There are hundreds of myths about cardio. Some believe it’s mandatory, while others think it’s just a waste of time. You must have heard many people arguing about this. But the most terrible myth is “Does cardio burn muscle?”
If you observe fitness enthusiasts carefully, you’ll notice that most people skip cardio. Those who do it often just move their joints for a few minutes before the session and think they’ve done cardio.
People have many questions and confusion in their minds about this.
Is cardio really my enemy? Is it working against me without my knowledge, or will it make my muscles vanish into thin air? What is the truth? “Should I incorporate this into my journey? How much can it benefit me, and what are the downsides?
This article will clear up all your confusion and assist you in adjusting cardio to your routine to get maximum results.
Does Cardio Really Burn Muscle?
Generally, no, but sometimes yes. Now, what does that mean? This means it will definitely benefit you, but only up to a certain point and in a specific situation. Once it exceeds that limit, then cardio also leads to burn muscle.
This happens because fat is used as energy, but not directly. Rather, it converts into energy through a complex process called “fat oxidation,” and some carbohydrates are needed to complete this process effectively. Because of the lack of carbohydrates, the body then enters into ketosis, or the process of breaking down proteins to generate glucose. As a result, protein synthesis decreases and protein breakdown increases.
On the other hand, in those who had enough carbohydrates in their bodies, the fat-burning process went smoothly, and energy could be produced without losing muscle mass. Cardio is always your friend, no matter what your target is—general fitness, muscle building, or fat loss. Always incorporate it into your routine.
What Research Says?
A study found that when the body does not have enough carbohydrates (for example, after eating low-carb for two days), aerobic exercise for a long time causes the body to break down muscle protein to make up for the shortage of energy. This state is called “Catabolic state”. It slows muscle growth and increases muscular breakdown. As a result, the net protein balance shifts negative.
Whether it will be beneficial or harmful for you depends on the intensity and volume according to your goal. Here, an expert is the only solution, because they have around 15-20 years of their own training experience. Plus, they have already trained hundreds or thousands of students and know what your body needs and how it will react in each state.Â
In simple terms, cardio does not burn muscle until you cross the limit.
When Does Cardio Burn Muscle?
You need to understand that along with glycogen and fat, muscle is also a part of your energy source. When you start doing cardio, your body first breaks down glucose to produce energy, then taps into your fat. After a certain period, your body will enter a catabolic state, and if your body lacks nutrition, it will enter this state too quickly. Here are some situations where your body starts to burn muscle to maintain its rhythm.
Excessive Cardio Without Proper Nutrition
In this situation, your body enters a catabolic state too quickly. During cardio, our body burns 5-15 calories per minute, depending on intensity. Which means you’re burning extremely high amounts of calories. These calories come from your food. If you’re performing for a long or highly intense cardio without proper nutrition, your body doesn’t have enough fuel to use. In this situation, your body starts burning muscle tissue for fuel. That’s how your muscle breaks down.
HIIT Overtraining
During the fat loss journey, people often do excessive cardio. Since cardio is considered mandatory, not knowing the body’s limit can lead to muscle loss. This is also a reason for muscle burning. Especially in HIIT training, where your body enters a state that starts releasing the cortisol hormone. This hormone can disturb your muscle protein synthesis process, which is essential for muscle repair. As a result, your body starts breaking down muscles.
Lack of Strength Training
If you’re neglecting strength training and only focusing on cardio, it will definitely contribute to muscle loss. Through strength training, you’re sending a signal to your brain to preserve muscle and build new muscle fibers. As a result, your body makes every effort to preserve muscle and uses glycogen or fat to generate energy during exercise or regular activities.
How to Prevent Muscle Loss from Cardio
To maximize the benefits of cardio and preserve muscle, you just need to adjust these three steps:
1. Nutrition with Proper Hydration
The first thing you need to correct is your nutrition, as your success largely depends on it. You need to determine your daily nutritional requirements (carbs, protein, and fat), divide them into proper portions, and add them to your meals.
Since you need more energy for cardio, and carbs are directly involved in energy generation, your carb portion needs to be a little larger, around 10%. In simple words, 60% carbs in your total macronutrient intake is an ideal portion.
Protein is essential for post-workout recovery and repairing damaged muscles. Since cardio puts your muscles under stress, your protein requirement also increases to support recovery and muscle preservation. 1-1.5 grams of protein per kg of body weight is enough for optimal muscle growth.
Healthy fat plays a crucial role in regulating hormone production. Anabolic hormones are mandatory to preserve and grow muscle, and you obtain them from healthy fats. Nuts, seeds, and avocados are some of the best sources of healthy fats.
Lastly, hydration, which people often neglect, is essential for our overall performance and recovery. Aim to drink at least 3 liters of water every day and make sure to drink before, during, and after your session. Dehydration can impair muscle function and lead to muscle breakdown.
2. Sufficient Recovery Time
In the pursuit of quick results, we often neglect recovery. But you need to understand that your muscles have already undergone stress, and they need to recover completely. If you go for another session without recovering, the muscles are not fully repaired, leading to more muscle breakdown, which equals muscle loss.
Proper recovery ensures that your body and muscle fibers are fully fueled and strengthened for future activity. The best recovery method is sleep. Getting quality sleep for 7-8 hours at night ensures that your muscles are properly recovered, your hormones are balanced, and your energy levels are at their peak.
3. Adjust Volume and Intensity
To prevent muscle loss, the volume and intensity of your cardio should depend on your goal. Whether you should increase or decrease it will depend on the specific goal you are working towards.
Generally, 3-5 sessions of 20-30 minutes a week is a standard volume for general fitness. For muscle gain and fat loss, this must be adjusted. If you don’t understand the appropriate volume and intensity to achieve your fitness goal, you should definitely seek help from your trainer.
Cardio During Muscle Gaining
People often neglect cardio during muscle gain, but it is very helpful for muscle building. It increases your metabolic system, improves cardiovascular health, and boosts strength, which helps keep your muscles toned. Additionally, cardio ensures that you’re getting enough energy for exercise.
A 2016 study showed that cardio does not have a negative effect on muscle growth if done correctly (after a short period of moderate cardio, resistance training); rather, it helps to increase metabolism and control fat.
Cardio increases the resting metabolic rate (RMR), which means you’ll burn calories even when you’re resting. It also helps with afterburn, meaning your metabolism remains high for a couple of hours after the workout.
Muscle gaining is a process where you gain muscle while also gaining fat. Reducing this fat is equally important, as it can hinder your progress. Cardio is the solution to avoid accumulating excess fat during this process.
However, the approach to cardio in this case is a bit different. You need to reduce the volume and frequency of your cardio. For muscle building, you should do cardio after strength training. 10-15 minutes of moderate cardio with 2-3 sessions per week will help bring the best results. Make sure you’re properly fueled before and after the workout.
Cardio for Fat Loss
If your goal is to lose fat, cardio is a very powerful tool and a necessary component. However, it’s important to understand how to use this tool effectively. Through cardio, you can burn extra calories, creating a calorie deficit. As a result, when your body needs energy, it starts breaking down fat. Additionally, cardio boosts your metabolism and improves oxidation, leading to fat loss.
A meta-analysis study published in 2023 found that doing HIIT-type cardio regularly can lead to real fat loss from the body. The participants did cardio for 20 to 30 minutes each day, 3 to 5 days a week. According to the results, on average, 1.86 kg of fat was reduced and the total fat percentage of the body was reduced by 1.53%. The most surprising thing is that in this process, instead of reducing the muscle, it has increased slightly, about 0.51 kg. These data prove that cardio can play an effective role not only in weight loss, but also in reducing body fat, if the time and method are right.
Before adjusting, it’s important to know your body starts burning fat when glycogen runs out. There are two times when your glycogen level remains at its lowest point: first, when you wake up in the morning with an empty stomach, and second, after your resistance training. If you can utilize these times for cardio, you will get better results compared to any other time.
The Bottom Line
Cardio is always beneficial for whatever goal you want to achieve. It’s all about finding the right balance. Cardio does not burn muscle; rather, it helps build muscle to reduce fat. It’s a powerful tool, and its effectiveness increases even more when combined with proper nutrition.
Sometimes, it can hold you back if you overdo it. So, avoid overtraining and add resistance training to your routine and see the magic. Cardio keeps your heart healthy, enhances blood flow, aids in the recovery process, and helps control body fat.
If you want to make the best use of it, just adjusting the intensity and volume according to your specific goal will make all the difference.
