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Interval Training Accelerates Fat Loss


I’m sure that most of you are looking for a quicker, more efficient workout. I’m also fairly sure that most of you are concerned with losing body fat and “toning up” too. Well, what if I told you there is a way to structure your exercise to maximize your body’s fat burning potential in a minimal amount of time? Would you be interested? I thought so!

Before we jump into a discussion about exercise, though, you need to keep in mind exactly how body fat is lost. Most of you have heard this before, but, in simple terms, fat loss occurs by creating a calorie deficit (expending more calories than what is consumed during the day). Now, obviously if this article is about exercise, we’re really only addressing one of the two requisite components to creating a calorie deficit (exercise), and not addressing probably the most important component (nutrition). So, please don’t think that fat loss is a certainty if you merely do what I outline in this article with respect to exercise. However, if you combine these exercise suggestions with a little bit of calorie restriction, you’ll be well on your way to amplifying your body’s fat burning potential.

The next thing that needs to be mentioned relates to a little bit of metabolic physiology and address the mistaken notion of “fat-burning exercise.” I say mistaken because it is just that – a mistake. Very little fat is actually burned during exercise. At the intensities nearly all of us exercise at, we burn almost 75-80% carbohydrate, with the other 20-25% coming from a mix of fat and protein. So, when someone tells you that you can burn fat by performing a particular exercise, or by doing an exercise a certain way you’ll lose fat, they’re wrong. The true role of exercise, for body fat reduction purposes, is: (1) preservation and/or increase of lean (muscle) mass, and (2) most importantly, increasing energy expenditure to assist in creating a calorie deficit. Interval-based exercise fulfills both of these critically important roles.

A simple definition of interval training is performing a higher intensity segment of exercise followed by a lower intensity segment (think alternating jogging and walking on a treadmill). There are two primary forms of interval training. The classic form of interval training is performed exclusively on a cardiovascular level (using a bike, treadmill, elliptical trainer, etc.). A more contemporary, hybrid form of interval training is circuit training. Circuit training combines resistance exercise (generally, calisthenics or exercises performed with small, weighted implements like dumbbells or medicine balls) with semi-continuous movement to produce an interval training-like effect.

Of these two forms of interval exercise, research suggests that circuit-type interval training is more effective from a body fat reduction perspective. This is true mainly because, by stressing both the muscular system and the cardiovascular system at the same time, you amplify the body’s energy expenditure during exercise (and it is even significantly elevated post-exercise). This makes it easier to create a calorie deficit. In fact, internal research we have performed on our client population at AFS suggests that individuals who perform circuit training see greater reductions in body fat than individuals who perform only resistance training, or who perform higher volume aerobic exercise for endurance performance (see graph to right, displaying change in body fat at 6, 12, and 24 week intervals). The reasons for this difference in body fat reduction, based on type of exercise, are likely related to (1) the energy expenditure response of circuit training (as it expends more calories, minute-by-minute, than the other two types of exercise); and (2) the favorable fat-burning hormone response that occurs as a result of circuit training (the response is not as prevalent with the other two types of exercise). Individuals who perform circuit training also preserve significantly more muscle tissue during fat reduction, when compared to individuals who perform only cardiovascular exercise. This also likely accounts for the body fat differences observed in our research.

Although there are a lot of ways to perform circuit training, as long as you’re doing some continuous movement, along with some resistance training, you really can’t go wrong. A simple sample circuit could be:
– Body Weight Squats
– Jumping Jacks
– Pushups
– Burpees
– Reverse Lunges
– Floor Crunches
– Planks

Perform 20 reps of each exercise in the circuit, and perform each exercise in immediate succession with no rest in between exercises. Take a one-minute break between circuits, and perform 3-5 circuits per exercise session. Again, this is merely a sample circuit; some of you might need something a lot more challenging, and others might need something considerably easier. One way or another, the framework outlined above – where resistance exercises are performed in back-to-back fashion – is really the most important thing.

Switching gears a bit, the cardiovascular form of interval training is much more conventional, and a little easier to implement. With this form of interval training, you need to choose your favorite cardiovascular exercise (this could be biking, the treadmill, the elliptical trainer, outdoor running, and so on). You’ll always want to “bookend” an interval cardio session with a 5 minute warm-up and a 5 minute cool-down. In between, the body of your interval workout can really be structured however you’d like in terms of work-to-rest ratios (for example, 3 minute work/1 minute rest, 2 minute work/30 second rest, etc.). The easiest interval to start with is a 1 minute work/1 minute rest combo. To illustrate how this type of workout would work, we’ll use treadmill jogging and walking as our example:

Following a light walking warm-up on the treadmill (approximately 3.5 mph) for 5 minutes, you would increase the treadmill to a fast jogging or running pace (approximately 7.0 mph) for 1 minute. At the end of that minute, you would slow the treadmill down (to approximately 4.0 mph) and walk for one minute at that pace. You would repeat this combination of running and fast walking anywhere from 10-25 times, and then you would perform a 5 minute cool-down at the end of the workout. If you’re counting, the 5 minute warm-up + 5 minute cool-down + 10 intervals = 30 minutes of exercise; if you do 25 intervals, the workout would last an hour.

Again, this is just a sample workout. You could reduce the intensity by fast- and slow-walking, rather than running and walking. Or, you could increase the intensity by sprinting and jogging. You can perform this same workout using any type of cardiovascular exercise as well, and you can even vary your work-to-rest ratios however you’d like.

So, you now have two forms of highly effective interval exercise to choose from. I would recommend performing a good mix of both of these types of interval training. For example, you could alternate between circuit interval training and cardiovascular interval training, performing a total of 3-4, 30-60 minute, sessions per week. And if you combine this type of exercise with a little bit of calorie restriction, you’ll be well on your way to reaching your fat loss goals!

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