions (sparring mistakes, dropping my gaurd, erent knees, pads mistakes, etc..), and often, with moderate to light force. besides the normal pain one would associate with such blows, my chest doesnt bother me. interestingly, the biggest downside i have found comes from incision irritation which sometimes follows clinching sessions and/or frequent front kicks (front kicks, or teeps in thai, are defensive moves used to back up an offensive strike). i plan to have my first fight within the next 9 months and i will not be using any chest protection. as with all martial arts, there is always the possibility of an errent blow; such is the case when one is learning. my instructor needed me in the face while demonstrating a clinch combo (it was my fault since i moved) and it was enough to give me a bloody nose. such things happen often. as always, i would suggest consulting your doctor.
