An apparatus for closed kinetic chain muscle strengthening and/or rehabilitation of the shoulder joint and of the upper limb includes a device for positioning the user or patient, a working assembly having a resistor, allowing the user or patient to exert efforts, support device which connects the working assembly to the positioning device, and which is fitted with an adjustor for positioning and orienting the working assembly in space. The support device and also the adjustor are configured such that the resistor can be positioned, relative to the user or patient, above and laterally on the side of the limb to be worked, which is positioned outstretched, raised in the plane of the scapula until it is along the extension of the subcutaneous part of the spine of the scapula.
