What is High Intensity Interval Training (HIIT)?

Walking into the gym is like stepping into another world. There are the focused, committed fitness enthusiasts wearing a look of intensity as they move from one exercise to the next. Some people work with a personal trainer on meeting a specific goal, the trainer guiding them like a guru in a fitness wilderness. Others look like guests at a party, made up, done up, and chatting away to their thousands of Instagram followers. The gym also seems to have another language entirely, punctuated with acronyms like AMRAP, DOMS, BMI, and PR. One acronym seems to stand out from the rest, batted about by fitness enthusiasts, personal trainers, and gym party guests alike – HIIT. High Intensity Interval Training can be quite a mouthful for some folks! This four letter combination – HIIT – holds the key to weight loss, muscle gain and greater overall fitness. Let’s HIIT it!

What is High Intensity Interval Training (HIIT)?

High Intensity Interval Training (HIIT) is a system of exercise that relies on repeated cycles of short bursts of really intense work followed by short periods of low intensity work or even rest. The science behind HIIT is very sound. High-intensity exercises performed close to a person’s VO2 max (as hard as they can go) for a length of time just before they are no longer able to perform the exercise, followed by low-intensity recovery allows the body to clear the lactic acid from the blood. This process helps the body recover just enough to perform another high-intensity exercise.

What are the benefits of HIIT?

As much fun as it sounds to get on the treadmill for an hour (there’s a reason why runners call it the “dreadmill”), HIIT has been shown to have several benefits over steady state cardio like running or walking.

  • Studies have shown that people who regularly incorporate HIIT into their workout routine lose more fat than those that rely on moderate cardio. This is especially important to someone who wants to lose weight while improving their overall fitness.
  • The fat burning effects of HIIT last long after the workout is over.
  • HIIT takes less time than traditional workout programs. A personal trainer will generally recommend incorporating two to three HIIT workouts a week, each taking as little as four minutes.
  • Alternating between high intensity exercise and low intensity exercise has been shown to improve your VO2 max and your heart efficiency as much as endurance training.
  • On a more practical note, you don’t need a gym membership, expensive equipment or a dedicated space to get a great HIIT workout. (More on that later!)

Lose weight with less exercise? Sign me up!

There is a common misconception that working out longer will help you lose weight. While moderate exercise in the so-called “fat burning zone” will help your body metabolize fat, it requires something too many people are not willing to give to their exercise program – time. One study published in the journal Metabolism found that people who worked out using HIIT expended less energy than those who participated in endurance training, but experienced nine times more fat loss.

Then there’s the afterburn…

While it is a widely accepted fact that exercise burns calories, what is less well known is the effect exercise has on the amount of calories you burn after you are done exercising. This process, known as the afterburn effect, happens with every exercise we do. How long it lasts and how many calories you burn depends on the level of intensity of the exercise. For instance, jogging at a conversational pace for 30 minutes will have a lower afterburn effect than sprinting as hard as you can in 30 second intervals for five minutes. In fact, one study found that 95 percent of the calorie burn that occurs as a result of HIIT workouts happens once the workout is over. This is mostly due to the anaerobic nature of HIIT. Where aerobic exercise, such as running or cycling floods the muscles with oxygen as you go, HIIT tends to create a large oxygen deficit in your body. Once your workout is over, your body’s work is just beginning as it tries over the next several hours to balance that oxygen deficit. What results is an increased metabolism long after you have showered and gone on with your day.

High Intensity Interval Training is perfect for busy people

Izumi Tabata revolutionized the way people look at exercise when he suggested in 1996 that a total body workout could happen in just four minutes. Hired by the Japanese speed skating program to assess the effectiveness of their workout program, he divided the team into two groups. Group A worked out five days a week at a moderate intensity for 60 minutes while group B worked out for 4 minutes and 20 seconds, just four days a week. However, group B had a specific workout pattern they had to follow. Athletes had to work as hard as they could for 20 seconds then rest for 10 seconds, repeating the cycle until they had reached the 4 minute and 20 second mark. What Tabata found was that the athletes in group B had improved stamina and a higher oxygen uptake than those in group A.

Since then, the name Tabata has become synonymous with that style of workout – 20 seconds of high intensity work followed by 10 seconds of rest, repeated eight times. Variations to those time restrictions exist in several HIIT workouts when a particular move is unsafe to perform at such a high rate of speed, but the concept remains intact. Short bursts of high intensity work followed by even shorter bursts of rest mean spending less time on your workout (without sacrificing your results).

High Intensity Interval Training = A total system overhaul

We know what you’re saying. “But what about my heart and lungs? Don’t I have to do long cardio workouts to have better cardiovascular fitness?”
Not necessarily.

A study published in the British Journal of Sports Medicine found that HIIT has a more positive effect on cardiovascular health, VO2 max (the body’s efficiency at consuming oxygen) and insulin regulation than extensive cardio exercise. In comparing those who did cardio with another group that did HIIT for just six weeks and found that the high intensity interval training group increased their VO2 max as well as their levels of enzymes that regulated blood sugar and burned fat. Best of all, this group saw these effects both while they were working out and while they were at rest.

Another study published in the same journal showed that HIIT has also been shown to increase left-ventricle heart mass and cardiac contractility at the same rate as continuous aerobic exercise. In other words, the hearts of people who engage in HIIT enjoy the same increased efficiency as those who only do cardio. This effect is especially pronounced in people who have a form of cardiovascular disease.

That’s not all. A study published in the Strength and Conditioning Journal found that HIIT enhances muscle glucose uptake and increases insulin sensitivity in people with Type II diabetes. In just two weeks study participants found that they had better control of their blood glucose levels, even if they were only able to perform exercises with moderate intensity.

Where do I start?

One of the best ways to start a high intensity interval training program is to enlist the help of a personal trainer. Not only can they help you maintain proper form as you learn how to do new exercises, they can customize a program for your current fitness level. They will even keep you accountable and answer any questions you may have in your first days doing HIIT workouts. Things like, “Why am I so sore?” Or, “I didn’t even know I had a muscle there! How do I keep working on it?”

Fortunately, you don’t have to set foot in a gym to work with a personal trainer or get a great HIIT workout. HIIT can be done in any space, on any timeline, with any equipment (or no equipment at all!).

Even if you opt to go on your own, be sure to consult with a doctor before beginning any new exercise program to make sure you are healthy enough for exercise. This will also give you an opportunity to get baseline measurements before you begin your HIIT journey so you can track your progress!