This is an running workout, so if you do not run or have very low fitness level, this is not your workout
I like to use a heartrate monitor to maintain a high to very high intensity level… your breathing is also a good way to tell how hard you are working.

Warm up for 5 to 10 minutes at moderate pace for your fitness level..

Run 1 mile at moderately hard level.  you should complete this mile in 10 minutes or less

For the next 2 miles, you will run sprints & recovery : depending on your fitness ability/level:

• Sprint between 7 & 9 mph for 2 minutes,  you should be gasping for air and need a recovery(if you are not extremely challenged, you will need more speed and/or incline)
• Recover at 6-7 mph for 2 minutes
• repeat until you completed 2 miles
• You should be very tired at this point
• Run another 1 to 3 miles at a steady hard pace
• cool down for 5 to 10 min
• Stretch: calves, hamstrings, hips & glutes and low back

This workout requires glucose storage… you need a  moderate intake of carbs.  If your carbs are too low, you will run out of energy and/or break muscle tissue down as a source of fuel…. this would be a bad thing… we want to keep our muscle tissue.