High intensity interval training (or HIIT, for short) sounds simple enough: go as hard as you can for a short period, rest, repeat, and reap the benefits. HIIT is great, for sure, except what most people consider HIIT isn’t actually HIIT. Your all-out effort makes all the difference.

There are a few different kinds of interval training, which is the more general term to describe periods of intense, close-to anaerobic activity interspersed with rest periods. HIIT is one kind, and the others include fartlek and Tabata (though it is a form of HIIT). But not all interval training is HIIT.


Will Levy, head trainer at Melbourne Strength & Conditioning, said to me in a short interview about interval workouts:

Where many tend to butcher HIIT is by chasing cardiovascular fatigue. The primary distinction is that HIIT is really focused on developing maximal effort—strength, speed, power—properties, while other more “in-between” forms of training are designed to improve cardiovascular conditioning.

So, there are two places where people go wrong with HIIT workouts:

  1. They don’t go HARD enough: Typically, most people might try going “pretty hard” for a period of time and then ease up by going slower to actively rest. That’s actually a form of fartlek training, according to Will. True HIIT is uncomfortable. It requires your nothing-held-back, lay-it-all-out maximal effort on a bike or run for typically 6 to 15 seconds. Will adds that sometimes as little as 3 to 4 seconds are enough, and 20 seconds would be the upper limit since it’s unlikely anyone—even a world-class athlete—can sustain true 100% intensity any longer than that.
  2. They don’t actually rest during the rest periods: Will also notes that rest during HIIT is not simply going slower, or easier, but actual rest.

You have a number of different ways to set your work-to-rest ratio. In general, the longer the rest and the shorter the actual work period, the more suitable the HIIT workout is for powerful, explosive exercises. For example, you can do 10 seconds of an all-out sprint and rest 50 seconds. If you want to get the most out of a real HIIT workout, make sure you’re really pouring all of your effort into those 10 seconds. By the end of it, you won’t feel all that great; you might even feel like passing out or puking, which is part of the reason that you shouldn’t overdo it on HIIT, especially if you’re just beginning.


Still, interval training in general can be very effective, so check out this article for some effective interval training ideas to get started.

Image by whologwhy.
