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Aerobic Myths: Truths and Falacies of Cardio Training
By Brad Schoenfeld, CSCS, CPT When it comes to fitness, whose advice can you really trust? There is so much misinformation promulgated by so-called "fitness experts" that is difficult for a woman to separate fact from fiction. Ultimately, the perpetuation of these myths can have a negative impact on your ability to achieve results. The following are common myths that have somehow been taken as gospel by the general public. By sifting through these myths and developing a sound training philosophy, you will be one step closer to actualizing your ideal physique: MYTH: Using the stairmaster will give you a big butt. FACT: This myth was put forth when a popular magazine suggested that the stairmaster was responsible for increasing the derrieres of exercising women across the country. Afraid that they would soon possess a rear end the size of a movie screen, women began to avoid the stairmaster like the plague. Fortunately, there is not a shred of truth to this myth. In fact, it is virtually impossible to substantially increase muscle mass through the performance of any endurance-related cardiovascular activity. The reason for this is simple: There are two basic types of muscle fibers, slow twitch (Type I) and fast twitch (Type II), and each respond to different stimuli. Fast twitch fibers are strength-related fibers that contract rapidly but are quick to fatigue. Most of their energy is derived by burning glucose, rather than fat, as a fuel source. These factors make them more sensitive to weight-bearing exercise (push-ups, squats, etc.) where short, intense periods of training are used. In order to accommodate the demands of anaerobic exercise, fast twitch fibers respond by growing larger and stronger. Therefore, they are the only types of fibers that have the ability to increase in size and promote muscular bulk. Slow twitch fibers, on the other hand, are endurance-oriented fibers that have only a limited ability to increase in size. These fibers get much of their energy by burning fat for fuel, contracting very slowly but having the ability to endure extended periods of activity. Slow twitch fibers are predominantly utilized during the performance of aerobic exercise, with almost no activation of fast twitch fibers. As such, little, if any, muscular growth can take place. Since the stairmaster is aerobic in nature, it stands to reason that it can't contribute to building a substantial amount muscle tissue in any part of the body, including your butt! MYTH: You cannot overtrain from performing cardiovascular exercise. FACT: Because cardiovascular exercise is an endurance-oriented activity and therefore is executed at a decreased level of intensity, many women feel that there is no limit to how much they can perform. However, while your body can tolerate a greater volume of aerobic exercise than anaerobic activity, too much of it eventually will set back your fitness endeavors and have a negative impact on your physique. While recovery ability varies among individuals, the body needs rest and recuperation to regenerate its glycogen stores. Glycogen reserves are your body's primary energy source, giving you the strength and endurance to perform everyday chores. Since cardio burns glycogen (as well as fat) during exercise performance, too much of it will deplete these reserves, ultimately causing you to become overtrained. Overtraining will make your body less efficient in utilizing fat for fuel, and is apt to feed on your muscle tissue (due to a secretion of stress hormones) for energy. Moreover, it can throw off your biochemical balance resulting in a variety of complications including cessation of your period (amenorrhea), chronic fatigue and other anomalies. Therefore, keen attention must be paid to symptoms related to overtraining, modifying your aerobic capacity according to your physical state. MYTH: Low intensity aerobic activities are better for fat burning than high intensity exercise. FACT: This myth was given credence when several research studies indicated that low-intensity activities burned a greater percentage of fat calories than high-intensity activities. These studies validated that the body prefers to use fat as its fuel source during low-intensity exercise (equating to roughly 60% of the calories burned, as opposed to about 40% from high-intensity exercise). However, it is misguided to believe that the selective use of fat for fuel will translate into burning more total fat calories. High-intensity exercise burns more fat calories on an absolute basis than lower intensity activities. Since the most important aspect of training intensity is the total amount of fat calories burned-not the percentage from fat-higher intensity exercise has the decided edge. Furthermore, when you consider the time related efficiency of training, low-intensity exercise provides a very poor cost/benefit dividend. After all, why would you want to spend an hour running on the treadmill when you can get better results from training for half that time? In final analysis, if fat burning is your aim, performing cardiovascular exercise at a high level of intensity is your best choice. MYTH: Sweat is a good indicator of exercise intensity. FACT:Most women mistakenly believe that you "gotta sweat" in order to have a successful workout. While sweat is usually associated with rigorous exercise, it is by no means essential to achieving results. When you exercise, sweat is brought on by an elevation of body temperature from metabolic heat. Your body regulates its temperature by activating your sweat glands, which then releases water through your pores as a cooling mechanism. Thus, sweat is an indicator that your body temperature is rising, not necessarily that you are exercising at an intense level. Thus, rather than judging your workout by how much you sweat, you should use barometers such as maximal heart rate or maximal oxygen consumption as a yardstick of how hard you are working. Moreover, contrary to popular belief, being out of shape does not increase your propensity to sweat. In fact, the more physically fit that you are, the more you will tend to perspire. Frequent exercise tends to make your sweat glands increasingly sensitive to rises in body temperature. Over time, your body begins to perceive when you're beginning to train, and, not wanting to store extra heat, signals the sweat glands sooner than in an untrained individual. MYTH: Aerobic classes are the best form of cardiovascular exercise. FACT: Mention the word aerobics and most women envision an instructor leading a class through various jumping, twisting, and other athletic movements. These classes look fun and can be a great place to socialize and meet new people. Every week there seems to be a new gimmick devised, with a catchy name and clever marketing angle; high impact, step, slide, spin-the list goes on and on. Unfortunately, any group-oriented fitness activity is generally inferior to a program that is specifically designed for an individual. Aerobic classes must cater to the masses and, most likely, will not optimally target your own heart rate. On the other hand, individual aerobic modalities allow you to the ability train within your target zone. Therefore, you can customize a routine to meet your specific needs, resulting in optimal fat burning potential. Moreover, because of the extreme, unorthodox nature of many aerobic movements performed in a class setting, the risk of injury is heightened. An injury can seriously curtail your workout regimen, potentially hampering your ability to train indefinitely. Conversely, individual modalities are executed in a controlled fashion. Thus, they tend to be much safer to perform with the potential for injury greatly reduced. This is not to say that aerobic classes are without merit. Since many women are not internally motivated to exercise, these classes can provide an impetus to become more active. This, in turn, can help to promote adherence to an exercise program. Hence, if you simply cannot motivate yourself to exercise or perhaps just want to have some fun, an aerobic class might be right for you. However, while anything that helps to increase your motivation to exercise is certainly worthwhile, experience has shown that the best way to encourage lasting adherence is to achieve results in the safest, most expedient way possible. There is no greater motivating factor than seeing your body change before your very eyes. Thus, from a cost/benefit perspective, a custom-tailored, individually designed cardiovascular regimen is the most effective way to train.
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发表于 2011-10-20 06:35:35
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