There are few cardio exercises as intense as running, but treadmill interval training can be the ultimate fat burner. Using the treadmill allows you to space your intervals at your discretion and push yourself for as long as you'd like, tracking your progress as you go.
Interval training will, over a few weeks, increase your speed and endurance and shock your body past a plateau. Perhaps more importantly, those extra bursts will call on your fat stores to fuel the energy that your body expels. The higher intensity will also allow you to achieve the same calorie burn and more fat burn in less time than a steady long run can. You can even use these intervals to call on different body parts to build strength and tone all over your legs.
Before beginning any of the intervals below, warm up for 5 minutes with a slow jog or quick paced walk to get your blood pumping. When you are moving at your active recovery pace, always keep the incline at 1% or higher to simulate road running, as treadmills are almost always at a slight downhill grade when they are in the 'neutral' position of a 0% incline.
1. Side Steppers
Start this low pace, but intense, walking interval on a low speed, around 3.5-3.8 on your treadmill speed dial. Walk for 20 seconds. Holding the side rail, turn your body to the side and shuffle feet in a side stepping motion. Play it safe and don't grapevine your feet, but do get low in an athletic position, almost like a squat as you shuffle. Continue the side steps for 20 seconds. You'll feel the burn in your glutes and outer thighs, and toward the end of the workout, your calves as well. Walk forward (normally) for 20 seconds and repeat on the other side. Continue for 10-20 minutes.
2. Hill Walk-Low Run
Begin at a jog for two minutes around a 6.5-6.8 pace. At the end of the two minutes, drop the speed to a brisk walk and raise the incline to 7%. Walk for another two minutes, maintaining a pace that is quick, but does not force you to hang on to the rails as you move. Repeat the intervals, bumping up the incline by 1% each time you hill walk.
3. Hill Run
See the above hill walk and low run, but maintain the jogging speed for the entire workout. Raise the incline for only 1 minute and increase by .5% each time rather than a full percent.
4. Sprint to Jog
Set the treadmill at a relatively easy jogging pace, around 6.5 on the treadmill speed. Jog for 1-2 minutes. Then, raise the speed to 7.0-7.5. This high interval speed should be difficult to complete toward the middle of your workout and/or during each interval. Match the length of the sprint with the recovery (1 minute for each or 2 minutes for each), then recover at 6.5 again. Repeat as many times as desired.
Once you stop laughing at the name, you'll see how great these are. Fartlek basically refers to speed bursts and recovery. Start running at a comfortable pace, around 6.0-6.5 or higher if you are an advanced runner. Every so often, bump up the pace or the incline until you are pushed to your limit, then drop it down to the original pace. Repeat the random intervals as many times as desired. This is the ultimate body shocker, (read: fat burn!) since your muscles never know what to expect.