• Should You Do Cardio When Building MuscleAre you ‘doing cardio’ alongside weight training?
  • Is your primary goal at this time to build muscle?

If you answered ‘yes’ to the 2 questions above, it is my position that you are actually working against yourself. In this article I will put forward the case that adding extra cardio sessions on top of your weight training is analogous to driving your car with one foot on the accelerator and the other on the brake.

While you may be moving forward, you’re heading to your destination at a slower rate than you would if you would just take your foot off the brake.

First, let’s look at the reasons people are adding cardio on top of their weight training:

(1) To burn calories i.e. try to stay lean all year-round while they build muscle simultaneously
(2) Maintain or improve cardiovascular fitness while they bulk up.

I’ll be clear on my position from the outset here; there is no merit to either of these points.

So let’s now examine these in greater detail.

First of all, cardio is recommended when fat loss is the priority. However, as it is the intelligent thing to split your bodybuilding lifestyle into periods of bulking and cutting, the question is, ‘Should you maintain cardio throughout your bulking cycle?’

Many bodybuilders and personal trainers will tell you that it is a good idea, others will tell you it isn’t. I agree with the latter group.

If you want to maintain a lean physique while stimulating growth all year round, here’s how to do it:

(a) Eat a diet that provides no more than what you need for growth most of the time. Remember the 80/20 rule; if you do things right 80% of the time, you can afford to do them wrong 20% of the time.
Ideally, control your blood sugar (and therefore the release of fat-storing insulin) by living a low-medium glycemic load lifestyle. This is the diet you need.
(b) Doing things wrong 20% of the time will lead to gradual fat-gain. Counter this with infrequent MuscleHack-style mini-cuts.

This is a MUCH better way of staying lean year-round.

Bear in mind that cardio isn’t as effective as you might think. When you hop on a treadmill, it will at least ask you to input your weight, this is for a specific reason: it’s calculating your resting metabolic rate (RMR).

This is important to understand because when you’ve finished your session and see ‘400 calories burned’ on the reader, this is 400 total calories INCLUDING the calories you would have burned just lying on the couch.

If your RMR was 1900 and you spent an hour burning that 400 calories, you really burned about an extra 320 calories, not 400. Eat an average chocolate bar and you’ve undone an hour’s work in 5 minutes.

We didn’t evolve to burn calories very easily. If we did, we probably wouldn’t be here right now. Our ancestors would have died of starvation during long periods without food because hunting would have expended mega-calories.

The fact that the body doesn’t burn calories very easily was a big plus for our ancestors but a big pain in the ass for modern man; we live in a society of food surplus where high-calorie snacks are never far away. For evolutionary reasons, our body will want to store this excess energy as fat for times of food scarcity that never actually come.

Check out this calculator by ‘Runner’s World’ magazine – https://www.runnersworld.com/cda/caloriecalculator. According to it, a 160lb man would need to run 29 miles to burn a single pound of fat! Wouldn’t it just be easier to not eat it in the first place?

We are always somewhere between the polar ends of anabolism and catabolism. From the perspective of the guy who wants to build muscle, (and be in anabolism as much as possible) all that running tips the scales more in favor of catabolism and must be seen as a NEGATIVE.

Let’s have a closer look at this anabolism/catabolism thing…

To understand this, you first need to understand the way in which the body builds muscle.

A bodybuilding workout does NOT build muscle, it just STIMULATES the body’s own growth machinery into action. So once you’ve stimulated growth with a workout that represented a progression and was of sufficient intensity, a 2 step process begins:

  • Recovery
  • Overcompensation (growth)

Your body will not build a gram of new muscle until it fully recovers that which was lost in the workout. This is important: Only once the recovery process is completed can your body then OVERcompensate.

Simple logic would dictate that ANYTHING that makes the recovery process longer is not good if your goal is to increase the total mass of muscle on your body.

The shorter the recovery, the quicker you get into ‘growth mode.’

Some may think that only further weightlifting (and especially working the SAME muscle group) will eat into recovery but that’s where another popular misconception lies.

As Dr. Doug McGuff puts it, “Mechanical work is mechanical work”. What is it that is actually providing the stimulus to the aerobic pathway that so many want to improve with extra cardio sessions? Answer: Mechanical work by the MUSCLES.

Since ANY mechanical work (of at least moderate intensity or higher) beyond that which is required to stimulate growth in muscle mass eats further and further into recovery and therefore prevents overcompensation, cardio is a bad idea from the perspective of the bodybuilder.

Basically – any extra work, cardio or otherwise (since it is ALL mechanical work), actually prevents you from building mass at the rate that would be possible for you if you would just rest and let the body do what it does all by itself. By all means, be Mr/Mrs.Intense in the gym and stimulate growth, but once you’ve done it, leave the body ALONE to RECOVER and then GROW. After all, you don’t keep picking at an open wound and hope it’ll heal faster, do you?

Now, are you ‘doing cardio’ for maximum improvements to your cardiovascular system? That is, do you want to be fit as well as muscular?

If so, cardio is STILL a bad idea.

A study at McMaster University, Canada, (published in the June 2005 edition of the Journal of Applied Physiology) showed that just 6 minutes of high intensity exercise, 2 to 3 times a week, was very effective in improving aerobic fitness. [1]

The study subjects’ endurance increased by almost 100%. This was in contrast to the control group who participated in jogging, cycling, and aerobics (though not in any structured manner), whose endurance did not improve at all.

The high-intensity group “showed a significant increase in a chemical known as citrate synthase, an enzyme that is indicative of the tissue’s power to use oxygen.”

The group that achieved such improvements were using a 30-second sprint protocol. Remembering that this is simply mechanical work by the muscles, high-intensity weight training will yield the same, if not better, result. In fact, after some sets, like deadlifts to failure, I’m more wiped than anything I could achieve with HIIT training on a bike or treadmill. Also remember that it is not desirable to do BOTH from the bodybuilder’s point of view for reasons stated above i.e. full recovery THEN growth.

Now, could weight-lifting, an anaerobic activity, benefit the aerobic pathways MORE than cardio/aerobics?

Sounds counter-intuitive but let’s have a closer look. When we talk about improvements to the cardiovascular system, we are really taking about are metabolic adaptations within the cells that the cardiovascular system supports.

It may seem surprising to you that it is actually during recovery from weight training/anaerobic activity that the aerobic system reaps benefits at least equal to, and often greater than, steady-state cardio/aerobics.

This will require a quick look at cell metabolism…

Step 1Anaerobic metabolism in the cytosol portion of the cell turns glucose into pyruvate

Step 2 – Pyruvate is then moved into the mitochondria where it is aerobically metabolized to become 36 molecules of ATP (adenosine triphosphate)cell metabolism

Step 3 – Glycolysis (step 1 above) only produces 2 molecules of ATP but, importantly, cycles MUCH faster than the Krebs cycle/respiratory chain (step 2) which produces 36 molecules of ATP.

Step 4 – When involved in high-intensity training, like lifting to failure, you turn the glycolytic cycle (1) and produce pyruvate faster than it can be used by the aerobic cycle (2).

Step 5 – As the ‘excess’ pyruvate builds up it is converted to lactic acid, explaining why you ‘feel the burn’ during your workouts.

Step 6 – It is only through this type of intense, anaerobic activity that you force the Krebs cycle (aerobic) to turn as quickly as possible to deal with the large intake of pyruvate into the mitochondria. Jogging, running, rowing etc. are just not as effective for this.

Step 7 – Additionally, when recovering from intense muscular contractions, the lactate that builds up is then converted back into pyruvate which then has to be aerobically metabolized. Yes, this means that your aerobic system is stimulated while you rest and recover from lifting weights. This is no small thing; the aerobic system works at its highest level when recovering from lactic acidosis. You are indeed getting much ‘fitter’ by working with weights and recovering from the same.

So, so much for the people who repeatedly accuse muscular guys of being unfit because they don’t ‘do cardio.’ Also remember that through progressive overload we are growing stronger all the time. Since the musculature is being served by the aerobic system, improvements in muscle strength and size will also result in upregulation of the aerobic system.

“But Mark, I want to burn fat and stay lean while I get big”

Aside from the above points about simply controlling caloric intake, intense weight training (or emergency situations) will mobilize stored fat by activating hormone-sensitive lipase. HSL releases these fatty acids which are then transported to the muscles; beta oxidation forms 35 molecules of ATP from them. This is unique to emergency situations and high-intensity muscular work that calls into play our powerful type 2b muscle fibers – an event well catered for in THT training.

I hope this article illustrates for you the inferiority, needlessness, and, in fact, counterproductivity of adding aerobic sessions on top of weight training when building muscle is your main priority.

Having said that, there is more to this topic that will further convince you if you aren’t already. I would consider the expert in this field to be Dr. Doug McGuff who has developed a system of total fitness (not predominantly muscle building) based solely on intense muscular contractions; no cardio/aerobics whatsoever. He refers to it as ‘Global Metabolic Conditioning.’

If I could summarize; if you’re ‘doing cardio’:

  • To burn calories – Just don’t eat them in the first place
  • To keep  fit – You are already ‘keeping fit’ with weight training; the added aerobics is counterproductive when we understand the processes of inroading and overcompensation.

Take Care. Your Buddy,


[1] https://edition.cnn.com/2005/HEALTH/06/06/sprint.training/index.html

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