Cardio is healthy: it improves your overall and specifically your cardiovascular health. Cardio training also improves your fitness, so that you recover faster between sets during your strength training. In addition, cardio can contribute to (permanent) fat loss. Enough reason to do cardio, but don’t fall into the following pitfalls.

1. THINKING CARDIO IS JUST AS EFFECTIVE FOR FAT LOSS AS DIETING

While an active lifestyle is undeniably important for health, it is not necessary for fat loss. Whether you lose fat depends on your energy balance: how many calories you ingest in a day minus the amount of calories you burn. And what you burn with cardio is disappointingly little: 30 minutes of cardio training burns an average of 200-400 calories, depending on your weight and intensity. That’s the equivalent of a single sandwich or a Snickers. It is much easier to eat calories than to burn them. For fat loss, it is therefore much more efficient to not eat something than to do cardio.

Even worse, research shows that cardio fat loss is on average 20-50% lower than you’d expect. On the one hand, this is due to compensatory eating, something that happens subconsciously when you do a lot of cardio. Cardio makes you hungry after all. On the other hand, there is metabolic adaptation: if you do a lot of cardio, your body adapts its energy expenditure, probably mainly by cutting back on spontaneous movements (NEAT). As a result, the net number of calories you burn with cardio is a lot lower than you calculated. This is known as the constrained energy expenditure model, a phenomenon that occurs especially strongly in people who are already quite lean while doing a lot of cardio, especially LISS (Low Intensity Steady State).

All this doesn’t mean you shouldn’t do cardio for fat loss. But the foundation of fat loss should be a calorie-restricted diet. Cardio is an excellent addition to this, which ensures that you do not have to cut the calories as deeply and is also healthy. In addition, research shows that people with an active lifestyle maintain their weight more easily after dieting.

The bottom line is that you shouldn’t have too high expectations with regard to cardio for fat loss.

2. BAD CARDIO TIMING AROUND STRENGTH TRAINING

As a strength athlete, you need to time your cardio sessions smartly so that they interfere as little as possible with your strength training. In any case, don’t do cardio immediately before your strength training (except for a short warm-up cardio): research shows that it comes at the expense of your strength and that your training performance can be negatively influenced for up to six to eight hours after the cardio. It is therefore wise to do your cardio after your strength training or, even better, on another day or during a different part of the day.

Separating cardio and strength training becomes more important the more advanced you are as a strength athlete, because the so-called interference effect, the ‘competition’ between aerobic and anaerobic training, becomes greater.

3. THINKING HIIT IS MORE EFFECTIVE

Provided: the best form of cardio is the one that you find most comfortable and can therefore best sustain. But what if you can’t choose?

We distinguish three types of cardio: LISS (Low Intensity Steady State, such as walking and cycling), MISS (Moderate Intensity Steady State, such as jogging, running and rowing) and HIIT (High Intensity Interval Training, where you work for 20-40 seconds for example high-intensity training followed by 2 minutes of low-intensity training). HIIT is often thought to be the most effective for fat loss. But is that really so?

HIIT is a useful tool to burn a lot of calories in a short time and thus also improve your cardiovascular fitness. In addition, HIIT has a large afterburn effect, officially Excess Post-exercise Oxygen Consumption (EPOC).

Now it is true that HIIT results in the largest EPOC, but the effect is much smaller than many people think. For example, see a study comparing EPOC after half an hour of continuous running with half an hour of 70% VO2 max with an interval session, namely 20 sprints of 1 minute each at 105% VO2 max followed by 2 minutes of rest. The EPOC of the interval group was approximately 69 kcal. That was admittedly twice as much as that of the continuous group, but you don’t get much from it calorie-wise.

In addition, HIIT requires much more from your recovery than LISS and MISS. As a bodybuilder in a heavy cut you can’t really afford that.

Coach Jackson Peos  therefore concludes that HIIT is often incorrectly called ‘anabolic’. HIIT is a useful tool to burn a lot of calories in a short time and thus improve your cardiovascular fitness. On the other hand, LISS/MISS burns calories less quickly and builds up cardio fitness, but has the advantage that it requires much less recovery. And the latter can be decisive, especially in a (heavy) cut. That is why we prefer LISS or MISS for bodybuilders in the cut.

4. DOING TOO MUCH CARDIO

Cardio kills gains is what bodybuilders often hear. And which they also like to hear, because it’s a nice excuse to avoid the cardio machines. The idea behind it is that cardio raises levels of the stress hormone cortisol, and cortisol is catabolic. In addition, we have already seen that there can be an interference effect if you do cardio in addition to strength training: the training forms ‘compete’ each other when it comes to recovery.

While both arguments are not false, we should not exaggerate them. A healthy body can take something and for an average person it should not be a problem to do cardio in addition to strength training. However, you have to do it in moderation. Especially during a (heavy) cut, too much cardio can thwart the goal of your strength training, namely muscle maintenance.

How much cardio can you do? We already saw in mistake 1 that you should not use cardio as the main means for fat loss, but as a supplement to a calorie-restricted diet. As mentioned, do no more than two or three HIIT sessions per week of 15 to 30 minutes each. Or do up to five LISS or MISS sessions per week of 20 to 40 minutes each. That’s what many coaches recommend to avoid the negative effects of cardio.

5. THINKING FASTED CARDIO LEADS TO EXTRA FAT LOSS

It’s traditionally something bodybuilders do: fasted cardio, or cardio on an empty stomach, usually (early) in the morning, before breakfast. The idea behind this is that, deprived of food, the body must use body fat as an energy source. But while you do indeed burn more fat during that cardio session, that doesn’t mean you will lose more fat. Because if you burn a relatively large amount of fat during your cardio, your body will use a relatively large amount of glycogen (carbohydrates) as an energy source at other times, as research shows. Viewed throughout the day, for fat loss, it doesn’t matter which energy source you use more on one than the other. This is about the difference between fat burning and fat loss.

Doing cardio on an empty stomach may even have drawbacks. In the early morning, even more of the muscle-destroying cortisol can be released than with cardio at other times of the day. In addition, you can train less intensively on an empty stomach and therefore burn fewer calories.

That fasted cardio does nothing extra for fat loss is shown in two meta-analyses, from 2017 and 2021, of a total of 28 scientific studies.

Is cardio on an empty stomach prohibited? Not that either. As long as you do it in moderation, just like other forms of cardio. If you like pre-breakfast cardio best, then you should do it, because the most important thing is that you can stick with your cardio over the long term.