A back support mechanism for a vehicle seat is provided with a track
mounted to a seat back of the vehicle seat. A carriage is mounted to the
track for linear translation along the track between a first position and
an actuated position. A support member is connected to the carriage for
supporting a back portion of an occupant of the vehicle seat. A biasing
member cooperates with the carriage to urge the carriage to the first
position. If the occupant back portion imparts a load to the support
member exceeding a predetermined force, the support member and the
carriage translate along the track over a range of translation. The range
of translation is sized to accommodate a corresponding translation of a
head of the occupant to a head restraint of the vehicle seat.