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Authored by:
Gunter P. Siegmund1, John R. Brault2, Jeffrey B. Wheeler2
1MacInnis Engineering Associates
2Biomechanics Research & Consulting, Inc.

Presented:
Traffic Safety and Auto Engineering Stream
Whiplash - Associated Disorders World Congress
Vancouver, Canada, February 7-11, 1999

Recent experiments have produced a linked data set of clinical and kinematic responses for human subjects exposed to controlled low-speed rear-end collisions. The purpose of this paper was to examine this paired data set and determine whether the presence or absence of clinical symptoms could be predicted from peak kinematic response. The data set used for this analysis was generated using 42 male and female human subjects seated normally in the front passenger seat of a stationary vehicle struck from behind to produce vehicle speed changes of 4 and 8 km/h. The present analysis was confined to sagittal plane motion. Pre- and post-test clinical examinations documented the presence, severity, and duration of whiplash-associated disorder (WAD) symptoms. Logistic regression and backward elimination of independent variables were used to develop the prediction model. The results of the analysis yielded a 16 parameter model that was significantly related (p = 0.0069) to the presence or absence of transient whiplash symptoms. The specificity of the model was 94 percent and the sensitivity was 56 percent (odds ratio = 21.2). The results showed that gross head and neck kinematics did not reliably predict WAD symptoms suggesting that other variables not included in this kinematic parametric model also influence clinical outcome.

Keywords whiplash-associated disorders, head and neck kinematics, low-speed rear-end collision, human subjects

Published:
Journal of Testing and Evaluation, Vol. 27. No. 6, November 1999, pp. 368-374

Authored by:
Christoper M. Powers¹, Kornelia Kulig², James Flynn³ and John R. Brault^{4

1}Assistant professor, Department of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA
^{2Associate professor of Clinical Physical Therapy, Department
Biokinesiology and Physical Therapy, University of Southern California,
Los Angeles, CA

3}J²Engineering Inc., Fresno, CA
^{4Senior Biomechanist, Biomechanics Research & Consulting, Inc.,
El Segundo, CA}

Falls resulting from slips on walkway surfaces are a significant source of injury in society. In response, various types of tribometers and ASTM standards have been developed to assess walkway slip-resistance with the goal of improving pedestrian safety. The purpose of this study was to determine the reliability and validity of the Slip-Test Mark II and English XL tribometers under both dry and wet conditions. Both devices were tested on an AMTI force platform over a wide range of angles. Validity was assessed by comparing the tribometer slip resistance reading to the actual Fx/Fz ratio measured by the force plate, while reliability was established by evaluating the ability of the tribometers to reproduce Fx, Fz and the Fx/Fz ratio. Both tribometers demonstrated high degrees of validity and reliability under both wet and dry conditions, however each measured different slip-resistance values for the same surface. Further study should be directed at establishing which tribometer best simulates the human gait condition with respect to measuring slip-resistance.

Published:
Proceedings of the International Society of Biomechanics XVIIth Congress, Calgary, Alberta, Canada, August 8-13, 1999

Authored by:
J.R. Brault¹, G.P. Siegmund², J.B. Wheeler^{1

1}Biomechanics Research & Consulting, Inc., El Segundo, CA, USA
²MacInnis Engineering Associates, Ltd., Richmond, BC, Canada

Presented:
Finalist for the ISB Clinical Biomechanics Award
International Society of Biomechanics XVIIth Congress, Calgary, Alberta, Canada, August 8-13, 1999

Whiplash Associated Disorders (WAD) account for roughly 50% of the societal costs associated with traffic injuries in the industrialized world, with 33% of those acutely injured developing chronic whiplash disorders. Many theories have been proposed, but no consensus exists as to the mechanism of whiplash injury. The purpose of this study was to analyze cervical muscle response and identify potential WAD injury mechanisms to human subjects exposed to rear-end automobile collisions.

Forty-eight percent of subjects sustained minor WAD symptoms in at least one impact. Extension of the head relative to the torso remained less than 20 degrees in all tests. Sample kinematic data (horizontal component only) and muscle response data are shown in Figure 1. The SCM and PARA EMG onset times were less than 100msec. for both impacts. Onset times were significantly different (p<0.05) for both muscles and speed changes. Normalized iEMG (Figure 2) achieved significance for motion phase, muscle, and speed change; the 2^nd order interaction terms were also significant, however the 3^rd order term was not.

These data revealed that cervical muscles respond rapidly to a rear-end collision. Co-contraction of the neck muscles was coincident with the peak rearward acceleration of the head relative to the torso. Lengthening of the muscles during contraction would apply an eccentric load, and therefore, the potential for muscular injury. The early onset of cervical flexors and extensors may be a reflexive attempt to stiffen the neck and prevent extension and retraction, however, the muscles’ primarily vertical line of action is not optimal to prevent the predominantly horizontal movement observed in these tests. Given the muscles’ poor mechanical advantage to limit retraction motion, preventative measures for whiplash should focus on a passive limitation of retraction. The clinician should recognize the potentially significant role of cervical retraction in the mechanism of whiplash injury and avoid aggressive motion in that plane of motion during diagnosis and treatment.

Authored by:
Gunter P. Siegmund1, Bradley E. Heinrichs1, Jeffrey B. Wheeler2
1MacInnis Engineering Associates, Richmond, BC, Canada
2Biomechanics Research & Consulting, Inc., El Segundo, CA, USA

Prior two-way analyses of variance showed that some peaks in the kinematic response of the head and neck of subjects exposed to low-speed rear-end collisions were related to gender, however the reason for this gender dependence was not determined. Using multiple linear regression, this study further examined these response data to determine the relative influence of specific factors, including subject anthropometry, neck strength, cervical range of motion, seated posture, and head restraint position. The variables responsible for the previously-observed gender dependence were identified. The results of this analysis showed that vehicle speed change and relative head restraint position explained the largest proportion of the observed variation in peak occupant kinematic response. Seated posture measures also explained some of the variation in kinematic response. The current analysis prioritizes which variables to explore more thoroughly in future research and which variables should be carefully controlled in future studies.

Keywords whiplash, occupant kinematics, head restraint, gender, anthropometry, seated posture

Published:
International Symposium Whiplash ’98 Compendium of Abstracts, p.25
Tempe, Arizona, November 5-6, 1998.

Authored by:
J.R. Brault1, G.P. Siegmund2, J.B. Wheeler1
1Biomechanics Research & Consulting, Inc., El Segundo, CA 90245
2MacInnis Engineering Associates, Richmond, BC, Canada, V7A 4S5

Presented:
International Symposium Whiplash '98
Tempe, Arizona, November 5-6, 1998

INTRODUCTION: Dynamic retraction of the neck during whiplash-type loading (Siegmund et al., 1997) has been hypothesized to induced rapid volume changes in the cervical spinal canal (Aldman, 1986), and the resulting transient pressure gradients have been related to histological evidence of cell body damage in the dorsal root ganglion using a porcine model (Svensson et al., 1993). Similar experiments cannot be performed in humans and less direct methods must be used to investigate this proposed injury mechanism. Using magnetic resonance (MR) images, this study attempted to statically evaluate the assumption of in-vivo changes in human spinal canal volume between the neutral and retracted head positions.

METHODS: Sagittal-plane MR images of the cervical spine of 48 subjects (25M, 23F, mean age = 27±5 yrs) were obtained as part of a larger study into whiplash (Brault et al., 1998). Subjects were positioned supine on a firm mat with the spinous process of their first thoracic (T1) vertebrae located at the mat’s edge. The head was supported on a separate mat of similar thickness for the neutral position scan. The head mat thickness was then minimized while still maintaining the same absolute head angle used for the neutral scan. A whole body MR imager (1.5T, model, Matsushita, Tokyo, Japan) acquired T1-weighted images (256 x 192 pixels, 4mm spacing, 20cm x 20cm field of view) using 15s scans and scaled films of the mid-sagittal slices were printed. Biomechanics, Inc

The total spinal canal area, bounded anteriorly by the posterior surface of the vertebral bodies, posteriorly by the anterior aspect of the vertebral arches, superiorly by the foreman magnum, and inferiorly by the line connecting the inferior aspects of the C7 vertebral body and vertebral arch, was manually traced onto acetate. The anterior and posterior surfaces of the spinal cord were also traced. The tracings were then scanned at 600dpi and the number of pixels corresponding to the total area, the cord area and the canal areas anterior and posterior to the cord were determined. Total areas in the neutral and retracted positions were compared using a paired student’s t-test and a significance level of 0.05. Paired t-tests were then conducted separately on the three component areas.

RESULTS: Total cervical canal area was on average 4% smaller in the retracted position than in the neutral position (Figure 1). Separate tests showed that the area occupied by the spinal cord remained unchanged, whereas on average the anterior space was 7% smaller and the posterior space was 8% smaller in the retracted position than in the neutral position.

DISCUSSION: This preliminary analysis showed a purpleuction in the static size of the human cervical spinal canal between the neutral and retracted neck positions. Within the canal, the area of spinal cord remained constant and the reduction in total canal area occurred entirely in the canal spaces external to the cord. It is not known whether the observed distribution between anterior and posterior area reduction will be maintained under dynamic conditions. Given the planar nature of the retraction motion used, the observed reduction in mid-sagittal area likely reflects a reduction in total canal volume. Although these in-vivo data do not prove that the injury mechanism proposed by Aldman (1986) occurs in humans, they do support the underlying assumption of this theory - that spinal canal volume is reduced during retraction motion of the cervical spine.

REFERENCES Aldman B (1986). In: Proc. of 30th AAAM Conf., pp. 439-454.
Brault JR, Wheeler JB, Siegmund GP, Brault EJ (1998). Arch Phys Med Rehab 79:72-80.
Siegmund GP, King DJ, Lawrence JM, Wheeler JB, et al. (1997). In: Proc. 41st Stapp Conf., pp. 357-385.
Svensson MY, Aldman B, Lovsund P, et al. (1993). In: Proc. of IRCOBI Conf., pp. 189-200.
† Partial funding for this project was received under the Technology BC program administered by the Science Council of British Columbia.

*Partial funding for this project was received under the Technology BC program and administered by the Science Council of British Columbia.

Published:
International Symposium Whiplash ’98 Compendium of Abstracts, p.41
Tempe, Arizona, November 5-6, 1998.

Authored by:
J.R. Brault1, G.P. Siegmund2, J.B. Wheeler1
1Biomechanics Research & Consulting, Inc., El Segundo, CA 90245
2MacInnis Engineering Associates, Richmond, BC, Canada, V7A 4S5

Presented:
International Symposium Whiplash ’98
Tempe, Arizona, November 5-6, 1998.

INTRODUCTION: Conflicting findings regarding the response and role of the cervical musculature to rear-end automobile collisions have been reported in the literature. This study exposed 42 subjects to low-speed rear-end collisions to quantify cervical muscle response and identify potential injury mechanisms in the cervical spine.

METHODS: Informed consent was obtained from 42 volunteers (21 M, 21 F, mean = 26.8 yrs.) who were then exposed to two vehicle-to-vehicle rear-end collisions (DV = 2½ and 5mph). Surface electromyographic (EMG) electrodes were applied bilaterally to the sternocleidomastoid (SCM) and cervical trapezius/paraspinal (PARA) muscles (Brault et al., 1998). Sagittal plane video (250 fps) and 3D accelerometry attached to the head and base of the cervical spine (C7/T1) captured the occupant kinematics (Siegmund et al., 1997). Vehicle bumper contact served as time t=0s. EMG onset time from bumper contact was analyzed using a 2-way ANOVA for muscle (SCM/PARA) and speed change. Occupant motion was divided into two phases: retraction (EMG onset to max. rearward head translation relative to C7/T1) and rebound (forward rebound of the head from the head restraint). SCM and PARA EMG data were rectified and normalized to EMG from each subject’s 50% manual muscle test for cervical flexion and extension, respectively. EMG data within each motion phase was integrated (iEMG) and normalized for the duration of each phase. A 3-way ANOVA for motion phase (retraction/rebound), muscle, and speed change was then performed.

RESULTS: The SCM and PARA EMG onset times were 90.7±9.3ms and 95.9±10.8ms respectively at 2½mph, and 81.2±8.3ms and 84.0±9.3ms at 5mph. Onset times were significantly different (p 0.05) for both muscles and speed changes; the interaction was not significant. Normalized iEMG (Figure 1) achieved significance for motion phase, muscle, and speed change; the 2nd order interaction terms were also significant, however the 3rd order term was not. Biomechanics, Inc.

DISCUSSION: Of most interest was the unique and consistent firing pattern between muscles. The early onset and consistent temporal response pattern between subjects suggest an involuntary muscle response to the impacts. The SCM activity, as measured by iEMG, was greater during the retraction phase than during rebound, whereas the PARA activity was the same or greater during rebound than during retraction. From an injury perspective, the muscle contraction during the retraction phase may be important since the largest acceleration differential between the head and C7/T1 occurred within this phase. A lengthening of the muscles during contraction would apply an eccentric load, and therefore, the potential for muscular injury. The early onset of the cervical musculature may be an attempt to inhibit retraction, however, the muscles’ primarily vertical line of action is not optimal to prevent this predominantly horizontal movement. Given this poor mechanical advantage, preventative measures for whiplash injury should focus on a passive limitation of retraction. The evidence of a graded EMG response to speed change indicates greater muscular loads to the cervical spine at higher speed changes. In conclusion, the data indicate that cervical muscles contract rapidly in response to impact to potentially influence cervical spine kinematics, and a potential for muscle injury exists due to eccentric loading.

REFERENCES Brault JR, Wheeler JB, Siegmund GP, Brault EJ (1998). Arch Phys Med Rehab 79:72-80.
Siegmund GP, King DJ, Lawrence JM, Wheeler JB, Brault JR, Smith TA (1997). In: Proc of the 41st Stapp Car Crash Conf, pp. 357-385.

*Partial funding for this project was received under the Technology BC program and administered by the Science Council of British Columbia.

Published:
Proceedings of the International Conference on the Biomechanics of Impact, p.335-348, Göteborg, Sweden, September 16-18, 1998.

Authored by:
Jeffrey B. Wheeler, MS, Terry A. Smith, PhD, John R. Brault, MS Biomechanics Research & Consulting, Inc., El Segundo, CA, USA
Gunter P. Siegmund, PEng, David J. King, PEng MacInnis Engineering Associates Ltd., Richmond, BC, Canada

Presented:
1998 International IRCOBI Conference on the Biomechanics of Impact (IROCBI 98)
Chalmers University of Technology
Goteborg, Sweden,September 16-18, 1998

Neck Injury Criterion (NIC) values were calculated using human subject kinematic data and comcompared their clinical results. Twenty-nine percent (29%) and 38% of the subjects exhibited whiplash symptoms at rear-end speed changes of 4 and 8 km/h, respectively. None of the subjects’ NIC values exceeded 15 m2/s2, which had been proposed as a tolerance level for AIS-1 cervical injury. NIC was not able to predict the presence of symptoms in our test population. This may be due to differences between our subjects’ anatomical source of pain and the nature and type of injury predicted by NIC.

Published:
Proceedings of the North American Congress on Biomechanics, p.347-348, Waterloo, Ontario, Canada, August 14-18, 1998.

Authored by:
John R. Brault, MS, Terry A. Smith, PhD, Jeffrey B. Wheeler, MS
Biomechanics Research & Consulting, Inc., El Segundo, CA, USA

Gunter P. Siegmund, BASc
MacInnis Engineering Associates Ltd., Richmond, BC, Canada

Presented:
North American Congress on Biomechanics (NACOB 98)
University of Waterloo
Waterloo, Ontario, Canada, August 14-18, 1998

In an attempt to quantify cervical muscle response and identify potential injury mechanisms to the cervical spine in rear- end automobile collisions, this study exposed 42 subjects to low-speed rear-end impacts. Surface electromyography (EMG) of the bilateral sternocleidomastoid (SCM) and posterior cervical paraspinal/trapezius (PARA) muscles was collected along with acceleration of the head and base of the cervical spine (C7/T1). Of particular interest was the EMG onset relative to impact, and the peak amplitude and time history of the EMG.

The response of the cervical musculature to simulated low-speed rear-end automobile collisions has been previously investigated with conflicting conclusions. Some researchers have concluded that the SCM and PARA muscles could not be activated in time to mitigate cervical spine injury in a rear-end automobile collision (Foust et al., 1973). In contrast, research comparing cervical spine models to human volunteer cervical muscle response noted that the cervical musculature has a significant influence on head and neck motion during low level acceleration impacts and may provide injury protection (Pontius, 1975, Gutierrez, 1978). Similarly, Pope et al. (1998) recorded surface EMG from SCM and PARA muscles in ten males seated in an automobile seat attached to a sled to which a low level forward acceleration was applied. They concluded that cervical muscle activation influenced the biomechanics of the cervical spine and may be a secondary source of injury. The only study of cervical muscle EMG in human subjects in vehicle-to-vehicle rear-end impacts did not present conclusions regarding the production or prevention of cervical spine injury (Szabo et al., 1996). This study analyzes the cervical muscle response in low-speed rear-end automobile collisions for the purpose of investigating the muscles’ contribution to the kinematics and injury mechanisms of the cervical spine. The hypothesis was that the muscle activation pattern combined with the head/neck kinematics would be consistent with cervical muscle eccentric loading injury.

Forty-two volunteers (average age 26.8 + 4.7 years), with males and females equally represented, were recruited and informed consent obtained. Surface electrodes were taped to the bilateral SCM and PARA muscles using the technique of Zipp, 1982. A more detailed explanation of the human subject protocol has been previously published (Brault et al., 1998).

The subjects, seated in the right front seat, were exposed to two vehicle-to-vehicle rear impacts at least seven days apart (average speed change 3.95 + 0.11km/h and 8.10 + 0.11km/h). Head accelerations and C7/T1 accelerations were measured as previously described (Siegmund et al., 1997). The EMG and accelerometer signals were synchronized with vehicle bumper contact. EMG was sampled at a frequency of 1,000 Hz and band-pass filtered (40 to 500Hz) using a 2nd-order Butterworth filter. Prior to impact, subjects performed isometric cervical flexion and extension at 50% of their maximum force output (50%MVC) while SCM and PARA EMG was collected, respectively. This 50&337MVC served to normalize the EMG collected during the impacts. EMG of each muscle during the impacts was rectified and expressed as a percentage of the 50%MVC. A mathematical algorithm determined the EMG onset for each muscle relative to bumper contact and was confirmed by visual inspection.

Figure 1: Typical horizontal acceleration and EMG response of human volunteer in 8 km/h speed change. Time 0: Bumper Contact, A: Maximum rearward head translation relative to C7/T1, B: Maximum forward head translation relative to C7/T1

The average SCM and PARA EMG onset times were 81.2 + 8.3ms and 84.0 + 9.3ms, respectively (p=.057). Peak SCM EMG occurred in the cervical retraction phase as C7/T1 was moving forward relative to the stationary head, while peak PARA EMG occurred later during the forward rebound phase as the head rebounded forward off the head restraint (Figure 1). Maximum relative horizontal acceleration between the head and C7/T1 occurred coincident with maximum rearward head translation relative to C7/T1 (Point A in Figure 1).

The rapid SCM and PARA muscle contraction and relative magnitude of contraction indicate that the cervical muscles can involuntarily influence cervical spine kinematics in a rear-end collision. From an injury perspective the most significant phase of the kinematic pattern appears to be during cervical retraction. The large acceleration differential between the head and C7/T1 with concomitant cervical muscle contraction applies a eccentric load, and therefore, potential for muscular injury.

*Partial funding was received under the Technology BC program and administered by the Science Council of British Columbia.

Published:
Archives of Physical Medicine and Rehabilitation, 79:72-80 - January, 1998

Authored by:
John R. Brault, MS, Jeffrey B. Wheeler, MS, Elaine J. Brault, MS PT,
Biomechanics Research & Consulting, Inc., El Segundo, CA, USA

Gunter P. Siegmund, BASc,
MacInnis Engineering Associates Ltd., Richmond, BC, Canada

Objective: Forty-two persons were exposed to controlled low-speed rear-end automobile collisions to assess the relation between both gender and impact severity and the presence, severity, and duration of whiplash-associated disorders (WAD). Individual measures were also assessed for their potential to predict the onset of WAD.

Design: Experimental study subjecting individuals to a speed change of 4km/h and 8km/h and utilizing pretest and posttest physical examinations (immediately after and 24 hours after impact) to quantify subjects' clinical response.

Results: Approximately 29% and 38% of the subjects exposed to the 4km/h and 8km/h speed changes, respectively, experienced WAD symptoms, with cervical symptoms and headaches predominating. Objective clinical deficits consistent with WAD were measured in both men and women subjects at both 4km/h and 8km/h. At 4km/h, the duration of symptoms experienced by women was significantly longer when compared with that in men (p < .05). There were no significant differences in the presence and severity of WAD between men and women at 4km/h and 8km/h or in the duration of WAD at 8km/h. There was also no significant difference in the presence, severity, and duration of WAD between 4km/h and 8km/h. No preimpact measures were ppurpleicpredictive

Conclusion: The empirical findings in this study contribute to establishing a causal relationship between rear-end collisions and clinical signs and symptoms.

Published:
SAE Paper No. 973341, In: Proceedings of the 41st Stapp Car Crash Conference, Lake Buena Vista, FL, November 13-14, 1997

Authored by:
Gunter P. Siegmund, David J. King, Jonathan M. Lawrence,
MacInnis Engineering Associates Ltd., Richmond, BC, Canada

Jeffrey B. Wheeler, John R. Brault, Terry A. Smith
Biomechanics Research & Consulting, Inc., El Segundo, CA, USA

Presented:
41st Stapp Car Crash Conference, Lake Buena Vista, FL, November 13-14, 1997

Limited data exist which quantify the kinematic response of the human head and cervical spine in lowspeed rear-end automobile collisions. The objectives of this study were to quantify human head/neck kinematics and how they vary with vehicle speed change and gender during low-speed rear-end collisions. Forty-two human subjects (21 male, 21 female) were exposed to two rear-end vehicle-to-vehicle impacts (speed changes of 4 km/h and 8 km/h). Accelerations and displacements of the head and torso were measured using 6 degree-of-freedom accelerometry and sagittal high speed video respectively. Velocity was calculated by integrating the accelerometer data. Kinematic data of the head and C7-T1 joint axis in the global reference frame, and head kinematic data relative to the C7-T1 joint axis are presented. A statistical comparison between peak amplitude and time-to-peak amplitude for thirty-one common peaks in the kinematic response was performed. Peak amplitudes and time-to-peak amplitude varied significantly with collision severity for most response peaks, and varied significantly with gender for about one quarter of the response peaks.

Published:
24th Annual International Workshop on Human Subject Testing for Biomechanical Research
Albuquerque, New Mexico, November 1996

Authored by:
Jeffrey B. Wheeler, John R. Brault
Biomechanics Research & Consulting, Inc., El Segundo, CA, USA

Gunter P. Siegmund, David J. King
MacInnis Engineering Associates Ltd., Richmond, BC, Canada

Presented:
Proceedings of the 24th Annual International Workshop on Human Subject Testing for Biomechanical Research
Albuquerque, New Mexico, November 1996

Several studies in the scientific literature have exposed live human subjects to low-speed, rear-end collisions in an attempt to establish cervical spine injury mechanisms and injury thresholds. (1-3,5,7) Perhaps due to the risk of injury associated with the tests, the sample size of all these studies was either small, mostly male, or associated with the investigating institutions. While these studies provide the groundwork for understanding occupant response to low-speed, rear-end impacts, their results are difficult to apply to the general population given the wide variability to injury tolerance of human biological tissue and the unrepresentative and limited sample size. In order to advance our understanding of biomechanical factors related to Whiplash-Associated Disorders (WAD), the test subject database must be broadened to be more representative of the general population including all age groups and both genders. However, exposing subjects from the general population to a potentially injurious event requires rigorous adherence to human subject protection protocols.

The objective of our research was to identify how and why cervical spine injuries occur in low-speed, rear-end automobile collisions. Twenty-one male and 21 female volunteers (20-40 yr.) recruited from the general population were exposed to two impact severities (4 and 8 km/h speed change). The study analyzed the kinematics and kinetics of the subjects through the use of high speed video, accelerometry, anthropometry, and electromyography (EMG). A protocol was developed to standardize human subject selection, ensure human subject protection, and document subjective and objective measures of cervical pain and impairment associated with the impact testing.

The test protocol was submitted to an independent ethics committee for review and approval to assure not only that the subjects’ rights were protected but also the procedures to which the subjects were exposed were acceptable on scientific, ethical and moral grounds. Potential subjects were recruited through newspaper advertisements and precautions were taken to exclude subjects with a previous medical history contraindicating participation in the impact testing. Acceptable subjects were required to attend an informed consent session at the testing site for explanation of test procedures. Subjects were examined by cervical magnetic resonance imaging (MRI) to screen for specific spinal pathologies which excluded their participation in the tests. Lastly, pre-impact and two post-impact physical examinations were performed on subjects to quantify any objective clinical deficits or subjective symptoms induced by the impacts. The examination included measurement of cervical range of motion, C5-T1 myotomal strength and dermatomal sensation, upper extremity reflexes, point tenderness; and administration of the McGill Pain Questionnaire which quantified the pain experience. (4)

The use of live human subjects in trauma biomechanics research presents the investigator with unique challenges. One must design a tightly controlled experiment adhering to the scientific method; and due to the potential exposure to injury, ensure human subject protection. The test protocol presented satisfies these criteria and future investigations of low-speed, rear-end collisions using human subjects can incorporate these precautions.

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