The purpose of this study was to document head and neck loading in a group of ordinary people engaged in non-injurious everyday and more vigorous physical activities. Twenty (20) volunteers that were representative of the general population were subjected to seven test scenarios: a soccer ball impact to the forehead, a self-imposed hand strike to the forehead, vigorous head shaking, plopping down in a chair, jumping off a step, a seated drop onto the buttocks, and a vertical drop while seated supine in a chair. Some scenarios involved prescribed and well-controlled stimuli, while others allowed the volunteers to perform common activities at a self-selected level of intensity. Head accelerations up to 31 g and 2888 rad/s(2) and neck loads up to 268 N in posterior shear, 526 N in compression, and 36 Nm in extension were recorded. Most head and neck injury criteria predicted a low risk of injury in all activities. However, rotational head accelerations and Neck Injury Criterion (NIC) values were much higher than some proposed tolerance limits in a large number of tests, all of which were non-injurious. The data from this study help us to establish an envelope of head and neck loading that is commonly encountered and presents a minimal risk of injury.
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The purpose of this study was to develop a numerical analytical model of collinear low-speed bumper-to-bumper crashes and use the model to perform parametric studies of low-speed crashes and to estimate the severity of low-speed crashes that have already occurred. The model treats the car body as a rigid structure and the bumper as a deformable structure attached to the vehicle. The theory used in the model is based on Newton's Laws. The model uses an Impact Force-Deformation (IF-D) function to determine the impact force for a given amount of crush. The IF-D function used in the simulation of a crash that has already occurred can be theoretical or based on the measured force-deflection characteristics of the bumpers of the vehicles that were involved in the actual crash. The restitution of the bumpers is accounted for in a simulated crash through the rebound characteristics of the bumper system in the IF-D function. The output of the model for a numerical simulation is the acceleration vs. time information for each vehicle in the simulated crash. Three low-speed crash tests were performed and the dynamic IF-D curve was measured in each crash. The analytical model was used to simulate the three low-speed crash tests in order to demonstrate the model's ability to describe the vehicle dynamics in a crash that has already occurred. The model is also used to perform parametric studies that show how the structural characteristics of the vehicles' bumpers and the closing speed affect the crash pulse and to demonstrate a technique to estimate the maximum severity of a low-speed crash that has already occurred.
Study Design.This study combined all prior research involving human volunteers in low-speed rear-end impacts and performed a comparative analysis of real-world crashes using the National Automotive Sampling System – Crashworthiness Data System.Objective.The aim of this study was to assess the rates of neck pain between volunteer and real-world collisions as well as the likelihood of an injury beyond symptoms as a function of impact severity and occupant characteristics in real-world collisions.Summary of Background Data.A total of 51 human volunteer studies were identified that produced a dataset of 1984 volunteer impacts along with a separate dataset of 515,601 weighted occupants in real-world rear impacts.Methods.Operating-characteristic curves were created to assess the utility of the volunteer dataset in making predictions regarding the overall population. Change in speed or delta-V was used to model the likelihood of reporting symptoms in both real-world and volunteer exposures and more severe injuries using real-world data. Logistic regression models were created for the volunteer data and survey techniques were used to analyze the weighted sampling scheme with the National Automotive Sampling System database.Results.Symptom reporting rates were not different between males and females and were nearly identical between laboratory and real-world exposures. The minimal risk of injury predicted by real-world exposure is consistent with the statistical power of the large number of volunteer studies without any injury beyond the reporting of neck pain.Conclusion.This study shows that volunteer studies do not under-report symptoms and are sufficient in number to conclude that the risk of injury beyond neck strain under similar conditions is essentially zero. The real-world injury analyses demonstrate that rear impacts do not produce meaningful risks of cervical injury at impacts of similar and greater severity to those of the volunteer research. Future work concerning the mechanism of whiplash-related trauma should focus on impacts of severity greater than those in the current literature.Level of Evidence: 3
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