It's a fair question. I didn't see any mention of injury in this study and I never see it discussed in these threads. I also admit my bias, I'm an older runner,

It's a fair question. I didn't see any mention of injury in this study and I never see it discussed in these threads. I also admit my bias, I'm an older runner, and I've seen a lot of people struggling, who've unwittingly, been over-optimizing training and just over-training.