The purpose of this DRDC dynamic biomechanical model research program is to improve the understanding of human load carriage capabilities and to understand the effects of load carriage design features on human health and mobility. This... more
The purpose of this DRDC dynamic biomechanical model research program is to improve the understanding of human load carriage capabilities and to understand the effects of load carriage design features on human health and mobility. This research is directed at creating a method of determining several of the biomechanical factors to be used as inputs to the Load Conditions Limit model as described in DRDC report# W7711-0-7632-01 entitled "Proposed Long Range Plan for a Research and Development Program of Dynamic Load Carriage Modeling." In the current study, a 3D solid model was split into an upper and lower torso coupled with a rigid join located at the location of the spine at the L3/L2 height. Acceleration histories of subjects wearing packs were previously recorded during human trials. Acceleration of a person was numerically integrated and used to drive the motion of the Dynamic Biomechanical Model (DBM) torso. Torso accelerations for a wide range of activities were rec...
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ABSTRACT
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The purpose of this study was to validate a 3D dynamic virtual model for lifting tasks against a validated link segment model (LSM). A face validation study was conducted by collecting x, y, z coordinate data and using them in both... more
The purpose of this study was to validate a 3D dynamic virtual model for lifting tasks against a validated link segment model (LSM). A face validation study was conducted by collecting x, y, z coordinate data and using them in both virtual and LSM models. An upper body virtual model was needed to calculate the 3D torques about human joints for use in simulated lifting styles and to estimate the effect of external mechanical devices on human body. Firstly, the model had to be validated to be sure it provided accurate estimates of 3D moments in comparison to a previously validated LSM. Three synchronised Fastrak units with nine sensors were used to record data from one male subject who completed dynamic box lifting under 27 different load conditions (box weights (3), lifting techniques (3) and rotations (3)). The external moments about three axes of L4/L5 were compared for both models. A pressure switch on the box was used to denote the start and end of the lift. An excellent agreement [image omitted] was found between the two models for dynamic lifting tasks, especially for larger moments in flexion and extension. This virtual model was considered valid for use in a complete simulation of the upper body skeletal system. This biomechanical virtual model of the musculoskeletal system can be used by researchers and practitioners to give a better tool to study the causes of LBP and the effect of intervention strategies, by permitting the researcher to see and control a virtual subject's motions.
Research Interests: Engineering, Computer Science, Dentistry, Biomedical Engineering, Low back pain, and 14 moreHumans, Movement, Human Body, Male, Three Dimensional Imaging, Computer User Interface Design, Validation Studies, Adult, Musculoskeletal system, Torque, Lifting, Computer Methods, Biomechanical Phenomena, and lumbar vertebrae
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ABSTRACT Anterior Cruciate Ligament (ACL) injuries are of concern in the military setting due to time loss and possible inability to return to pre-injury activity levels. This chapter aims at reviewing the current state of knowledge... more
ABSTRACT Anterior Cruciate Ligament (ACL) injuries are of concern in the military setting due to time loss and possible inability to return to pre-injury activity levels. This chapter aims at reviewing the current state of knowledge regarding this type of injury, as well as outlines our proposal to standardize patient evaluation procedures in the CF. Such standardization will allow development of clinical prediction rules for safe and effective return to duty. In the first part of the chapter, a synopsis is provided regarding the prevalence, extent, and costs associated with this particular injury in both the general population and in the military with elaboration provided on known risk factors and injury mechanisms, as well as general rehabilitative procedures. In the second part of this chapter, we present considerations for standardization of patient assessment methods, and in particular those related to measurements of knee muscular strength and psychological constructs. We then present work done to date concerned with several aspects of reproducibility and validity of scores obtained using the proposed procedures. Finally, we outline our future clinical and research goals.
ABSTRACT Introduction: Load carriage walking tasks performed by military personnel for extended time periods are thought to hamper performance as well as increase musculoskeletal injury risk. While the effect of different load... more
ABSTRACT Introduction: Load carriage walking tasks performed by military personnel for extended time periods are thought to hamper performance as well as increase musculoskeletal injury risk. While the effect of different load configurations and equipment has been tested on acute biomechanical and physiological responses, few investigations have assessed the influence of these factors over a prolonged period of time. Purpose: The purpose of this investigation was to assess whether lower extremity and trunk kinematics, heart rate, and subjective exertion ratings are altered due to the performance of prolonged load carriage walking. Methods: Seventeen male participants performed 60 min of treadmill walking at a speed of 1.53 ms-1 while carrying a military-issue backpack weighing 32.5 kg. Differences in sagittal plane kinematic waveforms obtained during the initial and final phases of the task were assessed using principal component analyses, as well as changes in heart rate, rated perceived exertion, and body discomfort. Results: The only kinematic change observed across the one hour of walking was that the foot became slightly more dorsiflexed throughout the gait cycle. Perceived exertion and neck and shoulder discomfort were rated higher at the end of the walk. Conclusions: Although changes in rated perceived exertion and discomfort were small, these variables were influenced in an ideal setting with the best available equipment issued to soldiers. Therefore, backpacks currently used by soldiers could benefit from further development and design modifications to reduce shoulder and neck discomfort.
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This study analyzed relative lumbar and pelvic motion during sagittal plane trunk motion. Patterns of movement were compared during loaded trunk flexion and extension. The purpose of this study was to examine the dynamic relationship... more
This study analyzed relative lumbar and pelvic motion during sagittal plane trunk motion. Patterns of movement were compared during loaded trunk flexion and extension. The purpose of this study was to examine the dynamic relationship between the lumbar spine and pelvis during trunk motion and to determine the effect of direction of lift (up vs. down) on lumbar-pelvic rhythm. There is disagreement in the literature regarding whether rotations of the pelvis and lumbar spine occur sequentially or simultaneously during bending and lifting tasks. Thirty healthy women, ranging in age from 19 to 35 years, participated in the study. The 3Space Tracker System, an electromagnetic tracking device, was used to monitor simultaneous lumbar and pelvic motion as subjects lifted and lowered a 9.5 kg box with knees extended. Although lumbar and pelvic motion occurred simultaneously during flexion and extension, there was greater separation of these movements during the "up lifts" than during the "down lifts." Lumbar-pelvic rhythm varied depending on whether the trunk was flexing or extending. During trunk flexion (down lift) there was a greater tendency for lumbar and pelvic rotations to occur simultaneously, whereas during extension (up life) they tended to occur more sequentially.
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The purpose of this study was to examine the change in load distribution characteristics associated with adding lateral stiffness elements (rods) to a rucksack (backpack). A load distribution mannequin was instrumented with two 3D load... more
The purpose of this study was to examine the change in load distribution characteristics associated with adding lateral stiffness elements (rods) to a rucksack (backpack). A load distribution mannequin was instrumented with two 3D load cells to allow determination of the load applied to the shoulders and upper torso independent of the load applied to the hips and lower trunk. Position and mass of the payload (25 kg) were fixed at the centre of the volume of the rucksack and held constant during all testing. It was hypothesized that lateral rods would provide a force bridge that transfers part of the vertical load of the pack from the upper back and shoulders to the hip belt thereby reducing the vertical load on the torso, and possibly reducing the horizontal reaction force that produces a shear load on the spine. Results showed that these active stiffness elements shifted 14% of the vertical load from the upper torso to the pelvic region with lumbar shear load remaining relatively unchanged for all combinations of shoulder strap and waist belt tension. The lateral rods also provided a mean increase of 12% in the extensor moment at the L3-L4 level, thus reducing some demand on the erector spinae muscles.
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Page 87. Advances in Occupational Ergonomics and Safety 73 GCH Lee (Ed.) IOS Press. 1999 Quantification of Lifting Technique in a Manual Materials Handling Plant Wayne J. Albert, Joan M. Stevenson and Patrick A. Costigan Ergonomics... more
Page 87. Advances in Occupational Ergonomics and Safety 73 GCH Lee (Ed.) IOS Press. 1999 Quantification of Lifting Technique in a Manual Materials Handling Plant Wayne J. Albert, Joan M. Stevenson and Patrick A. Costigan Ergonomics Research Group, Queen's University ...
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ABSTRACT The majority of lifting research uses male subjects, and thus it is necessary to investigate if gender differences exist in lifting technique that may limit extrapolation of these studies. Three-dimensional kinematics of the... more
ABSTRACT The majority of lifting research uses male subjects, and thus it is necessary to investigate if gender differences exist in lifting technique that may limit extrapolation of these studies. Three-dimensional kinematics of the ankle, knee, hip and lumbar and thoracic spine were collected for 30 subjects (15 males and 15 females) during lifting trials under two load conditions: 0% and 10% of maximum isometric back strength. Applying a principal component analysis (PCA) to the lifting waveforms, 30 principal components (PCs) were retained using a 90% trace criterion. There was a significant effect of load on PC2 of lumbar spine flexion and PC2 of hip rotation, but no effect of gender on any of the PCs. Therefore, independent of gender, under loaded conditions individuals demonstrated a semi-squat lifting technique. By employing a sophisticated statistical method such as PCA and standardising load to the individual's strength characteristics, there was no significant effect of gender on lifting technique.
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Research Interests: Physiology, Simulation, Population, Measurement, Value, and 3 morePhysical Fitness, SAND, and Test Methods
A second module, Module 2 - the Activity Assessment Module (AAM) - has been developed for the portable data acquisition system for human performance evaluation. The main purpose of the AAM is to permit the assessment of the type and... more
A second module, Module 2 - the Activity Assessment Module (AAM) - has been developed for the portable data acquisition system for human performance evaluation. The main purpose of the AAM is to permit the assessment of the type and intensity of work performed by a subject in the field, e.g. a soldier participating in a training exercise. This is done using two primary measures: upper body accelerations on three axes and heart rate (HR). The AAM was evaluated in an in-door trial. Upper body accelerations and HR were monitored in subjects as they completed a standardized circuit. The subjects carried either a very light load (battle order conditions); or a light, medium or heavy load (marching order conditions). The circuit comprised seven discrete activities: walking, balance beam, boulder hop, over-under barriers and fence climb, slalom run, up-down ramp, and sidehill ramp. The results of the trial revealed the following: 1) metabolic energy cost, estimated from HR, increases with ...
12.8 0.008 14.8 0.002 23.5 0.001 27.4 0.001 36.2 0.001 23.0 0.046 Lumbar ES 10.3 0.001 23.6 0.000 27.6 0.001 28.9 0.001 37.3 0.001 25.5 0.001
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The purpose of this study was verify the design of a novel Helmet System Support Device (HSSD) that can be used by military aircrew to help intervene on and reduce the high prevalence of neck trouble. Twelve healthy participants repeated... more
The purpose of this study was verify the design of a novel Helmet System Support Device (HSSD) that can be used by military aircrew to help intervene on and reduce the high prevalence of neck trouble. Twelve healthy participants repeated simulated helicopter aircrew tasks on 3 separate days. On each day they wore a different helmet configuration, where measures of performance, perceived demand/preference and muscular demand were recorded. The results showed that vigilance tasks were performed over 10% faster with the HSSD configuration compared to wearing the normal helmet configuration. Participants were able to maintain static (endurance) postures for 28% longer, and use of the HSSD helped to prevent neck muscle fatigue in the most demanding task. The results of this design verification study indicate that the HSSD may be a realistic, feasible near-term solution to intervene on the high prevalence of neck trouble among rotary-wing aircrew.
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Over my career I have been involved in research covering three different strategies to reduce workplace injuries, namely: (a) developing bona fide occupational requirements for physically demanding jobs, (b) conducting training programs... more
Over my career I have been involved in research covering three different strategies to reduce workplace injuries, namely: (a) developing bona fide occupational requirements for physically demanding jobs, (b) conducting training programs and a case-control study of low back pain in industry, and (c) developing ergonomically-designed equipment and tools. The purpose of this paper is to identify some areas where I believe research is needed to reduce the risks of musculoskeletal disorders. Hopefully, new researchers will pick up the torch on some of these topics and continue to enhance the impact of occupational biomechanics and ergonomics on improving jobs for workers.
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To assess the reproducibility of isokinetic eccentric and concentric knee extension and flexion strength indices obtained at two different angular velocities. Cohort study. University human performance laboratory. 45 healthy physically... more
To assess the reproducibility of isokinetic eccentric and concentric knee extension and flexion strength indices obtained at two different angular velocities. Cohort study. University human performance laboratory. 45 healthy physically active young adults (25 males). A non reciprocal protocol of concentric and eccentric contractions of the knee extensors and flexors was performed at 30 and 120°/s. Strength indices evaluated included peak moment; dynamic control ratios; and the difference between eccentric and concentric ratio at the two angular velocities. No evidence for inter-test bias in any of the strength indices was noted. Measurement precision for peak moment, as quantified using ratio limits of agreement, suggest that scores may be expected to vary up to 15% for the knee extensors in both eccentric and concentric contraction modes. An error of up to 19% was calculated for the peak moment scores of the knee flexors. Intraclass correlation coefficients revealed fairly robust p...
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Parents, educators and researchers have expressed concern about the long term impacts of children carrying excessive loads in their backpacks on a daily basis. Although many researchers have investigated appropriate weight limits for... more
Parents, educators and researchers have expressed concern about the long term impacts of children carrying excessive loads in their backpacks on a daily basis. Although many researchers have investigated appropriate weight limits for children's packs, little research has been conducted on the design of children's backpacks. The purpose of this study was to evaluate the changes in children's trunk forward lean (TFL), cranio-vertebral angle (CVA) and spinal lordosis angle (LA) that occurred with high, medium and low load locations during standing and walking. Ten-year-old children (n = 15) completed a repeated measures designed study while carrying 15% of each child's body weight in a typical backpack with only shoulder straps. A special instrumented backpack (IBP) was designed that allowed the weight to be placed in the proper location and continuously measure changes in spinal curvature. TFL and CVA postures were captured on digital video at five intervals including:...
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The Mark 3 (M3) water power pump is an integral piece of wildfire fighting equipment. However, it is provided to fire stations without a carrying harness. The currently-used carrying harness is very uncomfortable, especially when carrying... more
The Mark 3 (M3) water power pump is an integral piece of wildfire fighting equipment. However, it is provided to fire stations without a carrying harness. The currently-used carrying harness is very uncomfortable, especially when carrying the pumps considerable distance in a forest to reach a water source. The purpose of this study was to advise the Ontario Ministry of Natural Resources on the selection of a new M3 load carriage system. Twenty Fire Rangers wore the three systems (Original, Prototype, and Modified) through a circuit of tasks representative of their working environment. Subjective and objective approaches were combined to assess and rank the M3 carriage systems. Subjective visual analogue scale ratings were obtained for ease of loading/unloading, comfort, system stability, and overall performance. Tri-axial accelerometers were mounted on each pump and at the sternum of each participant to determine relative pump-carrier accelerations. Overall, the Prototype was ranked...
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ABSTRACT Introduction: Load carriage walking tasks performed by military personnel for extended time periods are thought to hamper performance as well as increase musculoskeletal injury risk. While the effect of different load... more
ABSTRACT Introduction: Load carriage walking tasks performed by military personnel for extended time periods are thought to hamper performance as well as increase musculoskeletal injury risk. While the effect of different load configurations and equipment has been tested on acute biomechanical and physiological responses, few investigations have assessed the influence of these factors over a prolonged period of time. Purpose: The purpose of this investigation was to assess whether lower extremity and trunk kinematics, heart rate, and subjective exertion ratings are altered due to the performance of prolonged load carriage walking. Methods: Seventeen male participants performed 60 min of treadmill walking at a speed of 1.53 ms-1 while carrying a military-issue backpack weighing 32.5 kg. Differences in sagittal plane kinematic waveforms obtained during the initial and final phases of the task were assessed using principal component analyses, as well as changes in heart rate, rated perceived exertion, and body discomfort. Results: The only kinematic change observed across the one hour of walking was that the foot became slightly more dorsiflexed throughout the gait cycle. Perceived exertion and neck and shoulder discomfort were rated higher at the end of the walk. Conclusions: Although changes in rated perceived exertion and discomfort were small, these variables were influenced in an ideal setting with the best available equipment issued to soldiers. Therefore, backpacks currently used by soldiers could benefit from further development and design modifications to reduce shoulder and neck discomfort.
Load carriage is recognised as a primary occupational factor leading to slip and fall injuries, and therefore assessing balance maintenance during such tasks is critical in assessing injury risk. Ten males completed 55 strides under five... more
Load carriage is recognised as a primary occupational factor leading to slip and fall injuries, and therefore assessing balance maintenance during such tasks is critical in assessing injury risk. Ten males completed 55 strides under five carriage conditions: (1) unassisted anterior, (2) unassisted posterior, (3) assisted anterior, (4) assisted posterior and (5) unloaded gait (UG). Kinematic data were recorded from markers affixed to landmarks on the right side of each participant, in order to calculate segment angles for the foot, shank, thigh and pelvis. Continuous relative phase (CRP) variability was calculated for each segment pair and local dynamic stability was calculated for each segment in all three movement planes. In general, irrespective of the assistive device or movement plane, anterior load carriage was most stable (lower CRP variability and maximum finite-time Lyapunov exponents). Moreover, load carriage was less dynamically stable than UG, displaying the importance of objectively investigating safe load carriage practices.
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The majority of lifting research uses male subjects, and thus it is necessary to investigate if gender differences exist in lifting technique that may limit extrapolation of these studies. Three-dimensional kinematics of the ankle, knee,... more
The majority of lifting research uses male subjects, and thus it is necessary to investigate if gender differences exist in lifting technique that may limit extrapolation of these studies. Three-dimensional kinematics of the ankle, knee, hip and lumbar and thoracic spine were collected for 30 subjects (15 males and 15 females) during lifting trials under two load conditions: 0% and 10% of maximum isometric back strength. Applying a principal component analysis (PCA) to the lifting waveforms, 30 principal components (PCs) were retained using a 90% trace criterion. There was a significant effect of load on PC2 of lumbar spine flexion and PC2 of hip rotation, but no effect of gender on any of the PCs. Therefore, independent of gender, under loaded conditions individuals demonstrated a semi-squat lifting technique. By employing a sophisticated statistical method such as PCA and standardising load to the individual's strength characteristics, there was no significant effect of gender on lifting technique.
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Background The purpose of this study was to assess the between-day reliability of the electromechanical delay (EMD) of selected neck muscles during the performance of maximal isometric contractions in five different directions. Methods... more
Background The purpose of this study was to assess the between-day reliability of the electromechanical delay (EMD) of selected neck muscles during the performance of maximal isometric contractions in five different directions. Methods Twenty-one physically active males participated in two testing sessions separated by seven to eight days. Using a custom-made fixed frame dynamometer, cervical force and surface electromyography (EMG) were recorded bilaterally from the splenius capitis, upper trapezius and sternocleidomastoid muscles during the performance of efforts in extension, flexion, left and right lateral bending, and protraction. The EMD was extracted using the Teager-Kaiser Energy Operator. Reliability indices calculated for each muscle in each testing direction were: the difference in scores between the two testing sessions and corresponding 95% confidence intervals, the standard error of measurement (SEM) and intra-class correlation coefficients (ICC). Results EMD values sh...
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A method by which the location of vertebral bodies can be estimated from the external profile of the spine in the sagittal plane is described. The technique involves a normalization of the curve from T1 to L5 and approximation using a... more
A method by which the location of vertebral bodies can be estimated from the external profile of the spine in the sagittal plane is described. The technique involves a normalization of the curve from T1 to L5 and approximation using a cubic spline. Mapping functions are developed that enable the transformation of a skin profile to a vertebral centroid curve. Data were obtained for 13 subjects between the ages of 13 and 17 who had undergone lateral spinal radiographs with radiopaque skin markers over the vertebral spinal processes. Results suggested that vertebral body centroids could be estimated from the skin profile to a precision having a standard error of the estimate of 0.4 cm. This was improved to 0.2 cm if the lumbar curve were considered separately.
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This study analyzed relative lumbar and pelvic motion during sagittal plane trunk motion. Patterns of movement were compared during loaded trunk flexion and extension. The purpose of this study was to examine the dynamic relationship... more
This study analyzed relative lumbar and pelvic motion during sagittal plane trunk motion. Patterns of movement were compared during loaded trunk flexion and extension. The purpose of this study was to examine the dynamic relationship between the lumbar spine and pelvis during trunk motion and to determine the effect of direction of lift (up vs. down) on lumbar-pelvic rhythm. There is disagreement in the literature regarding whether rotations of the pelvis and lumbar spine occur sequentially or simultaneously during bending and lifting tasks. Thirty healthy women, ranging in age from 19 to 35 years, participated in the study. The 3Space Tracker System, an electromagnetic tracking device, was used to monitor simultaneous lumbar and pelvic motion as subjects lifted and lowered a 9.5 kg box with knees extended. Although lumbar and pelvic motion occurred simultaneously during flexion and extension, there was greater separation of these movements during the "up lifts" than during the "down lifts." Lumbar-pelvic rhythm varied depending on whether the trunk was flexing or extending. During trunk flexion (down lift) there was a greater tendency for lumbar and pelvic rotations to occur simultaneously, whereas during extension (up life) they tended to occur more sequentially.
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This is a longitudinal study in which industrial workers without chronic low back pain (LBP) were initially assessed with a comprehensive test battery and surveyed every 6 months thereafter for 2 years. To determine factors that may... more
This is a longitudinal study in which industrial workers without chronic low back pain (LBP) were initially assessed with a comprehensive test battery and surveyed every 6 months thereafter for 2 years. To determine factors that may predispose industrial workers who lift over 5000 kg per shift to LBP. Prospective studies are small in number and often limited in breadth or depth of the test battery, methodologic issues, or investigator expertise. There are no prospective studies that focus on a homogeneous work sample of industrial employees. Production workers (n = 149) who volunteered for the 2-year study were assessed using physical measures (e.g., muscular strength, endurance, and flexibility), lifting kinematics (a sagittal plane box lift), and health, lifestyle, and work environment data (paper questionnaires). Follow-up questionnaires were distributed every 6 months for 2 years. Using self-report of LBP as the main outcome measure, eight variables predicted LBP in this sample with a 75% correct prediction rate. Predictor variables included age, thoracic acceleration during the trunk velocity test, median frequency intercept of electromyography of the right L3 erector spinae, quadriceps strength, quadriceps endurance, self-assessment of fitness, having a confidante, and number of medications currently taken. Results confirmed the multifactorial nature of low back pain and suggest that personal fitness is an important defense against low back pain, even in manual handling lifting tasks.
Research Interests: Biomedical Engineering, Life Style, Low back pain, Canada, Prospective studies, and 15 moreHumans, Female, Male, Electromyography, Clinical Sciences, Physical Fitness, Questionnaires, Adult, Longitudinal Study, Occupational Diseases, Lifting, Medicine and Science In Sports and Exercise, Exercise Test, Logistic Models, and Disability Evaluation
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Abstract: The purpose of this study was to provide an overview of contributions by biomechanical testing to the design of the final Canadian Clothe the Soldier (CTS) load carriage (LC) system. The Load Carriage Simulator and Compliance... more
Abstract: The purpose of this study was to provide an overview of contributions by biomechanical testing to the design of the final Canadian Clothe the Soldier (CTS) load carriage (LC) system. The Load Carriage Simulator and Compliance tester were used ...
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Bilateral knee strength evaluations of unilateral anterior cruciate ligament (ACL) deficient patients using isokinetic dynamometry are commonly performed in rehabilitation settings. The most frequently-used outcome measure is the peak... more
Bilateral knee strength evaluations of unilateral anterior cruciate ligament (ACL) deficient patients using isokinetic dynamometry are commonly performed in rehabilitation settings. The most frequently-used outcome measure is the peak moment value attained by the knee extensor and flexor muscle groups. However, other strength curve features may also be of clinical interest and utility. The purpose of this investigation was to identify, using Principal Component Analysis (PCA), strength curve features that explain the majority of variation between the injured and uninjured knee, and to assess the capabilities of these features to detect the presence of injury. A mixed gender cohort of 43 unilateral ACL deficient patients performed 6 continuous concentric knee extension and flexion repetitions bilaterally at 60°s(-1) and 180°s(-1) within a 90° range of motion. Moment waveforms were analyzed using PCA, and binary logistic regression was used to develop a discriminatory decision rule. For all directions and speeds, a statistically significant overall reduction in strength was noted for the involved knee in comparison to the uninvolved knee. The discriminatory decision rule yielded a specificity and sensitivity of 60.5% and 60.5%, respectively, corresponding to an accuracy of ∼62%. As such, the curve features extracted using PCA enabled only limited clinical usefulness in discerning between the ACL deficient and contra lateral, healthy knee. Improvement in discrimination capabilities may perhaps be achieved by consideration of different testing speeds and contraction modes, as well as utilization of other data analysis techniques.
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The personal lift-assist device (PLAD) is an on-body ergonomic aid that reduces low back physical demands through the restorative moment of an external spring element, which possesses a mechanical advantage over the erector spinae.... more
The personal lift-assist device (PLAD) is an on-body ergonomic aid that reduces low back physical demands through the restorative moment of an external spring element, which possesses a mechanical advantage over the erector spinae. Although the PLAD has proven effective at reducing low back muscular demand, spinal moments, and localized muscular fatigue during laboratory and industrial tasks, the effects of the device on the neuromuscular control of spinal stability during lifting have yet to be assessed. Thirty healthy subjects (15M, 15F) performed repetitive lifting for three minutes, at a rate of 10 lifts per minute, with and without the PLAD. Maximum finite-time Lyapunov exponents, representing short-term (λ(max-s)) and long-term (λ(max-l)) divergence were calculated from the measured trunk kinematics to estimate the local dynamic stability of the lumbar spine. Using a mixed-design repeated-measures ANOVA, it was determined that wearing the PLAD did not significantly change λ(max-s) (μ(NP)=0.335, μ(P)=0.321, p=0.225), but did significantly reduce λ(max-l) (μ(NP)=0.0024, μ(P)=-0.0011, p=0.014, η(2)=0.197). There were no between-subject effects of sex, or significant interactions (p>0.720). The present results indicated that λ(max-s) was not statistically different between the device conditions, but that the PLAD significantly reduced λ(max-l) to a negative (stable) value. This shows that subjects' neuromuscular systems were able to respond to local perturbations more effectively when wearing the device, reflecting a more stable control of spinal movements. These findings are important when recommending the PLAD for long-term industrial or clinical use.