Does Cardio Burn Muscle Mass Or Fat? Don’t Be Scared Of Doing Cardio!

I’ve been asked a few times now if I’m worried about losing muscle from doing cardio. To be honest, I’m really not. Yes, you can burn muscle from doing too much cardio, but you can also not burn muscle. It really just depends on how much you do and how you do it. So in reality, the answer is no, cardio does not burn muscle; training in an incorrect way is what burns muscle.

Does Cardio Burn Muscle or Fat?

After documenting my results of doing eight straight weeks of consistent cardio training on, I’ve been asked many different questions regarding muscle loss vs. fat loss. My overall reply is that I’m usually not too concerned because I don’t over-train or under-eat. In this article, I want to go into a little more detail.

Since this post isn’t about the benefits of cardio I won’t go into detail on that, but I am a fan of cardio. I feel that it is a good way for those of us who have desk jobs or are stationary for the majority of the day to get in some quality exercise. Lifting weights is good, don’t get me wrong, but getting your heart rate up, sweating a bit and doing some good ole’ cardio is good too. I personally don’t fall into the crowd who thinks cardio is dead. It may not be necessary to get in shape, but it certainly isn’t ineffective either.

When Does & Doesn’t Cardio Burn Muscle?

There are many different types of cardio. Some cardio is considered better for burning fat, some for increasing your lactate threshold and there is even some cardio designed for burning muscle. Overall, cardio can be a very powerful tool when used correctly. The so-called phenomenon around cardio burning muscle is more of a result of poor diet and/or over training than the type of exercise itself.

There are three situations where your body will burn muscle:

  1. Muscle is the only source of energy available
  2. You are not consuming enough protein
  3. Over training

Believe it or not, these shouldn’t be taking place too often. Whenever you exercise (or do any type of physical activity) your body has a pattern it follows. First, you burn carbs, then you burn fat and THEN you burn protein, which is what causes muscle loss. So it’s not the cardio that burns muscle, it’s the lack of proper diet and/or rest that burns muscle.

Where’s the proof?

There are quite a few studies that show muscle loss is a result of poor nutrition, extreme circumstances and just downright improper training. In addition to these, there are many that prove cardio to be very effective at burning fat, not muscle.

Take for example a study that was done back in 2009. In an in-depth evaluation of 22 runners, there were 15-17 exams done on each runner that proved the effectiveness that endurance running had on fat loss. In this study, the runners were tracked as they ran 2,500 kilometers (just over 2,796 miles) from April 19 to June 21, 2009. The results of the study …

“… showed that runners lost an average of 5.4 percent body volume … most of which was in the first 2,000 kilometers … Loss of muscle volume in the leg averaged 7 percent.”

You might be thinking, “but hey, that says right there that they lost 7 percent of their muscle.” Well, not quite. There are a few things we need to look at.

First, they lost ZERO muscle from their upper body. Again, these runners lost no muscle from their arms, shoulders, back, chest etc. What these runners did experience was muscle loss in their legs only. Why? Because they were over training.

So you can see why looking at a study like this and then saying cardio burns muscle would be crazy. Yes, if you run 43 miles everyday for almost two months, yeah, you’re going to lose a bit of muscle! But, does cardio burn muscle? No, it’s not cardio that’s burning muscle.

Unfortunately though, there are many who bash cardio for one reason or the other. Some feel it isn’t a cool enough form of exercise while others may feel that it is simply a waste of time. Don’t fall into that trap.

Cardio is a great form of exercise and it’s actually good for you. Not only does it NOT burn muscle, it aids in the muscle building process. That’s right, cardio actually helps you build muscle. Cardio can increase circulation to the muscle and that will increase the amount of nutrients as well as the time it takes for these nutrients to get to your muscles.

As long as you get enough protein … maybe not even as much as you think you need, do some sort of strength training and don’t run 43 miles everyday for two months you really don’t need to worry about cardio burning muscle.