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.

Abdominal biofidelity assessment of 5th percentile female ATD responses relative to recently developed belt and bar loading corridors.

OBJECTIVE: The objective of this study was the quantitative evaluation and comparison of the responses of the Hybrid III 5th percentile female (HIII-05F) and the 5th percentile female Test Device for Human Occupant Restraint (THOR-05F) anthropomorphic test devices (ATDs) subjected to abdominal loading conditions. METHOD: The HIII-05F and THOR-05F were subjected to 3 different abdominal loading conditions: fixed-back belt pull (low compression), fixed-back belt pull (high compression), and free-back rigid bar impact at 6 m/s. The stroke of the impact was controlled to represent injurious and noninjurious loading conditions as observed in the experiments with postmortem human subjects (PMHS). Quantitative comparisons were made between the ATD abdominal force and compression responses and biofidelity corridors obtained from matched-pair PMHS tests under identical loading conditions, using the most recent version of the NHTSA Biofidelity Ranking System (BRS). RESULTS: The overall THOR-05F BRS scores across all tests (BRS score = 1.84) indicated good biofidelity. For the belt loading test conditions, the average BRS scores for both THOR-05F (BRS scores = 1.45 and 1.34) and HIII-05F (BRS scores = 1.42 and 1.01) showed good biofidelity. For the rigid bar loading condition, the THOR-05F (BRS score = 2.74) showed better biofidelity compared to HIII-05F (BRS score = 10.63), with the HIII-05F exhibiting poor performance in this condition. The average pressures recorded by the abdomen pressure twin sensors (APTS) in the current study ranged from 45 to 130 kPa, increasing proportionally with higher stroke and loading rate. CONCLUSIONS: Overall, the THOR-05F BRS scores were better than the HIII-05F BRS scores, which suggests improved biofidelity of the THOR-05F abdomen. The abdominal insert in the HIII-05F did not provide enough room for compression, leading to higher stiffness and occupant motion as observed in the rigid bar tests. Because of practical challenges in measuring abdomen deflection in a soft ATD abdomen component, use of APTS in THOR-05F provides the ability to measure the restraint loading to the abdomen and assess the risk of abdominal injury. With good BRS scores observed in this study for THOR-05F, pressure and other measurements included in the THOR-05F may be used to develop abdominal injury risk functions in the future.

Thoracic responses and injuries to male postmortem human subjects (PMHS) in rear-facing seat configurations in high-speed frontal impacts.

Objective: One potential nonstandard seating configuration for vehicles with automated driving systems (ADS) is a reclined seat that is rear-facing when in a frontal collision. There are limited biomechanical response and injury data for this seating configuration during high-speed collisions. The main objective of this study was to investigate thoracic biomechanical responses and injuries to male postmortem human subjects (PMHS) in a rear-facing scenario with varying boundary conditions.Method: Fourteen rear-facing male PMHS tests (10 previously published and 4 newly tested) were conducted at two different recline angles (25-degree and 45-degree) in 56 km/h frontal impacts. PMHS were seated in two different seats; one used a Fixed D-Ring (FDR) seat belt assembly and one used an All Belts To Seat (ABTS) restraint. For thoracic instrumentation, strain gages were attached to ribs to quantify strain and fracture timing. A chestband was installed at the mid-sternum level to quantify anterior-posterior (AP) chest deflections. Data from the thorax instrumentation were analyzed to investigate injury mechanisms.Results: The PMHS sustained a greater number of rib fractures (NRF) in the 45-degree recline condition (12 ± 7 NRF for ABTS45 and 25 ± 18 NRF for FDR45) than the 25-degree condition (6 ± 4 NRF for ABTS25 and 12 ± 8 NRF for FDR25), despite AP chest compressions in the 45-degree condition (-23.7 ± 9.4 mm for ABTS45 and -39.6 ± 11.9 mm for FDR45) being smaller than the 25-degree condition (-38.9 ± 16.9 mm for ABTS25 and -55.0 ± 4.4 mm for FDR25). The rib fractures from the ABTS condition were not as symmetric as the FDR condition in the 25-degree recline angle due to a belt retractor structure located at one side of the seatback frame. Average peak AP chest compression occurred at 45.7 ± 3.4 ms for ABTS45, 45.6 ± 3.1 ms for FDR45, 46.7 ± 1.9 ms for ABTS25, and 46.9 ± 2.3 ms for FDR25. Average peak seatback resultant force occurred at 43.9 ± 0.9 ms for ABTS45, 44.6 ± 0.8 ms for FDR45, 42.5 ± 0.2 ms for ABTS25, and 41.5 ± 0.5 ms for FDR25. The majority of rib fractures occurred after peak AP chest compression and peak seatback resultant force likely due to the ramping motion of the PMHS, which might create a combined loading (e.g., AP deflection and upward deflection) to the thorax. Although NRF in the 45-degree reclined condition was greater than the 25-degree recline condition, similar magnitudes of rib strains were observed regardless of seat and restraint types, while strain modes varied.Conclusions: The majority of rib fractures occurred after peak AP chest compression and peak seatback force, especially in FDR25, ABTS45, and FDR45, while the PMHS ramped up along the seatback. AP chest compression, seatback load, and strain measured along the rib could not explain the greater NRF in the 45-degree recline conditions. A complex combination of AP chest deflection with upward deflection was discovered as a possible mechanism for rib fractures in PMHS subjected to rear-facing frontal impacts in this study.

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.

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.

Biomechanical Response Targets of Adult Human Ribs in Frontal Impacts.

Thorax injuries mainly due to rib fractures have been associated with high rates of morbidity and mortality in motor vehicle crashes. Thoracic biomechanics has been studied extensively, but there are no robust biomechanical response targets for ribs that consider age, sex, body size, and vulnerability factors. The objective of this study was to generate biomechanical targets for human rib response with respect to age, sex, and body size. Two-hundred sixty-one ribs from 171 individuals were dynamically loaded to failure in anterior-posterior bending. Force and displacement at the time of fracture in young adults were greater than in older adults (p < 0.0001). Sex differences were found in those over 40 years old (p < 0.0001). Fracture force from 5th percentile female ribs was lower than 50th and 95th male (p < 0.005). Vulnerable ribs were successfully identified by examining the percentile of both force and displacement at the time of fracture in the proposed samples. The biomechanical targets generated in this study will have useful applications to computational thorax and rib models to aid in injury prevention measures.

Low-Intensity Exercise Training Additionally Increases Mitochondrial Dynamics Caused by High-Fat Diet (HFD) but Has No Additional Effect on Mitochondrial Biogenesis in Fast-Twitch Muscle by HFD.

This study examines how the high-fat diet (HFD) affects mitochondrial dynamics and biogenesis, and also whether combining it with low-intensity endurance exercise adds to these effects. Six 8-week-old male Sprague-Dawley (SD) rats were put on control (CON; standard chow diet), HF (HFD intake), and HFEx (HFD + low-intensity treadmill exercise) for 6 weeks. As a result, no change in body weight was observed among the groups. However, epididymal fat mass increased significantly in the two groups that had been given HFD. Blood free fatty acid (FFA) also increased significantly in the HF group. While HFD increased insulin resistance (IR), this was improved significantly in the HFEx group. HFD also significantly increased mitochondrial biogenesis-related factors (PPARδ, PGC-1α, and mtTFA) and mitochondrial electron transport chain proteins; however, no additional effect from exercise was observed. Mitochondrial dynamic-related factors were also affected: Mfn2 increased significantly in the HFEx group, while Drp1 and Fis-1 increased significantly in both the HF and HFEx groups. The number of mitochondria in the subsarcolemmal region, and their size in the subsarcolemmal and intermyofibrillar regions, also increased significantly in the HFEx group. Taken overall, these results show that HFD in combination with low-intensity endurance exercise has no additive effect on mitochondrial biogenesis, although it does have such an effect on mitochondrial dynamics by improving IR.

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.

Effects of Swimming Exercise on Serum Irisin and Bone FNDC5 in Rat Models of High-Fat Diet-Induced Osteoporosis.

This study aimed to investigate the expression of PGC-1α/FNDC5/irisin induced by attenuation of high-fat diet (HFD)-induced bone accrual and determine whether swimming exercise could improve attenuating bone accrual through this mechanism. Eight-week-old Sprague-Dawley rats were divided into two groups for the first 8 weeks: CD, control diet (n = 10); and HFD, high-fat diet (n = 20). HFD-fed rats were again divided into two groups for further 8 weeks treatment: HFD (n = 10) and HFD with swimming exercise (HEx, n = 10). During this time, the CD group continuously fed the normal diet. Throughout the 16 weeks study period, the rats were weighed once every week. Samples were collected for analysis after last 8 weeks of treatment in the 16 weeks. Morphological and structural changes of the femur and tibial bone were observed using micro-CT, and Osteocalcin, CTX-1 and irisin levels in the blood were measured by enzyme-linked immunosorbent assay. The expression of IL-1, ß-catenin, FNDC5 and PGC-1α, in the femur were evaluated by immunohistochemistry. Eight weeks of HFD increased body weight and epididymal fat mass and decreased bone mineral density (BMD). Subsequent 8 weeks of swimming exercise improved obesity, BMD, bone microstructure, and bone metabolic factors in the HEx group. The irisin levels in the blood and the expressions of FNDC5 and PGC-1α in the bone were significantly lower in the HFD group than in the CD group, but elevated in the HEx group than in the HFD group. Swimming exercise is effective in improving obesity-worsened bone health and increases blood irisin and bone PGC-1α and FNDC5 levels.

Effects of ursolic acid on muscle mass and bone microstructure in rats with casting-induced muscle atrophy.

PURPOSE: Recent studies suggest that ursolic acid (UA) is a potential candidate for a resistance exercise mimetic that can increase muscle mass and alleviate the deleterious effect of skeletal muscle atrophy on bone health. However, these studies evaluated the effects of UA on skeletal muscle and bone tissues, and they have not verified whether such effect could occur concurrently on muscle and bone, as is the case with resistance exercise. Thus, the aim of this study was to analyze the effect of UA injection on muscle mass and bone microstructure using an animal model of atrophy to demonstrate the potential of UA as a resistance exercise mimetic. METHODS: The immobilization (IM) method was used on the left hindlimb of Sprague Dawley (SD) rats for 10 days to induce muscle atrophy, whereas the right hindlimb was used as an internal control (IC). The animal models were divided into two groups, SED (sedentary, n=6) and UA (n=6) to demonstrate the effect of UA on atrophic skeletal muscles. The UA group received a daily intraperitoneal injection of UA (5 mg/kg/day) for 8 weeks. After 10 days of IM, the data collected for the IC were compared with that of IM to determine whether muscle atrophy might occur. RESULTS: Muscle atrophy was induced and bone mineral density (BMD) decreased significantly. The 8-week UA treatment significantly increased the gastrocnemius muscle mass compared to the SED group. In regard to the effect of UA on bones, negative results such as a decrease in BMD, trabecular bone volume fraction, and trabecular number, and an increase in trabecular separation, were observed in the SED group, but no such difference was observed in the UA group. No significant difference was observed in atrophic hindlimbs between SED and UA groups. CONCLUSION: These results alone are insufficient to suggest that UA is a potential resistance exercise mimetic for atrophic skeletal muscle and weakened bone. However, this study will help determine the potential of UA as a resistance exercise mimetic.

Detailed subject-specific FE rib modeling for fracture prediction.

Objective: The current state of the art human body models (HBMs) underpredict the number of fractured ribs. Also, it has not been shown that the models can predict the fracture locations. Efforts have been made to create subject specific rib models for fracture prediction, with mixed results. The aim of this study is to evaluate if subject-specific finite element (FE) rib models, based on state-of-the-art clinical CT data combined with subject-specific material data, can predict rib stiffness and fracture location in anterior-posterior rib bending.Method: High resolution clinical CT data was used to generate detailed subject-specific geometry for twelve FE models of the sixth rib. The cortical bone periosteal and endosteal surfaces were estimated based on a previously calibrated cortical bone mapping algorithm. The cortical and the trabecular bone were modeled using a hexa-block algorithm. The isotropic material model for the cortical bone in each rib model was assigned subject-specific material data based on tension coupon tests. Two different modeling strategies were used for the trabecular bone.The capability of the FE model to predict fracture location was carried out by modeling physical dynamic anterior-posterior rib bending tests. The rib model predictions were directly compared to the results from the tests. The predicted force-displacement time history, strain measurements at four locations, and rotation of the rib ends were compared to the results from the physical tests by means of CORA analysis. Rib fracture location in the FE model was estimated as the position for the element with the highest first principle strain at the time corresponding to rib fracture in the physical test.Results: Seven out of the twelve rib models predicted the fracture locations (at least for one of the trabecular modeling strategies) and had a force-displacement CORA score above 0.65. The other five rib models, had either a poor force-displacement CORA response or a poor fracture location prediction. It was observed that the stress-strain response for the coupon test for these five ribs showed significantly lower Young's modulus, yield stress, and elongation at fracture compared to the other seven ribs.Conclusion: This study indicates that rib fracture location can be predicted for subject specific rib models based on high resolution CT, when loaded in anterior-posterior bending, as long as the rib's cortical cortex is of sufficient thickness and has limited porosity. This study provides guidelines for further enhancements of rib modeling for fracture location prediction with HBMs.

Anatomically-based skeletal coordinate systems for use with impact biomechanics data intended for anthropomorphic test device development.

Post-mortem human subjects (PMHS) are frequently used to characterize biomechanical response and injury tolerance of humans to various types of loading by means of instrumentation installed directly on the skeleton. Data extracted from such tests are often used to develop and validate anthropomorphic test devices (ATDs), which function as human surrogates in tests for injury assessment. Given that the location and orientation of installed instrumentation differs between subjects, nominally similar measurements made on different PMHS must be transformed to standardized, skeletal-based local coordinate systems (LCS) before appropriate data comparisons can be made. Standardized PMHS LCS that correspond to ATD instrumentation locations and orientations have not previously been published. This paper introduces anatomically-defined PMHS LCS for body regions in which kinematic measurements are made using ATDs. These LCS include the head, sternum, single vertebrae, pelvis, femurs (distal and proximal), and tibiae (distal and proximal) based upon skeletal landmarks extracted from whole body CT scans. The proposed LCS provide a means to standardize the reporting of PMHS data, and facilitate both the comparison of PMHS impact data across institutions and the application of PMHS data to the development and validation of ATDs.

Regional maps of rib cortical bone thickness and cross-sectional geometry.

Here we present detailed regional bone thickness and cross-sectional measurements from full adult ribs using high resolution CT scans processed with a cortical bone mapping technique. Sixth ribs from 33 subjects ranging from 24 to 99 years of age were used to produce average cortical bone thickness maps and to provide average ± 1SD corridors for expected cross-section properties (cross-sectional areas and inertial moments) as a function of rib length. Results obtained from CT data were validated at specific rib locations using direct measurements from cut sections. Individual thickness measurements from CT had an accuracy (mean error) and precision (SD error) of -0.013 ± 0.167 mm (R2 coefficient of determination of 0.84). CT-based measurement errors for rib cross-sectional geometry were -0.1 ± 13.1% (cortical bone cross-sectional area) and 4.7 ± 1.8% (total cross-sectional area). Rib cortical bone thickness maps show the expected regional variation across a typical rib's surface. The local mid-rib maxima in cortical thickness along the pleural rib aspect ranged from range 0.9 to 2.6 mm across the study population with an average map maximum of 1.4 mm. Along the cutaneous aspect, rib cortical bone thickness ranged from 0.7 to 1.9 mm with an average map thickness of 0.9 mm. Average cross-sectional properties show a steady reduction in total cortical bone area from 10% along the rib's length through to the sternal end, whereas overall cross-sectional area remains relatively constant along the majority of the rib's length before rising steeply towards the sternal end. On average, male ribs contained more cortical bone within a given cross-section than was seen for female ribs. Importantly, however, this difference was driven by male ribs having larger overall cross-sectional areas, rather than by sex differences in the bone thickness observed at specific local cortex sites. The cortical bone thickness results here can be used directly to improve the accuracy of current human body and rib models. Furthermore, the measurement corridors obtained from adult subjects across a wide age range can be used to validate future measurements from more widely available image sources such as clinical CT where gold standard reference measures (e.g. such as direct measurements obtained from cut sections) are otherwise unobtainable.

Human Response and Injury Resulting from Head Impacts with Unmanned Aircraft Systems.

Unmanned aircraft systems (UAS), commonly known as drones, are part of a new and budding industry in the United States. Economic and public benefits associated with UAS use across multiple commercial sectors are driving new regulations which alter the stringent laws currently restricting UAS flights over people. As new regulations are enacted and more UAS populate the national airspace, there is a need to both understand and quantify the risk associated with UAS impacts with the uninvolved public. The purpose of this study was to investigate the biomechanical response and injury outcomes of Post Mortem Human Surrogates (PMHS) subjected to UAS head impacts. For this work, PMHS were tested with differing UAS vehicles at multiple impact angles, locations and speeds. Using a custom designed launching device, UAS vehicles were accelerated into the frontal, parietal, or vertex portions of subjects' craniums at speeds up to 22 m/s. Of the 35 UAS impacts carried out, one AIS 2+ injury was observed: a 13 cm linear skull fracture resulting from a Phantom 3 impact. Additionally, injury risk curves used in automotive testing were found to over predict the risk of injury in UAS impact scenarios. Finally, localized skull deformation was observed during severe impacts; the effect that this deformation had on measured kinematics should be further evaluated. Overall, the study found that AIS 2+ head injuries may occur as a result of UAS impacts and that automotive injury metrics may not be able to accurately predict head injury risk in UAS impact scenarios.

A Novel Approach to Scaling Age-, Sex-, and Body Size-Dependent Thoracic Responses using Structural Properties of Human Ribs.

Thoracic injuries are frequently observed in motor vehicle crashes, and rib fractures are the most common of those injuries. Thoracic response targets have previously been developed from data obtained from post-mortem human subject (PMHS) tests in frontal loading conditions, most commonly of mid-size males. Traditional scaling methods are employed to identify differences in thoracic response for various demographic groups, but it is often unknown if these applications are appropriate, especially considering the limited number of tested PMHS from which those scaling factors originate. Therefore, the objective of this study was to establish a new scaling approach for generating age-, sex-, and body size- dependent thoracic responses utilizing structural properties of human ribs from direct testing of various demographics. One-hundred forty-seven human ribs (140 adult; 7 pediatric) from 132 individuals (76 male; 52 female; 4 pediatric) ranging in age from 6 to 99 years were included in this study. Ribs were tested at 2 m/s to failure in a frontal impact scenario. Force and displacement for individual ribs were used to develop new scaling factors, with a traditional mid-size biomechanical target as a baseline response. This novel use of a large, varied dataset of dynamic whole rib responses offers vast possibilities to utilize existing biomechanical data in creative ways to reduce thoracic injuries in diverse vehicle occupants.

Concurrent treatment with ursolic acid and low-intensity treadmill exercise improves muscle atrophy and related outcomes in rats.

The objective of this study was to analyze the concurrent treatment effects of ursolic acid (UA) and low-intensity treadmill exercise and to confirm the effectiveness of UA as an exercise mimetic to safely improve muscle atrophy-related diseases using Sprague-Dawley (SD) rats with skeletal muscle atrophy. Significant muscle atrophy was induced in male SD rats through hind limb immobilization using casting for 10 days. The muscle atrophy-induced SD rats were group into four: SED, sedentary; UA, daily intraperitoneal UA injection, 5 mg/kg; EX, low-intensity (10-12 m/min, 0° grade) treadmill exercise; and UEX, daily intraperitoneal UA injection, 5 mg/kg, and low-intensity (10-12 m/min, 0° grade) treadmill exercise. After 8 weeks of treatment, endurance capacity was analyzed using a treadmill, and tissues were extracted for analysis of visceral fat mass, body weight, muscle mass, expression of muscle atrophy- and hypertrophy-related genes, and endurance capacity. Although the effects of body weight gain control, muscle mass increase, and endurance capacity improvement were inadequate in the UA group, significant results were confirmed in the UEX group. The UEX group had significantly reduced body weight and visceral fat, significantly improved mass of tibialis anterior and gastrocnemius muscles, and significantly decreased atrophy-related gene expression of MuRF1 and atrogin-1, but did not have significant change in hypertrophy-related gene expression of Akt and mTOR. The endurance capacity was significantly improved in the EX and UEX groups. These data suggest that concurrent treatment with low-intensity exercise and UA is effective for atrophy-related physical dysfunctions.

Top tether effectiveness during side impacts.

OBJECTIVE: Few studies have looked at the effectiveness of the top tether during side impacts. In these studies, limited anthropomorphic test device (ATD) data were collected and/or few side impact scenarios were observed. The goal of this study was to further understand the effects of the top tether on ATD responses and child restraint system (CRS) kinematics during various side impact conditions. METHODS: A series of high-speed near-side and far-side sled tests were performed using the FMVSS213 side impact sled buck and Q3s ATD. Tests were performed at both 10° and 30° impacts with respect to the pure lateral direction. Two child restraints, CRS A and CRS B, were attached to the bench using flexible lower anchors. Each test scenario was performed with the presence and absence of a top tether. Instrumentation recorded Q3s responses and CRS kinematics, and the identical test scenarios with and without a top tether attachment were compared. RESULTS: For the far-side lateral (10°) and oblique (30°) impacts, top tether attachment increased resultant head accelerations by 8-38% and head injury criterion (HIC15) values by 20-140%. However, the top tether was effective in reducing lateral head excursion by 5-25%. For near-side impacts, the top tether resulted in less than 10% increases in both resultant head acceleration and HIC15 in the lateral impact direction. For near-side oblique impacts, the top tether increased HIC15 by 17.3% for CRS A and decreased it by 19.5% for CRS B. However, the injury values determined from both impact conditions were below current injury assessment reference values (IARVs). Additionally, the top tether proved beneficial in preventing forward and lateral CRS rotations. CONCLUSIONS: The results show that the effects of the top tether on Q3s responses were dependent on impact type, impact angle, and CRS. Tether attachments that increased head accelerations and HIC15 values were generally counterbalanced by a reduction in head excursion and CRS rotation compared to nontethered scenarios.

Sources of Variability in Structural Bending Response of Pediatric and Adult Human Ribs in Dynamic Frontal Impacts.

Despite safety advances, thoracic injuries in motor vehicle crashes remain a significant source of morbidity and mortality, and rib fractures are the most prevalent of thoracic injuries. The objective of this study was to explore sources of variation in rib structural properties in order to identify sources of differential risk of rib fracture between vehicle occupants. A hierarchical model was employed to quantify the effects of demographic differences and rib geometry on structural properties including stiffness, force, displacement, and energy at failure and yield. Three-hundred forty-seven mid-level ribs from 182 individual anatomical donors were dynamically (~2 m/s) tested to failure in a simplified bending scenario mimicking a frontal thoracic impact. Individuals ranged in age from 4 - 108 years (mean 53 ± 23 years) and included 59 females and 123 males of diverse body sizes. Age, sex, body size, aBMD, whole rib geometry and cross-sectional geometry were explored as predictors of rib structural properties. Measures of cross-sectional rib size (Tt.Ar), bone quantity (Ct.Ar), and bone distribution (Z) generally explained more variation than any other predictors, and were further improved when normalized by rib length (e.g., robustness and WBSI). Cortical thickness (Ct.Th) was not found to be a useful predictor. Rib level predictors performed better than individual level predictors. These findings moderately explain differential risk for rib fracture and with additional exploration of the rib's role in thoracic response, may be able contribute to ATD and HBM development and alterations in addition to improvements to thoracic injury criteria and scaling methods.

Quantification of Skeletal and Soft Tissue Contributions to Thoracic Response in a Dynamic Frontal Loading Scenario.

Thoracic injuries continue to be a major health concern in motor vehicle crashes. Previous thoracic research has focused on 50th percentile males and utilized scaling techniques to apply results to different demographics. Individual rib testing offers the advantage of capturing demographic differences; however, understanding of rib properties in the context of the intact thorax is lacking. Therefore, the objective of this study was to obtain the data necessary to develop a transfer function between individual rib and thoracic response. A series of non-injurious frontal impacts were conducted on six PMHS, creating a loading environment commensurate to previously published individual rib testing. Each PMHS was tested in four tissue states: intact, intact with upper limbs removed, denuded, and eviscerated. Following eviscerated thoracic testing, eight individual mid-level ribs from each PMHS were removed and loaded to failure. A simplified model in which ribs of each thorax are treated as parallel springs was utilized to evaluate the ability of individual rib response data to predict each subject's eviscerated thoracic response. On average across subjects, denuded thoraces retained 89% and eviscerated thoraces retained 46% of intact force. Similarly, denuded thoraces retained 70% and eviscerated thoraces retained 30% of intact stiffness. The rib model did not adequately predict eviscerated thoracic response but provided a better understanding of the influence of connective tissue on a rib's behavior with-in the thorax. Results of this study could be used in conjunction with the database of individual rib test results to improve thoracic response targets and help assess biofidelity of current anthropomorphic test devices.