Final answer:
Aerobic exercise is any physical activity in which muscles are used below their maximum contraction strength, but for long periods of time. Examples of aerobic exercises include cycling, swimming, brisk walking, and tennis.
Step-by-step explanation:
Aerobic exercise is any physical activity in which muscles are used below their maximum contraction strength, but for long periods of time. This type of exercise uses a relatively high percentage of slow-twitch muscle fibers that consume a large amount of oxygen.
Aerobic exercises are often used to increase cardiovascular endurance and include activities like cycling, swimming, brisk walking, and tennis.