Suppose you're running on the treadmill and want to increase the intensity. Would you rather increase the speed or the incline?
For example, suppose the following two levels are equivalent in effort level. Which one gives the better benefit?
OPTION 1
Speed: 9.2 (6:31 per mile); incline 1.0
OPTION 2
Speed: 9.0 (6:40 per mile); incline 2.0