The MET level during treadmill exercise corresponds to the intensity of the activity. The intensity is changed by varying the speed and the incline, so the same MET level is achieved at different paces. For example, a level 4 MET exercise corresponds with a speed of 3.0 mph at a 2.5 percent incline and at a 3.4 mph speed with a 2.0 percent incline. Medical professionals monitor the MET level during treadmill stress testing as a way to gauge your health. Different test protocols are used as the intensity of the exercise is raised by 1 to 2 METS for a pre-determined length of time. In other words, you walk at 1.7 mph at a 2 percent incline, 2 METs, for three minutes and then you walk at 1.7 mph at a 5 percent incline, 3 METs, for three minutes. The test gradually increases the MET level as you progress.