this explanation makes even to some of the heart health books I have read. The MAMIL type (read: we lol) are a sensitive group: many come out of a stressful life, family+kids and travelling too. This scenario is alredy considered unhealthy but unavoidable THEN boom! We jump on a bike (or swimming or weights etc) day in day out we give it all just to get that feeling of having worked out hard! That rush of dopamines or any other feel-good hormones, however, we are just adding stress on top of everything else. Based on this, I started to believe that what is healthy can be turned into unhealthy.
I know it does sound boring (it can be actually really boring) but started training based on my heart threshold and only every now and then, or a couple of sessions in a single week, where I apply some strenuous drills. The results were not only better, more power for longer and feeling not broken after the session, but I also do not feel anymore deprived of personal life, nor of sexual life. My stress remains decently low (the opposite of when I used to hammer the pedals very often) and because of that, I could finally reach a TTS that seemed impossible for me in a week (hey, I´m 47 years old).
In the build phase, I performed better and felt better after the workouts… I am sticking to it this year: accepting my age limits. If one is still before those family commitments years then, of course, one can hammer and rest more.