So what exactly is HIIT? Your Guide to Interval Training

HIIT — the abbreviation alone gives you a good idea of what to expect going into such a rigorous training session. It hits you, hard, and the effects roll in quite rapidly the more consistently you train. Originally a form of supercharged training for Olympic speedskaters by a much more rigorous training standard called the Tabata method, HIIT is leaned on the lessons learned from the Japanese doctor, but for the layman and athlete alike. Today, these interval circuits have taken shape on football fields and basketball courts alike, and it’s actually pretty common to hear about athletes doing HIIT. You may have heard of the term before, but do you know what it actually means?

What is HIIT?

HIIT stands for high-intensity interval/intermittent training, and that’s also the most succinct definition you’ll get. It’s a fast-and-loose training protocol that details a period of maximum or near-maximum exertion, followed by very short periods of rest, and that translated into a total number of rounds relative to an end-time of about 15-20 minutes of exercise.

The purpose of HIIT is almost purely cardiovascular — this isn’t to build strength, but rather, to build endurance. However, with exercises like pull-ups, push ups and sprints, you can easily glean some strength benefits from the program too.

For most people, the point of an HIIT program is to eliminate steady-state cardio. No more lounging on the elliptical, or jogging around for an hour. Your training is cut down to short, hardcore bursts. The science behind it all can be read and reviewed en masse through a number of studies, including this one in the Journal of Applied Physiology, but it all comes down to what you want to do. There are no distinct rules for how you do your HIIT training, as long as your rest is short, and your exertion remains high. Typically, the format goes something like this: 10 to 120 seconds of work, and 10 to 60 seconds of rest.

If you’re sprinting or doing hill runs, you’ll want to do 10 seconds of work and 20 seconds of rest (30 seconds in all) 40 times in a row, for a full 20 minutes. If you’re doing 30 seconds of calisthenics, 60 seconds of cardio (jumping jacks, rope jumps) and 30 seconds of something more intense (burpees or sit throughs) like I do, then you’ll want a minute rest, for a total of three minutes, and about 6 rounds. You can also just head onto a stationary bike and do 30 seconds of exertion with 30 seconds of low-effort work, repeated for 20 minutes. The possibilities are endless.

The Science Behind HIIT

As per the linked study, the usual recommendation for a healthy heart and good cardiovascular performance is steady-state training. That can be half an hour of power walking, or you can wake up at 5, swallow raw eggs and go for a jog through the city of Philadelphia. But one day, Izumi Tabata, a Japanese doctor specializing in exercise and physical performance and dean of the Ritsumeikan University, conducted a study pitting two groups of athletes against each other in an attempt to figure out what works best for aerobic and anaerobic endurance optimization: an hour of moderate-level exercise (running), or 4 minutes of the Tabata protocol (also running, but 20 seconds of sprinting with 10 seconds of rest of eight rounds).

The difference herein is insane. The end result was 1800 minutes versus 120 minutes of exercise over a six-week period, and the results where as follows:

  • Aerobic performance (VO2 max, or the maximum volume of oxygen the body can hold and use during exercise) increased, with an insignificantly larger increase for the Tabata group.
  • Anaerobic performance increased by an astounding 28 percent for the Tabata group, over an insignificant increase for the control group.

The Difference Between Aerobic and Anaerobic

Aerobic performance translates to how well your body uses oxygen. This means you can last longer while still breathing, you don’t run out of breath quite so quickly, and you can last on long, controlled belly breaths for longer before switching to gasps.

Anaerobic performance is a measurement of how long it takes the muscles to fatigue. Muscle fatigue is still a relatively unknown phenomenon. For a long time, it seemed like fatigue came from a release of lactic acid in the body following the conversion of sugar to energy in the absence of oxygen. Then, it was realized that this isn’t the case, and instead, muscle fatigue may be a bodily response in order to protect the integrity of your muscular tissue. Meanwhile, the release of lactate doesn’t affect your muscles but is a natural by-product, eliminated through your body’s stores of alkaline minerals.

Both are important in athletes. First, breath management and VO2 max allows you to last longer in your sport while oxygen is still a factor. Then, when you can’t get enough air to supply your body, your anaerobic endurance determines how long you can keep going before you no longer can.

What Dr. Tabata proved is that smart training — 4 minutes of HIIT — was more efficient than running for an hour.

Why doesn’t everybody do it?

Because it’s hard. That’s why. It may be 4 minutes, or 15, or 20 in different levels of rest and exertion, but they’ll be some of the hardest minutes of your life physically. That’s not easy to do consistently, and it requires you to be present and mindful of every movement.

On the other hand, training for an hour with moderate intensity allows you to set yourself to autopilot, drift off, and not dedicate yourself quite so much to your training. It’s easier.