The interval workout and the treadmill are a match made in fitness heaven because you can actually control both the speed and the incline of your walk, so you don't have to rely on RPE.

As you know, there are two ways to increase the intensity of your intervals. First, you can go faster; second, you can go uphill. This workout does both! It really mixes it up, so you are constantly challenging your body, both aerobically and muscularly.

For your warmup, start to walk at a comfortable pace, but by the end of 5 minutes, get up to 3.5 mph at a level-1 incline. For the workout, do the following:

• Walk 2 minutes at 3.9 mph with a 1 incline.

• Walk 2 minutes at 3.5 mph with a 1 incline.

• Walk 2 minutes at 3.5 mph with a 4 incline.

• Walk 2 minutes at 3.5 mph with a 1 incline.

• Walk 2 minutes at 4.0 mph with a 2 incline.

• Walk 4 minutes at 3.5 mph with a 1 incline.

• Walk 2 minutes at 3.5 mph with a 4 incline.

• Walk 2 minutes at 3.5 mph with a 1 incline.

• Walk 2 minutes at 4.0 mph with a 2 incline.

• Walk 2 minutes at 3.5 mph with a 1 incline.

• Walk 2 minutes at 3.8 mph with a 4 incline.

• Walk 2 minutes at 3.5 mph with a 1 incline.

• For your cooldown, walk for 5 minutes, returning the treadmill's settings to 3.0 mph with no incline.