That’s me yesterday, taking a break from riding my mountain bike in the 100 degree weather that we had in Denver this past weekend. The question is, “Why?”

For me mountain biking, and off-road triathlon are hobbies, and in the interest of full disclosure, I am not particularly good at either one. But I don’t care.

As a 47-year-old guy, I know that too much of a good thing is a bad thing. One common misconception I hear often is the idea that lots of endurance training is good for you. For guys over 40, this isn’t necessarily true.

Prolonged endurance training, like long bike rides, will tend to raise cortisol levels. This can lower sex hormone levels in both men and women.