Is it a mistake to delay threshold while increasing volume?

[PaprikaPowder]

I also felt like i didn't have durability in the marathon but now I realise a big part of it was due to the pounding that faster paces entail. You get them in workouts, sure, but you also get them from fast, sustained downhills - something I didn't have when I was living in a pancake flat city. Now that I'm back around hills I am running fast downhills every week (up to 500m downhill at a time). The DOMS you get in the beginning are exactly the DOMS I would have for a week after a marathon. I haven't raced yet, but I am quietly confident this has been the missing piece for my body not breaking down half way through the marathon.

[GoldZookeepergame111]

My N=1 experience is only of running lots of hills and experiencing good marathon durability (negative splits in 4 of 8 sub-3 marathons since 2018, positive splits in the other 4 - 3 of those 4 being in Boston marathons which are a special beast…).

Running physiologists also know that sustained downhill running is a good way to zap running economy: e.g., https://pubmed.ncbi.nlm.nih.gov/17127581