The Effects of Training and Subject Reproducibility during Vertical Impact Acceleration

To address questions regarding the effect of subject reproducibility and how it might affect date variability, a series of impact tests were conducted on the Vertical Deceleration Tower at AFRL/HEPA. Ten male and seven female subjects volunteered and were exposed to a combination of varying helmet weights and +Gz impact levels. Each combination was reproduced up to three times. The tests were first conducted in a sequential manner, with the lowest exposure experienced first for safety reasons. The last two replications were randomized so that the biodynamic response was not dependent on the last test configuration. Subjects were evaluated for reproducibility at 6, 6, and lOG with varying helmet weights. The bead and sternum accelerations in the Z direction were used to analyze the biodynamic response along with neck loads generated at the occipital condyles. These neck forces were calculated using the helmet inertial properties, subject anthropometry, and the recorded head accelerations. The results from the study revealed no effect of training on the subjects' biodynamic response. A reproducibility limit was calculated for all subjects and all test conditions to be approximately 30% for the dependent variables. Results also showed a significant difference for gender on the neck force and a significant difference for both gender and experience for sternum Z acceleration. There was no meaningful correlation per test condition as a function of gender, experience, and reproduced exposures. This work was completed under the work unit: Heck Protection with Advanced Helmet and Vehicle Systems.