What is "Cardio" or Aerobic Exercise?
Aerobic exercise is physical exercise of relatively low intensity and long duration, which depends primarily on the aerobic energy system. Aerobic means "with oxygen", and refers to the use of oxygen in the body's metabolic or energy-generating process. Many types of exercise are aerobic, and by definition are performed at moderate levels of intensity for extended periods of time.
The History
Both the term and the specific exercise method were developed by Kenneth H. Cooper, M.D. and Col. Pauline Potts, a physical therapist, both in the United States Air Force. Cooper, an exercise enthusiast, was puzzled why some people with excellent muscular strength were still prone to poor performance doing long-distance running, swimming, and bicycling. He began measuring systematic human performance using a bicycle ergometer, and began measuring sustained performance in terms of a person's ability to use oxygen. His ground-breaking book, Aerobics, was published in 1968, and included scientific exercise programs using running, walking, swimming and bicycling. The book came at the right time, when increasing weakness and inactivity in the general population was causing a perceived need for increased exercise.
Aerobic VS Anaerobic Exercise
Aerobic exercise can be contrasted with anaerobic exercise, of which strength training and short-distance running are the most common examples. The two types of exercise differ by the duration and intensity of muscular contractions involved, as well as by how energy is generated within the muscle.
In most conditions, anaerobic exercise occurs simultaneously with aerobic exercises because the less efficient anaerobic metabolism must supplement the aerobic system due to energy demands that exceed the aerobic system's capacity. What is generally called aerobic exercise might be better termed "solely aerobic", because it is designed to be low-intensity enough not to generate lactate acid, so that all carbohydrate is aerobically turned into energy.
Initially during increased exertion, muscle glycogen is broken down to produce glucose, which undergoes glycolysis producing pyruvate which then reacts with oxygen to produce carbon dioxide and water and releasing energy. If there is a shortage of oxygen (anaerobic exercise, explosive movements), carbohydrate is consumed more rapidly because the pyruvate ferments into lactate.
As carbohydrates deplete, fat metabolism is increased so that it can fuel the aerobic pathways. The latter is a slow process, and is accompanied by a decline in performance level. This gradual switch to fat as fuel is a major cause of what marathon runner’s call "hitting the wall". Anaerobic exercise, in contrast, refers to the initial phase of exercise, or to any short burst of intense exertion, in which the glycogen or sugar is respired without oxygen, and is a far less efficient process. Operating anaerobically, an untrained sprinter may "hit the wall" short of the full distance.
Aerobic exercise comprises innumerable forms. In general, it is performed at a moderate level of intensity over a relatively long period of time. For example, running a long distance at a moderate pace is an aerobic exercise, but sprinting is not. Playing singles tennis, with near-continuous motion, is generally considered aerobic activity, while golf or two person team tennis, with brief bursts of activity punctuated by more frequent breaks, may not be predominantly aerobic. Some sports are thus inherently "aerobic", while other aerobic exercises, like aerobic dance classes, are designed specifically to improve aerobic capacity and fitness.
Some of the benefits of doing regular aerobic exercise are:
Strengthening the muscles involved in respiration, to facilitate the flow of air in and out of the lungs
Strengthening and enlarging the heart muscle, to improve its pumping efficiency and reduce the resting heart rate, known as aerobic conditioning
Strengthening muscles throughout the body
Improving circulation efficiency and reducing blood pressure
Increasing the total number of red blood cells in the body, facilitating transport of oxygen
Improved mental health, including reducing stress and lowering the incidence of depression
Reducing the risk for diabetes.
Burns body fat, while building leaner muscle.
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| Heart-rate at various levels of exercise |
