The vehicle seat backrest has posts (20) are joined together by a crossmember (28) which is capable of deformation in the longitudinal direction by a passenger imposing an accident induced high load. The crossmember is placed at a greater distance from the upper edge (34) than the lower edge (36). The backrest frame also has a traverse (22) extending near the upper edge which is formed as a stiff structure. A passenger with a body weight of 100 kg can cause a deformation of at least 8 cm, but pref. at least 15 cm.
