This is interesting. I'm a lurker from the 50+ forum, but have been interested in this subject for years. I am a former NCAA D-I soccer player, former motorcycle racer (pavement circuit races only) and have always stayed in reasonable shape. Am now doing oly distance tri's regularly in about 3 hours.
About 20 years ago I read a detailed article about this subject. A group of exercise/health investigators put a varied group of athletes to the regular tests. Almost as an aside, they included at the last minute some of the top US motorcrossers. (I cannot recall their names now, but they were household names to those who read Cycle News) Anyway, the two motorcrossers were soon the darlings of the testors. Not only were they a little pudgy looking (a la McGrath) they were funny and competitive. To everyone's surprise, they tested better than everyone but the elite runners and the soccer players. (The professional jockeys were right there, also!)
What the testors were especially suprised about was how mental toughness allowed the motorcross guys to push themselves way past all normal thresholds. When others were stopping, they just would hang on like grim death and keep pushing the treadmill, lactic acid threshold be damned. Everything was a game to these guys and they just would not yield until they had wrung every last ounce of energy from their bodies.
BTW, I was in excellent shape when I raced motorcycles. I was disappointed to learn that my first race was to be an 8 lapper instead of a 15 lapper at Orange County Speedway (now departed and missed in So. Calif.). That first race lasted all of about 15 minutes. When I got off the bike I was totally spent. I was shocked at how much energy I had expended wrestling this small road race bike around at about 90 -110 mph. And this was just sitting on the seat, not at all like motorcross.
Sorry for the LOOONG post.
Tyson
Cushing, Oklahoma