I like to use a mixture of incline and no incline, I walk on an mid-range incline for 5 minutes, then lower it to flat and run at 7.5 speed (I have long legs, so it's not a sprint for me, just a comfortable fast run.) I find this way I don't get as bored, since I have a mixture of walking/incline (for the buns
) and running/no incline (for the legs in general)