In order to accurately represent the response of live occupants during pre-crash events and frontal crashes, computational human body models (HBMs) that incorporate active musculature must be validated with appropriate volunteer data that represents a wide range of demographic groups and potential crash conditions. The purpose of this study was to quantify and compare occupant kinematic responses for unaware (relaxed) small female and midsize male volunteers during low-speed frontal and frontal-oblique sled tests across multiple test conditions, while recognizing, assessing, and accounting for potential acclimation effects due to multiple exposures. Six 5th percentile female and six 50th percentile male volunteers were exposed to multiple low-speed frontal and frontal-oblique sled tests on two separate test days. Volunteers experienced one test orientation and two pulse severities (1 g and 2.5 g) on each test day. A Vicon motion capture system was used to quantify the three-dimensional (3D) kinematics of the volunteers. Peak forward excursions of select body locations were compared within a test day and between test days for the same test condition to determine if and how acclimation occurred. Differences between demographic groups were also compared after accounting for any observed acclimation. Acclimation was not observed within a test day but was observed between test days for some demographic groups and some test conditions. In general, head, neck, and shoulder responses were affected, but the elbow, hip, and knee responses were not. Males generally moved farther forward compared to females during the frontal tests, but both groups moved forward similarly during the frontal-oblique tests. Overall, this study provides new female and male biomechanical data that can be used to further develop and validate HBMs that incorporate active musculature in order to better understand and assess occupant response and injury risk in pre-crash events and frontal crashes.
<div>Previous volunteer studies focused on low-speed frontal events have demonstrated
that muscle activation (specifically pre-impact bracing) can significantly
affect occupant response. However, these tests do not always include a
sufficient number of small female volunteers to compare their unique responses
to the typically studied midsize male population. The purposes of this study
were to quantify the occupant kinetics and muscle responses of relaxed and
braced small female and midsize male volunteers during low-speed frontal sled
tests and to compare between muscle states and demographic groups. Small female
and midsize male volunteers experienced multiple low-speed frontal sled tests
consisting of two pulse severities (1 g and 2.5 g) and two muscle states
(relaxed and braced) per pulse severity. The muscle activity of 30 muscles (15
bilaterally) and reaction forces at the volunteer-test buck interfaces and seat
belt were measured before and during each sled test. Compared to the relaxed
muscle state, bracing generally increased pre-test muscle activity and pre-test
forces, delayed muscle activation (relative to the pre-test value) in response
to the sled pulse, and increased peak forces during the sled tests. However,
relaxed volunteers exhibited greater changes in muscle activity and reaction
forces relative to the pre-test value. Males exhibited higher peak forces across
all reaction surfaces during the sled tests compared to females, but peak muscle
activity varied as to whether males or females exhibited higher activation. The
upper extremity muscles activated the most during pre-test bracing, while the
upper extremity, trunk, and neck muscles activated the most during the sled
tests.</div>
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