I just broke in the first brand new motocross bike I have had in 25 years, My last brand new bike was a 81 YZ125G. Today I was running a 06CRF450R.
So I am a bit of a tech geek and took my heart rate monitor to check it out and see how it comperes to Cycling.
First two mellow twenty minute sessions beat all my cycling rates. Change the oil and start to give 'er for a 40 minute session. Stats were Max heart rate 188bpm, Minimum heart rate 154bpm (I started my watch after the first lap), Average 177, duration above 165 -39 minutes, duration below 165 -50 seconds. Better work my cardio training.
If I go by the rule of thumb of 220 - age= max heart rate, I am maxing out as if I was ten years younger.
Motocross, Fountain of Youth of Early Grave? Who cares.