Can Cardio Burn Muscle? (Yes, Here's How)

It’s a common recommendation to hear within the fitness industry that if you’re trying to gain strength and size, then it’s best to leave the cardio behind.

Statements like cardio will burn muscle or cause you to become catabolic, is something that’ll probably leave people ignoring the treadmill to only pick up the weights. But what’s the truth?

Can cardio burn muscle? Yes, cardio can burn muscle but only if you’re not doing enough weight training or supplementing your workouts with a nutritious diet. Cardio doesn’t automatically burn your muscle. But it can burn muscle if you (1) do it too much, (2) do it before your weight training session, or (3) do ‘high impact’ cardio.

There are other factors involved as well so it’s important to look just beyond the equation that cardio equals muscle catabolism. Let’s dive into the research!

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A Brief Overview Of How to Gain Muscle

Before we get into how cardio burns muscle, we need to go over how muscle is built in the first place. If you know all about caloric expenditure, then you can skip to the next section. If not, then stick with us and we will give you a quick overview.

Muscle is built through a combination of a good diet and weight lifting. In the gym, lifting weights is what breaks your muscle tissue down to then prompt them to rebuild bigger than before. You need to stimulate your muscle growth through weight training. In the kitchen, the food you eat is what fuels this process as well, especially protein as protein is the building blocks of muscle. This is why making sure you eat enough protein is vital to gain muscle, though the other macronutrients (fat and carbohydrates) also are important and play an essential role in the body.

Now, building muscle means that you need to eat in a caloric surplus, that is, eating more calories than your body burns. This gives your body enough fuel for protein synthesis. You may find it quite challenging to build muscle without being in a caloric surplus. That being said, it doesn’t mean that if you’re in a deficit (eating fewer calories than what your body burns), you’ll automatically lose your muscle. Even when you’re eating in a caloric deficit, eating enough protein and lifting weights will help you at least maintain the muscle mass that you have.

SO, WHERE DOES CARDIO COME INTO PLAY?

Cardio helps burn calories, meaning that it’s been mainly used as a way to be in or maintain a caloric deficit. This is why it’s always associated with burning muscle; it gives your muscle fewer calories to play with. However, like we said before, this is not always true.

If you supplement your workouts, whether you’re doing cardio or not, with adequate weight lifting and protein, then you can prevent muscle catabolism which is the breakdown of muscle tissue to be used as energy. In saying that, there are some ways that you can minimize this as well, through the choices you make such as choosing what cardio to do and when to do it.

Check out our other article on What Cardio Should You Do When Bulking?

3 Ways Cardio Burns Muscle

First, let’s go through how cardio can burn muscle. These are the ways you may be including cardio into your workouts that can be hindering your muscle growth processes and encouraging muscle catabolism.

YOU’RE DOING HIGH-IMPACT CARDIO

High-impact cardio is cardio that requires both your feet to be off the ground at the same time. We’re talking about running, jumping, high-knees and all that jazz. While there’s nothing wrong with high-impact cardio, what it can do is impede your recovery which can cause your muscle growth to slow.

Part of the muscle growth progress is the rest and recovery time. In fact, it can be just as important as what you do in the gym. So cardio that is intense and hard on the body and joints like running, can make it harder for you to recover from your workout and be ready for your next training session. High-impact cardio has much more of an effect on your body than other forms of cardio so if you have other goals than just improving cardiovascular endurance, it may not be the best choice.

What to do instead:

A great idea is to switch to low-impact cardio that will still give you the cardiovascular benefits without as much negative impact on your body. Some options include cycling, either outdoor cycling or on the stationary exercise bike, the elliptical machine, the rowing machine and the ski erg, You can even try hitting the battle ropes for a low-impact, intense workout. Not to mention, swimming is the ideal cardio session for those who want to work their cardiovascular system without causing too much stress to your joints and muscles.

YOU’RE DOING CARDIO BEFORE YOUR WEIGHT WORKOUT

The order in which you complete your training session depends on your priorities and goals. For those who want to gain muscle and fuel growth, you need to do your weight training before cardio. If you do cardio before your weight workout, then you just might be hindering the muscle gains that you could potentially be getting.

Tiring yourself out with cardio before you even start lifting means that you won’t be at your full potential for your weight training. It can limit your performance and you may very well find that you won’t be able to lift as heavy or as many reps or sets as you can if you’re lifting fresh. This is particularly important because a key component of growing muscle and strength is progressive overload. You need to ensure that you’re constantly challenging your body and making them work harder over time. If you’re completing your cardio before a workout and subsequently, not able to lift as much as you typically would, then you won’t be able to progressively overload efficiently.

What to do instead:

Stick to lifting weights first thing and then complete your cardio after all the weight training is completed for the session. This way, you get the best of both worlds while maximizing your performance and hence, your results. And remember to always warm-up and cool down in every training session.

Not sure what to do when lifting weights? Try the FitBod app! FitBod will generate a training plan for you so you can get stronger and lift more.

YOU’RE DOING TOO MUCH CARDIO

While doing cardio is not going to cause too much detriment to your muscle gaining goals, doing too much can. You need to find a balance between cardio and weight training so that you can work on your cardiovascular endurance without it taking away from your muscle. So yes, doing too much cardio is common and is something you should look out for.

Here are some ways you can tell that you’re doing too much cardio:

1. You’re Not Gaining Muscle

The most obvious way to tell that you’re doing too much cardio is if you’re not seeing progress in your muscle growth. Though it has to be said, this is when your nutrition is on point—you’re eating enough protein and are in a caloric surplus to fuel the muscle gains. If it’s not, then try getting a hand on the nutrition side of things before contemplating on cutting down on your cardio. If it is, then you might have to eliminate some cardio workouts from your fitness routine to see more muscle gain because the excessive cardio could be leading to a breakdown of muscle tissue, which is the opposite of what you want.

2. You’re Feeling Sore

It’s normal to feel sore after a session, especially if it’s something that you haven’t done for a while. However, after a few days, the soreness should go away. Doing too much cardio can actually mean that you’re constantly feeling sore when you should be feeling better. If your joints are hurting and your body is aching, excessive cardio may be the culprit.

3. You’re Excessively Tired

Feeling fatigued is one thing, feeling constantly tired is another and that’s something that is a symptom of too much cardio. Cardio is great for our bodies but it does place stress on them. While our bodies can do amazing things, there’s only so much it can take at a time. If you’re getting sleep (or even struggling to sleep) an
d ensuring that you’re taking a couple of rest days a week but are still really exhausted, then it’s time to cut back on the cardio.

What to do instead:

Ease up on the amount of cardio you’re doing in your fitness routine. This may be going from 4-5 times a week to 1-2 times a week. Also, making each session shorter is a good idea. Keep your sessions to 20-30 minutes at a time to ensure that you’re not doing too much. Also, incorporate some of our other recommendations such as switching to low-impact cardio and you may find that it can make a big difference.

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How To Incorporate Cardio Into Your Lifting Routine Without Losing Muscle

Cardio is important to improve your endurance and get your heart pumping so if you want to keep cardio in your routine, that’s nothing wrong with that! Here’s the good news too—you can still do it without it impacting too much on your gains so you don’t have to give it up entirely. Alongside the suggestions we made above, here are a couple more ways that you can incorporate cardio and still keep your muscle (including one method that can actually help fuel that muscle growth):

1. WALKING

Now, don’t scoff just yet. Walking is a really great way to improve your cardio in a simple and low-impact way. Walking can actually make the biggest difference to your fitness and there are many ways that you can incorporate it into your lifestyle without changing your routine too much. Take the stairs instead of the lift and elevator and walk to and from work if you can. All these things contribute to something called non-exercise activity thermogenesis, also known as NEAT. It may not seem like much but when you add up all the small things you do day in and day out, it can make a big difference.

Start by setting a goal of walking a minimum of 10, 000 steps a day. If you find that you’re under your goal, then take that as a sign to go for the walk and enjoy the fresh air. The extra walking will do wonders to improve your cardiovascular system without impeding on your muscle growth.

Check out our article on the differences between HIIT vs LISS Cardio.

2. CONDITIONING

Try conditioning instead of cardio. While they are pretty similar in definition, it is the intention that causes a distinctive difference between the two. Cardio is a generic term used to refer to any exercise that gets the heart pumping. While conditioning can technically be classified as the same, the end goal is to utilise your conditioning to improve your strength training. It’s about bettering your cardiovascular system, prime your muscles and work on that explosive power to enhance your performance in the weights so that you can build more muscle and strength. It’s cardio that won’t burn muscle but rather help grow it.

Conditioning also helps you to recover better and more efficiently while improving the quality of your lifting so it’s a win-win situation all around.

Related Article: Power Workouts: 16 Must-Do Exercises To Increase Explosiveness

Don’t Forget—Make Sure You’re Eating Enough

Lastly, your nutrition makes a huge difference to your muscle growth whether or not you’re doing cardio so make sure that you pay attention to it. If you do want to include cardio in your fitness routine with the goal of maintaining or growing muscle, then it’s incredibly important that you get your diet down. Ensure that you’re eating an adequate amount of protein daily. Protein is the building blocks of muscle so it’s necessary to see growth. Not to mention, if you are doing cardio, the nutrients will help aid in repair and recovery so you can be ready for your next session feeling refreshed.

Check out our article on calories and macros for bulking.

Final Notes

Yes, cardio can burn muscle if you go about it the wrong way. But if you approach it with the information we’ve talked about in this article, you can prevent or definitely minimize the muscle loss if you still want to include cardio into your fitness regime. Just remember to keep it short and light, low-impact and eat enough food to fuel and condition your body.

About The Author

Emily Trinh

As a health and fitness writer, Emily combines her two passions—powerlifting and writing. With a creative writing degree under her belt, she spends her mornings lifting weights, her nights putting pen to paper, and eating too many snacks in between.