Cardio is very rarely anyone’s favourite thing.

But somewhere along the line we all agreed it was a necessary punishment we all needed to endure in order to “get fit.”

But let’s explore the things Cardio does and doesn’t do for us, and how we can use it best.


Myth#1 – The Gamification Game

Every cardio machine at the gym comes with a display where we can choose between resistance levels and programs, input our bodyweight, measure our heartbeat and calories burned. And it can be a great motivator to see how hard we are working. It’s gratifying to see that every agonising minute of effort is working away at the pizza we ate the night before, or the pizza we are promising ourselves afterwards.

However – these numbers can be far from accurate. The calorie counters are made to be generous, and don’t take into account all the additional support the cardio machines give us.

If we power walk or jog on a treadmill, it’s nothing like the brisk pace we can set outside, we aren’t propelling ourselves forward with the same momentum, but the calorie counter acts as if the movements are the same. In the same way, we might set a steep incline to make ourselves work harder, but then hold onto the support bar – of course we’ll burn less calories that way, but that’s not what the calorie counter will tell you. The counters are often not connected to heart rate monitoring, and if they are, we often need to hold onto the machine for it to be continuously measured, again making our workout easier but also less effective.

Studies have shown that the elliptical trainer is the least accurate at calorie counting, with most machines overestimating calories burned by 42%. Treadmills have been shown to reduce total calorie burn by 2-10%, while the extra support gained from leaning forward on a stair stepper can reduce total calorie burn by up to 50%.


Myth #2 – We have to do Cardio to lose weight

When weight loss is dependent on energy balance, we can still lose weight by the old adage of eating less and moving more.

Often cardio’s primary role is to offset a sedentary lifestyle.

There are countless ways to stay active or to train. But when it comes to losing fat, or aiming to change body composition we need to prioritise our diet and nutrition.

We should create a deficit from our diet first, and our training, second.



Myth #3 – More is better

When we want to improve our fitness we often turn to running. But continually hitting the pavement for long stretches each week can actually take us further away from our goals. Sustained and repetitive distance running will make our bodies more effective at conserving energy.

Our bodies always strive to become more efficient. So if we are running every day, we are sending our bodies the signal that we need to become more efficient at running. In response, our metabolic levels decrease in order to use less calories, and we can actually lose muscle since it is a very expensive tissue for our bodies to maintain.

That’s why we should limit programmed cardio sessions to two-three times a week.


MYTH #4 – Longer is better

Steady state and LISS (low intensity steady state) cardio, such as going for a long run, condition our muscles and our bodies to work at low intensity for longer periods of time. We might be using this in between resistance training a few times a week, where we are conditioning our muscles to work explosively under load for shorter durations. However, when our aim is to alter body composition, such as lowering body fat, we want to minimise physiological conflict that might arise from sending the body mixed signals calling for opposing or conflicting adaptations.

This is another reason we often want to limit cardio, and can opt for high intensity for shorter periods that more closely mimic the work pattern of a resistance training session.

The benefits of HIIT include:

  • Increased resting metabolic rate for upwards of 24 hours after exercise
  • Improved insulin sensitivity in the muscles
  • Higher levels of fat oxidation in the muscles
  • Increase in growth hormone levels (which aid in fat loss) and catecholamine levels (chemicals your body produces to directly induce fat mobilisation).

These metabolic boosts can be seen from just 25-30 mins of high intensity interval training, and can result in far greater fat loss over time than doing stead-state cardio alone.


MYTH #5 – Fasted is better

We are all familiar with the concept that by doing fasted cardio first thing in the morning we will tap into fat stores. However, we also need to consider that without adequate fuel for our workout our bodies will first use carb and fat fragments in our bloodstream, rather than the fat cells around the body. Doing intense cardio in a fasted sate can also mean we become hyperglycemic and dehydrated, resulting in a drop in intensity where we can feel as if we are working far harder than we actually are.

While fasted cardio increases the proportion of calories burned from fat during exercise,  the total number of calories burned decreases according to our level of exertion. So if we have less fuel or energy to workout, it feels much harder even if we are working out less intensely.


Our bodies have a set order in which they use nutrients for fuel:

  1. Blood glucose
  2. Stored carbohydrates (muscle glycogen)
  3. Stored body fat
  4. Stored body protein (muscle)

That means when we exercise in a fed state, with readily available carbs, the body will burn those carbs over body fat. While if we exercise in a fasted state such as when we wake up in the morning, the body will use dietary fat and then stored body fat for fuel. However, research has shown that the body compensates for an increase in fat burning during fasted cardio with a decrease in fat burning during the rest of the day. Those that train fasted burn more fat during the workout, but then burn more calories from carbs and less from fat during the rest of the day, while those who train fed burn more readily available carbs during their workout, and more fat for the rest of the day.

Fasted cardio doesn’t lead to greater fat loss than fed cardio – what seems to matter most then is the number of calories burned in total over the course of the day.


Other popular myths: “In order to burn fat you need to stay in the Fat-burning Zone”

Steady-state or lower intensity cardio sessions do burn fat as fuel, when we are in that “fat-burning zone” of 65% of our max. BUT we need to focus on overall energy expenditure. Since the more intense a workout session is the more total calories we will burn, especially when we consider the EPOC effect, where the bodies has to work harder for the rest of the day to come back to its balance, meaning we continue to burn calories for upto a 24 hour period post-exercise.

This means that we need to vary the lower and higher intensity sessions, since high intensity is very taxing on the body.


“We should do Cardio BEFORE Weights”

The order in which we do cardio or weights matters less, and the intensity in which we do them matters more. If we are doing a cardio session then going into a resistance workout straight after, we aren’t going to have the same intensity as if we just focused on one. So we should separate or alternate our high intensity cardio days and weight training days to ensure we are training hard for both.

Lower intensity cardio could be beneficial AFTER a heavy weights session, when we consider that cardio can help the body repair muscle damage faster by increasing blood flow. By doing a cardio session after a heavy leg day, or going on the rowing machine after an upper body session, we could reduce soreness the next day, by allowing the body to remove waste products like lactic acid from the body quicker, and recover quicker.



  • We should rely less on calorie counters on cardio machines, and focus more on the intensity of the cardio we do.
  • HIIT cardio sessions result in more fat loss in less time than steady state cardio
  • However HIIT can be very taxing on the body so should be limited to 2-3 sessions a week
  • Fasted cardio alone does not burn more fat than fed-state cardio
  • We should use cardio alongside Resistance training in order to build more muscle and increase our metabolic rate, rather than opting for cardio alone.


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