@codinghorror Such a dial exists, btw. Cardio. As a distance runner, I’ve been aware since high school, but the research is much more recent.
I can’t find it now, but maybe 7 or 8 years ago, the first paper found that testosterone levels drop when your daily average run gets too much above 4 miles or so (lower than the commonly stated 40 miles a week).
I’ve noticed it with lower impact cardio as well, but it takes a longer workout to notice it. Running is hard on your body.
