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The response of the human head and neck to impact acceleration has been previously reported for the -X (chest to back) and +Y (right to left) directions. Wide ranges of sled peak acceleration, rate of onset of acceleration and duration of acceleration have been investigated and reported. A major mechanical effect on the dynamic response due to initial position for the -X direction has been reported. The purpose of this study is to report the initial position effect on the human head and neck response for +Y direction experiments. Four initial positions of the head relative to the first thoracic vertebral body (T1) have been investigated over a range of sled acceleration peaks from 2 to 7G. The data from six young adult male volunteers representative of a wide range of anthropometry will be presented. There are 18 experiments for each volunteer for a total of 108 experiments.

The systematic measurement of the inertial response of human subjects to impact acceleration has been underway for several years. The response of the head and first thoracic vertebra (T1) has been reported for a variety of sled acceleration profiles. In order to better describe the inertial response of man, it is necessary to measure the pelvic response in addition to the response of the head and T1. A pelvic anatomical mount has been constructed and used on one volunteer undergoing successively higher levels of -Gx impact acceleration. The description of the use of the mount is given. The data for four runs in a maximum rate of onset and maximum duration configuration from 2 - 7 G peak acceleration, using the 12-in HyGe® accelerator are reported. Data from this subject for -Gx impact acceleration experiments have been previously reported and are compared to data from the experiments with the pelvic mount.

The parameters of duration, rate of onset and peak acceleration of the sled have been identified by other investigators as determinants of the dynamic and injury response of man. A series of human experiments have been conducted to measure the response of the head and the first thoracic vertebrae to these parameters. Each subject was run at three conditions defined as high rate of onset-long duration (HOLD), high rate of onset-short duration (HOSD) and low rate of onset-long duration (LOLD) at peak accelerations of 6, 10 and 15G. Comparison time profiles of angular acceleration, angular velocity and linear resultant acceleration at the head anatomical origin and horizontal linear acceleration at the T1 origin are presented for 5 to 8 subjects at each of the three peak sled acceleration levels.

In preparation of an analog of human head and neck, the reports by R. G. Snyder and others were noted which stated that initial position of the head and neck had a definite effect upon resulting response. An investigation was undertaken to attempt to quantitate this effect, as a part of a much larger study underway for several years. Thirteen human volunteer subjects ranging from the 5th to the 97th percentile in sitting height were exposed to -Gx impact acceleration at peak sled accelerations of 6G and 10G. Two angles of the neck relative to chair and two angles of the head relative to the neck for a total of four conditions were tested for each subject for the 2 peak acceleration levels giving a total of 104 experiments. Instrumentation consisted of 6 accelerometers and two-axis rate gyro at the posterior spinous process of the first thoracic vertebral body, 6 accelerometers at the mouth, and a two-axis rate gyro at the top of the head.