Denise Cervantes
Fitness Trainer
ACSM-CPT, AFAA-CGFI
February is American Heart Health Month, making it an ideal time to focus on cardiovascular health and the role exercise plays in supporting it. As cardio takes center stage, a common question often comes up, especially among those who prioritize strength training: does cardio cause muscle loss?
This long-standing myth has fueled plenty of debate in the fitness world. Let’s take a closer look at the relationship between cardio and muscle mass and explore how both cardio and strength training can work together in a well-balanced fitness routine.
The Basics of Muscle Loss
Muscle loss, medically known as muscle wasting or atrophy, occurs when the body breaks down muscle protein faster than it can be rebuilt. This can be influenced by various factors, including age, nutrition, physical activity levels or illness.
Many people mistakenly believe that engaging in cardio exercise, especially prolonged, high-intensity sessions will lead to significant muscle loss. However, the reality is more nuanced.
The concept of "going catabolic" refers to a state where the body breaks down muscle tissue for energy, often in response to inadequate nutrition, excessive exercise, or certain stressors.
While it's true that the body can enter a catabolic state, the idea that this occurs easily or frequently is often exaggerated.
One of my favorite experts in the fitness space is Dr. Israetel who holds a PhD in sport physiology. He frequently shares insights across platforms such as the Renaissance Periodization website and YouTube channel, where he discusses nutrition, training, and muscle preservation.
He emphasizes several key points that I find interesting regarding catabolism (2026):
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Balanced Energy Intake: He highlights that maintaining a balanced caloric intake and proper macronutrient distribution is crucial for preventing catabolism. If you consume enough protein and calories, the body is less likely to break down muscle tissue.
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Context Matters: Catabolism doesn't happen overnight; it typically occurs under specific conditions, such as prolonged fasting, significant caloric deficits, or excessive training without adequate recovery.
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Muscle Preservation: Dr. Israetel advocates for strength training and proper nutritional strategies to preserve muscle mass. He suggests that with appropriate training and nutrition, muscle loss can be minimized, even during weight loss phases.
- Myth of Easy Catabolism: He often argues against the myth that one can easily "go catabolic." Instead, he points out that the body is resilient and has mechanisms to preserve muscle, if proper care is taken regarding diet and exercise.
In summary, while catabolism can occur, it is not as straightforward or frequent as some might believe. Understanding the balance of nutrition, exercise, and recovery is key to preventing unwanted muscle loss.
The Role of Cardio in Fitness
Cardiovascular exercise, or cardio, is any exercise that raises your heart rate and improves the efficiency of your cardiovascular system. Common forms of cardio include running, cycling, swimming, and high-intensity interval training (HIIT). Cardio is essential for:
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Improving heart health: Regular cardio strengthens the heart and improves circulation.
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Burning calories: Cardio is effective for weight loss and maintaining a healthy weight.
- Enhancing endurance: It boosts stamina for daily activities and other forms of exercise.
Despite these benefits, concerns about muscle loss arise from the misconception that cardio inherently leads to a catabolic state, where the body breaks down muscle for energy.
Does Cardio Cause Muscle Loss?
The Science Behind Muscle Preservation
Research indicates that moderate amounts of cardio do not necessarily lead to muscle loss. In fact, a study by Tan et al. (2023) showed that individuals who engaged in both cardio and strength training experienced improved muscle mass and strength compared to those who only focused on one type of exercise.
This suggests that when incorporated correctly, cardio can complement strength training rather than detract from it.
Factors Influencing Muscle Loss During Cardio
Certain factors can promote muscle loss if not managed properly:
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Excessive cardio: Engaging in long-duration cardio without adequate recovery can lead to muscle catabolism, especially if caloric intake is insufficient.
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Inadequate protein intake: Protein is crucial for muscle repair and growth. If your diet lacks sufficient protein, muscle loss is more likely to occur.
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Inadequate calorie intake: You need calories to stay alive and keep bodily functions functioning. If you do not have adequate calories coming in, the body is forced to get energy from somewhere else, namely, muscle tissue (Evens, 2010).
- Neglecting strength training: Relying solely on cardio without incorporating strength training can lead to muscle atrophy over time.
Striking the Right Balance
To maintain and build muscle while reaping the benefits of cardio, it's essential to strike a balance between the two. Here are some guidelines for incorporating both into your routine:
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Prioritize Strength Training: Aim to engage in strength training exercises at least two to three times a week. This will stimulate muscle growth and help preserve muscle mass.
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Limit Cardio Duration: Keep cardio sessions to moderate lengths, such as 20-30 minutes for high-intensity workouts or 30-60 minutes for moderate-intensity workouts. This can help prevent muscle loss while still improving cardiovascular health.
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Focus on Intensity: Higher intensity cardio workouts, such as HIIT, can be effective for burning calories without significantly impacting muscle mass. The SunnyFit app offers various HIIT workouts that blend cardio with strength elements, perfect for maintaining muscle while boosting heart health.
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Ensure Adequate Nutrition: Make sure to consume enough calories and protein to support your activity levels. Aim for a balanced diet rich in lean proteins, healthy fats, and complex carbohydrates.
- Listen to Your Body: Pay attention to how your body responds to your workout routine. If you notice signs of excessive fatigue or muscle loss, consider adjusting your cardio intensity or frequency.
Integrating Cardio and Strength Training with SunnyFit
The SunnyFit app is a fantastic resource for those looking to create a balanced workout routine that includes both cardio and strength training. Here are a few workouts to consider:
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Heart Health Challenge: Participate in the Heart Health Challenge offered by SunnyFit this month. This program integrates cardio and strength workouts designed specifically to improve cardiovascular health while preserving muscle mass.
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Full-Body Strength Workouts: Discover full-body strength sessions that target all major muscle groups, helping to build and maintain muscle.
- Cardio and Strength Fusion: Look for fusion workouts that combine cardio with strength training exercises. These workouts can help you achieve your fitness goals more efficiently while keeping things interesting.
Effective Cardio Practices
To improve quality of life and your heart health, here are some key principles you might consider:
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Frequency: Aim for at least 150 minutes of moderate-intensity or 75 minutes of high-intensity aerobic exercise each week (American Heart Association, 2021).
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Variety: Incorporate different forms of cardio, such as running, cycling, swimming, or group classes, to keep workouts engaging and effective.
- Intensity: Use heart rate zones to guide intensity levels. Moderate-intensity cardio should elevate your heart rate but still allow for conversation, while high-intensity cardio should push you to your limits.
Metabolic Conditioning: A Strength and Cardio Combo
Combining cardio and strength training can lead to optimal health benefits and help prevent muscle loss. This is where “metabolic conditioning training” comes into play.
Metabolic conditioning, commonly referred to as MetCon, is a high-intensity training approach designed to enhance the body’s energy systems by integrating strength, cardiovascular, and plyometric exercises into short, intense intervals with minimal rest.
This training method aims to increase calorie burn during workouts and sustain elevated calorie expenditure afterward, a phenomenon known as excess post-exercise oxygen consumption (EPOC).
By efficiently training multiple energy pathways, metabolic conditioning promotes fat loss, builds lean muscle, and improves overall fitness. It often involves circuits reminiscent of CrossFit or high-intensity interval training (HIIT), effectively driving adaptation for better fuel utilization and body composition.
Key characteristics of metabolic conditioning include high-intensity efforts, where athletes engage in brief, but intense, bursts of activity followed by short recovery periods or lower-intensity work. This approach challenges the body’s immediate, intermediate, and long-term energy systems simultaneously.
Workouts typically incorporate compound movements, utilizing full-body exercises such as burpees and kettlebell swings, and are often structured as circuits with little to no rest to maximize metabolic demand.
The benefits of metabolic conditioning are significant, including enhanced fat loss and improved body composition (more lean muscle!) through increased calorie expenditure, even hours after exercise due to the afterburn effect. Additionally, this training method boosts overall fitness by enhancing stamina, strength, and cardiovascular health while delivering substantial results in less time than traditional steady-state cardio workouts.
Common examples of metabolic conditioning formats include AMRAPs (As Many Reps As Possible within a set time), EMOMs (Every Minute On the Minute), and circuits that transition through strength, cardio, and bodyweight exercises with minimal breaks (Burgomaster et al., 2008). You can also find AMRAPS and EMOMS on our free SunnyFit app if you want to give one a try!
Do you Know How Many Calories Muscle Can Burn?
Muscle tissue doesn’t directly burn fat, but increasing your muscle mass allows you to burn more calories at a given body weight compared to having less muscle. Muscle is a metabolically active tissue that requires considerable energy for maintenance, unlike fat tissue, which is less active and requires less. Engaging in strength training to build muscle enhances your caloric expenditure, ultimately aiding in fat loss due to improved metabolic rate.
Success Stories
Many individuals have successfully incorporated both cardio and strength training into their routines without experiencing excessive muscle loss. For example, athletes often engage in cross-training, which includes a mix of cardio and strength workouts, to enhance overall performance. This approach not only improves endurance but also helps to maintain muscle mass.
I can use myself as an example as an athlete who masterfully balanced the demands of both training for my first triathlon and training for a bodybuilding contest, where I had to step on stage at a certain body fat percentage.
Training for my first triathlon, I incorporated long-duration cardio sessions, riding my road bike for hours at a time, swimming in the ocean, and running miles to build my endurance, while I was simultaneously performing hard lifting sessions in the gym for my bodybuilding contest. I was lifting very heavy and had to learn the unique nutritional needs of both sports. I meticulously planned my diet, ensuring I was taking in enough calories and consuming adequate protein and carbs to support muscle recovery and my energy levels.
Despite the challenge of cutting body fat for my bodybuilding contest and stepping on stage, I maintained a somewhat high-calorie intake to preserve my hard-earned muscle mass. My dedication paid off spectacularly. Not only did I place first in my bodybuilding competition, but I also completed my first solo triathlon. I proved to myself that with the right nutrition and training approach, muscle loss can be avoided while excelling in multiple athletic pursuits.
Conclusion
In conclusion, the myth that cardio causes muscle loss is primarily based on misunderstandings about how these two forms of exercise interact. When integrated correctly into a holistic fitness routine, cardio can complement strength training and support overall health.
As we celebrate American Heart Health Month, it’s a perfect time to focus on heart-healthy habits while ensuring that muscle preservation remains a priority. By utilizing resources like the SunnyFit app and following the outlined strategies, you can create a balanced routine that enhances your fitness journey without sacrificing muscle mass.
In closing, it is important to note that if you plan to participate in extreme long duration cardio sports, or decide to dramatically increase your training volume, you should seek the advice of a trained health professional to ensure you avoid any potential health risks. In addition, if you notice you have unexpectedly lost weight or muscle mass it’s important to seek medical advice.
Here at Sunny Health & Fitness we strive to bring you ideas to achieve your fitness goals, but our advice should never take the place of your personal care provider.
Stay safe, be smart and always listen to your body!
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