I think the gymnasts might have a point.
But more importantly, Skiers were after banging in movies before snowboarders. And it was Shane McConkey who was, once again, the innovator. The most memorable one I can think of is him skimming over a pond and back flipping out at the other end. He banged the the landing super hard.
I can't remember which movie this was other than it was MSP (fairly sure) and I think I have it on VHS (so obviously old) so it was definitely before the snowboard movie.
Yep, gymnast might afterbang off snow, but IMO Shane McConkey invented afterbanging on snow.
PS Anyone know the movie I mean?