Hills are one of the best ways to teach key sprinting concepts intuitively.

• You learn how to push hard and accelerate. You can't spin your wheels or stop, or you'll go nowhere and fall over.

• It teaches driving arm action. Try to run up a hill without pumping your arms, then add aggressive arm action in. How clear is the difference?

• Steep hills require your ankles to work well. If you don't have good enough ankle rocker, you aren't making it up the hill. That was Sweetness's secret.

The size and length of the hill can be used as different tools in the toolbox.

Baby hills are a fantastic teaching tool because it's just enough resistance to slow you down and force good positions. Longer sloping hills are fantastic for endurance work. Steep hills demand aggressive arm action and working ankles.

Take all of those workouts, and then flip it around and go downhill and you have a fantastic overspeed training tool.