When it comes to lowering your body fat percentage, HIIT cardio is the way to go.
You will burn more calories in less time, and even with less workout frequency. (1)
But what is the best interval length for fat loss?
This is a topic which is shrouded in confusion, because If you pick up the latest edition of Men's Health or any other popular fitness magazine, you'll see conflicting recommendations when it comes to structuring your HIIT workouts.
You'll undoubtedly get the "30 seconds on, 30 seconds off" approach. Later on you'll probably come across a plan which uses the "20 seconds on, 10 seconds off" method. And then there's the balls-to-the-wall style of interval training which has you going flat out for up to 3 minutes, such as Insanity.
I'm often sent emails asking questions like "Hey Russ, how long should my HIIT intervals be for maximum fat loss?" and they usually also mention that they feel bombarded by the amount of conflicting advice they get from people at the gym.
The next time you walk into your local gym you will see tons of people doing a variation of one of these three styles of HIIT, all claiming it's the best for results. From the guy who always seems to be on the treadmill no matter what time of day you train, to the girl who smashes the elliptical like an angry jockey.
It's no wonder most people feel overwhelmed.
The sad fact is most people are using something I call a "HIIT & Hope" mentality, whereby they try a different method every other week, hoping to find the one that gives them the greatest bang for our buck, but never progressing like they want to.
So today I'm going to break it down for you, and use the latest science surrounding high intensity interval training to determine what truly is the best interval length for fat loss.
Let's get stuck in..
There are several different forms of high intensity interval training, the most popular options being:
The Tabata principle is based upon the concept of an 8 minute workout, revolving around 20 second bursts at maximal intensity followed by short 10 second rest periods. repeated for time.
Back in 1996, Professor Tabata and his team of researchers published a study which changed the fitness game forever. (2)
In the study, they took a group of elite athletes and subjected them to the training protocol you see above. The results were simply astounding - an increase in the VO2 MAX of 28%!
Given that the participants were elite athletes, and results are typically much harder to come by at the highest level, this study had a huge impact on the fitness industry and it has been a mainstay of interval training fitness plans ever since.
Since then it has gone under several different names ("The 4 Minute Workout", "The 20/10 Method", etc) but it is all ultimately the same thing.
Fat loss is one of the most obvious benefits to running a Tabata-style interval program, such is the high intensity of the workouts itself, but it also has some surprising advantages when it comes to endurance training. I cover them in more detail in this article.
Timed HIIT is the most commonly used form of high intensity interval training.
You've probably heard people telling you to "do 30 seconds on, 30 seconds off, over 45 minutes", or "1 minute hard, 1 minute easy", right?
That's timed HIIT.
It's so popular because most cardiovascular machines come equipped with this style of HIIT plan built-in to the features, telling you when to kick into a high gear and when to ease off the pressure.
It's also one of the easiest forms of HIIT do get wrong, as it doesn't place any indication on how hard you should work during your interval periods.
I often tell my clients that if they're doing HIIT correctly, they should not be able to do it for an hour!
But this is one of the unclear variables of timed HIIT programming, which often results in people not working hard enough during their bursts to really drive their body to burn as much fat as they are aiming for.
If you've ever left your television on late at night, you've probably woke up the next morning reciting the script to these annoying infomercials.
But aside from all the lycra and hype, Insanity is a pretty good fat loss workout.
A 2006 study published in the Journal of Sports Science & Medicine found that a 6 week plyometric training program improved agility versus staying flat footed, and this is one benefit Insanity taps into with it's endless bouts of burpees, squat jumps and high knees. (5)
Strictly speaking, however, the Insanity workout is a distant relative of HIIT known as HISS.
It focuses on much longer intervals of up to 3-4 minutes, broken up by relatively short windows of recovery.
Action movie actor Adam Baroni stops by for an outdoor HRM HIIT session.
HRM stands for heart rate manipulation.
HRM-based HIIT asks for 10-30 seconds of maximal intensity work, with a rest period as long as necessary for your heart rate to return to optimal levels.
The total workout length with this style of training is typically around 30 minutes.
You may feel like you cannot perform very many bursts within that window to begin, as most people typically require 3 minutes to fully recover from a true maximum intensity burst.
But that's the point.
The idea is to increase the number of bursts you are able to perform over time as your fitness begins to improve (as less rest is needed between rounds).
If you've performed HIIT before, you're probably able to look at the four examples above and point out at least two that you've previously tried some variation of in the past. I've used all of these in my own training and with personal training clients, so it's important for me to say here that they do all work. They do all provide you with a good training session. And they will certainly burn body fat if you are consistent with your efforts.
But there is a winner.
Let’s look at some of the latest clinical studies.
In my opinion, the best study on the perfect interval length was performed by Dr. Peter Lemon and his team of researchers from the University of Ontario, Canada.
The team came to the conclusion that bursts of 30 seconds were optimal for maximizing training output and burning fat. (4)
That's right, 30 second intervals!
These findings confirmed what researchers from the University of Nebraska found back in 1994. (1)
The study, published in the Journal of Strength and Conditioning Research, not only found that performing 30 second bursts is superior for fat loss based HIIT, but that it even out-performs intervals lasting as long as 3 minutes. (1)
Right now you may be wondering "How the heck can a 30 second HIIT interval burn more fat than a 3 minute HIIT interval?!"
Well, the secret lies not in the interval itself, but in what you do immediately after it...
The “trick” here is to get your rest period right.
You see, getting the maximum benefit from HIIT is about heart rate manipulation.
If you have tried interval training before, you probably know that (regardless of which method you use) the main instructions are to ramp up your intensity for a period of time before taking your foot off the pedal.
Well, we want to be achieving this same up/down system inside your body, too.
In the Ontario study, researchers were keen to point out that subjects were forced to take a recovery period of up to 4 minutes after every 30 second burst. This recovery phase was deemed crucial to the overall effectiveness of the workout. (4)
Because by ensuring adequate recovery, every 30 second burst was performed to true maximum intensity.
Despite performing fewer total interval bursts, this defeats the concept of performing "30 seconds on, 30 seconds off" because that idea doesn't take into account the heart rate factor. There is no point beginning your next interval burst if you are still gassed from the one before.
Consider it the same as trying to hit a new squat PB without taking the necessary rest between sets.
The constant up and down nature of a proper HIIT workout wreaks havoc on our body’s energy systems and kickstarts the much hyped "Afterburn Effect".
Otherwise known as EPOC, it is the phenomenon which causes us to accelerate fat burning for up to 14 hours. (6)
It's the main benefit of HIIT.
But by not allowing proper recovery between intervals you do not fully engage said "Afterburn Effect."
In order to maximize your return from HIIT, you need to perform each burst at as close to your maximum intensity as possible.
And the best way to do this is by allowing your heart to properly recover between bursts.
This puts HRM HIIT ahead of the chasing pack, as the optimal form of high intensity interval training specifically for fat loss.
Both studies above concluded that the greatest fat loss results were obtained when subjects performed a HIIT workout consisting of six 30 second bursts, giving a total workout time of around 30 minutes.
In both studies, the participants used recovery periods of 3-4 minutes between each burst.
This recovery period will differ from person-to-person depending upon your fitness level, so I'd recommend trying a 3-4 minute recovery period in your first workout and then shortening or lengthening it based on your own needs.
Of course, I must also say that all of the methods I show above are effective and a side effect of each of them is good fat loss results (if you do them correctly and consistently). But if your main goal is to get the best interval length for fat loss then this would be a good place to begin:
And to maximize fat loss results, use these two rules:
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Olympic athlete Amanda Lightfoot stops by the gym for a HIIT workout.