What is High Intensity Interval Training and Why Do We Do It?

I want to give you a better idea of what we’re doing when we train.  You notice we do a lot of “Circuit Training” or “Interval Training.”  We do short bursts of intense exercise followed by rest periods.  What it’s known as is High Intensity Interval Training (HIIT).

What is HIIT? – High intensity or Maximal training is generally 80% – 90% of your maximum heart rate.  Humans can only do extreme high intensity, 90% of MHR, for about 20 seconds and less intense exercises for longer.  It depends on the individual and their conditioning.

Before I tell you the benefits of HIIT, let’s get some terms squared away:

  • Maximum Heart Rate – Typically calculated by 220 – Age.  So if you’re 30 years old, your MHR is 190 beats per minute.
  • SubMaximal Training – Heart rate between 60%-70%.  This is basically jogging or doing something that you can do for an extended period of time while still talking.
  • Maximal Training – 80%-90% of MHR.  This is something that you can only do for around 20 to 30 seconds.

With HIIT, there is no specific formula for how long the work should be or how long the rest should be (30 seconds on with 30 seconds off, 45 seconds on with a minute off, etc.) Many different researchers have done studies with different periods of work and rest.  All the studies I’ve read have shown one thing: HIIT is way better than long endurance training for many reasons.  Granted, long runs are needed for athletes training to do long events like marathons, triathlons, and even MMA, but for the normal person, HIIT, in my opinion, should be their main focus of exercise.

So let me give you some Science behind what we’re doing.

*     The main difference between submaximal training (jogging for long periods of time) and HIIT (shorter and more intense workouts) is that with jogging your body burns calories while you’re working out, but not so much after.  With HIIT, your body is working way harder AFTER the workout.

  • Science – Your body continues to burn calories up to 36 hours after your workout with HIIT.
  • Science – HIIT boosts metabolism significantly longer after the workout than a submaximal workout of even longer duration.
  • Studies show that HIIT for 27 minutes, 3 times a week produces the same anaerobic and aerobic benefits as submaximal training for 60 minutes, 5 times a week.

Source –

Source – “The Scientific Basis for High- Intensity Interval Training”.  Paul B. Larsen and David G. Jenkins.  Sports Med, 2002 .

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