The Characterization of Spinal Compression in Various-Sized Human and Manikin Subjects During +Gz Impact

Abstract : Background: During +Gz impacts such as those encountered during ejection, the human torso and spine compress or slump due to the inertial forces acting on the body. Spinal compression can be characterized by a second-order differential equation involving coefficients such as damping ratio, natural frequency and spring constant. Objective: To characterize spinal compression resulting from +Gz impacts and determine how well test manikins replicate responses of similar size humans. Methods: Various-sized humans were tested with identical conditions on a vertical deceleration tower. Seat and chest accelerations were used to calculate the damping ratio, natural frequency and spring constant of each subject. Data analysis was performed to determine what correlations may exist between spinal compression and sitting height, torso mass, gender or vibration parameters. Results: Results show that spinal compression had no significant correlation to sitting height, torso mass, gender, damping ratio, undamped natural frequency or spring constant.