There's combat and then there's mortal combat.
Tennis allows for the psychological strains of one-on-one combat minus the threat of annihilation or permanent physical injury, though I've seen psychological injuries result at all levels. Some are never the same after a certain loss.
Martial arts can be to the end, but primarily it is just pain or possibly permanent injury at risk. Then there is actual mortal combat with loss defined as death. None of the rest truly compare.
