Comparison of Adult Female and Male PMHS Pelvis and Lumbar Response to Underbody Blast.

The goal of this study was to gather and compare kinematic response and injury data on both female and male whole-body Post-mortem Human Surrogates (PMHS) responses to Underbody Blast (UBB) loading. Midsized males (50th percentile, MM) have historically been most used in biomechanical testing and were the focus of the Warrior Injury Assessment Manikin (WIAMan) program, thus this population subgroup was selected to be the baseline for female comparison. Both small female (5th percentile, SF) and large female (75th percentile, LF) PMHS were included in the test series to attempt to discern whether differences between male and female responses were predominantly driven by sex or size. Eleven tests, using 20 whole-body PMHS, were conducted by the research team. Preparation of the rig and execution of the tests took place at the Aberdeen Proving Grounds (APG) in Aberdeen, MD. Two PMHS were used in each test. The Accelerative Loading Fixture (ALF) version 2, located at APG's Bear Point range was used for all male and female whole-body tests in this series. The ALF was an outdoor test rig that was driven by a buried explosive charge, to accelerate a platform holding two symmetrically mounted seats. The platform was designed as a large, rigid frame with a deformable center section that could be tuned to simulate the floor deformation of a vehicle during a UBB event. PMHS were restrained with a 5-point harness, common in military vehicle seats. Six-degree-of-freedom motion blocks were fixed to L3, the sacrum, and the left and right iliac wings. A three-degree-of freedom block was fixed to T12. Strain gages were placed on L4 and multiple locations on the pelvis. Accelerometers on the floor and seat of the ALF provided input data for each PMHS' feet and pelvis. Time histories and mean peak responses in z-axis acceleration were similar among the three PMHS groups in this body region. Injury outcomes were different and seemed to be influenced by both sex and size contributions. Small females incurred pelvis injuries in absence of lumbar injures. Midsized males had lumbar vertebral body fractures without pelvis injuries. And large females with injuries had both pelvis and lumbar VB fractures. This study provides evidence supporting the need for female biomechanical testing to generate female response and injury thresholds. Without the inclusion of female PMHS, the differences in the injury patterns between the small female and midsized male groups would not have been recognized. Standard scaling methods assume equivalent injury patterns between the experimental and scaled data. In this study, small female damage occurred in a different anatomical structure than for the midsized males. This is an important discovery for the development of anthropomorphic test devices, injury criteria, and injury mitigating technologies. The clear separation of small female damage results, in combination with seat speeds, suggest that the small female pelvis injury threshold in UBB events lies between 4 - 5 m/s seat speed. No inference can be made about the small female lumbar threshold, other than it is likely at higher speeds and/or over longer duration. Male lumbar spine damage occurred in both the higher- and lower lower-rate tests, indicating the injury threshold would be below the seat pulses tested in these experiments. Large females exhibited injury patterns that reflected both the small female and midsized male groups - with damaged PMHS having fractures in both pelvis and lumbar, and in both higher- and lower- rate tests. The difference in damage patterns between the sex and size groups should be considered in the development of injury mitigation strategies to protect across the full population.

Explaining and predicting the increased thorax injury in aged females: age and subject-specific thorax geometry coupled with improved bone constitutive models and age-specific material properties evaluated in side impact conditions.

Predicting and understanding thorax injury is fundamental for the assessment and development of safety systems to mitigate injury risk to the increasing and vulnerable aged population. While computational human models have contributed to the understanding of injury biomechanics, contemporary human body models have struggled to predict rib fractures and explain the increased incidence of injury in the aged population. The present study enhanced young and aged human body models (HBMs) by integrating a biofidelic cortical bone constitutive model and population-based bone material properties. The HBMs were evaluated using side impact sled tests assessed using chest compression and number of rib fractures. The increase in thoracic kyphosis and the associated change in rib angle with increasing age, led to increased rib torsional moment increasing the rib shear stress. Coupled with and improved cortical bone constitutive model and aged material properties, the higher resulting shear stress led to an increased number of rib fractures in the aged model. The importance of shear stress resulting from torsional load was further investigated using an isolated rib model. In contrast, HBM chest compression, a common thorax injury-associated metric, was insensitive to the aging factors studied. This study proposes an explanation for the increased incidence of thorax injury with increasing age reported in epidemiological data, and provides an enhanced understanding of human rib mechanics that will benefit assessment and design of future safety systems.

Comparison of child and ATD belt fit and posture on belt-positioning boosters during self-selected, holding device, and nominal conditions.

OBJECTIVE: Pediatric anthropomorphic test devices (ATDs) are important tools for the assessment of child occupant protection and should represent realistic child belt fit and posture on belt-positioning boosters. Previous comparisons have been made to children in either self-selected or nominal postural conditions. This study compares belt fit and postural measurements between pediatric ATDs and a single cohort of children assuming different postures on boosters: self-selected, holding a portable electronic device, and nominal. METHODS: A cohort of children (n = 25) were evaluated in a stationary vehicle on five boosters and in three postural conditions: nominal, self-selected, and a representative holding electronic device position. The Hybrid III 6- and 10-year-old and Q-Series 6- and 10-year-old ATDs were evaluated in the same five boosters and in two postural conditions: nominal and a representative holding electronic device position. A 3D coordinate measurement device was used to quantify belt fit (shoulder belt score, lap belt score, maximum gap size, and gap length) and anatomic landmark positions (head, suprasternale, ASIS, and patella). Landmark positions and belt fit were compared between ATDs and children for each booster and postural condition, and Pearson correlations (r) were assessed across boosters. RESULTS: ATDs generally represented Nominal child postures across boosters. In the Device condition, ATDs were seldom able to be positioned to represent both the torso and head position of children, due to limited ATD spinal flexibility. When the torso position was matched, the ATD head was more rear by 63 mm. Correlations between Nominal child and ATD belt fit and belt gap metrics were generally weak and not significant, with the exception of lap belt score (all ATDs p < 0.07, r = 0.8549-0.9857). DISCUSSION: ATDs were generally able to represent realistic child postures and lap belt fit in Nominal and short duration Self-selected postures in a laboratory setting. However, these results display the potential difficulty of utilizing ATDs to represent more naturalistic child postures, especially the more forward head positions and flexed spinal posture associated with utilizing a portable electronic device.

Biofidelity assessment of the GHBMC M50-O in a rear-facing seat configuration during high-speed frontal impact.

The objective of this study was to assess the biofidelity of the Global Human Body Models Consortium (GHBMC) 50th male (M50-O) v6.0 seated in an upright (25-degree recline) all-belts-to-seat (ABTS) in a 56 km/h rear-facing frontal impact. The experimental boundary conditions from the post-mortem human subjects (PMHS) tests were replicated in the computational finite element (FE) environment. The performance of the rigidized FE ABTS model obtained from the original equipment manufacturer was validated via simulations using a Hybrid III FE model and comparison with experiments. Biofidelity of the GHBMC M50-O was evaluated using the most updated NHTSA Biofidelity Ranking System (BRS) method, where a biofidelity score under 2 indicates that the GHBMC response varies from the mean PMHS response by less than two standard deviations, suggesting good biofidelity. The GHBMC M50-O received an occupant response score and a seat loading score of 1.71 and 1.44, respectively. Head (BRS = 0.93) and pelvis (BRS = 1.29) resultant accelerations, and T-spine (avg. BRS = 1.55) and pelvis (BRS = 1.66) y-angular velocities were similar to the PMHS. The T-spine resultant accelerations (avg. BRS = 1.93) and head (BRS = 2.82), T1 (BRS = 2.10) and pelvis (BRS = 2.10) Z-displacements were underestimated in the GHBMC. Peak chest deflection in the anterior-posterior deflection in the GHBMC matched with the PMHS mean, however, the relative upward motion of abdominal contents and subsequent chest expansion were not observed in the GHBMC. Updates to the GHBMC M50-O towards improved thorax kinematics and mobility of abdominal organs should be considered to replicate PMHS characteristics more closely.

Analysis of injury mechanism and thoracic response of elderly, small female PMHS in near-side impact scenarios.

OBJECTIVE: In 2020, 17% of all crash fatalities were individuals aged 65 years or older. Crash data also revealed that for older occupants, thoracic related injuries are among the leading causes of fatality. Historically, the majority of near-side impact postmortem human subjects (PMHS) studies used a generic load wall to capture external loads that were applied to PMHS. While these data were helpful in documenting biofidelity, they did not represent a realistic response an occupant would undergo in a near-side crash. The objective of this research was to test small, elderly female PMHS in a repeatable, realistic near-side impact crash scenario to investigate current injury criteria as they relate to this vulnerable population. METHOD: Ten small, elderly PMHS were subjected to a realistic near-side impact loading condition. The PMHS were targeted to be elderly females age 60+, approximately 5th percentile in height and weight, with osteopenic areal bone mineral density. Each subject was seated on a mass-production seat, equipped with a side airbag and standard three-point restraint with a pretensioner. Other boundary conditions included an intruding driver's side door. PMHS instrumentation included strain gages on ribs 3-10 bilaterally to identify fracture timing. Two chestbands were used to measure chest deflection, one at the level of the axilla and one at the level of the xiphoid process. RESULTS: Injuries observed included rib fractures, particularly on the struck side, and in multiple cases a flail chest was observed. Eight of ten subjects resulted in AIS3+ thoracic injuries, despite previously tested ATDs predicting less than a 10% chance of AIS3+ injury. Subjects crossed the threshold for AIS3 injury in the range of only 1% - 9% chest compression. Additionally, mechanisms of injury varied, as some injuries were incurred by door interactions while others came during airbag interactions. CONCLUSIONS: This research points to two areas of concern that likely require further analysis: (1) the appropriateness of potentially oversimplified PMHS testing to establish injury thresholds and define injury criteria for complicated crash scenarios; (2) the importance of identifying the precise timing of injuries to better understand the effect of current passive restraint systems.

NextGEM: Next-Generation Integrated Sensing and Analytical System for Monitoring and Assessing Radiofrequency Electromagnetic Field Exposure and Health.

The evolution of emerging technologies that use Radio Frequency Electromagnetic Field (RF-EMF) has increased the interest of the scientific community and society regarding the possible adverse effects on human health and the environment. This article provides NextGEM's vision to assure safety for EU citizens when employing existing and future EMF-based telecommunication technologies. This is accomplished by generating relevant knowledge that ascertains appropriate prevention and control/actuation actions regarding RF-EMF exposure in residential, public, and occupational settings. Fulfilling this vision, NextGEM commits to the need for a healthy living and working environment under safe RF-EMF exposure conditions that can be trusted by people and be in line with the regulations and laws developed by public authorities. NextGEM provides a framework for generating health-relevant scientific knowledge and data on new scenarios of exposure to RF-EMF in multiple frequency bands and developing and validating tools for evidence-based risk assessment. Finally, NextGEM's Innovation and Knowledge Hub (NIKH) will offer a standardized way for European regulatory authorities and the scientific community to store and assess project outcomes and provide access to findable, accessible, interoperable, and reusable (FAIR) data.

Comparison of Low-Cost 5G Electromagnetic Field Sensors.

This paper compares different low-cost sensors that can measure (5G) RF-EMF exposure. The sensors are either commercially available (off-the-shelf Software Defined Radio (SDR) Adalm Pluto) or constructed by a research institution (i.e., imec-WAVES, Ghent University and Smart Sensor Systems research group (S³R), The Hague University of Applied Sciences). Both in-lab (GTEM cell) and in-situ measurements have been performed for this comparison. The in-lab measurements tested the linearity and sensitivity, which can then be used to calibrate the sensors. The in-situ testing confirmed that the low-cost hardware sensors and SDR can be used to assess the RF-EMF radiation. The variability between the sensors was 1.78 dB on average, with a maximum deviation of 5.26 dB. Values between 0.09 V/m and 2.44 V/m were obtained at a distance of about 50 m from the base station. These devices can be used to provide the general public and governments with temporal and spatial 5G electromagnetic field values.

Comparison of small female PMHS thoracic responses to scaled response corridors in a frontal hub impact.

OBJECTIVE: The purpose of this study was to generate biomechanical response corridors of the small female thorax during a frontal hub impact and evaluate scaled corridors that have been used to assess biofidelity of small female anthropomorphic test devices (ATDs) and human body models (HBMs). METHODS: Three small female postmortem human subjects (PMHS) were tested under identical conditions, in which the thorax was impacted using a 14.0 kg pneumatic impactor at an impact velocity of 4.3 m/s. Impact forces to PMHS thoraces were measured using a load cell installed behind a circular impactor face with a 15.2 cm diameter. Thoracic deflections were quantified using a chestband positioned at mid-sternum. Strain gages installed on the ribs and sternum identified fracture timing. Biomechanical response corridors (force-deflection) were generated and compared to scaled small female thoracic corridors using a traditional scaling method (TSM) and rib response-based scaling method (RRSM). A BioRank System Score (BRSS) was used to quantify differences between the small female PMHS data and both scaled corridors. RESULTS: Coefficients of variation from the three small female PMHS responses were less than 2% for peak force and 7% for peak deflection. Overall, the scaled corridor means determined from the TSM and RRSM were less than two standard deviations away from the mean small female PMHS corridors (BRSS < 2.0). The RRSM resulted in smaller deviation (BRSS = 1.1) from the PMHS corridors than the TSM (BRSS = 1.7), suggesting the RRSM is an appropriate scaling method. CONCLUSIONS: New small female PMHS force-deflection data are provided in this study. Scaled corridors from the TSM, which have been used to optimize current safety tools, were comparable to the small female PMHS corridors. The RRSM, which has the great benefit of using rib structural properties instead of requiring whole PMHS data, resulted in better agreement with the small female PMHS data than the TSM and deserves further investigation to identify scaling factors for other population demographics.

Biomechanical effects of a halo orthotic on a pediatric anthropomorphic test device in a simulated frontal motor vehicle collision.

Objective: Cervical spine injuries in children under 10 frequently involve the craniocervical junction. In patients too small for conventional spinal instrumentation, treatment may involve placement of a halo orthotic, and these patients will frequently be discharged home in a halo orthotic. To date, little research has been done on the biomechanics of motor vehicle collisions involving young children in halo orthotics. To better understand possible safety concerns, we applied a halo orthotic to an appropriately sized anthropomorphic test device (ATD, or crash test dummy) on an acceleration sled to simulate a frontal motor vehicle collision.Methods: For the tests, a Hybrid III 3-year-old ATD was instrumented with head and chest accelerometers, head angular rate sensors, a six-axis upper neck load cell, and a chest linear potentiometer. Four tests were conducted on an acceleration sled, and kinematics were recorded with high speed video. Testing variables included 1) with or without a halo orthotic and 2) with a standard booster seat or a commercially available harness vest.Results: The halo orthotic reduced flexion and extension but was associated with increased rotation, especially in the condition of a halo orthotic with a standard booster seat. Increased cervical distraction was noted with the halo orthotic, and this was especially increased in the condition of a halo orthotic with the harness vest.Conclusions: The biomechanics of a child involved in a motor vehicular collision may be dramatically altered with a halo orthotic, as modeled by an acceleration sled test. While cervical spine flexion and extension are reduced with the halo orthotic, rotation appears to increase. Immobilization from a halo orthotic also appears to increase cervical distraction, especially when used in conjunction with a harness vest. Further testing is needed to determine the safest restraints for this small, but at-risk, population.

IN-SITU 5G NR BASE STATION EXPOSURE OF THE GENERAL PUBLIC: COMPARISON OF ASSESSMENT METHODS.

New measurement methods and equipment for correct 5G New Radio (NR) electromagnetic field (EMF) in-situ exposure assessment of instantaneous time-averaged exposure (Eavg) and maximum extrapolated field exposure (Emax) are proposed. The different options are investigated with in-situ measurements around 5G NR base stations (FR1) in different countries. The maximum electric field values satisfy the ICNIRP 2020 limit (maximum 7.7%). The difference between Emax and Eavg is <3 dB for the different measurement equipment at multiple sites in case there is only self-generated traffic. However, in a more realistic scenario, Eavg cannot be used to assess the exposure correctly due to influence of other users as the spatial distribution of user equipment (UE) influences Eavg, while Emax is not affected. However, when multiple UEs are collocated, there is no influence of the number of UEs. A broadband measurement can give a first impression of the RF-EMF exposure up to 700 m, but is not enough to assess the 5G-NR exposure.

Development of a Strain-Based Model to Predict Eviscerated Thoracic Response From Dynamic Individual Rib Tests.

The objective of this study was to develop an analytical model using strain-force relationships from individual rib and eviscerated thorax impacts to predict bony thoracic response. Experimental eviscerated thorax forces were assumed to have two distinct responses: an initial inertial response and subsequently, the main response. A second-order mass-spring-damper model was used to characterize the initial inertial response of eviscerated thorax force using impactor kinematics. For the main response, equivalent strains in rib levels 4-7 were mapped at each time point and a strain-based summed force model was constructed using individual rib tests and the same ribs in the eviscerated thorax test. A piecewise approach was developed to join the two components of the curve and solve for mass, damping, stiffness parameters in the initial response, transition point, and scale factor of the strain-based summed force model. The final piecewise model was compared to the overall experimental eviscerated thorax forces for each postmortem human subjects (PMHS) (n = 5) and resulted in R2 values of 0.87-0.96. A bootstrapping approach was utilized to validate the model. Final model predictions for the validation subjects were compared with the corridors constructed for the eviscerated thorax tests. Biofidelity ranking system score (BRSS) values were approximately 0.71 indicating that this approach can predict eviscerated responses within one standard deviation from the mean response. This model can be expanded to other tissue states by quantifying soft tissue and visceral contributions, therefore successfully establishing a link between individual rib tests and whole thoracic response.

Evaluation of static belt fit and belt torso contact for children on belt-positioning booster seats.

Objective: Previous studies have indicated that gap between the seatbelt and torso (reduced belt torso contact) for children on belt-positioning booster seats (BPBs) may lead to less torso engagement and increased likelihood of shoulder belt slip-off during evasive vehicle maneuvers, potentially increasing injury risk during crashes. However, current BPB belt fit measures do not quantify belt gap and may not be able to fully discriminate between designs which provide good vs. poor dynamic outcomes. The goal of this study was to evaluate both novel (belt gap characteristics) and conventional measures of seatbelt fit for BPB-seated children.Methods: Ten BPBs and three seatbelt anchor locations were investigated. Fifty volunteers (4-14 years) were recruited and each evaluated on six unique combinations of BPB and seatbelt anchor location on a vehicle rear seat in a laboratory setting. A 3 D coordinate measurement system quantified positions of anatomic, seatbelt, BPB, and vehicle reference points. Novel belt gap (gap size, length, location, and percent torso contact) and conventional belt fit (position of belt on shoulder and pelvis) metrics were calculated using anatomic and seatbelt landmarks. Variation in belt fit and belt gap outcomes due to BPB, seatbelt anchor location, and anthropometry were investigated.Results: BPBs produced significantly different outcomes, while seatbelt anchor location did not. BPBs with features that directly routed the lower portion of the shoulder belt more forward on the buckle side produced the largest (29.3 ± 12.6 mm) and longest (106.9 ± 68.2 mm) belt gap on average, while BPBs that pulled the belt less forward or did not directly route the belt produced the smallest (13.9 ± 6.7 mm) and shortest (16.9 ± 33.9 mm) gap on average. Belt gap outcomes were not strongly correlated with conventional belt fit metrics, indicating that evaluation of belt gap may provide additional insight when attempting to discriminate between BPBs which provide good vs. poor seatbelt engagement during vehicle maneuvers and crashes.Conclusions: This is the first study to evaluate belt gap characteristics for BPB-seated children. Results suggest that belt fit and belt gap are influenced by BPB design, particularly lower shoulder belt routings, and may have implications for belt engagement during dynamic events.

Evaluation of LATCH vs. non-LATCH installations for boosters in frontal impacts.

OBJECTIVES: The objective was to understand how the use or nonuse of the Lower Anchors and Tethers for Children (LATCH) system affects the performance of booster seats during frontal impacts. METHODS: Sixteen frontal impact sled tests were conducted at 24.8 ± 0.3 g and 50.1 ± 0.2 kph. A production vehicle seat buck was attached to the sled. Four high-back boosters or combination seats in high-back booster mode and two backless booster models were tested. Each booster model was installed two different ways: using the LATCH system ("LATCH" installation) and without using the LATCH system ("non-LATCH" installation). All installations used a 3-point seat belt with retractor in emergency locking mode (ELR) to restrain a Hybrid III 6-year-old anthropomorphic test device (ATD). The retractor, belt webbing, buckle, vehicle seat cushion, and booster were replaced after each test. Some conditions were tested twice to establish repeatability. ATD and booster responses were compared between LATCH and non-LATCH tests. RESULTS: Using LATCH reduced the forward movement of the booster itself by 32.3% to 71.5% compared to non-LATCH installations. Differences in most other metrics were small and often within the range of normal test-to-test variation. Forward movements of the ATD head and heel were similar between LATCH and non-LATCH tests (typically less than 10% difference). HIC36 values trended slightly higher for LATCH installations compared to non-LATCH installations (0.8% to 17.2%). Chest resultant accelerations were typically 7.3% to 21.2% higher for LATCH installations, except for one booster for which it was lower with LATCH. Chest deflections trended higher for LATCH installations compared to non-LATCH installations for the backless boosters (6.9% to 14.1%). For high-back boosters, chest deflection was similar between installation conditions (less than 5% difference). Shoulder belt loads showed the greatest reductions when LATCH installations included a top tether (12.9% to 20.8%). Instances of the ATD submarining under the lap belt were not observed in these tests. CONCLUSIONS: Overall, the differences in kinematics and injury metrics were small between boosters installed using LATCH vs. non-LATCH.

Isometric, concentric, and eccentric neck strength in the sagittal and coronal planes of motion for adult females.

OBJECTIVE: Assess strength in adult females using multiple positions, motions, and contraction types, to better understand strength production of young and non-symptomatic of adult female subjects to help assess and improve the biofidelity of anthropomorphic test devices and human body models. METHODS: Fifteen adult females (25.4 ± 6.3 years) were recruited for this study. Strength measurements were collected for the sagittal and coronal planes during isometric, concentric, and eccentric muscle contractions in neutral and mid-range of motion anatomical positions. RESULTS: For both planes, subjects were strongest during eccentric muscle contractions and weakest in concentric muscle activations. In the sagittal plane, subjects were stronger in extension for all muscle activation types and anatomical positions. In the coronal plane, there were no side differences in isometric nor concentric strength. CONCLUSIONS: Neck strength of adult females depends on muscle activation type and anatomical positions. Future computational models should account for muscle activation type when quantifying responses of female subjects.

System providing automated feedback improves task learning outcomes during child restraint system (CRS) installations.

OBJECTIVES: The objective was to build and test an automated, interactive educational system to teach adults how to install a child restraint system (CRS) into a vehicle seat. METHODS: The automated feedback system (AFS) consisted of a mockup vehicle fixture, convertible CRS, and doll. Sensors were implemented into the equipment so that forward-facing (FF) CRS installation errors could be detected. An interactive display monitor guided users through the CRS installation process and alerted them when steps were done incorrectly. Sixty adult volunteers were recruited and randomized into either the treatment group or the control group. The treatment group used the AFS to guide them through a practice installation. The control group also completed a practice installation using the same equipment fixture without the feedback feature turned on; they only had standard printed instruction manuals to guide their tasks. Then, participants from both groups completed a second CRS installation in a real vehicle with standard instruction manuals only. The frequencies and types of errors in all the installations were evaluated by a Child Passenger Safety Technician (CPST). Error rates were compared between the treatment and control groups using lower-tailed t-tests and Pearson's chi-square tests. Error rates were evaluated considering minor and serious errors together and also considering serious errors alone. RESULTS: Compared to the control group, participants who trained with the AFS exhibited fewer overall errors (minor and serious) in their fixture installations (p < 0.0001) as well as their follow-up vehicle installations (p < 0.0001). Specifically, participants in the treatment group had fewer errors in choosing an installation method, locking the seat belt (SB), tightening the SB or lower anchors (LA), and tightening the harness (p = 0.0002, p = 0.0003, p = 0.0084, and p = 0.0098, respectively, compared to control group during follow-up vehicle installations). The treatment group also performed significantly better than the control group when only serious errors were considered. CONCLUSIONS: An automated feedback system is an effective way to teach basic CRS installation skills to users.

Efficacy of dance-based paradigms, wearable sensors, and auditory feedback for gait retraining in children: A feasibility study.

BACKGROUND: Different feedback modes such as auditory, visual and haptic have been used in the past for gait retraining or learning movement patterns. The primary goal of this study was to investigate whether real time auditory feedback would be effective in children learning novel, dance-based movement patterns. For this purpose, a prototype wearable sensor was developed to provide auditory feedback whenever a child touches their heel to the ground. METHODS: To test the effectiveness of the auditory feedback in learning new patterns, typically developing children were taught simple Indian dance protocols consisting of four counts of foot-work which involved alternating heel-toe movements. The effect of wearing the sensor was assessed by the maximum vertical force with which the subjects struck their foot on the plate. RESULTS: Auditory feedback reduced the learning time and increased the number of correct movement patterns for trial duration of 2 min. The prototype device did not alter the maximum force with which the subject placed the foot on the ground. CONCLUSIONS: Real time auditory feedback can be reliably used to learn novel movement patterns.

Age Differences in Occupant Motion during Simulated In-Vehicle Swerving Maneuvers.

BACKGROUND: With active safety and automated vehicle features becoming more available, unanticipated pre-crash vehicle maneuvers, such as evasive swerving, may become more common, and they may influence the resulting effectiveness of occupant restraints, and consequently may affect injury risks associated with crashes. Therefore, the objective of this study was to quantify the influence of age on key occupant kinematic, kinetic, and muscular responses during evasive swerving in on-road testing. METHODS: Seat belt-restrained children (10-12 years old), teens (13-17 years old), and adults (21-33 years old) experienced two evasive swerving maneuvers in a recent model sedan on a test track. Kinematics, muscle activity, and seat belt load distribution were determined and analyzed. RESULTS: Compared to teens and adults, children showed greater head and trunk motion (p < 0.03), but similar muscle activation in the into-the-belt direction of swerving. In the out-of-the-belt direction, children showed head and trunk motion more similar to teens and adults (p < 0.02), but with greater muscle activation. CONCLUSIONS: Children showed different neuromuscular control of head and trunk motion compared to older occupants. This study highlights differences in the relationship between kinematics and muscle activation across age groups, and provides new validation data for active human body models across the age range.

Biomechanical Responses and Injury Assessment of Post Mortem Human Subjects in Various Rear-facing Seating Configurations.

The objective of this study was to generate biomechanical corridors from post-mortem human subjects (PMHS) in two different seatback recline angles in 56 km/h sled tests simulating a rear-facing occupant during a frontal vehicle impact. PMHS were placed in a production seat which included an integrated seat belt. To achieve a repeatable configuration, the seat was rigidized in the rearward direction using a reinforcing frame that allowed for adjustability in both seatback recline angle and head restraint position. The frame contained instrumentation to measure occupant loads applied to the head restraint and seatback. To measure PMHS kinematics, the head, spine, pelvis, and lower extremities were instrumented with accelerometers and angular rate sensors. Strain gages were attached to anterior and posterior aspects of the ribs, as well as the mid-shaft of the femora and tibiae, to determine fracture timing. A chestband was installed at the mid sternum to quantify chest deformation. Biomechanical corridors for each body and seat location were generated for each recline angle to provide data for quantitatively evaluating the biofidelity of ATDs and HBMs. Injuries included upper extremity injuries, rib fractures, pelvis fractures, and lower extremity injuries. More injuries were documented in the 45-degree recline case than in the 25-degree recline case. These injuries are likely due to the excessive ramping up and corresponding kinematics of the PMHS. Biomechanical corridors and injury information presented in this study could guide the design of HBMs and ATDs in rigid, reclined, rear-facing seating configurations during a high-speed frontal impact.

Characterization of the motion of booster-seated children during simulated in-vehicle precrash maneuvers.

Objective: Precrash occupant motion may affect head and trunk position and restraint performance in a subsequent crash, particularly for young children. Others have studied seat belt-restrained adult drivers and adult and adolescent passengers in precrash maneuvers. For younger children, optimal restraint includes a belt-positioning booster seat, which in precrash maneuvers may contribute in unique ways to the overall body motion. Therefore, the objective of this study was to quantify booster-seated child occupant kinematic, kinetic, and muscle responses during precrash maneuvers and characterize booster movement with respect to the overall occupant kinematics.Methods: Vehicle maneuver tests were conducted with a recent model year sedan at the Transportation Research Center Inc. (TRC, Marysville, Ohio). Three precrash vehicle maneuvers were simulated: Automated and manual emergency braking (AEB and MEB) and oscillatory swerving or slalom (SLA). Each maneuver was repeated twice for each participant. Seven 6- to 8-year-old booster-seated children participated in the study and all subjects were seated in the right rear seat. Vehicle dynamics (i.e., motion, position, and orientation) were measured with an inertial and Global Positioning System navigation system (Oxford RT 3003). Kinematic data from human volunteers were collected with an 8-camera 3D motion capture system (Optitrack Prime 13 200 Hz, NaturalPoint, Inc.). Photoreflective markers were placed on participants' head and trunk. Electromyography (EMG; Trigno EMG Wireless Delsys, Inc., 2,000 Hz) sensors were placed on bilateral muscles predicted to be most likely involved in bracing behaviors.Results: Children demonstrated greater head and trunk velocity in MEB (head 123.7 ± 13.1 cm/s, trunk 77.6 ± 14.1 cm/s) compared to AEB (head 45.31 ± 11.5 cm/s, trunk 27.1 ± 5.5 cm/s; P < .001). Participants also showed greater head motion in MEB (18.9 ± 1.4 cm) vs. AEB (15.1 ± 4.8 cm) but the differences were not statistically significant (P < .1). Overall, the booster seats themselves did not move substantially (<3 cm) in the braking maneuvers. During the SLA, however, the booster seat moved laterally up to 5 cm in several subjects, contributing substantially to peak trunk (6.5-14.0 cm) and head (9.9-21.4 cm) excursion during the maneuver. Booster-seated children also exhibited a greater activation of biceps and deltoid muscles and abdominal and middle trapezii muscles than the sternocleidomastoids during these maneuvers.Conclusions: The quantification of booster seat motion and neuromuscular control and the relationship between kinematics and muscle activation in booster-seated children in precrash maneuvers provides important data on the transition between the precrash and crash phases for this young age group and may help identify opportunities for interventions that integrate active and passive safety.

Effect of automated versus manual emergency braking on rear seat adult and pediatric occupant precrash motion.

Objective: Emergency braking can potentially generate precrash occupant motion that may influence the effectiveness of restraints in the subsequent crash, particularly for rear-seated occupants who may be less aware of the impending crash. With the advent of automated emergency braking (AEB), the mechanism by which braking is achieved is changing, potentially altering precrash occupant motion. Further, due to anatomical and biomechanical differences across ages, kinematic differences between AEB and manual emergency braking (MEB) may vary between child and adult occupants. Therefore, the objective of this study was to quantify differences in rear-seated adult and pediatric kinematics and muscle activity during AEB and MEB scenarios. Methods: Vehicle maneuvers were performed in a recent model year sedan traveling at 50 km/h. MEB (acceleration ∼1 g) was achieved by the driver pressing the brake pedal with maximum effort. AEB (acceleration ∼0.8 g) was triggered by the vehicle system. Inertial and Global Positioning System data were collected. Seventeen male participants aged 10-33 were restrained in the rear right passenger seat and experienced each maneuver twice. The subjects' kinematics were recorded with an 8-camera 3D motion capture system. Electromyography (EMG) recorded muscle activity. Head and trunk displacements, raw and normalized by seated height, and peak head and trunk velocity were compared across age and between maneuvers. Mean EMG was calculated to interpret kinematic findings. Results: Head and trunk displacement and peak velocity were greater in MEB than in AEB in both raw and normalized data (P ≤ .01). No effect of age was observed (P ≥ .21). Peak head and trunk velocities were greater in repetition 1 than in repetition 2 (P ≤ .006) in MEB but not in AEB. Sternocleidomastoid (SCM) mean EMG was greater in MEB compared to AEB, and muscle activity increased in repetition 2 in MEB. Conclusions: Across all ages, head and trunk excursions were greater in MEB than AEB, despite increased muscle activity in MEB. This observation may suggest an ineffective attempt to brace the head or a startle reflex. The increased excursion in MEB compared to AEB may be attributed to differences in the acceleration pulses between the 2 scenarios. These results suggest that AEB systems can use specific deceleration profiles that have potential to reduce occupant motion across diverse age groups compared to sudden maximum emergency braking applied manually.