This drill is best done in a park, on a gentle downhill section of clean grass. A good grade for the downhill is four percent, or roughly the grade of a highway off-ramp. The hill can be slightly steeper, but don't make it too steep.
"Clean grass" means that you've inspected the hill and it's clear of holes and debris like rocks and glass. The hill should take you 20 to 30 seconds to run down at a fast pace.
After a warm-up getting to the park or running around the park, head to the top of the hill. My favorite way to do this drill is barefooted because it allows my feet to feel light and fast. If you are worried about debris on the grass or foot injury of any type, keep your shoes on.
• Four to eight sets of running downhill for 20 to 30 seconds
• When you are running down the hill, use a slight forward lean to make it easy to pick up some speed. Think about your feet being light and fast. Run fast, but not so that your arms swing wildly out of control. The recovery interval is walking back up the hill. The walk should take 60 to 90 seconds
• Finish the workout with a short cool down