Abstract: An apparatus for training and treating the muscles of the female pelvic diaphragm and having a form corresponding to the vagina includes an external shell (1) axially divided into a number of mutually separated segments (3-9) which are separately connected by connecting pieces (3'-9') formed as longitudinal cams to a displacement mechanism (10) mounted axially around a hollow shaft (12) inside the apparatus, the displacement mechanism being prevented from rotating around the shaft (12), and wherein a mechanical displacement of the mechanism (10) in one or the other axial direction through the connecting pieces (3'-9') as a result of the construction of the mechanism results in a radial movement of the segments (3-9), thereby dilating or retracting the shell (1).