This machine was named by the Star Trek Encyclopedia (4th ed., vol. 2, p. 58), which definted it as a, "free-rotating exercise device consisting of three concentric gimbals, each rotating on a different axis, with a harness at the center. The user shifts his or her weight to cause the device to rotate, providing a full-body workout."
It is noted by this reference work, "The device, which was a modified version of a commercially-produced exercise machine [...] is based on NASA's multiaxis space test inertia facility, used to train early astronauts. During the third season, the exercise device was modified to become part of the deadly Xindiweapon that nearly destroyed Earth."