Wheelchair soccer is a variation of association football, in which all of the participants are wheelchairs users due to physical disability. Intellectual disabilities can also be a factor, but this is not always the case. The wheelchairs can be either motorised, or manually pushed. In the senior division, rules also state that the attacking player is not allowed go into the semicircular area inhabited by the goalkeeper; and all the shots on goal must be taken from outside the semicircle. This is 'the last line of defence'.