Cardio vs. Bulking - Friends or Foes?

My interest was sparked after a conversation with my husband this morning. I made a comment to him that if he wants to build muscle he shouldn’t be doing a lot of cardio as well, because I had read in quite a few articles that cardio (aka: fat burning) and bulking (aka: muscle building) don’t go too well together. However when I tried to explain to him why that is, I had trouble. I stumbled over my words, and I couldn’t really put together a solid reason. That’s probably because the articles I’ve seen that information in were, well, less than credible, and they didn’t provide a solid reason either. Rather than being backed by fact, the idea that cardio and bulking don’t mix seems to be more of a myth. It's this common fear that doing cardio is going to eat up all your muscles.

“It is widely believed today that endurance training, also know as aerobic exercise or cardio, can interfere with your strength and muscle gains. In fact, there has been so much aerobics-bashing in the fitness and strength training community in recent years that debates between pro-cardio and anti-cardio camps sometimes get heated,” says Tom Venuto in his 2012 article.

Unfortunately, though, I took the myth to heart, and I cut my cardio wayyy back as a result. I wanted to build, so I figured I needed to spend less time on the treadmill. Rather than doing a steady amount of cardio, I limited myself to either none at all or once/twice a week for about 10 minutes at a time. My assumption is that if I got this impression from reading those fact-less articles, and I’m not entirely uneducated on the subject, then I must not be the only one.

So, I decided to do some research…

Like I said before, this idea that cardio squelches muscle gains is a myth. (My own personal opinion is that this myth grew out of the fear of overtraining with cardio.)

The real truth seems to be that there is always room for cardio, albeit less room when you’re trying to bulk. After all, it’s absolutely great for heart health, it can help build stamina, and can work to increase metabolism. As Brian Pronger points out in his book, Body Fascism, “…an increased capacity to metabolize fats, a high energy source, is the result of a combination of three factors – better cardiovascular function, which results from a rational program of aerobic exercise; greater muscle mass, which can follow from a program of resistance training; and a decreased ratio of fat to lean in body composition, which results from a combination of caloric restraint in diet, more aerobic activity, and increased muscle mass (which increases metabolism).”

Pronger makes the point in this statement that aerobic exercise (what we know as “cardio”) and resistance training to increase muscle mass work together along with caloric restraint (or dieting) to increase metabolism of fats (“fat burning”). They are not opponents, but rather team members, if you will. In this light, cardio and muscle building should not be treated as separate entities.

This piece of evidence speaks to the idea that cardio and resistance training are both effective and cohesive ways to burn fat. The message being that lifting won’t interfere with slimming down, but rather will help achieve that goal. However, when the goal is switched from fat burning/slimming to muscle building/bulking the question gets a bit more complicated.

Should I do cardio? How much at a time? What intensity? With what kind of frequency? Should I do it on the same days as my lifts, or should I alternate? …Sound familiar?

Well to simply answer this question I’ll say that moderate cardio can be implemented in reasonable amounts alongside resistance training. “…excessive endurance training  interferes with strength and especially power. However, several studies show that moderate amounts of aerobic training do not interfere with muscle size, as long as you don’t over do it. In fact, contrary to what the anti-cardio establishment says, there may be a syngery between strength training and cardio training” (Venuto).

Venuto’s article cites four different studies to support this claim. In the first three studies endurance training along with resistance training actually aided muscle growth, but in the last study, the opposite was true. [The article will be linked at the bottom if you're interested in the details.] So what was the difference?

The answer for that particular situation was the variable of recovery. In the study the muscle loss was found in the thighs, and it’s common sense that cardio mainly works the legs. Resistance training on the thighs was not followed by a long enough period of recovery before cardio began. This is what caused the decrease in muscle mass. While recovery is very important, it’s not the only thing that can cause cardio to interfere with muscle gains. As mentioned before, doing too much cardio can be detrimental as well.

As you might already know, resistance training stimulates fast twitch muscle fibers and endurance training stimulates slow twitch muscle fibers. The functions of these two different kinds of fibers, naturally, are different. Fast twitch fiber stimulation tells the body it needs to get stronger while slow twitch fibers tell the body it needs to increase stamina. Each type of stimulation results, again, in different physical adaptations within the body. “Therefore, your muscles are placed in a position of conflict when both types of training are performed — they can’t make the physical and metabolic changes you’re asking them to at the same time” (Venuto).  And, even further, high intensity cardio can actually cause fast twitch fibers (the ones you need to bulk) to take on the characteristics of slow twitch fibers; not good for builders!

And lastly; overtraining. Too much cardio is bad as well. Why?
Well, this goes back to the recovery issue… overtraining generally refers to “an imbalance between training and recovery,” and we’ve already said that lacking a sufficient recovery period can cause muscle loss or prevent further muscle growth.

So now the more detailed answer to all those questions; cardio? when? how much? how often?

For those looking to build muscle, you can safely do a reasonable amount of moderate intensity cardio along with your lifts IF; you do as many days, or less, of cardio as you do of lifting. What does reasonable amount mean? It means no more than 60 minutes (but I’d recommend between 25 and 45 based on personal experience) per session. If you’re going to do both exercises on the same day, do your lifts first! This will prevent your muscles from being already fatigued at the beginning a lift. And lastly, my own personal recommendation would be to never follow leg day with cardio. Your legs need time to recover that immediate cardio just won’t give them.

So it’s time to put the myth to bed and start using the treadmill (or whatever you prefer!) again… Cardio isn’t an enemy of bulking, and in fact, it can even help if done properly.

- - -

Sources used for this article:

Concurrent Strength & Aerobic Training: Does Cardio Interfere With Your Muscle Gains. Tom Venuto. 2012. Found at

Body Fascism:Salvation in the Technology of Physical Fitness. Brian Pronger. 2002. Found at