Aerobics is a form of physical exercise that combines rhythmic aerobic exercise with stretching and strength training routines with the goal of improving all elements of fitness (flexibility, muscular strength, and cardio-vascular fitness). It is usually performed to music and may be practiced in a group setting led by an instructor (fitness professional), although it can be done solo and without musical accompaniment. With the goal of preventing illness and promoting physical fitness, practitioners perform various routines comprising a number of different dance-like exercises. Formal aerobics classes are divided into different levels of intensity and complexity. Aerobics classes may allow participants to select their level of participation according to their fitness level. Many gyms offer a variety of aerobic classes. Each class is designed for a certain level of experience and taught by a certified instructor with a specialty area related to their particular class.
Both the term and the specific exercise method were developed by Dr. Kenneth Cooper, M.D., an exercise physiologist, and Col. Pauline Potts, a physical therapist, both of the United States Air Force. Dr. Cooper, an avowed exercise enthusiast, was personally and professionally puzzled about why some people with excellent muscular strength were still prone to poor performance at tasks such as 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 groundbreaking book, Aerobics, was published in 1968, and included scientific exercise programs using running, walking, swimming and bicycling. The book came at a fortuitous historical moment, when increasing weakness and inactivity in the general population was causing a perceived need for increased exercise. Aerobics gained world-wide popularity after the release of Jane Fonda's exercise videos in 1982.
Aerobic gymnastics, also known as sport aerobics and competitive aerobics, is a type of competitive aerobics involving complicated choreography, rhythmic and acrobatic gymnastics with elements of aerobics.  Performance is divided into categories by age, sex and groups (individual, mixed pairs and trios) and are judged on the following elements: dynamic and static strength, jumps and leaps, kicks, balance and flexibility. Ten exercises are mandatory: four consecutive high leg kicks, patterns. A maximum of ten elements from following families are allowed: push-ups, supports and balances, kicks and splits, jumps and leaps. Elements of tumbling such as handsprings, handstands, back flips, and aerial somersaults are prohibited. Scoring is by judging of artistic quality, creativity, execution, and difficulty of routines. Sport aerobics has state, national, and international competitions, but is not an Olympic sport.