Hills are the secret sauce for cross-country running.
Add hills to your system several times a week, and you will get stronger.
While Joe Mangan and I coached the Foothill XC team from 1990-1995, I observed Joe’s genius almost daily. He got our athletes, pretty typical distance runners, in the hills of Los Altos Hills daily. In our season’s six weeks, our team would go from barely racing over 4 miles to being competitive. Our number five on the guys’ side was a decathlete.
My personal experience was a two-time-a-week hill workout, repeat 800ms, with a final 200m downhill and fast. I built up to twice a week, 12-16 times, for ten weeks (not to be copied, please, no more than 8 for high schoolers). At the end of the season, in my final road race, I had run for 3 straight years over the same course, improved by 1:32.
Hills can do many things.
For your workout today, warm up well, six times 800m hill circuit, and 600m uphill, kick over the final 200m downhill, jog for five minutes, repeat, then, when you can breathe, fly for 20 minutes for cooldown, and hydrate.