Many sports are that way and perhaps you are too young to remember the Saturday afternoon television show, "Wide World of Sports". They did a series of shows for several years during the off season of football and base ball based on the world's best athlete. One year a race car driver won and who would have thought that a race car driver would beat out other noted athletes from other sports in a series of competitions.
Most people don't realize or understand how much some of these sports and activities take at a high level and being good in them and the amount of athleticism, training, and dedication they take. I see this a fair amount when people say they just want to learn how to fight and defend themselves but yet give up and quit almost as soon as they get started.
Depends on your definition of fencing. I too have done both arts.
If you are asking about Olympic Style fencing vs MMA than MMA requires more athleticism.
If you are referring to true historic fencing using either medieval or renaissance weaponry...
As mentioned both are very different, both are tough and demanding, and yes a swordsman would take an unarmed person any day and win 99% of the time.
BUT... in terms of athleticism and what is needed to perform at a top notch level in that sport, MMA takes the cake. Training is very demanding. Fights are very demanding. On a pro level training is at a different level. The average joe could not take a kick like this:
MMA... definitely MMA. you have to be able to go rounds and rounds with people trying hit you directly in the face and knock you out. fencing is hopping around with armor on. just as much deception and thinking is required in mma as fencing
I've done both, and I found them about equally difficult in different ways. Hell, fencing might edge it out a tiny bit just based on how much my thighs always felt wrecked the next morning.
Athleticism has no clear cut definition in terms of application. Someone who trains to run fast, vs., someone who trains to jump high; both can be equally athletic in their respective fields. It all depends on your goals.
No easy answer, I Have competed in Martial Arts, and have competed as a Fencer using both traditional and medieval swords.
The skillsets required are similar with some major differences. MMA is about strength, Stamina, and Size. Fencing is all about wrist strength, speed, dexterity, and cunning. However that being said I will almost always put my money on the guy with the sword over the guy with his fists assuming they have similar talent levels.
