Doping might be a factor also.
If you have rEPO or HGH in your system, it is bound to infiltrate reproductive
human system.
We've seen far too many young fit cyclists dying from cardiac arrest.
the effect of these products are still not fully understood in terms of the after effects.
Oh sure you'll ride like Merckx - but you don't know what effect this stuff has on ones systems.
Thats an interesting theory regarding the doping factor, and surely cant entirely be ruled as a possible influencing factor to reduced infertility.
After all the human body is wonderful machine at times, able to take severe punishment and recover, but sometimes there is only so much it can handle, before something gives.
Superfit sports persons are sometimes more prone to certain types of ailments that for the ordinary person perhaps wouldnt be a problem. I know of several superfit sports people who due to the excessive strains put on their bodies physically and perhaps mentally find they are unable to effectively cope with things like colds flu etc, this may be just their personal physiological make up who knows.