337 research outputs found
Supplemental Material - Cervical Spine Motion Requirements From Night Vision Goggles May Play a Greater Role in Chronic Neck Pain than Helmet Mass Properties
No full textSupplemental Material for Cervical Spine Motion Requirements From Night Vision Goggles May Play a Greater Role in Chronic Neck Pain than Helmet Mass Properties by Jeff M. Barrett, Laura A. Healey, Steven L. Fischer and Jack P. Callaghan in Human Factors</p
A procedure for determining parameters of a simplified ligament model
No full textThe final publication is available at Elsevier via http://dx.doi.org/10.1016/j.jbiomech.2017.10.037 © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/A previous mathematical model of ligament force-generation treated their behavior as a population of collagen fibres arranged in parallel. When damage was ignored in this model, an expression for ligament force in terms of the deflection, x, effective stiffness, k, mean collagen slack length, μ, and the standard deviation of slack lengths, σ, was obtained. We present a simple three-step method for determining the three model parameters (k, μ, and σ) from force-deflection data: (1) determine the equation of the line in the linear region of this curve, its slope is k and its x -intercept is -μ; (2) interpolate the force-deflection data when x is -μ to obtain F0; (3) calculate σ with the equation σ=2πF0/k. Results from this method were in good agreement to those obtained from a least-squares procedure on experimental data – all falling within 6%. Therefore, parameters obtained using the proposed method provide a systematic way of reporting ligament parameters, or for obtaining an initial guess for nonlinear least-squares.Jack P. Callaghan is supported by the Tier 1 Canada Research Chair in Spine Biomechanics
Jeff M. Barrett is supported by an NSERC PGS-D Scholarshi
British communism : a documentary history
No full textWide-ranging and richly researched, this is the first sourcebook to reconstruct the tumultuous history of the Communist Party of Great Britain. Drawing together over one hundred and fifty documents, including party statements, press releases, published correspondence, reviews, poems and articles, it presents a detailed portrait of theparty, its abiding concerns and its many contradictions from the 1920s to the 1980s. It samples voices from the full spectrum of the party’s diverse personnel, from long-standing party leaders (Harry Pollitt, Rajani Palme Dutt), to prominent twentieth-century British intellectuals (E. P. Thompson, Eric Hobsbawm), to significant cultural figures (Jack Lindsay, Alan Bush, A. L. Lloyd). Over half of the book is organised chronologically, bringing intosharp focus the CPGB’s trajectory: its emergence and consolidation; the adoption of new lines in response to shifting international contexts and Moscow directives; moments of damaging crisis and political isolation; the widening fault lines that eventually led to theparty’s dissolution. Running through this overarching narrative are thematic chapters providing magnified coverage of central issues: the party’s critique of imperialism and engagement with anticolonial struggles; the party’s cultural policies and interventions; its relationship with the Soviet Union and the broader British Labour movement. Balanced, comprehensive and framed by Callaghan and Harker’s detailed introductions, British Communism: A documentary history is not only a valuable addition to the historiography of Communism, but to the study of twentieth-century Britain
Automated Histological Analysis System for Quantifying Microstructural Damage Accumulation to the Annulus Fibrosus
No full textBen Daya, I., Noguchi, M., Callaghan, J. P., & Wong, A. (2016). Automated Histological Analysis System for Quantifying Microstructural Damage Accumulation to the Annulus Fibrosus. Journal of Computational Vision and Imaging Systems, 2(1). Retrieved from http://openjournals.uwaterloo.ca/index.php/vsl/article/view/100In this paper, we proposed an automated histological analysis system for quantifying microstructural damage accumulation to the annulus fibrosus. This system takes in a digital histology image and uses Gaussian mixture model based segmentation, followed by connected components analysis to extract and label possible clefts. The image is then refined through spatial and size constraints. Finally, the required statistics for quantifying microstructural damage are calculated.This research was funded by the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chairs Program, and the Ontario Ministry of Research and Innovation
The Role of Low Back Capacities on Loaded and Unloaded Functional Movements: Squat and Lunge
No full textVariability of movement patterns across individuals have been well documented in healthy young adults. Large heterogeneity of movement patterns within seemingly homogenous populations suggests the possible presence of subgrouping of individuals. This variability makes it difficult to study and draw conclusions based on group effects, since group means may not be representative of individuals within the group, and especially when subgroups respond differently to interventions. It is also well established that certain movements and movement characteristics are relevant to movement efficiency, tissue exposure, and injury risk, however, it is not fully understood why individuals utilize certain movement patterns over others. It is plausible that physical capacity related differences between subgroups of individuals can help explain differences in movement. As such, this thesis aimed to cluster individuals according to their lumbar movement profiles during functional movements, and then relate characteristic profiles of each subgroup to the low back capacities of strength, muscular endurance, proprioception, and motor control. Additionally, this thesis investigated the effects of introducing a moderate challenge (i.e., loading) to the lumbar movement profiles during functional movements.
Thirty-two healthy young adults (16 M, 16 F) performed two sets of ten repetitions each of squat (SQT) and lunge (LNG) in both unloaded (UL) and loaded (LD) conditions. Additionally, lumbar capacity tests of strength (S), endurance (E), joint position accuracy (P-A), joint position sensitivity (P-S), and motor control (MC) were assessed. State spaces of lumbar angle dynamics for each condition of movement were constructed, then discretized into 48 bins and averaged across repetitions. State spaces were then analyzed using spectral clustering with the number of subgroups selected based on the strongest silhouette score. Analyses of variance (ANOVAs) testing the effect of sex and group on each capacity test’s scores were conducted.
The results of the clustering produced two groups with weak clustering strength in each condition. In both the SQT UL and SQT LD conditions, a significant interaction between sex and group in P-S (p = 0.01), and a significant effect of sex in E (p = 0.04)were found. In the LNG UL condition, a significant interaction between sex and group in P-A (p = 0.04), and a significant effect of sex in E (p = 0.04) were found. Significant interactions between group and sex were found in both P-S (p = 0.04) and MC (p = 0.03) for the LNG LD condition. Differences in lumbar capacities between groups were related to features of the state spaces, including shape, diffuseness, and intensity of attractors.
This thesis highlighted the importance of physical capacities on movement patterns and affirmed the necessity of characterizing subgroups of individuals within a heterogeneous sample population. This thesis provides a framework for more comprehensive investigations into the relationships between specific capacities and movement profiles
The Efficacy of an Ergonomics Education Program on Sit-Stand Workstation Usage Behaviours: A Field Intervention Study
No full textAbstract
Background: Much is known about the negative aspects of sitting and standing for long periods of time. In recent years there has been a shift in office furniture from non-height adjustable workstations to those that fully accommodate sitting and standing whole body postures. In the past, the integration of sit-stand desks has shown positive but also negative consequences such as pain development or minimal use of the new workstation. Outcomes depend fundamentally on the training that new users of sit-stand workstations receive. Currently, there is no standardized training program provided to users on how they should integrate their new workstations into their day to ensure optimal use of the workstation. The objective of this research study was to determine if a training program that new users of sit-stand workstations received prior to their implementation could influence the long term usage of the workstations. It was hypothesized that the type of training program that individuals received would influence how much they would use the workstation over a period of two months, would influence reports of musculoskeletal discomfort, and influence mood states.
Methods: Thirty-five adults between the ages of 23 and 64 were recruited from a University of Waterloo research centre to assess the influence of training program on the long term usage of sit-stand workstations. Participants were divided into 1 of 2 groups based on their job tasks, age and sex. A baseline period (Phase 1) was collected as participants worked at their original non height adjustable workstations. Both groups received an initial training program that was an example of what is currently taught in industry. The one group then received an additional session that focused on transitioning between sitting and standing and proper sitting and standing techniques. The first four weeks after the training sessions represented the intervention phase (Phase 2) of the study. During this time, those in the group who received the additional training program also received weekly meetings from the experimenter to answer any questions that the participants had regarding their workstation as well as daily reminders to rotate between sitting and standing in a 1:1 ratio. These meetings were stopped for the subsequent four weeks as this time period acted as the follow-up phase (Phase 3). Desk transitions from sitting to standing were tracked using tri-axial data logging accelerometers that were securely mounted to each participants’ desk (Gulf coast solutions, Waveland, Mississippi) and a measure of self-perceived sitting and standing throughout the day was taken using the Occupational Sitting and Physical Activity Questionnaire. Musculoskeletal pain score was collected on a nine point Likert scale. The Active Hip Abduction Test was collected at the beginning and end of the study to determine if any differences occurred between groups. Lastly, the Profile of Mood States questionnaire was collected to determine if any changes in mood states would occur throughout the study.
Results: There was a main effect of group (p<0.0001) for the number of transitions completed each day. On average, those in the group that received the additional training session based on current best practice research transitioned 6.0 (±2.1) times a day whereas those who only received a training session that is currently delivered in industry transitioned 3.2 (±1.9) times each day. There was no main effect of phase (p=0.1161). There was a main effect of group p=0.0473 and phase p<0.0001 for self-reported time spent sitting each day as collected via the Occupational Sitting and Physical Activity Questionnaire. There was no effect of group or time on the musculoskeletal pain reported in the lower back, buttocks, and feet region. There was an influence of phase for neck pain and right and left shoulder pain. Group influence the percentage of days that pain was reported in the right and left shoulder regions. The percentage of days that pain was reported was higher for those who received the additional training session. Overall, those in the additional group reported sitting 6% less than those who received the industry example training. There was a main effect of group p=0.0401 and a main effect of period of p<0.0001 for self-reported time spent standing via the OSPAQ. Overall, those who received the additional training session reported standing 6% more than those who did not. Those who received the additional training session had fewer days where they did not use their workstation at all (p=0.0002). There was an influence of group on the mood state anger and depression. Those who received only the industry training session reported lower anger and depression scores by 1.3 and 1.2 respectively. Scores for confusion decreased in both groups as the study progressed (p<0.0001). There was no influence of group on the amount that participants walked each day as assessed by the Fitbit Zip (p=0.6934) and by the Occupational Sitting and Physical Activity Questionnaire (p=0.6174). There was an influence of outcome on the Active Hip Abduction Test (AHABD) on the number of days that pain occurred. Those who scored positive on the AHABD test reported more pain than those who scored negative.
Discussion: Those who received the additional training session prior to using their sit-stand workstation transitioned more often than those who only received the training session that was an example of what is currently bring completed in the industry. They also reported less time spent sitting throughout the day and more time spent standing. One of the major problems with the implementation of sit-stand workstations, as reported by industry practitioners and researchers, is the discontinued use of sit-stand workstations as time progresses. The current study found that with the delivery of a training program that was based on current best research practice in the topic of sit-stand workstation usage, there were less days where the workstation was not used at all. Behaviour change techniques, motivational interviewing approaches and hands on practice with the workstation should be incorporated into future training programs to develop sustainable habits centered around whole body posture variation
Effect of obesity on knee joint biomechanics during gait in young adults
No full textThis article is MacLean, K. F. E., Callaghan, J. P., & Maly, M. R. (2016). Effect of obesity on knee joint biomechanics during gait in young adults. Cogent Medicine, 3(1). https://doi.org/10.1080/2331205X.2016.1173778While there are many comorbidities associated with obesity, one of the more poorly understood is knee osteoarthritis through obesity. The purpose of this study was to compare the kinematics and kinetics of gait and cumulative knee adductor load, which represents the sum of repetitive exposures to medial knee loading during daily activity, between young obese adults with young, healthy-weight adults. Eight obese and eight healthy-weight young adults participated. Data from a three-dimensional motion capture system and a synchronized floor-mounted force plate were collected during gait trials. Participants wore accelerometers to determine step counts for seven consecutive days. Dependent t-tests were used to identify differences in gait kinematics, kinetics and cumulative knee adductor load between groups. Compared to the healthy-weight participants, obese young adults demonstrated a slower walking speed, greater stance duration, less knee flexion at heel contact, greater knee adduction in early stance and less knee abduction at terminal stance (p < 0.05). The obese young adults had a greater external knee extension moment (p < 0.05) and external rotation moment (p < 0.05) in early stance. The obese group had a greater cumulative knee adductor load. These results provide insight into a potential pathway by which obesity predisposes a healthy young adult for knee osteoarthritis.This research is supported by Canada Research Chairs, Canadian Institutes of Health Research, and Natural Sciences and Engineering Research Council of Canad
Exploring Low to Moderate Velocity Motor Vehicle Rear Impacts as a Viable Injury Mechanism in the Lumbar Spine
No full textEpidemiological research suggests that up to 50% of individuals involved in low speed rear impact collisions develop acute onset low back pain. Given that little information is known about the low back injury mechanisms as a result of these collisions the overarching goal of this thesis was to explore low to moderate velocity rear-end collisions as a potential low back injury mechanism. Using a combination of data mining, in vivo and in vitro mechanical testing of porcine functional spinal units, the global purposes of this thesis were to (i) explore the types of low to moderate velocity collisions that frequently result in claims of low back pain and injury (ii) explore the influence of low velocity rear impact collisions on peak in vivo joint loading, occupant pain reporting and passive tissue response of the lumbar spine, and (iii) characterize the effects of these mechanical exposures and explore facet joint capsule injury as a potential source of injury and pain generating pathways following low to moderate severity impacts. In-line with these global purposes, four independent studies were conducted, each with their own focused objectives.
Study I - Exploring Low Velocity Collision Characteristics Associated with Claimed Low Back Pain
Background: Up to fifty percent of individuals involved in low to moderate velocity collisions report low back pain. However, our understanding of the specific collision or occupant characteristics that result in such claims of low back pain remains limited.
Objectives: The primary objective of this study was to define the circumstances of low velocity motor vehicle collisions that result in litigation in Ontario with claims of low back injury.
Methods: Data for this investigation were obtained from a forensic engineering firm based in Toronto, Ontario, Canada. The database was searched and only cases with an evaluation of the injuries sustained in passenger vehicle to vehicle collisions, with a collision severity of 24 km/hour or less were included in this analysis. Each identified case was reviewed for collision characteristics, pre-existing medical conditions and injuries claimed. Descriptive statistics (mean, SD and ranges) across low back injury claims were computed for documented variables.
Results: Out the 83 cases reviewed, 77% involved a claim of low back injury. Specific to those who claimed low back injury, examination of the medical history revealed that pre-existing low back pain (LBP) or evidence of lumbar disc degeneration were particularly common with 63% of claimants either having had a history of LBP or evidence of lumbar disc degeneration, or both. Of all low back injury claims, 97% were accompanied by a whiplash and/or whiplash associated disorder claim. For low back injury claims, a rear-end impact was the most common configuration (70% of all low back injury claims involved a rear-end collision). The majority of all low back injury claimants experienced a change in velocity of 13 km/hour or less (69%), with 42% of all low back injury claims falling between collision severities of 10 – 12 km/hour.
Conclusions: Results indicate that rear-end collision severities of 10 – 12 km/hour appear to be particularly common with respect to low back injury reporting; more severe collisions were not associated with greater low back injury reporting. This result contrasts with previously published neck injury risk data, which demonstrated the risk of neck injury symptom reporting increases with collision severity. Evidence of lumbar disc degeneration was particularly common across claimants with low back injury claims.
Study II - Characterizing Trunk Muscle Activations During Simulated Low Speed Rear Impact Collisions
Background: The internal forces generated by the musculature of the lumbar region create most of the mechanical load placed on the spine. Thus, despite the anticipated low external forces generated between the occupant and the automobile seatback during a low speed rear impact collision, increased muscle tension may influence the resultant peak joint loads experienced in the lumbar spine. Consequently, the risk of low back injury may be altered by muscle activation.
Objective: The purpose of this study was to evaluate the activation profiles of muscles surrounding the lumbar spine during unanticipated and braced simulated rear-end collisions.
Methods: Twenty-two low speed sled tests were performed on eleven human volunteers (△v = 4 km/h). Each volunteer was exposed to one unanticipated impact and one braced impact. Accelerometers were mounted on the test sled and participants’ low back. Six bilateral channels of surface electromyography (EMG) were collected from the trunk during impact trials. Peak lumbar accelerations, peak muscle activation delay, muscle onset time and peak EMG magnitudes, normalized to maximum voluntary contractions (MVC), were examined across test conditions.
Results: While not statistically significant, bracing for impact tended to reduce peak lumbar acceleration in the initial rearward impact phase of the occupant’s motion by approximately 15%. The only trunk muscles with peak activations exceeding 10% MVC during the unanticipated impact were the thoracic erector spinae. Time of peak muscle activation was slightly longer for the unanticipated condition (unanticipated = 296 ms; braced = 241 ms).
Conclusions: Results from this investigation demonstrate that during an unanticipated low speed rear-end collision, the peak activation of muscles in the lumbar spine are low in magnitude. As such, muscle activation likely has minimal contribution to the internal joint loads that are experienced in the lumbar intervertebral joints during low speed rear impact collisions.
Study III - Characterizing In Vivo Mechanical Exposures of the Lumbar Spine During Simulated Low Velocity Rear Impact Collisions
Background: Historically, there has been a lack of focus on the lumbar spine during rear impacts because of the perception that the automotive seat back should protect the lumbar spine from injury. As a result, there have been no studies involving human volunteers to address the risk of low back injury in low velocity rear impact collisions.
Objectives: The primary objectives of this study were to explore lumbar kinematics and joint reaction forces in human volunteers during simulated rear impact collisions and to examine the influence of lumbar support on the peak motion and forces experienced in the lumbar spine. A secondary objective was to evaluate lumped passive stiffness changes and low back pain reporting after a simulated rear impact collision
Methods: Twenty-four participants (12 male, 12 female) were recruited. A custom-built crash sled was used to simulate unanticipated rear impact collisions, with a change in velocity of approximately 8 km/h. Randomized collisions were completed with and without lumbar support. Measures of passive stiffness and flexion-relaxation-ratio (FRR) were obtained prior to impact (Pre), immediately post impact (Post) and 24 hours post impact (Post-24). LBP reporting was monitored over the next 24 hours leading up to the final Post-24 measures. For collision simulations inverse dynamics analyses were conducted, and outputs were used to generate estimates of peak L4/L5 joint compression and shear. From the passive trials, lumbar flexion/extension moment-angle curves were generated to quantify time-varying changes in the passive stiffness of the lumbar spine, Post and Post-24 relative to Pre. FRRs were computed as the ratio of thoracic erector spinae and lumbar erector spinae muscle activation in an upright posture to muscle activation in a flexed position
Results: Average [± standard deviation] peak L4/L5 compression and shear reaction forces were not significantly different without lumbar support (Compression = 498.22 N [±178.0]; Shear = 302.2 N [± 98.5]) compared to with lumbar support (Compression = 484.5 N [±151.1]; Shear = 291.3 N [±176.8]). Lumbar flexion angle at the point of peak shear was 36 degrees [±12] without and 33 degrees [±11] with lumbar support, respectively, with 0 degrees being the lumbar posture in upright standing. No participants developed clinically significant levels of LBP after impact. Time was a significant factor for the length of the low stiffness flexion and extension zone (p = 0.049; p = 0.035), the length of the low stiffness zone was longer in the Post and Post-24 trial for low stiffness flexion and longer in the Post-24 for low stiffness extension.
Conclusions: Findings demonstrate that during a laboratory-simulation of an unanticipated 8 km/hour rear-impact collision, young healthy adults do not develop LBP. Lumbar support did not significantly influence the estimated L4/L5 joint reaction forces. Changes in the low stiffness portion of the passive flexion/extension curves were observed following impact and persisted for 24 hours. Changes in passive stiffness may lead to changes in the loads and load distributions within the passive structures such as the ligaments and intervertebral discs following impacts.
Study IV - Exploring the Interaction Effects of Impact Severity and Posture on Vertebral Joint Mechanics
Background: To date, no in vitro studies have been conducted to explore lumbar soft tissue injury potential and altered mechanical properties from exposure to impact forces. Typically, after a motor vehicle collision, the cause of a reported acute onset of low back pain is difficult to identify with potential soft tissue strain injury sites including the facet joint and highly innervated facet joint capsule ligament (FCL).
Objectives: The purpose of this investigation was to quantify intervertebral translation and facet joint capsule strain under varying postures and impact severities. A secondary objective was to evaluate flexion-extension and shear neutral zone changes pre and post impact.
Methods: A total of 72 porcine cervical FSUs were included in the study. Three levels of impact severity (4g, 8g, 11g), and three postures (Neutral Flexion and Extension) were examined using a full-factorial design. Impacts were applied using a custom-built impact track which simulated impact parameters similar to those experienced in low to moderate speed motor vehicle collisions. Passive flexion-extension and shear neutral zone testing were completed immediately prior to and immediately post impact. Intervertebral translation and the strain tensor of the facet capsule ligament were measured during impacts.
Results: A significant main effect (p > 0.001) of collision severity was observed for peak intervertebral translation and peak FCL shear strain (p = 0.003). A significant two-way interaction was observed between pre-post and impact severity for flexion-extension neutral zone length (p = 0.031) and stiffness (p>0.001) and anterior-posterior shear neutral zone length (p = 0.047) and stiffness (p>0.001). This was a result of increased neutral zone range and decreased neutral zone stiffness pre-post for the 11g severity impact (regardless of posture).
Conclusions: This investigation provides evidence that overall the peak vertebral translations observed across 4g to 11g impacts are below previously published ultimate shear failure displacements. FSU’s exposed to the highest severity impact (11g) had significant NZ changes, with increases in joint laxity in flexion-extension and shear testing and decreased stiffness, suggesting that soft tissue injury may have occurred. Despite observed main effects of impact severity, no influence of posture was observed. This lack of influence of posture and small FCL strain magnitudes suggest that the FCL does not appear to undergo injurious or permanent mechanical changes in response to low to moderate MVC impact scenarios.
Study V - Characterizing the Mechanical Properties of the Facet Joint Capsule Ligament
Background: The facet joint capsule ligament (FCL) is a structure in the lumbar spine that constrains motions of the vertebrae. Previous work has demonstrated that under physiological motion the FCL is subjected to significant deformation with FCL strains increasing in magnitude with increasing flexion and extension moments. Thus, it is important to characterize the mechanical response of the FCL for investigations into injury mechanisms. Sub failure loads can produce micro-damage resulting in increased laxity, decreased stiffness and altered viscoelastic responses. Thus, the objective of this investigation was to determine the mechanical and viscoelastic properties of the FCL under various magnitudes of strain from control samples and samples that had been exposed to an impact.
Objectives: The purpose of this investigation was to quantify the mechanical properties and viscoelastic response of control and impacted FCL.
Methods: 200 tissue samples were excised from the right and left FCL of 80 porcine cervical functional spinal units (FSU’s). Tissue samples were excised from FSU’s obtained from Study 4. Twenty FCL tissue samples served as the control group. The remaining 180 FCL tissue samples were randomly obtained from FSU’s that had been exposed to one of nine impact conditions (impacted tissue). Each specimen was loaded uniaxially, collinear with the primary fiber orientation. The loading protocol was identical for all specimens: preconditioning with 5 cycles of loading/unloading to 5% strain, followed by a 30 second rest period, 5 cycles of 10% strain and 1 cycle of 10% strain with a hold duration at 10% strain for 240 seconds. The same protocol followed for 30% (cyclic-30% & 30%-hold) and 50% strain (cyclic-50% & 50%-hold). All loading and unloading were performed at a rate of 2%/sec. All impacted FCL properties were compared back to controls. Measures of stiffness, hysteresis and force-relaxation were computed for the 30% and 50% strain conditions.
Results: No significant differences in stiffness were observed for impacted specimens in comparison to control (30% Control = 2.64 N/mm; 4 g = 2.20 N/mm, 8 g = 2.07 N/mm, 16 g = 2.16 N/mm)(50% Control = 5.06 N/mm; 4g = 4.60 N/mm, 8 g = 4.07 N/mm, 16 g =4.64 N/mm). Impacted specimens from the 8g Flexed and 11 g Flexed and Neutral conditions exhibited greater hysteresis during the cyclic-30% and cyclic-50%, in comparison to controls. In addition, specimens from the 8g and 11g Flexed conditions resulted in greater force relaxation for the 50%-hold conditions.
Conclusions: Results from this study demonstrate viscoelastic changes in FCL samples exposed to moderate and highspeed impacts in the flexed posture. However, it is interesting that these viscoelastic changes were not accompanied by changes in stiffness. Findings from this investigation provide novel insight and provide mechanical and viscoelastic properties of the FCL both in control and impacted scenarios.
Global Summary: Findings from this thesis demonstrate that (i) rear-end collision severities of 10 – 12 km/hour appear to be particularly common with respect to low back injury reporting (ii) during a laboratory-simulation of an unanticipated 8 km/hour rear-impact collision, young healthy adults do not develop LBP, however, changes in the low stiffness portion of the passive flexion/extension curves were observed following impact and persisted for 24 hours and (iii) the observed peak displacements in porcine functional spinal units exposed to varying impact severities are below ultimate shear failure displacements and does not support a lumbar spine injury mechanism resulting in acute traumatic bone fractures and/or acute traumatic IVD herniations in previously “healthy” tissues. Overall, the small FCL strain magnitudes during impacts and unchanged FCL mechanical properties post-impact suggest that the FCL does not undergo injurious or permanent mechanical changes in response to low to moderate MVC impact scenarios. Collectively, the findings from this thesis indicate that there are no direct mechanical changes that would indicate the high incidence of low back pain reporting following low to moderate severity rear-end motor vehicle impacts. However, changes in passive tissue properties were observed, and if persistent over time, may predispose individuals to secondary pain pathways. It is also important to note that this thesis tested healthy conditions and the results do not directly apply to pre-existing LBP cases being exposed to the same impacts
Assessing pre-existing movement and muscular recruitment differences in prolonged standing, transient low back pain developers compared to non-pain developers
No full textEpidemiological studies have reported occupational prolonged standing to be associated with low back pain (LBP). Studies that have conducted simulations of prolonged standing work in healthy individuals have demonstrated a proportion of them will develop transient LBP (termed pain developers or PDs), while others will not (termed non-pain developers or non-PDs). Investigations into differences between pain groups using low-demand tasks have predominantly reported neuromuscular differences involving the hip musculature and have shown capacity to distinguish pain groups. However, misclassification persists. There is little published data on pain groups in response to higher-demand challenges, which may elicit previously unseen or larger differences. Thus, the purpose of this study was to examine movement behavior and muscle recruitment patterns in healthy individuals that are non-PDs or PDs during a variety of tasks with increased functional demand and variety. It was hypothesized that the higher demand challenges will elicit previously unseen or enhanced differences in movement behavior and muscle recruitment in PDs relative to non-PDs.
Healthy university students were recruited to participate in two sessions. The first session involved participants performing a prolonged standing work simulation to determine their pain status. The second session involved participants performing a movement screening protocol involving low and high demand variations of the following tasks: symmetric trunk flexion-extension, symmetric floor-to-knuckle lift, modified star excursion balance test, active hip abduction, and reverse side bridge. Participants were outfitted with 3D motion capture markers and surface electromyography prior to task performance. Depending on the task, the kinematic data of the trunk and lower limbs were characterized into the following dependent variables: thorax segment angular velocity, peak lumbar spine flexion angle, frontal plane knee excursion, limb length normalized reach distances, and movement arc length. Depending on the task, surface electromyography of the external obliques, lumbar erector spine, gluteus medius, and gluteus maximus muscles were processed into the following dependent variables: phase lags at maximum correlation between muscle pairs and regression slope of median power frequencies for assessment of muscle fatigue.
A total of 39 participants were recruited and categorized, resulting in a subtotal of 22 non-PDs (12 females) and 17 PDs (8 females). Mixed-design analysis of variance analyses revealed no statistically significant main or interaction effects between pain status groups in most of the aforementioned kinematic and surface electromyography dependent variables. Interestingly, performance during the active hip abduction (AHA) revealed a pain status and task difficulty interaction effect (F(1,35) = 5.22, p < 0.05), with PDs exhibiting larger angular displacement arc length during AHA performance with an external weight relative to no external weight; not observed in non-PDs.
The results of this investigation showed that although task demands demonstrated changes in various kinematic and muscle activation patterns across participants, it did not always coincide with an individual’s pain status. Nonetheless, a significant finding to emerge from this study is the potential interaction an external weight has on pain status with their performance during the AHA. Taken together, these results suggest that there is minimal evidence for tasks with increased functional demand and variety to elicit unseen or larger aberrant movement behavior and muscle activation patterns in PDs relative to non-PDs
Playbook for the G20 Brisbane summit
No full textAustralia will chair the G20 for 12 months from 1 December 2013. It will be the largest international economic meeting ever held in Australia. This paper outlines the strategy, priorities and steps required for the Brisbane G20 summit to be a success – it is a ‘playbook’ for Australia’s G20 presidency.Key findings:For the Brisbane summit to be a success, Australia will need to improve the way the G20 works, define a focused agenda and directly engage leaders. A pragmatic, business-like approach is required. Priorities for the Brisbane leaders’ summit should include: developing a ‘G20 coordinated growth strategy’; breathing life back into the multilateral trading system; tackling climate change financing; delivering tangible progress in the international effort to combat tax evasion and avoidance; and, mainstreaming development into the G20 agenda. To achieve these outcomes will require a strategic game plan and a co-ordinated 12 month campaign, led by the Prime Minister and involving all aspects of Australian society
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