The severity of occupant injuries sustained during automotive collisions can increase when an occupant is out‐of‐position prior to the crash. Several studies have shown that muscle activation significantly affects human kinematics in low severity impacts or pre‐crash car movements. As such, it is important to quantify the influence of this behaviour to effectively design safety systems. Reactive behaviour can be simulated with a recently developed computer human model that stabilises to a predefined position. The objective of this study was to adapt this model to simulate realistic bracing behaviour during braking. A new neck model was developed as well as a new arm model. In an anterior‐posterior frequency perturbation test the new neck model showed a more comparable response to that of a volunteer than the previous model. In arm pulse perturbation tests the new arm model showed comparable behaviour to a volunteer in relaxed as well as in braced conditions. Finally, a simulation of a braking event with the new active human model showed that bracing has a substantial effect on the head and thorax displacement. It is concluded that the new neck and new arm model improved the active human model for the development of active safety systems.