If you want to lose fat and not muscle, speed up your metabolism, and improve your conditioning, then you want to do high-intensity interval training.
If your goal is to get or stay lean and maintain your cardiovascular health, you don’t have to grind out a single long session of grueling cardio.
- No boring jogs.
- No droning away on one of the hamster wheels in the gym.
- No sacrificing hours and hours every week.
In fact, if you know what you’re doing (and you will by the end of this article), you can get a lot more out of doing a lot less cardio than you think.
Case in point? Here’s a recent shot of me:
I dieted for about 6 weeks before this shoot to go from 9 to 7% body fat and did no more than 2 hours of cardio per week, with individual sessions never going for more than 25 to 30 minutes.
Some people are shocked to hear these numbers because they’re a far cry from what most coaches and trainers prescribe. And every day I hear from the victims of their “expert” advice, who are being ordered to suffer through 1 to 2 hours of cardio per day to get lean.
Well, I’m going to be honest–if it took 7 to 14 hours of cardio plus 3 to 5 hours of weightlifting per week to get ripped, I wouldn’t even bother. Life is too short to spend 15+ hours per week exercising for a stupid six pack.
Fortunately it doesn’t take that though. It doesn’t take anywhere near that, actually.
If you know what you’re doing with your diet, you don’t need to exercise more than 4 to 6 hours per week to get as lean as you’d like.
Yup, just 3 to 5 hours of weightlifting and 1 to 2 hours of cardio per week is more than enough.
So, in this article, I’m going to explain 5 reasons why high-interval intensity training is my cardio of choice and almost a bit of a “secret weapon” for getting and staying lean.
Let’s start with a simple explanation of what high-intensity interval training actually is.
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- What Is and Isn't High-Intensity Interval Training
- HIIT Burns More Fat in Less Time
- HIIT is Better For Preserving Muscle
- HIIT Helps Curb Cravings
- How to Create the Optimal HIIT Routine
- The Bottom Line on High-Intensity Interval Training
- What's your take on high-intensity interval training? Have anything else to share? Let me know in the comments below!
Table of Contents
High-intensity interval training, or HIIT for short, is a method of exercising where you alternate between periods of (almost) all-out intensity and low-intensity recovery.
The idea is simple: during your high-intensity bouts, you’re pushing yourself almost as hard as you can, and during your low-intensity periods, you’re trying to catch your breath in preparation for the next sprint.
Chances are you probably knew that, but it leaves you with some important questions, such as…
- How “intense” do the high-intensity intervals need to be in terms of exertion and length?
- How “restful” and long should the rest periods be?
- How long should the workouts be?
- How frequently should you do HIIT workouts?
Basically: what actually qualifies as a HIIT workout and how do you get the most out of this type of training?
Well, let’s find out.
When you start looking into research on HIIT, you’ll often find that exercise intensity is discussed in terms of percentage of VO2 max. This is the maximum rate of oxygen consumption during exercise and is a major factor in determining one’s endurance during longer bouts of exercise.
What you’ll find in most studies that demonstrate the advantages of HIIT is that subjects reached between 80 and 100% of their VO2 max during the high-intensity periods of the exercise routines.
This is nice to know but not very useful because VO2 max is hard to approximate while exercising. It’s tough to know with any certainty whether you’re at, let’s say, 60 or 80% of VO2 max without being hooked up to a metabolic cart.
A more practical way of prescribing intensity in your HIIT training is thinking with your Vmax. This is the speed where breathing becomes labored and you feel like you can’t bring in as much air as your body wants. It’s about 90% of your “all-out” effort.
The first thing to know is your goal during your high-intensity intervals is to exercise at your Vmax.
That is, you need to get moving fast enough that your breathing becomes labored and you can’t quite suck in air as quickly as you want to, and you need to hold that speed for a period of time.
As you can imagine, this requires a pretty significant amount of effort. Think sprinting, not jogging.
Repeatedly achieving and sustaining this level of exertion is the whole point of high-intensity interval training.
If you don’t do this–if you can chat away on the phone during your “high-intensity” periods–you’re not doing HIIT.
The second thing to know is the total amount of time you exercise at your Vmax determines the effectiveness of the HIIT workout.
If your workout racks up just a couple minutes of Vmax exertion, it’s not going to be as effective as one that involves double that amount.
This is just a matter of proper workout programming, and the factors at play are the duration and intensity of both your high- and low-intensity intervals and of the workouts as a whole.
We’ll talk more about how to create an effective HIIT routine soon, but first, let’s talk a bit more about the advantages of this style of training.
If a supplement or workout or claims to be a “shortcut” for gaining muscle or losing fat, it’s likely a sham.
Well, high-intensity interval training actually delivers the goods. It’s significantly more time effective for losing fat than traditional “low-intensity steady-state” cardio (LISS).
For example, this study conducted by researchers at the University of Western Ontario found that people lost more fat doing 4 to 6 30-second sprints (with 4-minute rest periods) than 60 minutes of incline treadmill walking.
If you do the math here, that’s pretty impressive. 17 to 27 minutes of high-intensity interval training resulted in more fat loss than 60 minutes of traditional bodybuilder cardio. This wasn’t a one-off occurrence, either–these results have been replicated in quite a few other studies as well.
The science is clear: if your goal is to burn as much fat in as little time as possible, then HIIT is the way to go.
Although the exact mechanisms behind this advantage aren’t fully understood yet, scientists have isolated several factors. Research shows that HIIT…
- increases your metabolic rate for up to 24 hours,
- improves insulin sensitivity in the muscles, which helps your body better absorb and use the food you eat (rather than store it as fat),
- increases your muscles’ ability to burn fat for energy,
- elevates growth hormone levels, which aids in fat loss,
- spikes catecholamine levels, which are chemicals that mobilize fat for burning,
- and decreases post-exercise appetite, which helps prevent overeating.
When you’re dieting for fat loss, your number one goal after, well, losing fat, is preserving muscle. And when it comes to muscle preservation, cardio has a pretty bad rap.
Some of this is justified–research has shown that the longer your cardio sessions are, the more they impair strength and hypertrophy–but that doesn’t mean you have to fear cardio.
There are four simple steps you can take to maximize fat loss and minimize muscle loss:
1. Use an aggressive but moderate calorie deficit.
2. Eat a high-protein diet.
3. Do 3 to 5 hours of resistance training per week.
4. Keep cardio to a minimum.
The reasoning behind point #4 is this: As a general rule, the less cardio you do, the more muscle you’ll preserve while in a calorie deficit.
You can do no cardio whatsoever and lose fat, but this will only get you so far.
If you want to get really lean (sub-10% for men and sub-20% for women), there’s a point where you have to include cardio in your routine to continue losing fat. And the leaner you want to get, the more help you’re going to need from cardio.
And so the predicament: you need to use cardio to bolster your daily energy expenditure and fat loss but you also need to keep it to a minimum to best preserve muscle. How do you go about this?
Many people want to be lean more than they want to preserve muscle and, unaware of any other alternative, choose the Dark Side: hours and hours of grueling cardio every week to burn both fat and muscle away.
Combine this with very-low calorie dieting, which is all too common, and you have a perfect storm of misery and muscle loss.
Well, you can have the best of both worlds with high-intensity interval training.
You don’t need to do more than a couple hours per week to significantly increase fat loss, with each session lasting only 20 to 30 minutes.
When I’m cutting I keep myself in about a 25% calorie deficit, I use a handful of fat loss supplements, I lift weights about 4 to 5 hours and do 1.5 to 2 hours of HIIT per week, and here’s an example of what I’m able to achieve:
Before My Fat Loss Routine
After My Fat Loss Routine
That “transformation” took about 11 weeks and, as you can see, I lost little-to-no muscle and very little strength (a few reps on a few different exercises).
The overeating is the biggest enemy of fat loss and the biggest temptations to overeat are hunger and cravings.
This becomes particularly problematic as you get leaner and your “margins for error” with your calorie intake become very slim.
Well, while the claim that low-intensity cardio stimulates the appetite and leads to greater food intake is probably not true, research shows that HIIT in particular can cause changes in the brain that decrease hunger and the desire to eat and increase fullness from food eaten.
Anything that improves dietary compliance is a boon to your fat loss regimen, and HIIT does just that.
Alright, let’s now talk about creating the right HIIT workout for you.
There are five aspects to this that we need to consider:
- The type of cardio.
- The duration and intensity of the high-intensity periods.
- The duration and intensity of the rest periods.
- The duration of the workouts.
- The frequency of the workouts.
Let’s look at each point separately.
The Best Types of HIIT Cardio
While you can use HIIT principles with any type of cardio, if your goal is to preserve muscle and strength, your best choices are biking, rowing, and sprinting.
Research shows that the type of cardio you do has a significant effect on your ability to gain strength and size through weightlifting.
What scientists found is the more a cardio exercise mimics the movement used in hypertrophy movements, like the squat or barbell row, for instance, the less it impairs strength and muscle growth.
In the study cited above, the subjects that bicycled in addition to the weightlifting program gained more strength and size than those that ran or walked, and they suspect this was because the cycling movement imitates the squat.
Keep in mind this is a minor point of optimization. If you can’t or don’t want to bike, row, or sprint, use whatever method of cardio you enjoy most–swimming, jump roping, stairmaster, and so forth. It’s not going to whittle your muscle away.
It’s also worth noting that you want to adjust your speed in your training more than the resistance settings offered by various machines. The goal of HIIT is to go fast and hard, not slow and hard.
I do my HIIT on a recumbent bike and do raise the resistance slightly for my high-intensity intervals, but only enough to give me something to pedal against.
How Long and Intense Your High-Intensity Intervals Should Be
As you now know, the total amount of minutes spent at Vmax is the key factor in determining the effectiveness of your HIIT workout.
Too little time at this almost-all-out level of exertion results in a “kinda-high-intensity” workout and too much can lead to exhaustion and overtraining. So let’s make sure you get both of these things right.
First, just to reiterate, the intensity target is Vmax, which is the speed where breathing becomes labored and you feel like you can’t bring in as much air as your body wants. It’s about 90% of your “all-out” effort.
Don’t build up to this effort when you launch into a high-intensity interval. Give it everything you’ve got right out of the gate. You should be breathing hard within 10 to 15 seconds.
In terms of duration of high-intensity intervals, 50 to 60% of Tmax is sufficient if your goal is losing fat and improving metabolic health.
In case you don’t remember, Tmax is the amount of time you can move at your Vmax speed.
So, for example, I find that I can bike at Vmax for about 3 minutes before having to stop (Tmax of 3 minutes). Therefore, my high-intensity intervals are 90 to 120 seconds long (yeah, it’s tough!).
For your intervals, you can either test your Vmax (all you need is a stopwatch) or if you’re new to HIIT, start with 1-minute high-intensity periods.
If your goal is also to improve your conditioning, then you will need to make your workouts progressively tougher.
The reason for this is as you get fitter, your Tmax is going to improve. And as it improves, the duration of your high-intensity intervals will need to increase if you want to continue increasing your cardiovascular capacity.
As you can imagine, these workouts can get pretty damn intense for experienced athletes. In three HIIT studies conducted with highly trained cyclists, high-intensity intervals were 5 minutes long (and improved their performance). In contrast, other research conducted with endurance athletes found that 2- and 1-minute intervals weren’t enough to improve performance.
How Long and Intense Your Low-Intensity Intervals Should Be
Start out with a 1:2 ratio between high- and low-intensity intervals. For example, 1 minute at high-intensity and 2 minutes at low.
As you get fitter, you can work toward a 1:1 ratio.
Your rest periods should also be active recovery, where you keep moving, not a standstill.
Studies have shown that active, not passive, recovery is advantageous for reaching Vmax during the high-intensity periods and eliciting the adaptive response to the exercise that we’re after.
How Long Should Your HIIT Workouts Be?
The great thing about HIIT is how much you get out of relatively small amounts of it. That said, it can be quite stressful on the body, which means you don’t want to overdo it.
Start your workouts with 2 to 3 minutes of low-intensity warm-up and then do 20 to 25 minutes of intervals followed by 2 to 3 minutes of warm-down and you’re done.
There’s just no need to do more than this in each workout.
How Frequently Should You Do HIIT Workouts?
This depends on your goals and what other types of exercise you’re doing.
I’ve found that 4 to 7 total hours of exercise per week is plenty for losing fat quickly and efficiently. Optimally you will combine resistance training and HIIT, which is best for both losing fat and preserving muscle.
When I’m cutting, I like to do 4 to 5 hours of weightlifting and 1.5 to 2 hours of HIIT per week. This allows me to get as lean as I’d like without burning out and suffering the consequences of overtraining.
Whether you want to lose fat or improve athletic performance or both, you want to include HIIT in your workout routine.
Follow the advice in this article and you’ll reap all its benefits and avoid its only drawback, which is the potential for overtraining due to the added stress it puts on the body.
What’s your take on high-intensity interval training? Have anything else to share? Let me know in the comments below!