That's an ambitious session!
It's useful to think about your vertical climbing speed when working out how hard a treadmill session is going to be.
12km/hr = 5min/km = 150m(Vert)/5 mins = 30 m climb / minute.
That's a vertical km pace of 33:20. I'm fairly terrible at VKs and have a 38 minute PB. You may well be better than me but that's still a fairly aggressive session.
The other way to gauge expected effort is to use the 'calories/hr' display on the treadmill. I find that's fairly consistent, eg if 20km/hr@1% and 10km/hr@10% are both 1500kcal/hr then they probably feel comparably tough. (making up numbers a bit here, can't remember what my treadmill tells me)
Hmm okay on second thoughts that was quite ambitious.. especially as I’ll be way slower than you ever where at the vertical km.
That’s really useful thanks for the advice, I shall take that into consideration at my next attempt. That cal/hr sounds like a clever way of gauging it, will check that out too!