Because of the increased availability and use of both safety belts and air bags, neck injuries resulting from tension and bending due to air bag contact and non-contact, inertial loadings represent a new and continuing trend in injuries. Unfortunately, injury prevention depends upon a virtually unknown understanding of the muscular and ligamentous response of the human neck in bending and tension. Therefore, ligamentous and muscular contribution to tension and bending was studied through a validated computational model to injury. Experimentally determined tolerance and response of the cadaveric ligamentous neck in tension and bending were used to develop and validate a ligamentous computational model. Biomechanical testing of upper cervical spine bending was coupled with imaging and landmark digitizing to determine the location of the occipital condyles and centers of rotation. The center of rotation for OC-C2 is located at the occipital condyles. The computational model incorporated new tension and bending ligamentous properties, new upper cervical spine properties, and passive and active properties of twenty-three anthropometrically correct neck muscles. Optimization, using Response Surface Methodology and Latin Hypercube Design, was used to determine muscle activation schemes. Relaxed (unaware) and tensed (aware) activation schemes were determined. Previously published volunteer studies were used to validate the muscular model. Isometric bending studies were simulated with activation schemes determined for maximum voluntary contraction. Volunteer isometric bending strength along the cervical spine was predicted. Maximum activation of all muscles is unrealistic, but distinct activation schemes can maintain head-neck equilibrium. Co-activation was found for every activation scheme, even with linear performance objectives. The hyoids were necessary flexors. Multi joint muscles, including non-traditional cervical muscles like trapezius, were predicted to be active and major contributors for a tensed individual and in isometric extension. The range of tensile tolerance estimation was reduced from between 1.8 kN to 4.8 kN to between 3.1 kN and 3.7 kN, while the muscle bending strength potential is greater in the lower cervical spine than the upper cervical spine. The validated computational muscular model provided insight into muscle contribution to the overall strength of the cervical spine and the estimation of tolerance of the human cervical spine.