Cardio. Fast and short or Long and Slow? What’s the best option?

Cardiovascular exercise is any activity that raises your heart rate for an extended length of time, in order to improve your heart and lung function. It also has several other health benefits such as improved mood, decreasing blood pressure, and improving bone density to name a few.

There are a wide range of activities that fall under the umbrella of cardiovascular exercise. When we define them by their intensity, they are known as LISS (Low Intensity Steady State), or HIIT (High Intensity Interval Training).  There is also MISS, (Medium Intensity Steady State) which falls between the two.

Depending on who you speak to you may get conflicting responses as to what is ‘best’.  Do you have to go slow and steady to make sure you stay in the “fat burning zone”, as you’ll often see flashing up at you on the cardio equipment at the gym? Or do you need to jump around doing a hundred burpees in five-minute intervals to keep your body burning calories even after you’ve finished exercising?

Let’s look at some of these assumptions, and the pros and cons of each one.

LISS (Low Intensity Steady State)

Low Intensity Steady State exercise is any form of activity where you are moving at a moderate pace for a long period of time. This is usually walking, using an elliptical machine or the exercise bike.

The Claim: “LISS keeps you in the fat burning zone”

The Evidence: Depending on the intensity and duration of the exercise you’re doing, your body will either use fat or carbohydrates, or a combination of them as its main fuel source. When you are at rest or performing lower intensity exercise, your body does predominantly use fat as fuel.  Through the process known as lipolysis, fat stored in your fat cells is converted to energy via fatty acid (beta) oxidisation.

Basically fat gets moved out of the fat cell for energy use. This sounds great. Now you never want to get your heart rate up ever again so you can stay in that fat burning zone and melt all the fat away! Not so fast. That is just the short-term acute response. Your body is constantly moving fat in and out of its cells throughout the day, depending on your energy requirements.

If by the end of the day you’ve eaten a bit more, or were more sedentary than usual, any extra fuel will still go back to being stored as fat in the adipose tissue.  Fat loss is just dependent on being in a consistent energy deficit over time. You could therefore achieve the same goal by doing any mode and intensity of exercise if it results in helping to keep you in an energy deficit.  So whilst it may burn fat whilst you’re doing it, the net result will only be fat loss if your overall energy expenditure is more than your intake.

The Negatives
LISS is very time consuming, taking an hour or more in most cases.  It can also get rather boring.  Additionally, as it is so low impact, it’s not the optimal choice for increasing your heart and lung capacity compared to the other variations.

The Advantages
LISS requires pretty much zero skill, is very easy to do, and has a low injury risk.  This makes it ideal for beginners.  It’s literally a walk in the park.  Because it is low impact in nature, it is also suitable for those who have joint issues and may struggle to perform more dynamic movements.

Fitting it into your life is easy to do and can quickly become a positive habit.  For example, all you need to do is take the dog for a longer walk, go for a cycle ride with friends, or walk to get your shopping instead of drive.  You don’t even need to change into your gym kit.

On the other end of the spectrum, it is also popular among those who weight train for sports such as powerlifting, weightlifting, or for aesthetics like bodybuilding.  Because the main source of fuel used is fat, it enables their muscle glycogen stores to be reserved for heavy resistance training. It is a mode of cardio that can contribute to their overall activity levels, with minimal negative effects on their training.

HIIT (High Intensity Interval Training)

High Intensity Interval Training is where you perform short bursts, of traditionally sprints lasting anywhere between 10 seconds and a minute with short rest periods in between.  It is usually performed for no more than half an hour in total.

The Claim: “HIIT means you keep burning calories all day even once you stop exercising”

The Evidence:  This afterburn affect is known as EPOC (exercise post oxygen consumption).  It is the increased rate of oxygen consumption after you do strenuous exercise. This means that you burn more calories even once you stop exercising, compared to a lower intensity mode.  And it’s true.  This does happen.  But the effect is not as impressive as is commonly made out to be.

Depending on how strenuous the workout is, EPOC would only comprise 6-15% of the net total oxygen cost of the exercise.  For example, if you burned 400 Kcals in your workout, the afterburn would only account for an extra 24 – 60 calories. Given that HIIT style workouts usually only last for up to half an hour, the total calories burned compared to an hour of LISS are probably about the same.

The Negatives

HIIT requires you to work at maximum capacity for short periods of time.  If you’re new to exercise you would probably only be able to sustain this level of intensity for less than the recommended number of minutes in total. Given that many HIIT protocols involve moves like burpees and jumps, it isn’t the best option for those with joint issues.  Additionally, because it is quite taxing, psychologically it may be harder to stick to over the long term.

HIIT primarily uses carbohydrates for fuel.  If your focus is building muscle and getting stronger then doing frequent HIIT sessions may compromise your performance and ability to recover.  However, a study by the American Counsel on exercise found that it actually improved strength outcomes.  It is worth noting that the study was done on a small number of subjects over a short period of time, and they had not engaged in any previous weight training for the past six months.  The same results may not be shown for more experienced lifters. If you weight train and want to include some HIIT, just don’t overdo it and maybe stick to one or two sessions per week to ensure you can properly recover.

The advantages

HIIT is very time efficient, needing only about 20-30 minutes to complete, and you can in theory burn the same number of calories as a longer slower cardio session.  You don’t need any equipment to do it, and you can perform a variety of moves which may help if you get bored easily.  It has also been reported in some instances that HIIT can help curb your appetite if you are trying to manage your hunger.

Decisions Decisions

So does it matter which one you do? Not really.  We know including a form of cardio is a good idea for your health and weight management, but there is no stand out “best” option.  It will depend on the amount of time you have, your experience, and your goals.  Try a bit of everything and see which one works for you. Maybe it’s a bit of both, or something in between (medium intensity steady state).  Whichever you chose, try to enjoy it, don’t abuse it and find a way to continue with it over the long term.


FreeGym Blogger Legend. Personal Trainer at Fitology. Powerlifting Level 1 Coach.

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