Running hill repeats is a tough, challenging workout physically and mentally. I have to say it's one of the hardest workouts to face head-on in a training program. However, running hill repeats is, by far, the best fitness booster for runners. It is also the perfect cross-training for cyclists.
Our goal as runners, cyclists, and triathletes is to cover the pavement as quickly and efficiently as possible. As your body becomes fitter, it will move you over the asphalt farther with each stride and farther with each pedal stroke. Running fast on an uphill grade puts a greater stress on the glutes, hamstrings, calves, and core. This increased resistance is adding strength work to your run workout. By changing the angle of the road and allowing gravity to take its effect, you are stressing the total body and asking the heart to pump more blood per beat. I love the feeling of running hills because it has an even effect on the muscular and cardiovascular systems.
In training, we do not make big changes in our run turnover or pedal cadence, but we do in our ability to go farther per stride or pedal stroke. Hill repeats will produce strength in your run push-off and power in your cycling pedal stroke. The goal is more distance per stride and bigger gears, all at the same turnover or cadence... Getting fitter as an athlete is simply going farther at the same effort level in the same amount of time.
My coaching goal is to make you stronger, fitter, and faster. Grow stronger to be fitter, and fitter to be faster. Your efforts will not change, just the distance you cover.