Aerobics is a term that was coined in the late 1960s by Dr. Kenneth Cooper, then a physician at the San Antonio Air Force Hospital, to identify a series of cardiovascular exercises he had developed to combat coronary artery disease.

The exercises were designed to lessen the buildup of a form of cholesterol on the walls of the coronary arteries, which are the arteries that are the conduit of blood to the heart muscle. The cholesterol buildup (plaque deposition) reduces the internal diameter of the arteries, which restricts the flow of oxygen-laden blood to the heart. Plaque formation can also stress the heart by making the pumping of blood to other areas of the body more difficult. The consequences can include chest pain (angina), high blood pressure, and/or a heart attack.

Aerobics involves oxygen; aerobics literally means "with oxygen." In contrast, anaerobic means "without oxygen." Oxygen is a vital part of the energy-generating process for muscles. In concert with fats and glucose, oxygen is used to produce adenosine triphosphate (ATP), which fuels most cellular activity. As oxygen, fats, or glucose are depleted, muscles can acquire energy from anaerobic processes. However, the generation of lactic acid as a byproduct of anaerobic pathways more rapidly fatigues muscles. Establishing a higher level of aerobic fitness permits more strenuous and prolonged exercise before the aerobic threshold is reached.

Following the publication in 1968 of Aerobics, Cooper's book about the exercise system, aerobics quickly became a popular form of exercise. Ten years later, the estimated number of Americans who

Walking combines the cardiovascular and muscular activities necessary to strengthen the heart. Here, Japanese walking exercise guru Duke Saraye (center) gives a lesson on technique.
regularly did aerobics was six million. By 1987, the estimated number had reached 22 million.

In devising aerobics, Cooper viewed the cardiovascular benefits of aerobics as being central to overall physical fitness. The initial military version of aerobics concentrated on endurance, specifically, completing a 1.5-mile (2.4-km) run in 12 minutes. At about the same time, the sport of running was growing in popularity; aerobics helped boost the sport's appeal.

Following his military service, Cooper founded The Cooper Aerobics Center in Dallas, Texas, where he adapted the military-fitness focus of aerobics to fit the general population. His approach has proven to be spectacularly successful. Now called The Cooper Fitness Center and The Cooper Institute, the 30-acre facility has burgeoned into a health- and lifestyle-improvement complex staffed by hundreds of exercise physiologists, physical therapists, and dieticians. Additionally, aerobics research is carried out at another facility in Denver, Colorado.

During the 1970s, aerobics evolved from its running base to encompass cardiovascular activity, calisthenics, and dance. Aerobics became synonymous with a music-based group workout involving choreographed dance moves or repetitious motion. Celebrities such as Richard Simmons and Jane Fonda popularized different versions of aerobic workouts in the 1980s, from milder versions that beginners or less physically able people could handle to intense sessions that challenged even elite athletes. Other seminal personalities include Judi Sheppard Missett, who devised a fusion of aerobics and dance called Jazzercise, and Billy Blanks, who in the 1990s popularized Tae-Bo, an aerobic workout that incorporates martial arts movements. Aerobic workouts remain a staple of fitness club classes in 2006.

Aerobic activities are all designed to increase the oxygen that is available to muscles by increasing the physical capacity of the heart, lungs, and blood vessels. The number of red blood cells—which transport oxygen throughout the body—also increases. These aerobic benefits are produced by a regular exercise regimen involving activities that are prolonged (a typical aerobic workout lasts about 60 minutes), use large muscle groups such as the arms and legs, and are rhythmic.

The general consensus among physicians and exercise physiologists, including aerobics founder Cooper, is that aerobic exercise should be the main component of a fitness program, but that it should be complemented by strength training. The latter becomes more important with age, as the loss of muscle and bone mass becomes more of a concern.

In addition to studio-based aerobics, many traditional athletic activities combine the cardiovascular and muscular activities necessary to strengthen the heart. These include running, walking, swimming, cross-country skiing, bike riding, basketball, and roll-erblading. Exercise machines that mimic stair climbing and bicycle riding also offer aerobic workouts.

One of the main benefits of aerobics is the elevation of the basal metabolic rate, which is the rate at which energy, measured in calories, is used up (burned) to maintain the normal function of the body. This elevation occurs as the body adjusts to the increased physical demands being imposed. The visible result for the majority of people is the loss of weight.

Aerobics is vitally important for competitive athletes, as many athletic endeavors require cardiovascular fitness.

SEE ALSO Pilates.