The Science Behind High Intensity Interval Training

What is HIIT?

By now, you’ve probably heard of HIIT, or High Intensity Interval Training. If you haven’t, sit back and soak up this info like a sponge.

HIIT became popular in the 90’s when a study suggested that you could burn up to 9 times more body fat using short, very high-intensity intervals. It compared it to the old-school steady-state aerobic training that we all knew and loved 😉


There were some negatives to HIIT, such as how hard it was and it can only be effective when done in short cycles. Well, creator of TurboFire, Chalene Johnson was intrigued with the time-efficient structure, which promised great results, so she and Beachbody decided to see if they could create a training program based around it!

What is The AfterBurn Effect?

HIIT training increases the resting metabolic rate (RMR) for the 24 hours following a workout due to excess post-exercise oxygen consumption, which explains how a short interval workout can have a longer-lasting effect on body composition change than a much longer cardio session. We, (Beachbody and Chalene), termed this phenomenon the AfterBurn Effect.

But, many studies were saying that fitness gains made with HIIT training began to plateau sometime after the 3rd week. We had a lot of work to do! We had to figure out how to create a whole fitness program using HIIT or maybe it could work in conjunction with HIIT that also yielded results.

Muscle Burns Fat

In ChaLEAN Extreme, you often hear Chalene say, “Muscle Burns Fat.” TurboFire combines both of the philosophies of ChaLEAN Extreme and Turbo Jam. And it’s not just talk! The physiological principle that adding muscle to your frame increases your metabolism and leads to changes in body composition is valid, and you’ll find that resistance work is a major component of TurboFire.

Advanced Cardio Conditioning–a unique Chalene program

TurboFire is a HIIT program but also a very unique, Chalene program JIf you’ve done Turbo Jam or Turbo Kick, you’ll soon find that TurboFire is the next level of Turbo Kick. And it definitely has that, ‘exercise class at the gym’ feel.

Cardio is an umbrella term that covers a lot of different styles of training, from easy aerobic to intense HIIT. No matter where between these extremes your workout falls, you’re going to be targeting different human energy systems that have different physiological benefits. For the TurboFire system, Chalene created different cardio classes to make sure each of these energy systems were being targeted, to achieve an effect she calls Cardio Confusion, a play on words referencing P90X’s Muscle Confusion.

Cardio Confusion is more than a slogan. The cardio phases of the TurboFire program combine different styles of interval training with recovery-oriented aerobic training to create a steady growth curve in your fitness levels. This accelerates your body’s ability to get ready for your next round of HIIT, but it also takes advantage of the AfterBurn Effect by targeting different energy systems.


Recovery is an essential part of TurboFire. Active recovery helps your body grow strong much more quickly than does rest alone. During targeted rest and recovery phases, you target the body’s aerobic system, stabilizer muscles, and use techniques, which stretches out overworked muscle fibers and heals connective tissue microtrauma.

A program for one.A program for all.

It’s often difficult to find one fitness program that would work for everyone, and it’s generally not best to recommend that everyone do the same program, rather than steering each person toward the program that best fits their needs. Reality, though, has taught us that people often want to do what inspires them, whether it fits their ability level or not.

With TurboFire, however, we’ve done our best to allow nearly anyone to attempt the program safely. In fact, we included a 2-month preparatory schedule for anyone who thinks they may not be ready for the rigors of HIIT training. Not only that, every move in the program comes with a modified version that almost anyone should be able to follow. Furthermore, Chalene recognized that some men can be rhythm-challenged, so she purposely made the choreography a lot easier to follow than it is in Turbo Jam and her health club classes.


The final element of the program is diet. TurboFIre’s diet tries to give you a variety of different ways to alter your eating habits, with the same end purpose as our other plans: a balanced diet that fuels exercise recovery.

TurboFIre’s focus or slogan is that getting fit can be fun and eating healthy doesn’t need to be a complex task. We know there’s a lot of science behind what you’ll see as you follow along, but we wanted to make it as simple as theBeachbody tagline: Just Push Play.

If you’re looking to get started with your workouts but need some help getting going, check out Keith’s 4 part video series at:

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