Is it better to run uphill or flat?
Is it better to run uphill or flat? But generally speaking, both running uphill and running on a flat road are important, says Paul. Running on an incline engages different parts of your muscle fibers, like your upper hamstrings, and targets your glutes more than a flat run. And since running uphill is more intense, your heart rate increases faster. Does running hills make you slower? Uphill. Jack Daniels, author of "Daniels' Running Formula," estimates that for every percent of incline you experience in an uphill, your running time will slow by 12 to 15 seconds per mile. Building hill...