Does Aerobic Exercise Burn Muscle & What Does It Do?

You may have heard a fitness instructor holler, “Feel the burn!” However, he isn’t only referring to torching calories. During aerobic exercise, your body uses energy from different sources for fuel to meet the demand of more oxygen and blood by the muscles, according to the American Council on Exercise. The type of energy you burn depends on your fitness level, intensity and duration of exercise.

  1. Energy Sources During Aerobic Exercise

    • Your body responds to exercise by using energy from two main sources: fats and carbohydrates, notes ExRx. At rest, 33 percent of the body’s energy comes from carbohydrates and 66 percent comes from fat. During the first several minutes of aerobic activity, your body uses primarily carbohydrates for energy. After 20 to 30 minutes of aerobic activity, though, your body will burn 50 percent of its energy from fat and 50 percent from carbohydrates. The longer you exercise, the more your body relies on fat for fuel.

    Muscle Burn

    • Aerobic exercise does not burn muscle. Your muscles are made up of proteins, which contribute less than 2 percent of the energy used during exercise of less than an hour, says ExRx. Your body only dips into its protein reserves, or lean muscle tissue, if calories from fats and carbohydrates are not sufficient. If you follow a nutritionally balanced diet, you should not shy away from aerobic exercise because you don’t want to burn muscle. According to the Academy of Nutrition and Dietetics, before exercising you should ensure you are fueled with an adequate amount of carbohydrates and protein, with fiber and some fat included. Carbohydrates top off your muscle’s energy stores, and protein helps build and repair muscle tissue post workout. A small meal three to four hours pre workout, such as a fruit and yogurt smoothie with low-fat granola, will provide your body with the fuel it needs to get through an aerobic exercise session.

    High-Intensity vs. Low-Intensity Activity

    • Aerobic activities like running, walking, swimming or cycling build endurance and provide a base of fitness, according to Peak Performance. Aerobic workouts are performed at a comfortable, steady pace that allows for a balanced energy supply of fats and carbohydrates. Once you’ve established your base fitness level, you can increase your intensity, or effort, and your body will use anaerobic energy systems, which rely primarily on carbohydrates for fuel. Incorporating short bursts of higher-intensity exercise into your routine will torch calories and improve your VO2 max, or maximum aerobic threshold. As your fitness level improves, you will reach a steady aerobic state sooner and be able to stay in the fat-burning zone longer, says ExRx.

    Health Benefits of Aerobic Activity

    • The American College of Sports Medicine recommends adults get at least 150 minutes of moderate-intensity cardiovascular exercise per week. To reap the most health benefits, you should gradually increase the time, frequency and intensity of your workouts. According to MayoClinic.org, consistent aerobic exercise will keep your heart strong and reduce your risk of obesity, high blood pressure, type 2 diabetes, stroke and certain cancers.