The HIIT Trend: High-Intensity Interval Training

What is HIIT? It's a quick and effective way to improve your physical fitness. Here's how high-intensity interval training works.

stationary bike

High-intensity interval training (HIIT) means pushing yourself to 80 to 100 percent of your ability while working out.

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High-intensity interval training, or HIIT, might sound like something just for über athletes, but it isn’t. It’s a great method for just about anyone who wants to quickly take their fitness to a new level. And according to researchers from the University of Kansas Medical Center, the added bonus is that high-intensity aerobics is a great way to keep your brain fit, too.

“For improved brain function, the results suggest that it’s not enough just to exercise more,” said Eric Vidoni, a research associate professor of neurology at KU Medical Center. “You have to do it in a way that bumps up your overall fitness level.”

How High Should You Go?

High-intensity is a relative term. You determine how long to do each interval and you define the intensity (difficulty) according to your current fitness level. The HIIT method is typically used for cardiovascular fitness but it can also be applied to resistance training. A warm-up and cool-down are important to each application, as are flexibility exercises.

At peak intensity you want to be at 80 to 100 percent of your ability. You do, however, need a good warm-up phase because you’ll be going all-out at your high-intensity phase. This kind of training keeps your heart rate up moderately during the recovery phase, which makes it especially beneficial for cardiovascular conditioning.



High-intensity interval training is highly effective and doesn’t require a lot of time, so it can easily fit into busy schedules. Quick hits on HIIT:

  • The workouts are intense but short, with minimal recovery times.
  • Intensity is defined as 80 to 100 percent maximal effort.
  • Warm-up, cool-down, and stretching should be included.

Because this kind of exercise does increase your heart rate, it’s best to know what your target heart rate is and how to stay within safe zones. For more information on determining your target heart rate, check out the details on the American Heart Association. Likewise, talk to your doctor to make sure your heart is healthy enough for this kind of exercise.

Many machines (stationary bikes and eliptical machines) have pre-programmed intervals that automatically alternative between hills and flat terrain or easy and more difficult pedal strokes. They also allow you to easily change intensity if it becomes too hard or too easy. The built-in heart monitors on the machines are helpful but they aren’t the most accurate. Another way to judge how hard you are working is by noticing your breathing pattern.

HIIT requires concentration and deliberate intention. You have to time your interval phases and control your effort levels. That kind of focus can make an exercise session fly by more quickly because your mind is very much involved in the process. This more mindful process also helps you become more aware of your body.

How to Do HIIT to Get Fit

The HIIT method is based on the Tabata protocol workout, which was first described by the Japanese scientist Izumi Tabata in 1996. The workout was created to maximize results in athletes. The entire sequence takes about 20-minutes. It was designed as follows:

  • 5 minute warm-up
  • 8 intervals of 20 seconds all-out intensity exercise followed by 10 seconds of rest
  • 2 minute cool-down

According to research presented at the American Heart Association’s Scientific Sessions 2015, short bursts of high-intensity exercise improved cholesterol, blood sugar, and weight among Type 2 diabetes patients more effectively than 30 minutes of sustained, lower-intensity exercise. The study was conducted in 76 patients with Type 2 diabetes (70 percent male, average age 67) who were recruited for the study shortly after their diagnosis.

Originally published in June 2016 and updated.

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JoAnn Milivojevic

JoAnn Milivojevic became the executive editor of UCLA Health’s Healthy Years in 2015 and has written numerous articles featuring some of the most preeminent and passionate scientists, researchers, physicians, and … Read More

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