Prediction of head/neck dynamic response of selected military subjects to -Gx acceleration

Eighteen young male subjects with NAMRL sled test experience to 15 G in --Gx acceleration were measured for physical characteristics of the head and neck and general body anthropometry. Measurements taken include head/neck range of motion, neck muscle stretch reflex time, neck muscle isometric strength capabilities, and seated and standard anthropometry. Data from these tests were tabulated and five subjects whose physical characteristics were most similar were selected for use in simulations. Experimental data from NAMRL sled tests were obtained for the five subjects in 6- and 15-G test runs. Measurements data from the five subjects were used to establish a data set for the MVMA-2D Crash Victim Simulator and acceleration profiles for 6- and 15-G sled runs were used as input to the model. Simulation results for head angular acceleration, head angular velocity, head angular position, head resultant acceleration, and T1 resultant acceleration were compared with the averaged experimental curves for the five subjects. In general, excellent agreement between simulation and experimental results was obtained although some consistent differences were noted. Effects of varying levels of muscle activation were investigated. Variations in muscle tension level were found to have significant effects on simulation results at both 6 and 15, G, especially on head angular position. The effects were noticeably greater at lower acceleration's, however. The model was also used to investigate some of the biomechanical mechanisms behind observed response characteristics.