Bicycle moto cross was in the London Olympics, 4 cross mountain bike racing is the 'adult' equivalent {aging out by 30)

a down hill sprint with jumps and corners .

seems the skate bowl X games stuff is the thing now..

in the 70s You had more gear for the DHMX light wheels 20" sew up knobby tires .

But, by the 80s it all went on closeout sales. Even Campag had BMX parts..