Some of the best athletes in the world are motocross racers, bar none. As proven in medical testing.
Hey, there are some great dirt bike courses around, including through MSF. Also, my friend Ned Suesse is a former A class enduro rider who gets some side money from first rate dirt classes, any level. He is a superb instructor. And former MTB rider. Search www.advrider.com
for Neduro and 'class' (user name).