An exercise bicycle comprising: an exercise bicycle frame and at least one adjustment assembly comprising: a receiver comprising an elongate aperture; a slider, a first wedge block and a second wedge block, the slider positioned within the elongate aperture of the receiver and having an outer surface which substantially matches a shape of said elongate aperture to provide frictional engagement of the elongate aperture and the slider, the slider defining a first channel arranged to receive the first wedge block moveable fore and aft within the first channel, the first wedge block defining an engagement surface, the slider further arranged to receive the second wedge block, the second wedge block configured to move in a transverse direction within an aperture of the outer surface of the slider, said transverse direction being transverse to the first channel; and a handle operably coupled with the first wedge block to move the first wedge block within the first channel in a first direction or a second direction such that the engagement surface causes the movement of the second wedge block in said transverse direction to cause a frictional coupling between the slider and the receiver when the first wedge block is moved in the first direction and to release the frictional coupling when the first wedge block is moved in the second direction such that in use the slider is moveable substantially fore and aft relative to the receiver in order to adjust the position of the slider within the elongate aperture of the receiver. an exercise bicycle frame and at least one adjustment assembly comprising: a receiver comprising an elongate aperture; a slider, a first wedge block and a second wedge block, the slider positioned within the elongate aperture of the receiver and having an outer surface which substantially matches a shape of said elongate aperture to provide frictional engagement of the elongate aperture and the slider, the slider defining a first channel arranged to receive the first wedge block moveable fore and aft within the first channel, the first wedge block defining an engagement surface, the slider further arranged to receive the second wedge block, the second wedge block configured to move in a transverse direction within an aperture of the outer surface of the slider, said transverse direction being transverse to the first channel; and a handle operably coupled with the first wedge block to move the first wedge block within the first channel in a first direction or a second direction such that the engagement surface causes the movement of the second wedge block in said transverse direction to cause a frictional coupling between the slider and the receiver when the first wedge block is moved in the first direction and to release the frictional coupling when the first wedge block is moved in the second direction such that in use the slider is moveable substantially fore and aft relative to the receiver in order to adjust the position of the slider within the elongate aperture of the receiver. a receiver comprising an elongate aperture; a slider, a first wedge block and a second wedge block, the slider positioned within the elongate aperture of the receiver and having an outer surface which substantially matches a shape of said elongate aperture to provide frictional engagement of the elongate aperture and the slider, the slider defining a first channel arranged to receive the first wedge block moveable fore and aft within the first channel, the first wedge block defining an engagement surface, the slider further arranged to receive the second wedge block, the second wedge block configured to move in a transverse direction within an aperture of the outer surface of the slider, said transverse direction being transverse to the first channel; and a handle operably coupled with the first wedge block to move the first wedge block within the first channel in a first direction or a second direction such that the engagement surface causes the movement of the second wedge block in said transverse direction to cause a frictional coupling between the slider and the receiver when the first wedge block is moved in the first direction and to release the frictional coupling when the first wedge block is moved in the second direction such that in use the slider is moveable substantially fore and aft relative to the receiver in order to adjust the position of the slider within the elongate aperture of the receiver.