A device comprising a unit (1) through which a subject can breathe, the unit comprising: an opening (AA) to allow airflow communication to the outside of the device； a mouthpiece element (2) through which the subject can breathe air in from and out into the device； and means for providing resistance (4) to airflow positioned between the opening and the mouthpiece element, said means being arranged to controllably vary the resistance to airflow during inspiration or expiration. Also provided are methods for the use of such a device.
