Cardio does not directly burn muscle. In fact, it can actually help build muscle under certain circumstances. Let me explain. When you engage in cardio, it primarily sends a signal to build endurance and burns calories. This means that your body adapts by becoming more efficient and improving endurance, but it doesn't necessarily send a muscle-building signal. However, there are scenarios where cardio can indirectly contribute to muscle growth.
For example, if your cardiovascular fitness is poor and it's impacting your strength training, incorporating cardio can improve your overall fitness and allow you to perform better during strength training sessions. By improving your VO2 max and stamina, you'll be able to push through sets with less fatigue, leading to better muscle-building potential. Additionally, cardio can help with work capacity and stamina, which are important components of the strength-building process.
It's important to note that cardio should not be the primary focus if your goal is solely muscle building. Strength training should still be the dominant force in your training routine. However, incorporating some cardio to improve cardiovascular fitness and endurance can have positive effects on your overall fitness and indirectly support muscle growth. Remember, it's all about finding the right balance that aligns with your goals and individual needs.