participates in swiss ball exercise stability ball fitness ball swiss ball An exercise ball is a ball constructed of soft elastic, typically in 5 diameters of 10 cm increments, from 35 to 95 cm (14 to 37 in), and filled with air. The air pressure is changed by removing a valve stem and either filling with air or letting the ball deflate. It is most often used in physical therapy, athletic training and exercise. It can also be used for weight training. balance ball exercise ball swiss exercise ball Ball Device