High Intensity is Highly Effective
by Dave Williams
Walk into any commercial gym on a Monday morning, and the cardio machines are chock full of guilty feeling dieters and people trying to “burn off the weekend.” I can almost hear the pitter patter and the swirling belt of the treadmill. And I feel sorry for those people.
What do most of those cardio bunnies have in common? Most of them look exactly the same as they did a year ago, and even two years ago. Why is that? Because for 99.9% of the population, steady-state cardio is NOT the best way to burn fat and get into better shape (the minuscule amount of people left over consists of people like competitive bodybuilders who lose fat using precision cardio separate from their strength training along with a painstakingly strict diet, but I digress).
The reason that slow cardio has become the go-to method of fat loss is because of an incomplete understanding of how the body works. There are two basic energy systems that fuel physical activity: aerobic and anaerobic. “Aerobic” literally means “with oxygen,” and “anaerobic” means “without oxygen.” During aerobic activity, fat is the primary energy source, and during anaerobic activity, glycogen (stored carbohydrates) is the primary energy source. To make matters more confusing, since long, slow cardio simply takes longer, you actually do burn more calories during the session (more on this later). It’s easy to see why so many people are led to believe that slower, aerobic activity is more effective at burning fat. Where science fails, however, is that it does not tell the whole story. What seems like the truth in theory simply does not hold up in practice because the comparison of energy systems is very superficial.
There is one benefit of running for a long period of time: you get better at running for a long period of time. I’m not knocking marathon runners for that accomplishment, because it is no easy task, and if your goal is to be good at running for five straight hours, so be it, but that is certainly not the way to have a great looking body. As legend has it, the first ever marathon was run out of necessity. Why? Because back in 490 B.C., that Greek guy couldn’t pull out his iPhone and call his buddies back in Athens, so he ran 26.2 miles to get there. You want to know what happened next? He died. Sounds like a losing argument for running marathons if you ask me.
I’ll bet this guy can run for a long time.
Now I don’t know about you, but I would never want my body to look like this. But this is what long, slow cardio will do for you over time. Long, slow cardio is a sure fire way to break down muscle (which kills your metabolism), build up a ton of cortisol (which leads to excessive fat storage, especially in the belly area), fry your immune system, destroy your joints, waste your time, and leave you frustrated and more likely to give up all together. Sign me up! (Kidding)
There is a better way to lose that stubborn fat, improve your muscle tone, and increase your overall fitness level. And all of those benefits can be achieved in less than half the time it takes to unleash your inner hamster and spin your wheels on a cardio machine for an hour.
Unless you’ve been living under a rock since the 90’s, you have probably heard of High Intensity Interval Training, or HIIT, as I’ll refer to it. HIIT is basically an exercise method in which you alternate between high intensity work and low intensity work, i.e. sprint for 20 seconds and walk for 40 seconds. High Intensity Interval Training sessions should be fairly short, and very intense. In fact, duration and intensity should be inversely proportional, meaning that, the more intense your training, the shorter the duration should be. I’ll get into specifics on intensity and some examples of workouts later.
There are some cardio fanatics out there who will tell you that they did intervals for an hour, and let me say very clearly, that is NOT High Intensity Interval Training. Just because you changed the speed on the treadmill every so often does not mean you did a HIIT session. That is called LOW intensity interval training, and it doesn’t have the same physiological effect.
There are a plethora of reasons why HIIT is superior for improving body composition, but three in particular stand out above the rest. The first reason is that HIIT provides much more of a stimulus on the high-threshold muscle fibers. High-threshold muscle fibers have much more potential for gains in strength and size than low-threshold muscle fibers, which happen to be the only fibers used during low intensity exercise. Here’s why that matters: muscle fuels metabolism. In fact, muscle tissue is the location where body fat is actually burned. Bigger, stronger muscles give you a bigger, stronger (faster) metabolism, which will burn more fat and calories in the long run.
Sprinting: 1 – Slow Cardio: 0
The second reason that HIIT is better than slow cardio for improving body composition is because it cranks up your metabolism for up to 36 hours after you are done. Think about that for a second. If you do a HIIT session at 8:00 AM Monday morning, your metabolism will be running at a higher rate until 8:00 PM Tuesday night! With long, slow cardio, as soon as you stop the session you are right back at your baseline metabolic rate. In other words, you don’t boost your metabolism at all. As I mentioned before, with long, slow cardio, you burn more calories during the session. But which would you rather have? You can either burn more calories for 60 minutes, or set yourself up to burn more calories for 36 times as long. I’ll take Option B, please.
If you want to break out the science-y terms, this phenomenon is called Excess Post-Exercise Oxygen Consumption, or EPOC. Basically what it means is that your body is still in an oxygen debt when the workout is done, and it takes energy (calories) to get back to normal. Your body is an incredibly adaptive creature, and it wants nothing more to remain unchanged, or in equilibrium, and obviously, sprinting is much further away from your body’s equilibrium than a light jog. The take-home point here is that the greater the demand you place on your body, the harder it will have to work (read: the more calories it will have to burn) to get it back to its normal state.
The third and most important reason why HIIT is so much better than slow cardio is because of those tricky hormones. They often fly under the radar, but these devious little devils are the X-Factors that control everything.
As I mentioned before, long, slow cardio can cause a buildup of cortisol, commonly known as the stress hormone. Cortisol usually pops up in stressful situations (i.e. workouts) that last over 45 minutes, and it is quite a nasty chemical. Cortisol has been shown to increase the appetite and blood sugar levels, inhibit the breakdown of stored fat, while stimulating fat production, especially in the belly area. But it gets worse. Not only does cortisol make you fat, it also catabolizes (destroys) muscle and bone tissue. Suffice it to say that cortisol is not the kind of guy you want hanging around at your party. Here’s the good news: HIIT eliminates this problem because the sessions shouldn’t be any longer than about 20 minutes.
Not only does HIIT take down the bad guy, but it also stimulates the production of a hormonal powerhouse. That hormonal “big gun,” if you will, is called epinephrine, which you have probably heard of referred to as adrenaline. Epinephrine is a part of a larger category of hormones called catecholamines, which are essentially the “fight or flight” hormones. Catecholamines are released into your bloodstream in response to highly stressful situations like bench pressing cars, running away from bears, or I guess, High Intensity Interval Training.
When adrenaline is released into your bloodstream, it triggers the release of a fat-blasting enzyme called Hormone-Sensitive Lipase, whose function is to make its way into your fat cells and break apart those fatty acids to make them available for energy. And since the primary energy source during the HIIT session is glycogen, your body is going to need some form of energy to carry out its basic functions for the rest of the day.
This is where EPOC comes into play, because since your body has to expend more energy to return to its normal state of equilibrium, guess who is now freed up and available to burn for that energy? Body fat! So even though slow cardio might burn more fat during the session, High Intensity Interval Training ends up burning more body fat in the long run.
Like I said before, your body is a very adaptive machine, and we have our ancestors like Mr. Caveman up there to thank for that. We have essentially been conditioned for survival, and if you had to run from a bear once, your body is going to make damn sure that if you have to do it again, you will be better equipped to handle it. That means that your body is going to shed excess baggage (fat) and build more muscle, so you are stronger, faster, and ready to outrun bears.
Here’s How to Do It
Anyone from complete beginners to advanced athletes can see great results from HIIT. You just have to start at a level that is right for you. Instead of using heart rate to gauge intensity, we will use a scale of 1-10 in physical exertion.
1/10: standing still
3/10: normal walk (recovery pace)
6/10: “cardio” (you could keep this pace steadily for at least 30 minutes)
10/10: Running from bears (this is overkill for interval training)
Your work intervals will fall somewhere is the 7-9 range, depending on your fitness level. Beginners will obviously start closer to the 7/10, and more advanced trainees will work at a 9/10. To do a HIIT session, you can obviously sprint on the road, or you can use a treadmill, stationary bike, rowing machine, stair machine, elliptical, jump rope, or even your own bodyweight.
Keep in mind: the intensity of the interval is dependent on the speed and the duration. What I mean by that is, wait until the end of the work interval to gauge how intense it was. If you are planning on doing a 60 second work interval, you obviously couldn’t be at the same speed as if you were doing a 10 second all-out sprint. However, both alternatives could be considered a 9/10 intensity. Also, beginners will probably feel like they can do more intervals because they simply cannot exert themselves like a more advanced athlete. A well-conditioned athlete will tell you that 6 all-out intervals is absolutely brutal. My general recommendation is not to do more than 6 intervals, and progress by increasing the speed, resistance, or duration of the interval, or decrease the rest periods.
I’m not a big fan of assigning specific rest periods right off the bat. I think it is more effective to simply start another interval when you are ready to perform at your optimal level. However, it is a good idea to keep track of how long you rest so you can make quantifiable progress in the future. Sometimes, however, your rest period just isn’t a variable that you can control. For instance, my personal favorite way to do HIIT is hill sprints, so I sprint up the hill, walk back down, and repeat until my legs feel like jello. In this situation, I have to walk all the way back to the starting point in order to start my next sprint, so my rest period is simply the amount of time it takes me to get back down the hill, and there isn’t much I can do about that. Below are some examples of High Intensity Interval Training sessions for you to try.
Run up a hill, walk back down, and repeat.
Run, bike, climb, row, etc. anywhere from 8 seconds to 60 seconds at a 7/10 intensity for beginners, 8/10 for intermediate, and 9/10 for advanced trainees. Rest as long as you need to in order to complete the next interval at the same intensity.
Pick any bodyweight exercises that aren’t limited by your strength (If you can only perform 5 pushups, choose a different exercise. You want conditioning exercises, i.e. burpees, mountain climbers, jumping jacks, etc.) and perform them in blocks of 10-60 seconds. You can do several different exercises in circuit fashion, or you can just do one exercise for a certain amount of time, then rest and repeat. For example, do burpees for 30 seconds, rest 30-60 seconds, and repeat until you are cursing my name.
Don’t get bogged down by the specifics at first. If you do one sprint for 30 seconds, and then on the next one you feel like you’re going to die at 25 seconds, don’t worry about it. Structure isn’t as important as intensity, so just get moving. If you want to build that fat-burning furnace and sculpt a better body, all while saving your precious time, joints, and sanity, High Intensity Interval Training is the way to go. So crank up the intensity, and crank up your results.
About the Author
Dave Williams is a Certified Personal Trainer, Certified Specialist in Sports Nutrition, and an unapologetic pretty boy from a small town north of Pittsburgh, PA. He graduated from Mercyhurst University with a degree in business and economics, but couldn’t seem to shift his mindset from workouts to Wall Street, so has set out to help make people unleash their inner hotness. Check out his Facebook page at facebook.com/DaveWilliamsFitnessConsulting
- 5 Interval Cardio Workouts that Burns Fat, Sculpts Your Figure (herfitnesshut.com)