High Intensity Interval Training: Explained (Why Your Cardio Workout Might Be A Waste Of Time)

Graham Ryan

19 Jul 2013

Get stronger, fitter and leaner in less time...

Let me start by clarifying the title a bit...cardiovascular fitness is far from a waste of time - on the contrary it is indispensable for anyone seeking vibrant health and high performance in all areas. What is certainly a waste of time is the way most people approach cardio workouts. While an hour on the elliptical or running at a moderate pace are better than no cardio at all, with a bit of informed strategy you can get 2 times the benefit in half the time. (seriously) Who wouldn't want that?

What we'll cover in this article

Benefits of Cardio Training
Key Concepts For Understanding How Your Body Responds To Cardio Training
Fundamentals of High Intensity Interval Training (HIIT)
Example HIIT Sessions
Supporting Your Training With Proper Nutrition

Why Cardio? (way beyond burning calories...)

Perhaps the reason so many people have crap cardio workout regimens is because they don't fundamentally understand the value the workout can provide. It seems most people think of their cardio workouts as a means to burn off some excess calories (and hopefully body fat). While cardio workouts will (of course) burn calories, the benefits to your body/mind system run much deeper. Knowing the potential gain from a well-designed cardio regimen makes it a lot more likely you'll work to integrate your new workouts and continue to progress in them.

Potential Benefits of Cardio Training:

Increased Metabolic Activity - metabolic activity is a good predictor for how much energy a person experiences. Increased metabolic activity will translate to increased fat burning, particularly if your metabolism is accustomed to using fat preferentially
Build Lean Muscle - How much lean muscle you build depends greatly on how your cardio session is structured. Since it is muscle tissue that is responsible for consuming fat stored in fat cells, this is pretty important.
Increase Insulin Sensitivity - Critical for maintaining a healthy + vibrant metabolism. Insulin resistance (the opposite of insulin sensitivity) is essentially pre- Type-II diabetes.
Improved Athletic Performance - If you care at all about your athletic performance, you need to maximize your cardivascular fitness.
Improved Sleep - As I covered in Synchro Life Design #8, this has a huge impact on several markers of performance and well-being.

So as you can see, cardio fitness is about a lot more than burning a few calories. Being truly fit translates to feeling, looking and performing better. But as I mentioned before, the extent to which you experience these benefits depends hugely on the type of workout you're doing. By utilizing the techniques I'll outline here, you'll get stronger, fitter and healthier in a fraction of the time.

Understanding Your Body

To get the maximum benefit from your cardio training, it's critical to know your own body and how it responds to different types of training. Being familiar with a few key concepts will quickly deepen your understanding of what's going on in your body during a training session.

Max Heart Rate - At a certain point, your heart simply cannot beat any faster, and it can't pump any more oxygen and nutrients to your muscles. It's not necessarily important to know your own max heart rate, rather just think of sections of your workout relative to a "maximum intensity". If you're curious what your max heart rate is, buy a heart-rate meter. Do a warm-up for 10 to 15 minutes at moderate intensity and then sprint for 90 seconds as hard as you can possibly go. Whatever your heart-rate meter records during this exercise will be pretty close to your max HR.
Aerobic/Anaerobic Energy Production - There is a fixed amount of oxygen the body can take in at any one time. Oxygen is needed to power certain metabolic processes responsible for energy production (these are referred to as aerobic metabolism). When exercise is very intense and the body needs more energy than can be produced by aerobic metabolism, anaerobic metabolism (which does not require oxygen) kicks in to make up the difference. The cardio workouts most people do stay comfortably in the aerobic range, but maximum benefit comes when both aerobic and anaerobic are developed together.
Lactate Threshold (LT) - Put simply, this is the point where anaerobic metabolism kicks in. Although anaerobic metabolism will kick in and make up the energy deficit, it has the undesirable consequence of generating lactic acid as a byproduct. At lower intensities, your body is able to clear lactic acid out of your muscles as fast as it is produced. When your workout gets intense enough that you cross the lactic threshold, lactic acid will start to accumulate in your muscles, eventually resulting in muscle fatigue. You know when you sprint up some stairs and your legs start to burn after a couple flights? Yep, that's lactic acid. Becoming familiar with that level of intensity in your workout when your muscles start to burn will serve you well in making sure you get the most out of your training. FOr most people, LT occurs at a heart-rate somewhere around 85% of max.
Rate of Perceived Exertion (RPE) - This is the important one. To get the most out of your workouts, you need to put in the time to become familiar with what a real maximum effort feels like. From there you need to figure out what a 50% or 80% or 90% effort feels like (and being honest in this is part of the challenge). The chart below will be very useful in learning what these different intensities feel like.

High Intensity Interval Training (HIIT)

High Intensity Interval Training (HIIT) is a technique that was initially developed in the 70's by German coach and university professor Woldemar Gerschler and the Swedish physiologst Per-Olof Astrand. It was used to great success by several high-profile athletes and quickly became the global standard for cardio training. Over the past four decades it has been studied extensively and refined by researchers, athletes and coaches.

The technique involves several short periods of very high intensity activity, broken up by short periods of low intensity for recovery. This is in contrast to the traditional cardio training paradigm which encouraged long periods of consistent activity at medium-high intensity. For whatever reason, this old paradigm is still what most people practice during their time on a treadmill or on their runs and rides.

The effectiveness of HIIT is very well established at this point. A 2008 study showed that 2.5 hours of interval training produced similar gains in cardiovascular fitness to 10.5 hours of traditional endurance training. That's 4 times the fitness gain for every hour invested! Beyond gains in cardio performance, HIIT also delivers gains in other areas far beyond what traditional training would deliver. Fat burning, lean muscle building and insulin sensitivity all see far better results with HIIT relative to traditional cardio training.

And perhaps the best part? Spend less time working out! (if you want to) 1/2 hour of HIIT will deliver 2x the results of 1 hour of "normal" running or similar cardio activity. If you're a weirdo like me and actually enjoy spending 5 hours on your bicycle, incorporating a section of HIIT into your ride will still get you far better results from your ride than if you didn't include it.

Example HIIT Sessions

The example sessions below will serve as a great entry point into using HIIT. These can be applied to running (outdoor or treadmill), cycling, elliptical machine, rowing, jumping rope or any other endurance activity. It's good practice to change up the structure of your HIIT workouts over time so you're building all different types of cardiovascular fitness. If you want to move beyond what's supplied here, a google search will yield endless example HIIT sessions designed to specialize in everything from building lean muscle to extreme endurance.

If you're new to HIIT (or particularly if you're new to cardio training altogether) start with this session:

Warm Up - 10 Minutes at 50-60% of max intensity (RPE 5-6)
Interval Block A - 30 seconds at 85% intensity followed by 45 seconds at 40% intesity. Repeat this 4 times. You will be going into anaerobic metabolism in these 85% periods, which means your legs should be burning, particularly in the 3rd and 4th intervals.
Recovery - 5 minutes at 50-60% of max intensity
Interval Block B - (same as Block A)
Cool Down - 5 Minutes at 50% intensity

This workout will take you 30 minutes, but you'll have burned more fat, built more lean muscle, and made greater gains in fitness than if you had spent an hour doing a "normal" workout.

Once you're comfortable with HIIT, progress to more intense sessions such as the ones below.

To build deep, balanced cardiovascular fitness:

Warm Up - 10-15 Minutes at 50-60% of max intensity (RPE 5-6)
Interval Block A - 60 seconds at 85% intensity followed by 60 seconds at 40% intensity. Repeat this 4-5 times. You will be going into anaerobic metabolism in these 85% periods, which means your legs should be burning, particularly in the 3rd and 4th intervals.
Recovery - 5 minutes at 50-60% of max intensity
Interval Block B - (same as Block A)
Cool Down - 5-10 Minutes at 50% intensity

To prioritize explosive strength and building lean muscle:

Warm Up - 10-15 Minutes at 50-60% of max intensity (RPE 5-6)
Interval Block A - 30 seconds at 100% intensity followed by 30 seconds at 40% intensity. Repeat this 8 times. If you're doing these right, your legs will be burning like crazy by about the 5th interval.
Recovery - 5 minutes at 50-60% of max intensity
Interval Block B - (same as Block A)
Cool Down - 5-10 Minutes at 50% intensity

Nutrition: More Important Than Ever

The potential gains in fitness, lean muscle and fat-burning are much, much greater when using HIIT compared to 'normal' cardio training. Your body will want to begin building as soon as you've finished your session. As I covered in Synchro Life Design #13, optimizing your nutrition before and particularly after your training sessions is critical to making sure your body builds the strength and fitness you worked hard for. Failing to give your body the nutrition it needs immediately after a workout is equivalent to 'throwing away' a large portion of the work you've just done.

I can say without hesitation that Synchro Genesis is hands-down the planet's most powerful and effective post-workout nutrition. Nothing does a better job supplying your body the minerals, antioxidants and macronutrients it craves after a workout.

If you reference the aforementioned article, you'll see that the relative amounts of carbohydrate and protein your body needs differs based on the type and duration of the workout. For these HIIT sessions, a 1:1 ratio of carbohydrate-to-protein will be ideal for maximizing the benefit you take from your session. A serving or two of Synchro Genesis (depending on body weight) immediately post-training is the best possible thing you could hope to give your body.

Stay Synchro,

Graham Ryan