Did somebody say Van Damme?
As I pursue my interest in Chinese martial arts, I pause sometimes to wonder how much better offensive linemen, defensive backs and safeties would do with some serious kung fu/tai chi chuan under their belts.
Just imagine some running back trying to stiff arm you. No problem. Give him a bit of "grabbing the sparrows tail" to break his arm at the elbow and dislocate it at the shoulder, on to double push to cave the guy's rib cage in, and to make sure he stays down maybe a quick groin strike with a touch of "needles at the bottom of the sea". Properly executed, these moves are very elegant, take a minimum of effort, but alas take a lifetime of learning.
In all seriousness, the England rugby team were assigned some heavy duty judo training which they thought helped them to a World Cup win. Subsequent coaches dropped the training, and England got stuffed by South Africa in the next World Cup final. I think there would be a place for martial arts as part of conditioning, although I hasten to add I would not advocate any Kill Bill antics on the field.