Exercise benefits everyone, and there is really no downside. It builds a stronger heart, improves your immune system, boosts cognitive function, decreases stress, and lowers disease risk. It simply will provide you with longer, happier life. Isn’t that what we all really want?
Of course, we do, but most of us are also busy. That means we don’t really have an hour every day to devote to exercise like maybe we should.
So, we need to get a good workout, but we have a limited time to devote to it. Fortunately, there is a solution called high-intensity interval training.
Let’s start off with a little background to help you understand why this type of exercise is effective and how we do it.
The Two Types of Exercise
There are two main categories of exercise, the first of which is often referred to as “cardio.” Doing a cardio-type exercise is simply a matter of keeping your heart rate elevated for about 20 minutes or more. These sorts of exercises literally force your heart to work harder, and over time, your body adapts by increasing the strength and efficiency of your heart and blood vessels. Common cardio exercises are running, biking, or playing soccer.
The second type of exercise is strength training. This category includes things like weightlifting, which requires short, powerful bursts of energy as you push or pull something heavy. Doing this causes tiny tears in muscle tissue that soon heal bigger and stronger than before. This doesn’t do much for your heart but does cause adaption through bigger, stronger, more efficient, and flexible muscles.
In an ideal situation, you would do both cardio and strength training exercises because you really need both. That means at least 45 minutes of cardio twice a week and at least 45 minutes of weightlifting twice a week to see any real health benefits. Notice I said minimum. You really should do quite a bit more, but who even has time for 3 hours of exercise every week?
Intensity vs. Duration
That brings us to the next subject; the correlation between intensity and duration. Cardio is typically a low intensity, long-duration activity. Think about jogging for 5 miles. You can’t run all that fast because otherwise, you won’t last very long. Instead, you run at a lower intensity so you can actually finish. On the other hand, when you lift weights, at least the way you should, you lift a heavyweight for just a few seconds, but you give it all you have.
But you CAN’T do both. There is no such thing as a high-intensity exercise that lasts a long time. Could you sprint for 45 minutes straight? Of course not. The more you give to intensity, the less you can give to time and vice versa. Heart muscle (called cardiac muscle) is engineered to be really good at low intensity, long-duration activity. After all, it has to beat about every second for your whole life.
That’s why cardio exercise (low intensity, long duration) benefits your heart so much. Skeletal muscle, the muscles you use to move with, are really good at powerful, short-lived activities which include- lifting weights (high intensity, short duration) is what you need to build muscle size and strength.
Now let’s apply this to burning fat, which is really the objective for most of us. Let’s do a thought experiment to illustrate this. Imagine you walk 3 miles. It makes sense that as you do so, you are burning fat but very little at any given time. But you are also doing it for about an hour. Now imagine you run the same 3 miles about as quickly as you can. At any one time, you’d be burning a lot more fat than walking, but it also lasts for less than half as much time. The question is, which activity burns the most total fat? Low intensity, long duration or higher intensity, shorter duration? It turns out the running burns more fat but does so in less time. But of course, it requires higher intensity. Now imagine if it were possible to sprint for 3 miles. You would burn a huge amount of fat but for only about 15 minutes. Clearly, this is impossible, but we can do something similar.
High-Intensity Interval Training
This brings us to the idea of High-Intensity Interval Training or HIIT. It combines the ideas we just talked about to provide the greatest fat-burning benefit in the least amount of time. We know we burn as much fat as possible by being as intense as possible, but we can’t keep that up for long. That’s where HIIT workouts come in. We know that the more intense we are, the more fat we burn. Thus, if we sprint, and I mean sprint like a lion is chasing you, you’ll burn the most fat per unit of time as humanly possible. Since it is only possible to even do that for about 20 seconds, that’s how long you do it. After about 2-3 minutes, you’ll be ready to do it again. Repeat this a few times, and in a matter of 10-15 minutes, you’ll have burned more fat than if you had run 5 miles.
Pros of HIITs
a) Perhaps the best reason to do HIITs is that they don’t take long- warm-up for 3 minutes; stretching, slow jogging, etc. You sprint for 20 seconds, followed by a 2-minute rest. Then repeat this 4 more times and follow it up with 3 minutes of cooldown; again, stretching, slow jogging, etc. In total, your workout is less than 15 minutes. You would need to run more than 5 miles to achieve a similar fat burning result, which would take an hour or more.
b) HIITs are a hybrid between cardio and strength training, and so you get some benefits from both. You are working your heart muscle and skeletal muscle really hard for a short duration. Since you are going all out, the effects on your leg muscles are quite similar to strength training, and so your body tends to build muscle there. Since pretty much every muscle in your body is required for a ‘running from a lion’ sprint, you get some of the same muscle-building benefits throughout your body. Think about the last time you watched the Olympics. The guys who run long races (low intensity, long duration) always have skinny legs, and in fact, they are skinny all over. On the flip side, the sprinters always have beefy legs, but they are also pretty muscular all-around.
c) While I sort of implied it above, there are some heart health benefits to HIITs. It is pretty obvious that if you are sprinting for 20 seconds, your heart has to do some serious work to pump blood to all the muscles you are using. This exerts the heart, which, like other muscles, responds by becoming stronger. So, while you may be doing HIITs because you want to burn fat as quickly as possible, you are getting some benefit to your heart whether you like it or not.
The Downside to HIITs
a) First, let me be clear. HIITs are not “bad” in any way, but you are giving up other benefits if they are all you do. HIITs are not exactly cardio or weight training, and so you can’t get the full benefits of either. Like I said before, the heart benefits the most from low intensity, long-duration activities. HIITs are high intensity, low duration. Of course, HIITs still provide benefits to the heart but not nearly as much as if you ran a long-distance instead.
b) Likewise, HIITs are not entirely a strength-training activity. Of course, HIITs will encourage some muscle growth because of the intensity they require, but that intensity is not focused on any single muscle group. In other words, while HIITs will encourage some muscle growth, no one ever became (or could become) a bodybuilder by doing only HIITs. Interestingly enough, many of them do use HIITs to lose weight before a competition, but HIITs didn’t get them looking like that.
In Case You Missed It
In summary, HIITs are a combination of cardio and strength training exercise that maximizes the fat-burning aspects of both. They are difficult and require some real mental resolve to perform, but anyone can do them, and the real benefit is that you save time. Ideally, you want to do cardio and weight training for a total of several hours per week, but not many of us can or are willing, making time for that. We just want to stay thin! Doing HIITs provide exactly what we need to meet our fat-burning goal but with relatively small time investment.