High Intensity Interval Training

(HIIT) is a workout that includes bursts of high intensity followed by low-intensity rest periods. It’s a system used by athletes since the 19th century (1) to improve performance, speed, power and cardiovascular fitness.

Now, it’s the hottest workout sweeping the fitness industry with no lack of hype.

I can’t go a day without seeing some high intensity program online or in magazines claiming you can get more benefit from a 20, 7, or 4 minute high intensity interval workout than you can in an hour of a regular one.

In my last article, I covered how higher intensity workouts can cause greater calorie burn and fat loss overall. But, can you actually get the same benefits out of a 4 minute or 7 minute workout as you do in an hour?

In this article I explain the reality of HIIT so you can

  • Understand what it is
  • Determine whether it’s something you’d want to include in your workout routine
  • Decide what kind is right for you

A popular, but often misused name in HIIT training today is “Tabata”

named after Dr. Izumi Tabata who did a high intensity interval study in 1996. Tabata’s subjects (elite speed skaters) performed 20-seconds of extremely intense exercise (140% of VO2 Max – an effort at 100% of Heart Rate Max) followed by 10 seconds of rest, 8 times, for a total of 4 minutes of exercise.

The significance of Tabata’s study was that it showed V02Max (the body’s ability to consume, distribute, and use oxygen) and anaerobic capacity (the body’s ability to work at higher intensities for longer) could be significantly improved after 4 minute workouts, 5 days per week. The cardiovascular benefits were greater than than training for 70% V02 max (about 82% of max heart rate) for 60 minutes 5 days per week.

What lit the media on fire were the number of calories burned in Tabata

Studies found it burns the same number calories in 4 minutes as a 20 minute brisk walk, and it can double the post exercise calorie burn for about 30 minutes afterwards  (8).

The one caveat is that real Tabata intervals are extremely taxing (even for elite athletes).

The study was done with elite athletes pushing all out at 140% of V02 max . When interviewed, Dr. Tabata himself said “ This protocol [was] invented to stress the cardiovascular systems of top Japanese [speed] skaters who got medals in the Olympic games. Therefore, the protocol is very tough. “The subjects lay down on the floor after the training”. “If you’re doing these intervals correctly, your aim is to get 8 rounds but you’ll most likely get 6 or 7 [and] the last 2 rounds will feel impossibly hard” (8,9).

True Tabata intervals are just right for the elite athlete, but not practical, or fun, for the average exerciser. In fact, you might like the 20 minute brisk walk a little better.

Even so, you’ll find a generous offering of “Tabata” workouts in gyms and online.

Most likely they’re not Tabata.

Current research on high intensity interval workouts (not Tabata) shows if you want to just double your calorie burn

the high intensity segment needs to be done at higher than 80% V02 Max (about 88-100% of your Max Heart Rate). You’ll need to do 20 – 30 minutes of this workout, with 1- 2minute high intensity and 1-2 minutes rest intervals to  get the same calorie burn and cardio benefits that you would get from a steady-state, one-hour workout at 50-75% of your V02 max (70-88% of your Max Heart Rate) (1, 6,13).

Some of you reading this might be able to do that workout just fine.

But, for some, raising your heart rate to 90-100% of your max might sound like a scary concept. And for sure, it’s not a workout for the beginner.

You’ll get benefits from interval training that doesn’t take your heart rate to 90% or 100% max – but not the huge benefits in the short amount of time the media would have you think.

A variety of high intensity aerobic interval workouts (like the kind you see in the gym these days) have been found to burn 6 – 15 % more calories during a 30-60 minute workout and burn more calories for 2 hours after exercise than the average training session (12). So, if you normally burn 100 calories every ten minutes while you’re running, you would probably burn 110-115 for every ten minutes, and your calorie burn is elevated higher than a normal exercise session for up to 2 hours afterwards. That’s not too bad of a deal.

You won’t be burning an hour’s worth of calories in 4, or 10, or even 20 minutes, but there are benefits of high-er intensity interval training that are real.

  • You’ll see greater gains from your workouts because, due to the higher intensity you’ll be accomplishing more at any given time (2,3,4,5). You’ll get better at your sport with more power and more speed, and greater cardiovascular ability (1).
  • You’ll burn more calories during your workout. When you add bursts of high intensity, naturally you push harder than you would during steady state exercise. These higher workout levels lead to greater calorie burn during and after the workout (2,3,4,5,6).  Think of it like a sliding scale. The harder you work, the more calories you’ll burn in the same amount of time. I covered that in my last article here.
  • You’ll train your muscles to use fat more efficiently. In fact, the fitter we get, the more fat we burn at all intensity levels  (1,3, 5,6).

One thing’s for sure, if you go for an hour, or even 30 minutes, and add some high intensity bouts, you’re going to burn more calories and get more benefits than if you go for that same amount of time without them.

This is the second of three articles. In my next article, find out if you’re ready for HIIT

and get an outline of the signature HIIT program I build for clients based on their own, personal physical needs. Click here to read.

Read the first post here.

I lead clients

through the basics of foundational fitness and into higher intensity fitness levels in a safe and effective way in one-on-one training and coaching. In my upcoming, online group class Mind Body Blast, we have a high intensity component where students learn and practice a safe and effective way of increasing the exercise intensity with my guidance. If this sounds like something you’re interested in, contact me, or head over to the Mind Body Blast Class Site and check out the class that’s starting soon.

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References for this article can be found here.