The main objective of this thesis is to develop a computational human musculoskeletal model to investigate the change in the kinematic behavior of the model's lower extremities under the influence of activated (active) and deactivated (passive) muscles during a representation frontal collision using OpenSim software. Since OpenSim is seldom used in crash simulations, an appropriate model evaluation is performed by comparing the model's kinematics, obtained from the OpenSim's inverse dynamic simulation, against LS-DYNA's explicit non-linear side impact simulation of a finite element model for a car-pedestrian collision. The required musculoskeletal model is constructed in OpenSim and scaled to meet the requirements of the Hybrid III 50th Percentile crash test dummy. For evaluating the developed model, the kinematics from both programs (OpenSim and LS-DYNA), containing identical displacement data, is compared by visual observation of identical time frames. Using the evaluated model in the forward dynamics domain of OpenSim, a representative frontal crash simulation is conducted for the active and passive muscle states of the model, and the kinematic difference in its lower extremities is observed and compared. The results were also compared to MADYMO's human body model simulations conducted under similar conditions. This study indicates that the role of the muscle activation on the human body responses during a car collision is important. The novel technique developed and utilized in this study is shown to be quite useful in modeling and simulation of a car occupant's real kinematic response during a car collision.