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The objective of this study was to characterize the ES-2 head and neck response to lateral impacts at varying low magnitudes of impact velocities. A pendulum and mini sled were used to deliver inertial acceleration pulses to an isolated ES-2 head and neck. The base of the neck was attached to a cart which slid along the direction of impact from left to right on two precision ground rails. The shape of the cart acceleration was controlled by altering the momentum transfer of the pendulum. Eighteen tests were conducted at velocities ranging from 1.0 to 4.3 m/s. The head was instrumented with an internal nine accelerometer package to measure the linear and angular head accelerations. Upper and lower neck load cells measured the forces and moments. Cart and pendulum acceleration were measured from uniaxial accelerometers. All data was sampled at 20 kHz and filtered according to SAEJ211. A six-camera 1 kHz Vicon system measured the 3-d kinematics of retroreflective targets affixed to the head and neck. All forces and moments increased with velocity. Peak axial and shear forces at the upper and lower neck were similar, however moments at the lower neck were up to three times higher. The Head to T1 (Head-T1) and Head to Upper Spine (Head-US) angles were calculated from the marker position data. The Head-US angle plateaued at about 10 degrees at the high velocity due to the physical constraints of the upper neck joint. Peak Head-T1 angle increased up to about 50 degrees at the end velocity; however the overall percentage contribution of the Head-US angle to the Head-T1 angle decreased. The ES-2 head displayed a characteristic head lag that was demonstrated in Head-US angle and upper neck moment plots in velocities above 1.0 m/s which have also been reported in the human head neck complex studies. Matched paired tests with isolated Post Mortem Human Subjects are necessary to fully compare the ES-2 head and neck biofidelity.

Experimental studies indicate age and degeneration affect spinal biomechanics. In vitro biomechanical experimentation is used to validate finite element cervical spine models. A high percentage of experimental studies have utilized older specimens. Computer models based on these experimental studies may not accurately represent the normal population. Younger full-column and C5-C6 motion segments were tested under pure sagittal plane moments. A review of literature was conducted, and results from previous studies were compared to present data to determine whether age was an influencing factor in spinal biomechanics. Findings indicate younger specimens under equivalent pure moment loading magnitudes underwent greater ranges of motion between 0.5 and 2.5 Nm. Based on these preliminary findings, validation of finite element modeling to ensure biofidelity should consider age as a factor that may affect biomechanics.

To accommodate the needs of women in participating in expanded combat roles, NAWCAD is investigating the dynamic strength capabilities of small stature females (54.4 kg (120 lb.) or less) to eject, support added head weight, and fly under G-stress. Within the scope of these tests, small stature females demonstrated the strength and endurance to safely fly physically strenuous missions and safely initiate ejection during severe physically taxing dynamic conditions. However, cockpit accommodation and pilot reach limits may hinder the small stature pilot during flight emergencies requiring full stick authority or ejection during flat spin and arrestment. Additionally, some small stature female pilots may not be able to properly position their heads due to a combination of inadequate restraint and lack of sufficient neck strength to read critical displays during flat spin recovery conditions and arrestment.