Will aerobic exercise make me lose muscle mass?

Column by John Parrillo from Parrillo Performance.

Question: I’ve heard that doing aerobic exercise is a good way to burn body fat, but won’t it cause me to lose muscle mass?

Never underestimate the power of aerobics in your training program. It has numerous benefits, from fat-burning to cardiovascular health to improved recovery mechanisms. Many bodybuilders, however, typically shy away from aerobic exercise, particularly in the growth season, fearing that it will cause a loss of muscle mass. This loss, however, has less to do with aerobics and more to do with improper diet. A bodybuilder who loses muscle during a period of aerobic training is simply not eating enough to compensate for the calories spent by the aerobic activity. Take in enough quality calories, and you’ll preserve muscle mass while your body fat drops. Aerobics forces oxygen through your body, increasing the number and size of your blood vessels. Blood vessels are the “supply routes” that transport oxygen and nutrients to body tissues, including muscles, and carry waste products away for muscular growth, repair and recovery. the expansion of this circulatory network is called “cardiovascular density.” Your ability to build additional muscle is limited by your degree of cardiovascular density. Without aerobics in your total bodybuilding program, your body can’t create any new supply routes for your newly developed muscles.

The more blood vessels you have and the bigger they are, the longer and more intense your workouts can be. In other words, the better your cardiovascular density, the greater potential you have for building bigger muscles. Do your aerobics in the morning for 45 to 60 minutes – before breakfast. By exercising before your first meal, you begin burning fatty acids for energy in the absence of glycogen. You become leaner as a result. Then later, the carbohydrates you eat are efficiently re-supplied to muscles, without being turned into body fat. Plus, your metabolism is activated for the entire day. Most people don’t understand the importance of “aerobic intensity.” For a long time now you’ve probably been urged to achieve your “target heart rate” during aerobic activity. This is the elevation of the pulse to approximately 60 to 80 percent of your maximum heart rate (220 minus your age).

Reaching target heart rate and keeping it there for at least 20 minutes is supposed to boost general cardiovascular conditioning. Also, it’s always been assumed that if you exercise at your target heart rate long enough, you burn more fat. Optimal cardiovascular is not achieved by just raising your heart rate, but is rather optimally achieved by increasing “oxygen uptake” or VO2max. This represents your body’s maximum capability to deliver oxygen to the working muscles. So how do you boost your VO2max? By exercising so intensely that Absyou’re breathing hard. The harder you breathe the more energy you expend, and the more fat your burn. Granted, less of a percentage of fat is being burned compared to total calories, but more fat is being burned because more work is being performed. Train consistently like this, and some important metabolic changes take place inside the body. First, the mitochondria (cellular furnaces where fat and other nutrients are burned) increase in size and total number inside muscle fibers. Second, muscle fibers build up more aerobic enzymes – special chemicals involved in fat-burning.

Third, Aerobic exercise appears to increase levels of myoglobin, a muscle compound that accelerates the transfer of oxygen from the bloodstream into the muscle fibers. Remember to eat more protein so that you don’t develop sports anemia. Larger mitochondria and more of them, greater levels of aerobic enzymes, and increased blood flow – these factors all boost the fat-burning capability of muscle fibers. The more aerobically fit you become and the harder you train, the more your body learns to burn fat for energy. So you can see why intense aerobic is so important for leaning out. Endurance athletes have known these things all along. That’s why bodybuilders can learn a lot from the training regimens of endurance athletes. They train regularly and at long duration at or near their VO2max, and as a result their muscles are conditioned to rely more heavily on fat for energy and less on stored carbohydrate (glycogen). To approach the training level of an endurance athlete, perform aerobics several times a week, at my recommended duration. But don’t “coast.” Work out hard, so that you’re breathing hard. The harder you breathe, the more fat you burn.

John Parrillo
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