A yoga ball is a large, lightweight, air-filled ball, usually made of elastic rubber and averaging about 14 to 34 inches (35 to 85 centimeters) in diameter. This kind of ball is also known as a birth ball, body ball, balance ball, gym ball, fit ball, physioball, fitness ball, pilates ball, stability ball, Swedish ball, therapy ball, exercise ball, and Swiss ball. Th[...]