The seat depth adjustable motor vehicle seat comprises a first seat part, a second seat part and a longitudinal adjustment device interposed between the first seat part and the second seat part and allowing for displacement movement in a first seat direction of the first seat part relative to the second seat part. A support arm in accordance with an exemplary embodiment of present invention comprises a first strut, a second strut, a proximal link, and a distal link. The core element is composed by a first and a second core part that are arranged along each other.