WHICH CARDIO IS BEST FOR YOU?
Words by Belinda Potter
WE SETTLE THE DEBATE ONCE AND FOR ALL AND PIT – HIIT AND LISS – AGAINST EACH OTHER. SO WHICH CARDIO CAME OUT ON TOP WHEN IT COMES TO FAT LOSS? READ ON TO FIND OUT.
Ever wondered how to start a fight in the cardio room of your gym? No, don’t throw a fantail in front of a bunch of
“hangry” women running on the treadmills (although that could be fun), instead, casually ask their opinion on which is better for fat loss High Intensity Interval Training (HIIT) or Low Intensity Steady State (LISS). Then back away and watch the cardio war unfold!
Before you chime in with your two cents worth, it’s useful to know your HIIT from your LISS and what the – sometimes convoluted – science says. Science, yawn. Don’t worry, I’m here to break it down for you and let you in on a little known secret method for turning yourself into a fat-burning furnace!
WHAT IS HIIT
HIIT, which stands for High Intensity Interval Training, cardio is characterised by alternating bursts of high intensity (maximum output), short duration exercise with low intensity periods of recovery. The work-to-rest ratio may vary depending on your fitness level ie. 1:1 or 1:2 or if you are starting out, perhaps think 1:4.
WHAT IS LISS
LISS on the other hand, is as it sounds: continuous exercise of low-intensity exercise for a prolonged period of time (usually within what is considered your optimal ‘fat-burning zone’ of 60-70 percent of your maximum heart rate (MHR)). It’s about as exciting as watching paint dry.
WHAT THIS MEANS
So what do these two types of cardio look like in practical terms? In principle, you would alternate timed bursts of ‘all out effort’ with recovery on a treadmill, but sprinting over marked distances can be equally effective – lace up your sneakers and hit the track, footy field or stairs. For a low-impact option, head indoors and hit the cross-trainer or spin bike following the same principles of alternating work and recovery ie. 30 seconds of work: 60 seconds of recovery. In terms of LISS, think of walking/jogging the perimeter of the footy field or watching an entire episode of Dr Phil while cruising on the treadmill.
But which is best? In an Australian study published by the Journal of Obesity in 20141, it was found that although HIIT could provide extensive health benefits including increased cardiorespiratory fitness, increased number of mitochondria (the powerhouse of our cells) and improved insulin sensitivity, the data suggested that HIIT cardio did not elicit the same benefits as LISS in reducing body fat levels.
So have we been sold a lemon? Not exactly. This study examined the efficacy of HIIT versus LISS training in previously inactive, overweight adults, which is not necessarily representative of the typical Oxyen girl. What this study did, however, was demonstrate that HIIT is an immensely time-effective method for significantly improving overall health and fitness in around half the time it took to achieve similar results by using low intensity aerobic exercise.
So, there are definite time advantages to utilising HIIT cardio for us time-poor gals.
A second study published in the Journal of Sports Science and Medicine2, concluded that both training methods resulted
in overall improvements to body composition with HIIT producing slightly better results for the reduction of visceral fat loss - the body fat around your middle. Now before you ditch your LISS class schedule, there is an ‘after burn’. Known as the Excess Post-exercise Oxygen Consumption (EPOC) or the oxygen debt, this keeps our metabolism elevated from 15 minutes to a whole 48 hours after high-intensity exercise.
The reason, is that our body needs to fulfil three basic tasks: metabolise additional nutrients, refill energy stores, and replenish depleted oxygen in the blood and muscles3. Within the study, this didn’t equate to significantly different
outcomes between the two test groups.
WHO’S THE WINNER?
Over the years, I have found that there is actually a place for both methods of cardio which will elicit fantastic results: in fact, it’s my secret weapon against body fat with my personal clients. Now here is where the science gets really geeky!
If you know anything about your body’s energy pathways - anaerobic (HIIT) or aerobic (LISS) - then you’ll know that
you body preferentially uses different substrates to supply it with energy depending upon the demands. In activity
lasting longer than 10-12 seconds and up to two minutes (your typical sprint interval in HIIT), the glycolytic system is
largely responsible for energy supply. Just as the word suggests, ‘glycolytic’ refers to using muscle glycogen or, in
layman’s terms, your stored carbohydrates as fuel. If an activity lasts longer than two minutes (yes, here comes
LISS) then your oxidative system kicks in, and it uses a combination of muscle glycogen, intramuscular fatty acids, free fatty acids and amino acids for fuel3. Now that sounds a little more like it!
Perhaps the reason that HIIT cardio alone doesn’t have the expected benefits on fat loss that we have all been led to believe, is that high intensity exercise produces lactic acid. And that burns!
Lyle McDonald, author of the Stubborn Fat Solution, explains that high levels of lactic acid in the blood traps fat in the fat cells. As we know, fat is not the preferred energy substrate during high intensity exercise. But, a few minutes after HIIT ends, there is a big dump of fatty acids into the bloodstream - and this is where LISS is your hero mopping up the fat and using it for energy.
So, how do we ‘out smart’ this dilemma and potentially get the best of both worlds? McDonald suggests taking a short break of approximately five minutes (to allow for the fatty acids to be released into your bloodstream and reduce heart rate into your ‘fat-burning zone’) after your HIIT intervals. Then, complete a steady cardio workout, which will put you in a better metabolic position to burn off the mobilised fat stores.
Now, before you run out the door to get your HIIT/LISS er, hit, let me give you a few important caveats here. If you are a beginner with very little endurance, then chances are starting out with HIIT could be a little ambitious. Work up to it instead. HIIT can also mess with your recovery, so aim to do no more than three sessions per week. If you are already
fatigued or following a lowcarbohydrate nutrition plan, then be smart and stick with LISS or, at the very least, lesstaxing
HIIT knowing that you are starting out with impaired muscle glycogen before you even hit the treadmill.
So whilst the jury may still be out and the cardio war continues over which is best for burning body fat, you can comfortably sit on the fence and say - both!
Your Secret Weapon Protocol
- 5-10 minutes easy warm-up
- 10-15 minutes HIIT interval training as outlined above
- Complete rest 5 minutes (perfect time to stretch or re-fill your water bottle)
- 20-40 minutes LISS aerobic activity at 60-70% MHR
1. S. E. Keating et al (2014), ‘Continuous Exercise but Not High Intensity Interval Training Improves Fat Distribution in Overweight Adults’, Journal of Obesity, Volume 2014, Article ID 834865.
2. K. Hottenrott, S. Ludyga and S. Schulze (2012), ‘Effects of high intensity training and continuous endurance training on aerobic capacity and body compositon in recreationally active runners’, Journal of Sports
Science and Medicine 11, 483-488.
3. J. Berardi and R. Andrews (2010), ‘The Essentials of Sport and Exercise Nutrition’, 126-130.
4. L. McDonald (2008) ‘The Stubborn Fat Solution’, 71-72.