In this master thesis it have been investigated how the stiffness of a seat affect the risk of neck injuries, e.g whiplash associated disorders, in a rear end low velocity car collision using a female human body model, HBM, and if dividing the seat into several sections with different stiffnesses. The project is performed in collaboration with CEVT, China Euro Vehicle Technology, a innovation center of the Geely Holding Group. The HBM used is the VIVA open source HBM developed by Chalmers University of Technology together with Volvo Cars, The Swedish National Road and Transport ResearchInstitute (VTI) and Folksams forskningsstiftelse. Two different seats were investigated, a generic seat and the seat of the existing Lynk&Co 01. The stiffness of the seat had a significant impact on the risk of neck injuries, but does not seem to be a good idea to divide the seat into several sections since the height of the individual in the seat influence what stiffness is optimal for each section. It was also discovered that the relative distance between the head and the headrest at the moment of impact has a great affect on the risk of neck injuries.