The present invention concerns a device for preventing or relieving pain in the lower back of a human subject, the device being configured for use while the subject lies in a supine position on an underlying surface, the device comprising: (i) at least one body-engaging element configured for engaging the rear surface of the knee of a subject； and (ii) a drive mechanism mechanically linked to said at least one body-engaging element, said drive mechanism being configured to move said engaging element. a tensioning portion having a primarily vertical lifting motion followed by a primarily horizontal tensioning motion to thereby apply tension to the lower back of the subject.
