Excerpted from Running With Joy:
I love to climb! Hill running is a great way to build strength and knee drive without zapping your body. Because of the low impact and slow speed, I can come back a few days after a hill run and do a hard long run. The hills provide many of the benefits I otherwise get in the gym, and I get a cardiovascular benefit as well. I have had some of my best races after doing substantial hill work. Here are two options you can try:
Uphill Threshold. Run at the same effort as a tempo run (the pace you run for a race) for 30 minutes on a road with a grade you like. I enjoy a consistent 5 percent to 9 percent grade. If you’re training for a marathon, gradually build up to 60 minutes. I never run back down because of the high impact of downhill running (unless I am training for a course like the Boston Marathon, which demands callusing to downhill running).
Hill Sprints. Find a steep hill and sprint for 20 to 50 meters (10 repetitions). The key is to keep the distance short so you can sustain maximum effort with proper form.