Aerobics is a system of exercises designed to promote the supply and use of oxygen in the body. These exercises include biking, running, dancing, rowing, skating, and walking (the term "aerobic"means "with oxygen," or "living and working with oxygen"). The system originated and remains primarily a fitness activity, but has also developed into an intense competitive sport: "the toughest two minutes in sport." Aerobic exercise increases cardiorespiratory fitness, the heart's ability to pump blood and deliver oxygen throughout the body. The result is increased endurance, energy, weight control, and ability to manage stress, and decreased blood pressure, heart disease, and cholesterol levels.