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July 7, 2023

Does Cardio Ruin Your Muscle Gains?

In today’s blog, we are going to cover the current up-to-date research if cardio ruins your strength gains. We’ll discuss these three points: 

1. At what point cardio might actually ruin your strength gains? 

2. When cardio might be beneficial for you to add in to your weight training?

3. What are some best practices to get the most out of both weight training and cardio?

My name is Annie Miller, and I help you learn as you train and enjoy your lifts. Today, that involves getting to the facts about cardio and weight training and ultimately answering…

Can you do both and get the results that you want?

Watch the video version of this blog post here:

Dispelling the Myth About Cardio and Muscle Definition:

Now, I don’t know how many women actually are concerned about cardio ruining their Hypertrophy. But I do think that a lot of women think cardio is the only way to look muscular or lean or to lose body fat, and that’s also not the case.

So let’s just bust that myth right there…

If you want to look toned, which is to have the appearance of muscle at rest, you need to acquire muscle mass and you also need to have a decently low amount of body fat in between that muscle mass and your skin. 

Cardio is one way to expend extra energy and burn calories.

It does not inherently burn fat more than any other mode of exercise. If you would like to burn more calories, by all means, implement cardio into your exercise regime. If you enjoy a form of cardio, do it. 

Whether that is going to affect your Hypertrophy or Strength Gains is what we are going to cover in today’s blog. 

Balancing Cardio and Strength Training:

We can create a spectrum if we look at maximal strength or maximal muscle gain on one end and endurance in the form of cardio on the other.

I would argue that for most people partaking in concurrent training, which is some sort of cardio and strength training, you can benefit from both, but you likely won’t be able to maximize either. 

Now, that is not to say that one automatically takes away from the other, it’s just to say that the body simply adapts to whatever stimulus we give it. So if your goal is to put on as much muscle mass as possible and you add in a bunch of endurance training, that endurance training at some point is going to impede on the adaptations that you’re attempting to drive through that strength training. 

The caveat here is that in order to adapt from mainly the strength training side of things, that actually has to do with your recovery and nutrition. If you’re taking in adequate amounts of macronutrients and total calories to where you are not in a deficit, you can likely increase your endurance and still make those muscular gains that you want from the strength training.

If cardio is driving you into a caloric deficit, you are potentially impeding your hypertrophy. 

Back to that spectrum, again, I would argue that if you are training somewhere in the middle, you’re probably fine. The sport of CrossFit has shown us that you can push that bell curve out in both directions very far. Much further than the average gym goer. 

If we increase the cardio and move towards that end of the spectrum, you may start to see plateaus in strength gains and your ability to put on muscle mass because you are beginning to train in a more aerobic manner. 

But again, I presume that you can push a lot further than most people think. Most of us should add in cardio in addition to strength training because cardio is generally good for your health.

This article literally proves my point: 

The background of the study states both Whole Muscle Hypertrophy does not appear to be negatively affected by concurrent aerobic and strength training, compared to strength training alone. 

However, there are contradictions in the literature regarding the effects of concurrent training on Hypertrophy at the myofiber level. Research shows that if strength training is your primary focus, you want to ideally separate your Strength Training from Cardio. 

The cardio can be a steady low-intensity state, or it can be high-intensity. As stated, there is research that supports both and also argues that both impede strength gains. 

One argument is that high-intensity exercise may increase cortisol and have a higher central nervous system demand. Therefore, fatigue is a negative side of things, making it harder to recover from. But also that it trains the muscles in more of a lactic manner, which could favor type two muscle fiber development.

And on the low-intensity side of things, there are benefits to increasing your overall mitochondria and capillary density within the muscles. This is great for overall fitness, but also that you are training in an endurance manner, which is counter to strength training. 

My point is, there are arguments to be made on both sides. 

This Systematic Review done in 2022 looked at actual individual muscle fiber types – type 1, type 2 and 2b and how they are affected by concurrent aerobic training and strength training compared to resistance training alone. 

Here are three key points from this meta-analysis: 

What I think you can take from that is to do whatever form of cardio you enjoy, separate from your strength training if you have that luxury. If you do not have that luxury, then do your strength training FIRST, and tack on your conditioning at the end of your street training. 

Experiment with what feels best for you. 

As far as FORM of cardio, perhaps running and its eccentric load is not the best for retaining muscle mass. Is this something I think you should lose sleep over if you enjoy running or if it is the only form of cardio you have access to? Absolutely not. 

Remember, the interference effect is small, if there is one. Don’t sweat it! Pun fully intended…

For time’s sake, you could add low-intensity cardio on upper body days if those tend to be quicker lifts for you. You can also tack on some short, high-intensity cardio at the end of leg day if that day tends to be a high-intensity training day. 

We just want to make sure that you are adequately recovering with sleep, hydration, protein intake, and rest between sessions. That way, you’re getting the benefits of BOTH the cardio training and the weight training.

My Personal Experience: 

I made a mistake in my early 20s of doing the stair climber aggressively before leg day. And I mourn the gains that I left on the table because of it. 

If strength is your goal, you do not want to enter a training session fatigued. Don’t make it more complex than it needs to be. 

Join the Discussion:

Do you incorporate cardio alongside strength training? Share your preferred cardio exercises and how you integrate them into your routine in the comments below.

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I'm an adventurous introvert from Vancouver, Washington who lives on sleep + "me time." I'm a lover of lifting weights, dinosaurs, real talk and traveling with my husband. I am here to help you move better, lift more, bust the myths of the fitness industry, and inspire you to love the process.

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