What a great introspective.

I did a z2 run the other day in a 35C dry heat. For me, z2 is 130 - 135 HR, and I ended up with an avg pace of 8:00/km or worse.

Also, I’ve been told there’s some downsides to doing training runs that go much over 2 hours - which limits the distance you can reasonably run. Unless you either pick up the pace (and therefore your HR) or your pace naturally increases while keeping your HR low.

How does someone start getting their body used to longer distances to train for a full marathon, doing z2 runs? It doesn’t compute, so I guess to train for that I’d have to start doing 25-30km z2 runs, going for 3hrs or more.