

“Now this, bhikkhus, is the noble truth of suffering: birth is suffering, aging is suffering, illness is suffering, death is suffering; union with what is displeasing is suffering; separation from what is pleasing is suffering; not to get what one wants is suffering; in brief, the five aggregates subject to clinging are suffering.”
He didn’t say anything specifically about the ethics of human reproduction. He taught that craving sense pleasures leads to suffering. The monks that followed him were celibate. But he knew few would follow that path. So he taught a simplified code of ethics for householders (don’t kill, don’t lie, etc.) and assumed that there would always be people who want to make more people. Rebirth was an important part of his doctrine. The volitional actions you perform in life create karma which then, after your death, produces another birth. Escaping the cycle of karma and rebirth by letting go of the concept of self, of the idea of me and mine, was the ultimate goal of his path. And it’s only possible to get there in a human body. So in that sense he was not an anti-natalist.
I’m 57 and I started running this year. Overtraining is the biggest issue for me. I’m up to about three miles maybe four times per week, but most of those miles are zone 2 HR, really slow and easy runs. On the weekend I’ll do a tempo run, or intervals, alternately. If I maintain that schedule for more than a month or so I end up a little more sore every time I go running and my time starts to drop. So I have to take most of the week off every four or six weeks. I also take a lot of supplements; creatine, L-carnitine, Beta-Alanine, protein, etc. They help. I feel I can exert myself more since I started taking them. I also take EFAs for joint health, collagen for connective tissue recovery, and sometimes MSM, though evidence on that one is spotty.