Cardio is one of them subjects that gets more air time than it’s worth.
Firstly; if fat loss is the main objective, before thinking about cardio think about nutrition, then think about resistance training, then (further down the line) think about cardio.
Cardio is not the immediate answer for fat loss.
If we’re talking cardio for fitness, then that’s a different matter. To become fitter, we need better or more efficient cardiovascular endurance which enables us to perform better. Therefore cardio, for CARDIOvascular improvement is the main focus.
For the purpose of this article, let’s say we’re concerned about cardio and it’s relevance to fat loss; not performance.
One commonality; they both burn calories. So if we are just looking to get into a deficit, either method does that.
Okay; next – what are their differences?
Well, HIIT is high intensity interval training, so we are bringing the heart rate UP, then back down again repetitively. Whereas LISS (low intensity steady state) our heart rate (HR) remains consistent throughout. Typically you would do HIIT for shorter durations & LISS for longer durations in order to burn the same amount of calories.
So, what’s best?! Here’s my general rule of thumb – in the grand scheme of things it won’t really make a blind bit of difference or at least the difference will be marginal. Fat loss comes to calories in vs calories out HOWEVER and this is my only however, LISS is repetitive usage of low resistance movements. One thing we should be conscious of, is this may lead to mechanoreceptors depositing muscle mass. If we are already in a calorie deficit and now we are repetitively doing small, low resistance movements our bodies will literally think “why the hell am I carrying this muscle round un-necessarily” and it simply gives your body the go ahead to start depositing muscle – simply because it is deemed unnecessary and the stresses on your body aren’t intense enough to stimulate and uphold keeping it.
Now, if we use HIIT as a form of cardio (when on lower calories particularly at the final stages of a diet), we are using shorter bursts of explosive movements (more muscle required) followed by short rest periods. Not only does this reinforce the fact to our mechanoreceptors that we NEED to hold onto our muscle mass but it also burns the same amount of calories to enable us to chip away at body fat. This is the only time I personally would consider being more meticulous with cardio – don’t get skinny, get lean!