About a week ago I replied to a thread asking about whether to increase the speed of a treadmill or increase the incline. At first I thought it didn’t matter, but obviously doing both is best. After giving it some thought, I am revising my position. You will get better results if you increase the incline versus increasing the speed. On a treadmill your basically running in place. Raising the incline forces you to lift your legs higher which will be more resistance than just running in place faster. On the street you’re pushing off of the stationary ground. There it would make little difference between running faster and running uphill, but obviously doing both is best.