Last week we started talking about the two cardio styles I get the most questions about—  HIIT and LISS— two very different approaches to cardiovascular exercise.  

So which method really is better?  

The answer to that question is going to be different for everyone, depending on your personal history, your fitness level, and your goals.  This week, let’s take a closer look at the HIIT method to help you decide if it’s the right approach for you.

What exactly is HIIT?

HIIT stands for high-intensity interval training—  cardio workouts designed to push your body to the limit in order to create an increase in your overall metabolic rate.  

In short, it means you’re taxing your body to the point of exhaustion in order to increase the number of calories you’re burning.

With HIIT routines, your goal is to spend a set amount of time working at max effort, followed by a recovery period.  These intervals of work and recovery are strung together to create your workout.  For instance, you might jump on the treadmill for 30 seconds of all-out sprinting, followed by 90 seconds of walking at an easy pace to recover.  By performing 10 of these intervals, you’ll be knocking out a 20-minute workout.

HIIT-style workouts have become increasingly popular in recent years, largely because they can get more work done in less time.  In fact, some HIIT workout styles, like Tabata, are traditionally designed to be done in under 10 minutes.  Instead of spending an hour doing traditional steady-state cardio— or LISS— HIIT workouts allow you to get your cardio in quickly and get on with your day.  In fact, if you’re giving an all-out effort, you won’t be able to keep up the pace for an extended period (hint: if you think you’re able to do an hour of HIIT, you’re not pushing hard enough).

The other major benefit to HIIT (and the more important one, in my humble opinion) is its ability to increase the body’s excessive post-exercise oxygen consumption, or EPOC.

After a workout, your body requires time to recover and return to its pre-workout state.  This happens after any type of exercise, from cardio, to weightlifting, to yoga.  During this period, your body continues to work, burning stored energy in the form of calories.  And because HIIT workouts tax your body in an extreme way, it takes much longer to return to that resting state after you’ve finished.  This results in higher levels of EPOC, creating an afterburn effect that raises your metabolism and burns more calories for hours— or even days— after your workout is finished.

I know— a workout that can burn more calories days after it’s completed might seem too good to be true.  But when done correctly, that’s exactly what HIIT does for the body.  

The problem, though, is that most people don’t do it right.  

For HIIT to be truly effective, it requires 100% effort.  For me, that means actually visualizing yourself in an extreme situation, like running for your life as a cheetah chases you or sprinting away from a tornado on your bike.  If that’s not the kind of stress you’re putting your body through, you’re not working hard enough to reap the benefits of HIIT.

(And don’t be discouraged if you don’t fit in this category, LISS training, which we’ll talk about next week, is actually a more effective method of cardio for many people.)

When should I do a HIIT session?

It might be tempting to perform your cardio sessions in a fasted state— in the mornings, before you’ve eaten breakfast— but that’s actually counterproductive to a HIIT workout.  

Remember, HIIT is intense.  And to perform at those extreme levels, your body needs to be fed.  You have to make sure you’re prepared with the right fuel so you can push hard enough to reach that EPOC afterburn (which is really the point of HIIT, anyway).  In my experience, you’ll see the best results by performing HIIT workout later in the day, after you’ve had a chance to eat 1-2 quality meals.

Also, keep in mind that HIIT is as much about recovery as it is about work.  That period of time after workouts is key— not only because of the calories it burns, but because it allows you to stay healthy and keep pushing.  Without an adequate recovery period, you’re opening the door to fatigue and possible injury.  I suggest performing no more than 1 or 2 HIIT workouts a week, mixed into your normal fitness routine.

And believe me— if you’re doing it right, 1-2 HIIT workouts a week will get the job done.

My favorite HIIT protocol is the 30/90 split we’ve already talked about— a 30-second, all-out effort, followed by a 90-second recovery period.   Work your way up to performing 10 of these intervals for a killer workout that will reap serious rewards.

You can also try a Tabata-style workout to get your HIIT fix.  For this method, you perform at max effort for 20 seconds, followed by a 10-second rest period.  Tabata protocols traditionally call for 8 intervals, adding up to a 4-minute workout.  Sure, it might sound easy, but I promise those will feel like the longest 4 minutes of your life once you’re in it.

HIIT can also be performed on a rower, stepmill, doing burpees, even in a pool— the possibilities are almost unlimited.   All that matters is that you give it everything you’ve got.

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