A cross race isn't really all out for 45 minutes. Typically my pacing will look like:
- 100% maximum sprint for 15 seconds
- Really hard for 6 minutes or about 1 lap. You basically go as hard as you need to to stay with the lead group. At the end of the first lap I am always about to black out and DNF. I never placed well in cross races until I realized just how hard you need to go in this first lap.
- Settle into a sustainable pace for the next 30 minutes. This is usually a high tempo pace for me.
- Last lap 100% - attack on the parts of the course you think you can get a gap.