High intensity interval training, interval training, HIIT, all of these are terms used to describe a specific type of training for our cardiovascular health. It involves very high intensity exercises done in a short time period with a small amount of rest in between sets. This is definitely not something that’s new to the fitness community. It has been practiced before and has been phasing in and out throughout the years.
With something as popular as HIIT, there are bound to be questions as to it’s effectiveness. Does it really work as well as its proponents propose? How does it compared to cardio? Are there additional benefits besides the obvious? How come some fitness gurus suggests that running is the only type of HIIT that’s effective? Can we use other exercises for HIIT? Read on to find out the answers to these questions and more.
What Is HIIT?
HIIT comes in as many forms as people can think of. The central theme to HIIT is to maintain a high heart rate throughout the entire session. In order to do this, we need to engage in very intense activities with short amount of rest in between sets. This way, our heart rate never drops below a certain threshold.
What is this threshold? Well, it all depends on what percentage range of our maximum heart rate we choose to work within. A common method of estimating max heart rate is subtracting our age from 220. I personally no longer estimate my max heart rate. I simply go by feel.
If we’re just starting out and have never been exposed to HIIT or only done it a few times, I suggest going by a percentage of our max heart rate and see how the different ranges feel. Once we get the hang of it, it should be easy to tell approximately what range we’re in just by how it feels.
Keep in mind that as we get more fit over time, our max heart rate will increase. So 190 beats per minute now may not feel as lung busting as they were before. And this is the primary reason I go by feel. The other reason being that I’m not a fan of tracking my heart rate during every workout, it just gets annoying.
Variations On A Theme
One of the protocols that made HIIT popular is the Tabata Method. This is a form of HIIT that involves 20 seconds of all-out work, followed by 10 seconds of rest. This goes on for 4 minutes, which results in 8 rounds of the 2:1 work:rest sets. This is the shortest version of HIIT and it’s obvious appeal is short period of time involved compared to slow and steady cardio.
So only 4 minutes, should be easy right? I mean, even with 20 seconds of all-out effort, I still get a 10 second rest. And it’s ONLY 20 seconds, how bad can it be? If that’s what you’re thinking, you mostly have never tried it before or not going as hard as you could be. This protocol is promised to make those 4 minutes the longest of your life, give 100% effort is put into each 20 seconds interval.
As mentioned before, there are as many protocols out there as people can imagine. But they all differ in the work to rest ratio. Tabata is strictly a 20 seconds work and 10 seconds rest protocol, which works out to be a 2:1 work to rest ratio. We can have everything from 1:5 work to rest for the beginner to 4:1 work to rest for the masochist.
Comparison to Steady State (SS) Cardio
We see this in all commercial gyms globally. People running on the treadmills, working on the ellipticals, stairmasters, and other cardio equipment that packs in popular gyms everywhere. Like a hamster in their wheel, the pace is kept steady. Breathing pattern is kept at a specific rhythm, work is being done continuously, and heart rate is at a specific range with very little variance. This can go on for 15 minutes or for 2+ hours.
The above description is not meant to demean steady cardio in any way. Although I find it extremely boring, it does have its place it endurance training. If it wasn’t effective, it wouldn’t have stood the test of time. But where does HIIT fit in? What benefits is HIIT bringing to the table?
When discussing the benefits of HIIT, we’ll be discussing it in reference to steady state cardio since most people are familiar with that already. We know steady cardio builds endurance, burns fat, increases blood flow, etc. So how does HIIT compare?
Go Harder For Longer Periods Of Time
In a study conducted that compared HIIT to traditional steady pace cardio training, subjects that performed the HIIT had significantly higher mitochondria oxidative enzymes compared to the steady pace cardio group¹. Mitochondria oxidative enzymes are responsible for the metabolic function of our muscles by helping break down carbohydrates and fat as fuel. ATP synthesis is also supported by these enzymes.
So with more of these enzymes, we’re able to break down more carbs and fats for fuel and synthesize more ATP. All of this leads to us sustaining a harder pace for longer a duration.
Burn More Fat AND For Longer Periods Of Time
Some of us that have research HIIT may have read that it helps us burn fat up to 48 hours after the workout. Although the exact time period varies from individuals, there is indeed an increased level of fat burning after a session of HIIT compared to steady state cardio.
A review article stated that our Excess Post-Exercise Oxygen Consumption (EPOC) is significantly higher after a session of HIIT compared to steady state cardio². Higher EPOC translates into more calorie burned for longer periods of time.
Increase in VO2 Max
What is VO2 Max and why should we care? VO2 Max is simply the most oxygen we can consume during exercise. On to the part why we should care, oxygen is required for proper energy production and body function. This is important for every human being. For endurance athletes, the higher our VO2 Max, the more oxygen we consume, and the more oxygen is delivered to our muscles.
A study conducted on subjects that trained using HIIT or steady state cardio for eight weeks showed an increase in VO2 Max for both groups. However, the HIIT group increased their VO2 Max by 15% while the steady state cardio group increased it by 9%. The HIIT group also spent less time training compared to the steady state cardio group³.
HIIT-Be All And End All?
It’s obvious that HIIT holds many physical advantages over traditional steady pace cardio. The time savings that comes with HIIT is also a huge bonus for those of us with time constraints. Not to mention other benefits such as improved lactate threshold and lowering risk of heart disease. With all this in consideration, why would anyone even consider doing steady state cardio ever again?
There is at least one advantage that steady state cardio has that HIIT does not.
A study was performed by researchers at the University of Western Ontario on 20 volunteers. All the volunteers trained 3x per week for 6 weeks, half doing steady state cardio while the other half trained using HIIT. At the end of the 6 weeks, the steady state cardio group increased their max cardiac output by almost 10% while the HIIT group did not show any improvement in this aspect.
Max cardiac output is the amount of maximum amount of blood that our heart can pump within a given amount of time. So an increase in this attribute allows for more blood to be pumped to our muscles, lungs, and other areas of our body.
Best Of Both Worlds
This goes back to the old saying that everything should be done in moderation.
There is no need to cut steady state cardio out of our training. As matter of fact, we’ll be missing out on an important part of endurance training if we do. However, if we implement both HIIT and steady state cardio, we’ll reap the benefits of both.
More To Come
We’ve covered quite a bit of information in this article, but we’re only about half way done! Are there any other benefits to HIIT than just that for our physical bodies? Some argue that if we’re not strictly using running as the exercise for HIIT, we’re not doing HIIT properly. Is that really true? And how do we incorporate HIIT into our training?
Stick around to find out the answers to these questions and more on Part 2 of this 2-part series!
- Burgomaster, K.A., et al. 2008. Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans. Journal of Physiology, 586 (1), 151-60.
- LaForgia, J., Withers, R.T., & Gore, C.J. 2006. Effects of exercise intensity and duration on the excess post-exercise oxygen consumption. Journal of Sports Science, 24 (12), 1247-64.
- Daussin, F.N., et al. 2008. Effect of interval versus continuous training on cardiorespiratory and mitochondrial functions: relationship to aerobic performance improvements in sedentary subjects.American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, 295, R264-72.