Hills are so beneficial for all runners, and there is plenty of different kind of hill workouts to choose. Long and short hills, hilly routes, even treadmill hills. Ascent plays a big role in hill training. As not every hill has the same effect.
It’s often difficult to know to hill ascent, except on the treadmill. One good way to check how steep some hills are is to run them up and check the data from your watch. This of course requires a watch that can measure such a thing.
0-1% ascent: Zero is of course flat and fastest to run, excluding downhills. In the reality “flat” routes are somewhere around 1%. That’s why you should always but at least 1% on your treadmill, this also reflects wind on the outside.
2-4% ascent: Moderate hills, you feel them, but not particularly good for hill sprints. More like a hilly running.
~8% ascent: Proper hills, which are suitable for longer hill repeats.
10-14% ascent: Steep hills that are good for short hill sprints.
Anything above 20% ascent: start to be too steep, walk. They are too steep to be able to maintain a good running posture. Of course, if you are training for a mountain race, where would be very steep hills, you will get familiar with these.
Choosing the right ascent
Most of the running happening around 0-4% ascent, if the route includes some hills. Besides this, it’s good to do some hill reps sometimes. You can vary between ~8% and steeper hills. Just remember that the steeper the hill the shorter the sprints are. You can also run a hilly course run, which is continuously running on the route that varies between flat and different kinds of hills.