What are small, medium, and long hills? How do I know where to go?

The size of the hill refers to how much vertical climbing is involved, which is how much you run straight up over the course of the hill. A long shallow slope could still count as a small climb. Without knowing altitude, it’s easier to go by how long it takes you to get to the top of the hill. A small hill should take 10-20 seconds to run up, a medium hill 20-45 seconds, and a long hill is anything over a minute to climb. We recommend you just run until you find hills that match these parameters, and stick to them for future workouts.