We shouldn't be afraid of hills, hill training runs provide an all-round body workout. And here are the reasons why;
The muscles you use to run up hills are the same ones used for sprinting, so the strength you build will improve your speed.
Hill training is an excellent workout for speed, strength, confidence, and mental endurance.
Hills are important because they create variety and intensity, which improves your endurance, anaerobic capacity, power and running economy.
Hills increase the difficulty or the intensity of a run. Climbing a hill naturally increases your heart rate, which improves both your aerobic (endurance) and your anaerobic capacity. In this way, hills can actually be used as a form of speedwork because they can simulate the heart rate intensity of a track workout but without the actual speed of the track. Hence why we were all puffing away like steam trains!
Running uphill forces you to lift up your knees higher than usual, which improves stride length and speed. Have I mentioned that this helps muscle development to increase power.