All About Interval Training

by | October 10, 2017 | Fitness

There has been a battle in the fitness industry for years, and I assume it will continue to be an issue for years to come:

Long, slow cardio or intervals?

This is not an article on which one is better – they both have there place and as in all things in life – the truth likely lies somewhere in the middle or is dependent on the individual.

But, here’s the deal – I know you’re busy, I know you don’t have a ton of time to do exercise, so we want to be as efficient with our workouts as possible.

This is why we are going to talk about how you can accelerate your fat loss in less time by using some high intensity interval training.

Before we dive in, let’s geek out a little bit and talk about how our body produces energy for exercise.


The primary energy molecule in your body is a little fired-up unit called adenosine triphosphate or ATP. ATP drives all actions in your body. Picking up your mug to sip some coffee – ATP does that. Walking to get a bagel – ATP does that too. Sitting on the couch digesting your food – ATP does that. Your heart beating right now – you bet that’s ATP.

So, as you can see, this is a pretty important molecule to, you know….stay alive. And, by now, I am sure you are starting to see how this relates to exercise.

Exercise needs ATP

In order to perform your exercise, your body needs to produce ATP, but here’s the deal – your body has different ways of producing it.

Which way is selected is based on 4 factors:

1. How hard you are working
2. How long you are working
3. How many bouts of work you are doing
4. How much you are resting between bouts of work

Let’s see how this relates to the three pathways:

The three pathways

Anaerobic alactic energy pathway

This pathway uses stored ATP in the muscles to do exercise. Unfortunately, the storage is pretty limited. Therefore, the anaerobic lactic energy system is able to produce energy really quickly, at really high intensity but for a really short period of time – about 12s. So, if you were to chase down a bus that you missed or smash a golf ball, you would be using your anaerobic alactic energy system.

Ps. Anaerobic = no oxygen is required to produce ATP and alactic = no lactic acid is produced from producing ATP…which leads us to our next energy pathway

Anaerobic lactic energy pathway

This pathway produces ATP quickly but the system is not very efficient. Also, it tires out rather quickly, about 90s, so we cannot use it for sustained efforts. Typically, this energy system would be dominant in a 400m sprint in the olympics. The intensity is still high but we gas out in a relatively short period of time. Also, this system produces lactate, a byproduct that can cause a burning sensation when it builds up too high in the muscle, but it also can serve a useful purpose in that it can produce some more ATP if the conditions are right. Nonetheless, the anaerobic lactic energy system is dominant in higher intensity activities of low/moderate duration.

Aerobic energy pathway

The final energy pathway is probably the one you are using right now – sitting and reading this article. This energy pathway produces ATP for activities of lower intensity and longer durations. The thing is there is a pretty wide range of activities that fit in here. Anywhere from watching Masterchef on the food network to walking your dog to running a marathon. This system is a little slower to kick in, usually firing up in about 3 mins but it can produce ATP for hours.

Ps. Aerobic = oxygen required to produce ATP

So, which one is favoured when?

Like we mentioned above, four factors determine which energy system predominates.

These include:

1. How hard you are working – intensity
2. How long you are working – time
3. How many bouts of work you are doing – number of repetitions
4. How much you are resting between bouts of work – rest periods

Let’s examine these in more detail:

A. How hard you are working – intensity

This is ultimately what determines the energy system that will work. Higher intensity activities will favour anaerobic alactic energy production. Lower intensity activity will favour aerobic energy production. Moderate/high activity will favour anaerobic lactic energy production.

Here’s the deal. If you are walking for 10s, but the intensity is really low – you are still  favouring the aerobic energy system because the intensity is low.

B. How long you are working – time

This is the next factor in line to determine energy production.

Here is the breakdown:

Activities of high intensity lasting 0.1-12s = anaerobic alactic energy production

Activities of moderate/high intensity lasting 20-90s = anaerobic lactic energy production

Activities of low intensity lasting >3 minutes = aerobic

So, your son throwing a ball at baseball (about 0.2 seconds) = anaerobic alactic

Your daughter’s shift in hockey (about 45 seconds) = anaerobic lactic

And taking your dog for a 30 minute walk = aerobic

Does that make sense?

C. How many bouts of work you are doing – number of repetitions

Let’s keep this simple – the more bouts of a particular exercise you do, the more it becomes aerobic

So, if your daughter’s shift lasts 45 seconds, that is anaerobic lactic. She rests and then goes out for another shift. That second shift is probably still anaerobic lactic BUT the intensity will be going down (she’s probably tired) and the activity is becoming more aerobic. She rests, goes again, eventually (if she does not rest enough ie. the bench is really short) the intensity of the effort will get so low that the aerobic energy system will take over (remember – intensity is the number one factor that determines that energy system that dominates).

D. Rest between bouts of work – rest periods

Let’s keep this simple as well, the shorter your rest period, the lower the intensity of successive bouts. So, if you start at a high intensity for 10s, rest 10s, then go again, you may still be using the anaerobic alactic system, but by the fourth or fifth rep of that, you will be in the aerobic energy system. There is just not enough rest for the system to replenish itself. Your intensity will drop and the energy will therefore be produced by the aerobic energy system.

So, what’s the problem with lower intensity methods?

Well, actually not much. There is a ton of value in going on a walk with your family, gardening in the backyard or going on a nice little jog. It just takes up some time, but if that time is with loved ones or doing things you love…do it!

This article is to highlight the efficiency of interval training.

I would never tell someone not to go for a walk with their family because it wasn’t optimal from a physiological perspective.

What is optimal is what you are most likely to do.

Now, back to geeking out.


EPOC stands for Excess Post-exercise Oxygen Consumption and it basically refers to the elevated metabolic rate that results after exercise.

If the intensity of your work bout is high, your metabolic rate could be fired up for hours after you finish your workout! So awesome!

So, now to the practical side of things

We usually throw our intervals at the end of the strength training workout or as a stand-alone session on off-days. We aim for 2-3 days per week of intervals.

We call our intervals boosters (some people call them finishers – a term we see as a slightly negative) because they boost your metabolism after your workout is finished.

The Guidelines

Here are a few Booster options for looking hot:

Work for 10 seconds, rest for 50 seconds for 5-10 minutes

Work for 20 seconds, rest for 40 seconds for 5-10 minutes

Work for 30 seconds, rest for 60 seconds for 5-10 minutes

Work for 60 seconds, rest for 120 seconds for 5-10 minutes

Work for 30 seconds, rest for 30 seconds for 5-10 minutes.

Notice how the rest period is at least equal to the work period. Again, that is to keep the intensity high and therefore the metabolic rate boosted long after the booster is finished.

Great home exercise options

I am assuming you are doing this at home, with minimal equipment, so exercise options include:

Squat jumps

Lateral squat jumps

Speed squats

Jumping Jacks

Front jacks

Mummy jacks

Squat jacks

Mountain climbers

Cross-body mountain climbers

Split squat jumps – cyclic

Split squat jumps – acyclic

Speed split squats


Broad jump

Jump landings

Vertical jumps


Skater jumps

Kettle bell swings

1-arm kettlebell swings

Booster intensity

In order to get the benefits of the boosters, the intensity needs to be high – aim for 8 out 10 for longer work periods (ie. 60 seconds) , 9 out of 10 or even 10 out of 10 for shorter work periods (ie. 10 seconds or 20 seconds).

Any lower and you will not get the benefits of the EPOC that really fire up that metabolic rate.

A word of caution

Again, the intensity of these boosters should be quite high, so if you feel light-headed, nauseous or anything sketchy – STOP!

You can still do the movements at lower intensity but see a doctor before proceeding with the high-intensity boosters.


High intensity interval training is an incredibly efficient way of boosting your metabolic rate to get in the best shape of your life. The ticket is to rest at least as much as you work in order to keep intensity high. If you rest less, you may feel like you are working really hard, but your absolute intensity may be low. So, be sure to get lots of rest between work bouts and attack that short time you are working.

Go get ‘em!

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