I used to, still have all my equipment, but since I opened the race track some 5 years ago, I have had to bust my ass dragging fire hose, lifting big water pumps, cutting up trees and moving the logs, etc.....
Then when I do get to ride my bike, wrestling with a volatile MX bike to maintain control of it is a real workout.
(I believe that a cardio test was done once, and Motocross was more strenuous to the body than soccer or hockey.)
My other sport is slalom water skiing, another real workout, playing tug of war with a motor boat.