This set is not just a great way of practising maintaining ‘momentum’ (physical and psychological) at the top of the short sharp hills that often occur on cross country courses, but also of improving the bodies ability to ‘shuttle lactate‘.
In a grassy park (or similar location) find a short (30 seconds to 2 minutes) hill to run up with a large flat area at the top.
Run at 5km race effort (not pace!) up the hill, continue running for 90 seconds at 5km race pace, turn around to go back to the top of the hill (still at 5km race pace), run at a steady pace downhill. Have a standing or walking rest until you are breathing normally.
When running down the hill make sure to lift your feet high during the recovery phase (think high-heels/butt kicks type drill), lean forward to get as close to 90 degrees to the surface (and not gravity) as you can, put your arms out for stability if you need to and avoid at all costs striking the ground with a straight leg to try and slow down.
This set is inspired by one from this article.