ultra endurance

So this racing thing has taken hold, and I'm annoyingly close to the front of the field. Problem is I don't know what to focus on first to improve my position in the pack. Is it pure strength? Aerobic capacity? Muscle endurance? The only MTB focussed info I can find here, or anywhere, is either...

Probably time there was a separate Bikepacking Forum thread somewhere here ... OK boys and girls ... entries open January 1. You still have time to get fit for this... Starting 15 September 2018. From the tip of Australia at Cape York finishing at the bottom, Wilson's Promontory in Victoria...