I am dutch and I have never heard of this issue/myth. Even tour de grance cyclists manage to have kids just fine after 20 years of full time cycling, so I wouldn’t worry.

What subject do you want to create a bibliography for?

Mundane goal to accompany this: get flexible enough that you can put your foot up anywhere and tie your shoe laces without bending over.

I get workout euphoria/runners high about 10-15 minutes into anything that gets my heart rate up significantly. It makes cardio very addictive, but means I have trouble with low intensity work and strength training. Also… the high is sometimes followed by a low about 15-30 minutes after exercising, although sometimes that is related to refuelling or simple fatigue.