Cardio – It’s not what you think

To the naked eye, exercise can seem fairly simple

It’s often categorised into just 2 or 3 parts, lifting weights, cardio, and mobility/flexibility, maybe core training too.

But with the first 2, there are different effects you get depending on how you do them.

You can do pure strength training, lifting weights heavy enough you can only do 5 or fewer reps

Functional strength training, doing 6-12 reps

And muscular endurance, where you do 12+ reps

There are benefits to all so it’s important to cycle through different phases of these as we do when designing programmes at SF

And when it comes to cardio, not all cardio is the same too

There are different energy systems your body uses depending on the intensity of the exercise

Low-intensity exercise primarily uses the aerobic system, where there’s always oxygen present to keep the body moving. You can do this for long periods without much fatigue and it’s easy to recover from. Depending on your fitness level this could be walking, hill walking, cycling, running etc. Anything where its easy enough to hold a conversation throughout.

High to moderate-intensity exercise would use more of the anaerobic (without oxygen) system, using glycogen (carbs as its main fuel source) this is what we target with the heart rate training sessions at SF and is fantastic at making your heart and lungs stronger. This type of exercise is more fatiguing and is harder to recover from.

Then there’s the alactic system used for short, high-intensity bursts of around 10s or less, think sprinting for a bus or lifting something heavy.

So while low-intensity exercise like walking is great. It’s important not to neglect the anaerobic system, it burns more calories per minute and can help make your heart & lungs stronger.

But other benefits may not seem so obvious…

  1. Increases cellular energy – Interval training increases the number of mitochondria, the powerhouses of your cells. Meaning your cells get more energy and so everything you do becomes easier.
  2. Increases fat loss – Interval training helps preserve muscle mass, especially when dieting. Low-intensity cardio won’t have this same effect. And if you lose muscle on a diet it means you’ve missed out on a chunk of fat burning. Conversely, if you’re holding onto your muscle it means you’ll burn more fat as a percentage of total weight lost.
  3. Reduces risk of type 2 diabetes – Interval training increases the amount of glycogen (sugar) you burn. This makes sense as it uses carbs as its main fuel source. But it also makes your muscles more adept at using and storing glycogen for fuel when you’re not even exercising which means less sugar floating around your bloodstream.

To get the most out of your interval training there are 2 key parts

First, elevate your heart rate to about 85/90% of its maximum and then allow yourself to recover back down to 70/65%.

Too often interval training is butchered and not enough rest is taken. Meaning it becomes too intense. Training at too high an intensity with sub-optimal recovery will over fatigue you in your day-to-day life. 

Allowing your heart rate to get down to 70/65% means you are recovered and your body is ready to go again. And even though it’s tough it’s not so tough that it feels impossible.

So embrace the recovery part and a great way to notice your progress at interval training is the time it takes to recover. This will reduce (especially in the first few intervals of each session) meaning you end up getting more intervals done in the same time. More work done = more calories burned.

About the Author John O'C

John O'Connell is the owner of SF Fitness & Health Centre. He started working in the fitness industry in 2002 after suffering a back injury. He has worked with many professional organisations including Leinster Rugby, An Garda Siochana, New Zealand Rugby, Dublin GAA, Spar and CBRE. He has also appeared muliple times on both RTE & TV3 as a health & fitness expert. John is the co-author of 2 international best selling books - Total Body Breakthroughs and The Fit Formula.

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