Does HIIT Live Up to the Hype And is it Right For You?

When you enter the fitness world, you realize that trends are always changing. It’s as if every other month there’s a new ‘miracle’ exercise. Well, I assure you there’s no one exercise fits all, but when it comes to HIIT (high-intensity interval training) the benefits may be too good to ignore.

HIIT is a sequence of brief, highly intense spurts of exercise followed by longer periods of rest or less intense cardio. Imagine sprinting or cycling for 20-30 seconds with maximum effort, then walking or slowly peddling for 1-3 minutes. Repeat this cycle a few times and you’ve done a HIIT workout.

“Based on everything we know, there’s no substitute for these exercise programs when it comes to delaying the ageing process.” Says study senior author Sreekumaran Nair, a medical doctor and diabetes researcher at the Mayo Clinic in Rochester, Minnesota. “These things we are seeing cannot be done by any medicine.”

Whether your goal is simply upping your fitness level, preventing cardiovascular disease, strengthening muscle, optimally losing fat or keeping your blood sugar in check, HIIT may be right for you. But, like I said before there’s no one exercise fits all, likewise let’s dig into the research around high-intensity interval training and go over some of the advantages and… yes, disadvantages to see if it lives up to the hype.

If HIIT is so good then why is everybody still jogging along?

treadmill-testing-630The times have certainly changed, and tons of new research has helped clarify the body’s response to exercise. Regardless of how many people sit on an elliptical for hours reading about Selena Gomez’s new relationship, we now know that cardio is inferior to weightlifting when it comes body composition changes, but how does it compare to HIIT? As someone who wants the best return on investment (ROI) while training, I wanted to know how HIIT stacked up against weightlifting and traditional low-intensity cardio.

To explain why so many people train at such a low intensity, we need to understand how the body uses its fuel. Under different intensity levels, the body utilizes different fuel sources. Low-intensity exercise, if you’ve ever seen 60% printed on a treadmill (referring to 60% of your maximum VO2 output) is an example of low intensity and utilizes fat as the main energy source to power you through your workout. As the intensity of exercise increases, our body can’t process the conversion of fat to glucose quick enough. Therefore as our intensity level goes up we start relying on a quicker conversion to glucose; carbohydrates. At the time, the interpretation of these findings was somewhat logical: exercise at low intensities to burn fat in addition to the capability of training for longer periods of time and increase total energy expenditure. Well, that was easy when all is said and done right? WRONG!

Burning Fat & Changing Your Body Composition

Several studies from East Tennessee State University, Baylor College of Medicine, and Laval University to name a few, show that high-intensity interval training burns more fat than low-intensity sessions.

study conducted by The University of Western Ontario shows us just how much more effective HIIT cardio can be. Researchers had 10 men and 10 women train 3 times per week, with one group doing 4 to 6 30-second treadmill sprints (with 4 to 6 minutes of rest in between each), and the other group doing 30 to 60 minutes of steady-state cardio (running on the treadmill at the “magical fat loss zone” of 65% VO2 max). The results? Fat mass decreased 12.4% in the sprinting group compared to 5.8% in the steady state low-intensity group.

Quoting Mark’s Daily Apple,

“A study (PDF) from the University of New South Wales followed the fitness and body composition changes in 45 overweight women in a 15-week period.

The women were divided into two groups and assigned interval or continuous cycling routines. The interval “sprint” cycling group performed twenty minutes of exercise, which repeated eight seconds of “all out” cycling and then twelve seconds of light exercise.

The continuous group exercised for 40 minutes at a consistent rate. At the end of the study, the women in the interval group had lost three times the body fat as the women in the continuous exercise group”.

The mechanism behind HIIT’s fat burning success isn’t fully understood. In general, researchers have pointed out a few potential contributing factors, including an increased resting metabolic rate, improved insulin sensitivity within muscles, higher levels of fat oxidation, significant spikes in growth hormones and even post-exercise appetite suppression all following HIIT.

As the science points out, if you’re goal has anything to do with burning fat or changing your body composition with the most ROI, then HIIT should be your cardio of choice. But, if you’re really trying to change your body composition, how does HIIT compare to lifting weights?

Steady State Cardio Vs. HIIT Vs. Weight Training

Seeing that within the last 20 years, thousands of studies have come out comparing the effects of weight training vs. cardio, we know what the compelling evidence says. Here’s an example:

“Researchers assigned overweight subjects to three groups: diet-only, diet plus aerobics, diet plus aerobics plus weights.

The diet group lost 14.6 pounds of fat in 12 weeks. The aerobic group lost only one more pound than the diet group. Their training was three times a week starting at 30 minutes and progressing to 50 minutes over the 12 weeks. Nothing special.

But the weight-training group lost 21.1 pounds of fat. That’s 44% and 35% more than diet and aerobic-only groups respectively. The addition of aerobic training didn’t result in significant fat loss over dieting alone.

Thirty-six sessions of up to 50 minutes is a lot of work for one additional pound of fat loss. But the addition of resistance training greatly accelerated fat loss results”.


This study not only highlights the fat loss benefits of weight training, but also the importance of diet in the fat loss process. Nutrition and dietary choices may play the biggest role in our body composition. This is only one study, but it has been replicated time and time again. For changing your body composition, the results almost always show that weight training blows lower intensity aerobic activity out of the water. In fact, there’s research that shows the more intense your resistance session the more calories you’ll burn! This is the case even if you’re only lifting half the total volume (total weight lifted during the workout, for example, say you do 8 reps of deadlifts at 200lbs for four sets. Volume = 200x8x4= 6400 lbs) in the entire workout.

The study compared a traditional weight-training program with a higher intensity resistance-training (HIRT) program. The traditional program consisted of 8 exercises each for 4 sets of 8-12 reps, the last one taken to failure.

The HIRT program consisted of 3 exercises for 3 sets of 6 reps, while an additional set was performed in a rest-pause fashion.

The traditional program took 62 minutes to complete and the total session volume was around 17,000 pounds. However, the HIRT group finished their workout in 32 minutes, lifted only 8,500 pounds, but had a post-caloric burn the next day that was 450% greater than the traditional lifting group.

So if you’re willing to do whatever it takes to lose body fat and change your body composition, then incorporating both HIIT and weight lifting into your routine will be optimal. This doesn’t necessarily have to be cardio. The example above shed light on how you can weight train in a highly intensive manner and reap major benefits.

The Benefits of HIIT on Metabolic Health

HIIT has also been shown to significantly improve blood sugar scores and aerobic capacity. The study was done on healthy but sedentary people who performed only one total minute of HIIT three days a week for six weeks. This was done in 10-20 second spurts followed by rest for total workout duration of ten minutes.

If you aren’t aware, sleeping less than 7-8 hours a night will inhibit the body’s proper insulin response to food. Why is this important? Because having an inhibited or fluctuating glucose response wrecks havoc on our cell metabolism. According to a very recent study, if you know you’re going to be sleep deprived the following day, doing a HIIT session before could significantly minimize these effects.

Want to give your energy powerhouse a boost? Several studies show doing HIIT improve mitochondrial function, like this one that stated “6 weeks of HIIT enhanced mitochondrial OXPHOS capacity and attenuated the HE-depressed mitochondrial ETS efficiency in platelets. Therefore, the HIIT regimen effectively improved platelet bioenergetics, possibly by enhancing mitochondrial quality rather than quantity in platelets”. The keywords here are “enhancing mitochondrial quality”. The quality of our mitochondria has been linked to aging, energy levels, and much more. Yes HIIT might require a lot of energy in a short duration of time, but the payout could be well worth it in the long run.

HIIT and Your Heart

If you think you’re too old or out of shape to do HIIT, think again. Even people with heart disease have been shown to gain twice the amount of cardiorespiratory fitness while doing HIIT compared to low intensity running cycling and other aerobic activities.

jamie-street-94242Having flexibility is important, but not only in your muscles. “HIIT increases the flexibility and elasticity of arteries and veins better than continuous aerobic exercise,” says Weiss. “Because HIIT increases pressure demand on your blood vessels, they actually get a workout as well.” In fact, high-intensity interval training is not only safe but also easier to tolerate than a more moderate workout in people with coronary artery disease, according to one study.

So as you can see, there are many advantages of incorporating HIIT into your workout routine. You can even do HIRT, incorporating the fast-paced intensity with lifting weights and shredding even more fat than your conventional weight lifting routine. You’re going to be doing both your mitochondria and heart a favor. Nevertheless, there are a few downsides to be aware of when training with HIIT.

The Disadvantages Of HIIT

Compared to other forms of cardio, HIIT requires a longer recovery period. If you’re only doing short 5-minute HIIT workout sessions as a trained athlete, you may be able to do HIIT daily. But, doing 20-30 minute sessions is likely to require a few days rest before you can do another session.

When you’re doing a HIIT workout, you’ll find that it’s considerably harder to maintain correct form. The quick succession of exercise intensity can consequently result in injury if not properly performed. The most important exercises are always going to be the ones you’re willing to do, and do safely. Try to get some experience under your belt before jumping into a HIIT workout; it may not be suitable for beginners.

Which brings us to our next point. HIIT is really hard! It requires our heart to pump at around 85 percent of our maximal output. Working out shouldn’t leave you with a yucky feeling in your stomach. It should be enjoyable. Although some people love the challenge that HIIT brings, if you like to workout in a less intense manner that’s great too! If you’re into lifting super heavy weights, that’s awesome. Exercise should be something you look forward to, and everybody looks forward to different workouts.

The Bottomline

Doing HIIT can work wonders for changing your body composition. Moreover, this is especially true when coupled with weight lifting, more so than slower less intense cardio. Your mitochondria and heart will thank you. If you’re short on time and want the best return on your investment, then HIIT is the way to go. This is not discouraging you from performing lower intensity cardio; there is still wonderful benefit from doing so. Rather, experiment with your own body, that’s where the best research takes place. On a closing note, remember that your primary relationship to nature, the food you eat, can have a bigger role in your body composition than any exercise. Stay healthy, stay happy.

We’d love to hear your input:

What’s your preferred training method and why?

What popular fitness advice have you had to modify or avoid because you listened to your body?


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