Device suitable for a bicycle ergometer. The invention relates to a device for safely adapting a bicycle ergometer for elderly, obese or disabled subjects for the purposes of medical treatment, sports training or fitness training. It consists of a base (1), receiving a motorised articulated leg (4) influencing the height and inclination of the seat (5) with the extensions thereof (18) and (30), controlled from the end of a handle (1 1) and receiving in support the seat (5) mounted on a sliding support (6), which can be adjusted manually or by means of a motor. The seat (5) comprises a backrest (8) consisting of two vertical elements with extensions (20), separated by a ventilation slot (9), mounted on the axis (10) and facing the seat (5), a handlebar (16) attached to a frame (14) with a control screen (15) and, in the lower portion, a housing (12) having a pedal arrangement with staged resistors (13) controlled from the end of a handle (32). The backrest (8) with the extensions thereof mounted on the axis (10) can be positioned horizontally in the extension of the seat (5) so that the ankles of a subject lying on the seat (5) can be positioned at a level higher than the head on ankle rests (17) located on either side of the handlebar (16). The device according to the invention is particularly intended for elderly, obese or disabled subjects for the purposes of treatments, fitness tests, scans, relaxation techniques, sampling and other medical or non-medical uses.Dispositif adapté à un cycloergomètre. Linvention concerne un dispositif permettant dadapter en toute sécurité un cycloergomètre pour les sujets âgés, obèses ou handicapés, aux soins médicaux, aux entraînements de sportifs ou de fitness. Il est constitué dun socle (1), recevant une jambe articulée motorisée (4) agissant sur la hauteur et linclinaison du siège (5) avec ses extensions (18) et (30), commandée depuis lextrémité dune poignée (11) et recevant en appui, le siège (5) monté sur un support coulissant
