Abstract: A device for stimulating the human respiratory system by making breathing more difficult and limiting lung ventilation. The device comprises a mouth-piece for insertion in the mouth of a person, or a mask attachable to the face of this person. The mouth-piece or mask has a central opening through which the person may breathe. A tubular body defining an air duct is connected at one end to the mouth-piece or to the mask with the air duct in alignment and communication with the opening. The device also comprises a membrane mounted in the tubular body at the other end thereof to put up a breathing resistance in at least one respiratory direction. Proper stimulation is obtained when use is made of a tubular body long enough to increase the dead space of the respiratory system of the person using the device.