Back exercise device

PURPOSE: To selectively transmit driving force to a force adding means from a driving means by arranging a pair of output shafts mutually arranged in the shaft direction in parallel to an input shaft in a gear box, and arranging a means to rotate a selected output shaft in either rotational direction by selectively connecting the input shaft to selected one of the output shafts. CONSTITUTION: The back of a patient is bent and stretched by a back rest 92, and the back of the patient is rotated by a back rest 80. An input shaft 112 can be selectively connected to either one in gear wheels 114 and 116 or either one in sprockets 118 and 120, and when the input shaft 112 is connected to the gear wheel 114, an output shaft 104, that is, the back rest 92 is rotated in one direction, and on the other hand, when the input shaft 112 is connected to the sprocket 118, it is rotated in the inverse direction. When the input shaft 112 is connected to the gear wheel 116, the output shaft 104 is rotated in one direction through an output shaft 126, and when the input shaft 112 is connected to the sprocket 120, the output shaft 126 is rotated in the inverse direction.