Biomedical subjects

Matthew P Reed

Publications and source records attributed to Matthew P Reed.

12 recordsLinked to original sources

PubMed2006

Influence of visibility out of the vehicle cabin on lane-change crashes.

The influence of lateral visibility from the vehicle cabin on safety was evaluated by examining the differences in lane-change crashes of four-door and two-door body styles of the same vehicle models. These two vehicle styles were used because B-pillars (the pillars between the front and rear seats) on four-door models are farther forward, and thus nearer the fore-aft position of the driver. (Furthermore, the B-pillars on two-door models can be narrower, and some two-door models have no B-pillars at all.) To control for driver differences between these two body styles, going-straight-ahead crashes were used for comparison. The analysis used 2000-2003 North Carolina crash data, and considered the crash experience of four-door and two-door body styles for the same 10 vehicles for model years 1995 and newer. The main finding is that four-door body styles are more likely to be involved in lane-change crashes than are two-door body styles of the same vehicle models. This finding suggests that lateral visibility out of the vehicle cabin affects safety.

Accidents, Traffic↗

PubMed2006

The effects of tethering rear -facing child restraint systems on ATD responses.

A series of sled tests was performed to analyze the responses of an anthropomorphic test device (ATD), particularly neck forces, when rear-facing child restraint systems (CRS) are tethered. Nominally identical rear-facing CRS were tested in four tether conditions: untethered, tethered down to the floor, tethered down to the bottom of the vehicle seat, and tethered rearward to a point above the back of the vehicle seat. The CRABI 12MO ATD with head, upper neck, and chest instrumentation was used in all tests. The tests were conducted using the ECE R44.02 test bench. Both frontal and rear impacts were performed and each condition was repeated for a total of 16 sled tests. Motions of the CRS and ATD were recorded using high-speed digital video (1000 fps). The highest ATD accelerations, forces, and moments were observed during the primary impact of a frontal test, rather than on rebound. The loads observed during rebound from frontal impact were similar in magnitude to the peak loads collected during rear impact. The four tethering geometries produced distinct loading patterns. The lowest HIC, neck forces, and chest accelerations in both impact directions were observed with the rearward tether. The upper neck moment data did not show a clear trend relative to tethering geometry. ATD and CRS motions were best controlled in frontal impact by the rearward tethering geometry while the motions in rear impact were best controlled by tethering to the floor. The data show a potential benefit in both frontal and rear impacts of tethering rear-facing CRS to a point above the vehicle seatback.

Anthropometry↗

PubMed2005

A pilot study of a method for assessing the reach capability of wheelchair users for safety belt design.

A method was developed to assess the reach capability of people seated in wheelchairs for purposes of establishing design and placement requirements for safety belts used by vehicle occupants who are seated in wheelchairs. The method uses simple technology and is intended to be readily implemented in the field. Participants use a marker to draw their acceptable reach zone on a vertical surface placed adjacent to the wheelchair. A pilot study with 10 wheelchair users showed that the method generates easily interpreted data quickly. Even with a small number of participants, the results from the pilot study provide useful information for designers of restraint systems for wheelchair-seated vehicle occupants.

Adult↗

PubMed2005

Representing and identifying alternative movement techniques for goal-directed manual tasks.

Differences in motion patterns subserving the same movement goal can be identified qualitatively. These alternatives, which may characterize 'movement techniques' (e.g., the stoop and the squat lifting technique), may be associated with significantly different biomechanical constraints and physiological responses. Despite the widely shared understanding of the significance of alternative movement techniques, quantitative representation and identification of movement techniques have received little attention, especially for three-dimensional whole-body motions. In an attempt to systematically differentiate movement techniques, this study introduces a quantitative index termed joint contribution vector (JCV) representing a motion in terms of contributions of individual joint degrees-of-freedom to the achievement of the task goal. Given a set of uncharacterized (unlabeled) motions represented by joint angle trajectories (motion capture data), the JCV and statistical clustering methods enable automated motion classification to uncover a taxonomy of alternative movement techniques. The results of our motion data analyses show that the JCV was able to characterize and discern stoop and squat lifting motions, and also to identify movement techniques for a three-dimensional, whole-body, one-handed load-transfer task. The JCV index would facilitate consideration of alternative movement techniques in a variety of applications, including work method comparison and selection, and human motion modeling and simulation.

Cluster Analysis↗

PubMed2005

Pilot study of safety belt usability for vehicle occupants seated in wheelchairs.

This study investigates the usability of wheelchair occupant restraint systems (WORS) that are used for crash protection of individuals seated in wheelchairs during motor vehicle transit. Ten independent adults with significant functional limitations who use wheelchairs for primary mobility were observed and interviewed while performing reach and manipulation tasks associated with WORS usage. Participants' opinions on ease of use and comfort-related factors were obtained for four occupant restraint scenarios. The study results show evidence of user problems with common WORS designs for use by wheelchair-seated individuals with significant functional limitations. Results from this pilot study suggest redesign of latch plates and buckles used in WORS to enable wheelchair-seated individuals with functional limitations to don and buckle belt restraints more easily and independently. Additionally, this study provides guidance to occupant-restraint manufacturers and wheelchair designers regarding belt-restraint usability. Improved WORS usability will complement other efforts to increase frequency of safety belt usage and lead to improved occupant safety.

Consumer Behavior↗

PubMed2005

Test-retest reliability, internal item consistency, and concurrent validity of the wheelchair seating discomfort assessment tool.

Discomfort is a common problem for wheelchair users. Few researchers have investigated discomfort among wheelchair users or potential solutions for this problem. One of the impediments to quantitative research on wheelchair seating discomfort has been the lack of a reliable method for quantifying seat discomfort. The purpose of this study was to establish the test-retest reliability, internal item consistency, and concurrent validity of a newly developed Wheelchair Seating Discomfort Assessment Tool (WcS-DAT). Thirty full-time, active wheelchair users with intact sensation were asked to use this and other tools in order to rate their levels of discomfort in a test-retest reliability study format. Data from these measures were analyzed in SPSS using an intraclass correlation coefficient (ICC) model (2,k) to measure the test-retest reliability. Cronbach's alpha was used to examine the internal consistency of the items within the WcS-DAT. Concurrent validity with similar measures was analyzed using Pearson product-moment correlations. ICC scores for all analyses were above the established lower bound of .80, indicating a highly stable and reliable tool. In addition, alpha scores indicated good consistency of all items without redundancy. Finally, correlations with similar tools, such as the Chair Evaluation Checklist and the Short Form of the McGill Pain Questionnaire, were significant at the .05 level, and many were significant at the .001 level. These results support the use of the WcS-DAT as a reliable and stable tool for quantifying wheelchair seating discomfort. Its application will enhance the ability to assess and to research this important problem and will provide a means to validate the outcomes of specialized seating interventions for the study population of wheelchairs users.

Persons with Disabilities↗

PubMed2005

Development of ATD Installation Procedures Based on Rear-Seat Occupant Postures.

The initial positioning of anthropomorphic test devices (ATDs) can influence the outcomes of crash tests. Current procedures for positioning ATDs in rear seats are not based on systematic studies of passenger postures. This paper compares the postures of three side-impact ATDs to the postures of 24 men and women in three vehicle rear seats and 16 laboratory conditions. When positioned using current procedures, the locations of the ES-2 and SID-HIII ATD heads are generally rearward of those observed with similar-size passengers. The SID-IIs head locations matched the expected locations of heads of passengers of similar size more closely. As the seat back angle was increased, people reclined less than the ATDs. Based on these findings, a new ATD positioning procedure for rear seats was developed. The primary objective of the new procedure is to place the ATD head in the location that is most likely for people of similar size. Linear regression equations specify the fore-aft location of the ATD hips and head with respect to the seat H-point as a function of seat back angle (SAE A40) and seat cushion length. The new procedures have been tested with the SID-HIII, ES-2, and SID-IIs side impact ATDs, but are also applicable to frontal impact testing.

Journal Article↗

PubMed2004

Development of a consumer-driven Wheelchair Seating Discomfort Assessment Tool (WcS-DAT).

This study examined the concept of seating discomfort in a population of full-time wheelchair users with intact sensation. The goal was to construct a tool that would quantify seating discomfort experienced by wheelchair users. Ten participants were interviewed using ethnographic interview techniques. Data were analyzed using a cross-classifying matrix to examine commonalities among the 10 participants' responses. There were 16 discomfort and 13 comfort descriptors used by the participants. Of these, eight discomfort and five comfort descriptors were selected to include in the Wheelchair Seating Discomfort Assessment Tool (WcS-DAT). The discomfort descriptors selected were: aches and pains, need to move, pressure points, feeling poorly positioned, unable to concentrate, instability, not comfortable, and feeling too hot, cold or damp. The comfort descriptors selected were: absence of discomfort, feeling good, having no pain, able to concentrate, and feeling stable. The WcS-DAT also includes general information, such as the amount of time spent sitting and whether the individual was transferred into the chair properly--factors thought to affect discomfort--and ratings of discomfort intensity--in general and differentiated by body area. The WcS-DAT is a comprehensive tool for quantification of wheelchair seat discomfort for this population.

Adult↗

PubMed2004

Cervical spine geometry in the automotive seated posture: variations with age, stature, and gender.

In the mid 1970s, UMTRI investigated the biomechanical properties of the head and neck using 180 "normal" adult subjects selected to fill eighteen subject groups based on age (young, mid-aged, older), gender, and stature (short, medium, and tall by gender). Lateral-view radiographs of the subjects' cervical spines and heads were taken with the subjects seated in a simulated automotive neutral posture, as well as with their necks in full-voluntary flexion and full-voluntary extension. Although the cervical spine and lower head geometry were previously measured manually and documented, new technologies have enabled computer digitization of the scanned x-ray images and a more comprehensive and detailed analysis of the variation in cervical spine and lower head geometry with subject age, stature, and gender. After scanning the radiographic images, 108 skeletal landmarks on the cervical vertebrae and 10 head landmarks were digitized. The resulting database of cervical spine and head geometry was used to study cervical spine curvature, vertebral dimensions, and head/neck orientation as functions of age, gender, and stature. The data were used to characterize neutral posture cervical spine curvatures using two methods: a curvature index and Bézier spline functions. Lateral-view vertebral dimensions were also calculated for each subject, and a cascading series of equations was developed to estimate vertebral size and shape for a selected age, stature, and gender. The orientation of the cervical spine was defined using a neck chord angle, where the neck chord was varied to use different anatomical landmarks and estimates of joint centers for the top and bottom of the neck chord. Results from the study have been incorporated into a MS-Access based software package that allows researchers and modelers to generate cervical spine geometries for occupants of a specified age, gender, and stature. The program allows selection of individual occupants from the database that meet age, stature, gender, or curvature criteria, or creation of a composite cervical spine geometry representative of the selected age, gender, and stature. This tool will allow researchers to configure and vary cervical spine geometry in computer models and experimental test setups used to study head and neck impact response and injury risk.

Journal Article↗

PubMed2003

Effects of hip posture on the frontal impact tolerance of the human hip joint.

The pattern of left- and right-side hip injuries to front-seat occupants involved in offset and angled frontal crashes suggests that hip posture (i.e., the orientation of the femur relative to the pelvis) affects the fracture/dislocation tolerance of the hip joint to forces transmitted along the femur during knee-to-knee-bolster loading in frontal impacts. To investigate this hypothesis, dynamic hip tolerance tests were conducted on the left and right hips of 22 unembalmed cadavers. In these tests, the knee was dynamically loaded in the direction of the long axis of the femur and the pelvis was fixed to minimize inertial effects. Thirty-five successful hip tolerance tests were conducted. Twenty-five of these tests were performed with the hip oriented in a typical posture for a seated driver, or neutral posture, to provide a baseline measure of hip tolerance. The effects of hip posture on hip tolerance were quantified using a paired-comparison experimental design. In six pairs of tests, one side of each cadaver was tested with the hip joint oriented in the neutral posture and the contralateral hip from the same cadaver was tested with the hip joint adducted 10 degrees from the neutral posture. In four pairs of tests, the hip was tested in neutral and 30 degrees flexed postures. The average fracture tolerance of the hip in the neutral posture was 6.1-/+1.5 kN. Hip tolerance decreased by an average of 34-/+4% with 30 degrees of flexion from the neutral posture (p<0.0001) and by 18-/+8% with 10 degrees of adduction from the neutral posture (p=0.008).

Journal Article↗

PubMed2002

A statistical method for predicting automobile driving posture.

A new model for predicting automobile driving posture is presented. The model, based on data from a study of 68 men and women in 18 vehicle package and seat conditions, is designed for use in posturing the human figure models that are increasingly used for vehicle interior design. The model uses a series of independent regression models, coupled with data-guided inverse kinematics, to fit a whole-body linkage. An important characteristic of the new model is that it places greatest importance on prediction accuracy for the body locations that are most important for vehicle interior design: eye location and hip location. The model predictions were compared with the driving postures of 120 men and women in five vehicles. Errors in mean eye location predictions in the vehicles were typically less than 10 mm. Prediction errors were largely independent of anthropometric variables and vehicle layout. Although the average posture of a group of people can be predicted accurately, individuals' postures cannot be predicted precisely because of interindividual posture variance that is unrelated to key anthropometric variables. The posture prediction models developed in this research can be applied to posturing computer-rendered human models to improve the accuracy of ergonomic assessments of vehicle interiors.

Adult↗

PubMed2002

The tolerance of the human hip to dynamic knee loading.

Based on an analysis of the National Automotive Sampling System (NASS) database from calendar years 1995-2000, over 30,000 fractures and dislocations of the knee-thigh-hip (KTH) complex occur in frontal motor-vehicle crashes each year in the United States. This analysis also shows that the risk of hip injury is generally higher than the risks of knee and thigh injuries in frontal crashes, that hip injuries are occurring to adult occupants of all ages, and that most hip injuries occur at crash severities that are equal to, or less than, those used in FMVSS 208 and NCAP testing. Because previous biomechanical research produced mostly knee or distal femur injuries, and because knee and femur injuries were frequently documented in early crash investigation data, the femur has traditionally been viewed as the weakest part of the KTH complex. However, the relative risk of hip injuries to the risks of knee and thigh injuries in frontal crashes of late-model vehicles suggests that this may not be the case. This study investigated the frontal-impact fracture tolerance of the hip in nineteen tests performed on the KTH complexes from sixteen unembalmed human cadavers. In each test, the pelvis was rigidly fixed by gripping the iliac wings with the thigh-to-pelvis angle set to correspond to a standard automotive-seated posture. A dynamic load was applied to the knee along the axis of the femur at loading rates that are representative of knee-to-knee bolster impacts in frontal crashes. Rigidly fixing the pelvis minimizes inertial effects along the KTH complex, which results in similar force levels along the KTH complex. Consequently, in these tests, the weakest part of the KTH complex failed first. All seventeen fixed pelvis tests that produced usable data resulted in acetabular fractures at an average applied force of 5.70 kN (sd = 1.38 kN). The lack of injuries to the femoral shaft and distal femur in these tests indicates that the tolerance of the hip is less than that of the femur under frontal-impact loading. To further explore the tolerance of the femur relative to the hip, thirteen uninjured knee/femur specimens from seven cadavers previously used in hip tolerance tests were dynamically loaded. In these tests, the head of the femur was supported in a fixed "acetabular cup" to minimize inertial effects, and load was applied at the knee along the axis of the femur. All of these tests resulted in femoral neck fractures. Two tests also resulted in fractures to the femoral shaft. The average tolerance of the femoral neck from these tests is 7.59 kN (sd = 1.58 kN), which is significantly higher (p < 0.05) than the tolerance of the acetabulum. These results suggest that the mid and distal portions of the femur have a higher tolerance under these loading conditions than the pelvic and femoral portions of the hip.

Journal Article↗