Physical fitness consists of various components, including strength and flexibility, all of which are required for a dancer. Jumps, floor work, partner work, and adagio (slow controlled movements) all need physical strength for control, graceful execution, and safety. Dancers must be flexible to perform dances that require smooth transitions from one movement or position to another. Dancers can build their own muscle mass, but most dance schools provide classes with an array of fitness activities designed to strengthen key muscle groups. These classes may include resistance training, such as weight lifting, and balance exercises such as yoga, tai chi, and pilates. Dance is not considered an aerobic activity, so dancers do not need to work out in order to maintain their health. However, it is important for dancers to stay fit if they want to continue dancing into older age. The most common muscles used in dance are those involved in moving the feet (peroneals, flexors, and extensors), toes (abductor hallucis, peronaeus brevis, and longus), and fingers (flexor digitorum profundus). The hips and legs are also used, especially in ballet where many jumps are performed. Muscles are used even when not thinking about them, such as when walking or standing still. Thinking about what body parts are being used during a dance exercise can help a person improve his or her fitness level.