A foot bar assembly for use on a reformer exercise apparatus (100; 400) having a generally rectangular frame (102; 402) with parallel side portions (108; 408), a head end (104; 404) and a foot end (106; 406), each side portion (108; 408) having an outwardly open slot (136; 436) extending along at least part of the side portion (108; 408), the foot bar assembly comprising: a generally U shaped foot bar (111; 411) sized to span the parallel side portions (108; 408), of a reformer exercise apparatus, the foot bar (111; 411) having a first end and a second end; and a pair of foot bar support assemblies (170; 470), wherein each foot bar support assembly (170; 470) comprises: an elongated slide plate (172, 204; 538) configured to be movably supported by an outwardly open slot (136; 436) of one of the side portions (108; 408) of the reformer exercise apparatus; a hook plate (174; 474) parallel to the slide plate (172, 204; 538) fastened to the slide plate (172, 204;538); and a foot bar support arm (158; 458) rotatably and slidably fastened to the hook plate (174; 474) and having an end (156; 456) fastened to one of the first and second ends of the foot bar (111; 411); characterised in that the foot bar assembly further comprises: a locking member (200; 530) operably coupled to the hook plate (174; 474) to permit movement of the slide plate (172, 204; 538) along the outwardly open slot (136; 436) only when the foot bar support arm (158; 458) is in a predetermined position with respect to the hook plate (174; 474) and prevent movement of the slide plate (172, 204; 538) along the outwardly open slot (136; 436) when the foot bar support arm (158; 458) is in other than the predetermined position. a generally U shaped foot bar (111; 411) sized to span the parallel side portions (108; 408), of a reformer exercise apparatus, the foot bar (111; 411) having a first end and a second end; and a pair of foot bar support assemblies (170; 470), wherein each foot bar support assembly (170; 470) comprises: an elongated slide plate (172, 204; 538) configured to be movably supported by an outwardly open slot (136; 436) of one of the side portions (108; 408) of the reformer exercise apparatus; a hook plate (174; 474) parallel to the slide plate (172, 204; 538) fastened to the slide plate (172, 204;538); and a foot bar support arm (158; 458) rotatably and slidably fastened to the hook plate (174; 474) and having an end (156; 456) fastened to one of the first and second ends of the foot bar (111; 411); an elongated slide plate (172, 204; 538) configured to be movably supported by an outwardly open slot (136; 436) of one of the side portions (108; 408) of the reformer exercise apparatus; a hook plate (174; 474) parallel to the slide plate (172, 204; 538) fastened to the slide plate (172, 204;538); and a foot bar support arm (158; 458) rotatably and slidably fastened to the hook plate (174; 474) and having an end (156; 456) fastened to one of the first and second ends of the foot bar (111; 411); characterised in that the foot bar assembly further comprises: a locking member (200; 530) operably coupled to the hook plate (174; 474) to permit movement of the slide plate (172, 204; 538) along the outwardly open slot (136; 436) only when the foot bar support arm (158; 458) is in a predetermined position with respect to the hook plate (174; 474) and prevent movement of the slide plate (172, 204; 538) along the outwardly open slot (136; 436) when the foot bar support arm (158; 458) is in other than the predetermined position.