cvlwr:

“Chris [Evans] worked his butt off for four months—doing gymnastics, fight training, stunt training—so that he could stand in in a scene like this and then go toe to toe with Georges St-Pierre and then make it look really credible. And I think he did a fantastic job…Once the helmet comes off, 95% of this is Chris.”

– Captain America: The Winter Soldier audio commentary by directors Joe and Anthony Russo and writers Christopher Markus and Stephen McFeely