Biomedical Physiology and Kinesiology - Theses, Dissertations, and other Required Graduate Degree Essays

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Mechanics and energetics of step-to-step transitions

Date created: 
2009
Abstract: 

The major determinant of walking’s metabolic cost is the work required to redirect the centre of mass velocity during step-to-step transitions. My first aim was to isolate transitions from other contributors to walking mechanics. The results demonstrated that sagittal plane rocking reproduced the important characteristics of walking’s transitions including a strong dependence of work on step length and a proportional increase in metabolic cost. My second aim was to use rocking to gain insight into pathological gait’s elevated cost. Physics-based mathematical models predict sub-optimal transitions occur when one or both legs are unable to generate mechanical power with the optimal timing and magnitude, requiring a greater magnitude of total work and an increase in metabolic cost. I tested this prediction by immobilising the ankle joints of healthy subjects to simulate sub-optimal transitions and found that joint immobilization indeed caused sub-optimal transitions thereby increasing transition work and metabolic cost.

Document type: 
Thesis
File(s): 
Senior supervisor: 
J
Department: 
School of Kinesiology - Simon Fraser University
Thesis type: 
Thesis (M.Sc.)

Changes in patterns of EMG activity in post-stroke subjects following robot-assisted hand rehabilitation.

Author: 
Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2009
Abstract: 

A feasibility study of robot-assisted hand rehabilitation post-stroke was conducted to investigate changes in activation patterns of forearm and hand muscles. Four stroke survivors received robot-assisted hand rehabilitation twice a week for two months. Eight healthy age-matched control subjects performed the same exercises as stroke subjects in a single training session. The pattern of activation of forearm and hand muscles was analyzed by performing Principal Component Analysis on the root-mean-square electromyogram. No differences were found in the number of principal components required to account for 95% of the variance between stroke and healthy subjects or pre- and post-rehab even though the majority of subjects used different muscle activation patterns for different exercises and changed their activation patterns from pre- to post-rehab. Stroke subjects were found to have more co-contraction of antagonistic muscles than healthy subjects pre-rehab. In most cases, the amount of co-contraction did not decrease from pre- to post-rehab.

Document type: 
Thesis
File(s): 
Senior supervisor: 
T
Department: 
School of Kinesiology - Simon Fraser University
Thesis type: 
Thesis (M.Sc.)

Src homology 2 domain-containing inositol-5’ phosphatase in a murine model of Amyotrophic Lateral Sclerosis

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2009
Abstract: 

As Src homology-2 domain-containing inositol-5’ phosphatase (SHIP-1) expression has been implicated in inflammation, immunoreactivity against SHIP-1 was evaluated in mice over-expressing mutant superoxide dismutase (mSOD-1) and wild-type (wt) mice. Spinal cord sections were examined at 11 weeks, 15 weeks of age and at end-stage. SHIP-1 immunoreactivity was detected in mSOD-1 mice at end-stage when considerable motor disability is evident, and at 15 weeks, but not in wt mice. At 15 weeks, SHIP-1 was prominent in the ventral horn, and by end-stage, immunoreactivity was detected throughout the ventral and dorsal regions. SHIP-1 localization was explored further using SHIP-1 immunoreactivity and antibodies directed against microglia and astrocytes. SHIP-1 was not detected in microglia but was detected in astrocytes and this cell specific localization of immunoreactivity suggests that astrocytes can express SHIP-1. The expression of SHIP-1 in astrocytes may be involved in the pathogenesis of murine amyotrophic lateral sclerosis.

Document type: 
Thesis
File(s): 
Senior supervisor: 
C
Department: 
School of Kinesiology - Simon Fraser University
Thesis type: 
Thesis (M.Sc.)

Assessment of Low Back Injury Risk in Residential Care Workers

Author: 
Date created: 
2004
Abstract: 

Low back injury continues to be a problem for residential care workers. There is an absence of an assessment tool that will determine probability of low back injury based on occupational exposure. This study analysed injury incidence among residential care workers and determined perceived stress and exertion, hand forces, postures, and task frequencies encountered in routine work tasks. Biomechanical analysis determined joint forces at the low back to be in the range of 467N to 381 1 N compression and 66N to 471 N A-P shear over all tasks. Task frequencies, joint compression forces, population low back injury data and material fatigue characteristics were used to model risk of low back injury as a function of occupational exposure. The fatigue model predicts that 50% of residential care workers will experience a low back injury by their eighth year of work experience, and 95% by their fifteenth year of work.

Document type: 
Thesis
File(s): 
Department: 
School of Kinesiology - Simon Fraser University
Thesis type: 
(Kinesiology) Thesis (M.Sc.)

Physiological mechanisms of nutrient transport: Vitamin A and retinol-binding protein

Author: 
Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2009
Abstract: 

Biologically active metabolites of retinol (vitamin A) affect growth, differentiation, and survival of cells. Retinol-binding protein (RBP) is a specific circulatory transport protein for retinol and participates its delivery to cells. Based on evidence for receptor-mediated endocytosis of RBP, experiments were carried out to further characterize (a) the RBP receptor and (b) the fate of endocytosed RBP in a human epithelial cell line. Additional experiments were performed with mice to examine (c) possible age-related changes in tissue accumulation of injected RBP. The results provide the first size characterization of an RBP receptor in these cells, a 157 kDa species, and the first evidence for recycling of endocytosed RBP. Age-related decreases in transport were suggested by a 23-27% decrease in the accumulation of exogenous RBP in old vs. young tissues (early post-injection times). Additional work on related transport mechanisms was carried out for RBP and the iron carrier transferrin.

Document type: 
Thesis
File(s): 
Senior supervisor: 
A
Department: 
School of Kinesiology - Simon Fraser University
Thesis type: 
Thesis (M.Sc.)

Neuromuscular and behavioural influences on balance and falls

Author: 
Date created: 
2009
Abstract: 

Falls are the number one cause of accidental injury and exert an especially heavy toll on the elderly. Most falls involve a common sequence of events. First, a particular event results in loss of balance. Second, there is a failed attempt at recovering balance, and finally, once the fall is "recognized" to be inevitable, attempts may be made to lessen its severity. My thesis research focuses on neuromuscular and behavioural aspects of balance maintenance and protective responses during falls. In Chapter 2 and 3, I describe efforts to develop and apply a novel technique to determine how risk for imbalance during daily activities depends on behavioural versus neuromuscular factors. Specifically, I developed the “Reach Utilization Test” to determine whether the tendency to approach imbalance is different between young and elderly women who resided either in nursing homes (Chapter 2) or in the community (Chapter 3). In Chapters 4 to 7, I focus on the measurement and analysis of protective responses during sideways falls. In Chapter 4, I describe the results of experiments to determine whether unexpected sideways falls in young adults elicit a common sequence of responses that might protect against hip fracture. I used a novel experimental paradigm which challenged participants to focus on maintaining balance after experiencing a single large perturbation, which in the vast majority of cases elicited a sideways fall. In Chapter 5, I describe the results of experiments to test whether the ability of humans to alter their body configuration during the fall depends on the time when the response is initiated. I hypothesized that a critical time window exists, beyond which one is unable to avoid hip impact. In Chapter 6, I describe the results of experiments to determine whether individuals are able to accurately recall the details of their falls. I addressed this question by interviewing young adults immediately after they experienced an unexpected sideways falls. Finally, in chapter 7, I describe results from a modelling study to address how fall severity depend on the cause of the fall (slip vs. trip).

Document type: 
Thesis
File(s): 
Senior supervisor: 
S
Department: 
School of Kinesiology - Simon Fraser University
Thesis type: 
Dissertation (Ph.D.)

Remote management of chronic heart failure patients using Internet supported technology

Author: 
Date created: 
2008
Abstract: 

Background: Heart failure results in high morbidity and mortality rates and is increasing in prevalence. Symptom and weight monitoring is essential as it has been associated with improved outcomes for patients. Purpose: To investigate the use of a website for the telemonitoring of heart failure patients, to assess its uptake, and evaluate its effect. Methods: Twenty patients were recruited and entered their daily weight and symptoms onto the website for six months. Patients were remotely monitored by a nurse and contacted as required. Results: Trends toward improvement were observed on the maintenance (p=0.039) and confidence subscales of the Self-Care of Heart Failure Index (p=0.069), Minnesota Living With Heart Failure® Questionnaire (p=0.337), six-minute walk test (p=0.124) and NT-proBNP (p=0.210). Participants and nurses demonstrated a favourable uptake of the website. Conclusions: The website was favourably accepted by both patients and nurses and its use is associated with improved outcomes.

Document type: 
Thesis
File(s): 
Senior supervisor: 
S
Department: 
School of Kinesiology - Simon Fraser University
Thesis type: 
(Kinesiology) Thesis (M.Sc.)

Factors affecting the efficacy of hip protectors during falls

Date created: 
2008
Abstract: 

Hip protectors represent a promising strategy for preventing fall-related hip fractures in the elderly. However, fractures still occur when wearing a protector. From a biomechanical perspective, the protective benefit of a hip protector should depend on the wearer’s body habitus, the fall orientation, and the position of the hip protector relative to the greater trochanter. This thesis is comprised of two studies designed to test this hypothesis. In the first study, I conducted experiments with human subjects which demonstrate that the reduction in peak magnitude and change in pressure distribution provided by a hip protector depends on body habitus and fall direction. In the second study, I conducted experiments with a hip impact testing system to show that force magnitude and distribution are affected by the position of the hip protector relative to the greater trochanter.

Document type: 
Thesis
File(s): 
Senior supervisor: 
S
Department: 
School of Kinesiology - Simon Fraser University
Thesis type: 
(Kinesiology) Thesis (M.Sc.)

Biomechanical testing of hip protectors and energy-absorbing floors for the prevention of fall-related hip fractures

Date created: 
2008
Abstract: 

The general objective of my thesis research was to characterize the stiffness and force distribution characteristics of the hip region during the impact phase of sideways falls, and to advance our understanding of the potential for external engineering interventions (e.g. hip protectors and compliant floors) to reduce hip fracture risk by reducing the force applied to the proximal femur during such falls. This thesis is comprised of five studies. In the first I characterized the degree of non-linearity in pelvic stiffness, and examined the influence of stiffness characterization methods on the accuracy of mathematical models (mass-spring and Voigt) in predicting impact dynamics during falls on the hip. In the second study I employed a pelvis release paradigm (a method of inducing low severity but clinically relevant falls) to examine whether soft shell hip protectors alter the distribution of force throughout the hip region during impact. The third study entailed a sensitivity analysis to determine the influence of mechanical test system properties on the force attenuation provided by hip protectors. In the fourth study I used pelvis release experiments to determine how the force applied to the pelvis is affected by body impact configuration and floor stiffness; I also examined the ability of a mass-spring model to predict these relationships. The final study used a mechanical fall simulator to assess the attenuation in femoral neck force provided by four low stiffness floors compared to a standard rigid floor, and assessed the influence of these floors on fall risk through a range of static and dynamic balance tests with fifteen elderly women. Overall, this thesis demonstrates that compliant floors and soft shell hip protectors substantially reduce the force applied to the proximal femur during the impact stage of sideways falls. Of equal importance, this work demonstrates the need for international standards for the biomechanical testing and market approval of these devices. These are essential steps for increasing the quality of hip protectors and compliant floors available in the marketplace, and consequently, for enhancing their ability to reduce hip fracture risk in vulnerable populations.

Document type: 
Thesis
File(s): 
Senior supervisor: 
S
Department: 
School of Kinesiology - Simon Fraser University
Thesis type: 
Dissertation (Ph.D.)

Flavonoids and neuroprotection: biochemical and population-based analyses of potential neuroprotective factors related to dementia.

Date created: 
2008
Abstract: 

Dementia is a leading contributor to burden of disease in Canada and the world. With an aging population, there are projected increases in its global prevalence. Evidence suggests that some neurodegenerative disorders, such as Alzheimer’s disease, that lead to dementia are partly preventable, and that dietary intake of flavonoids may have relevant neuroprotective effects. The purpose of this study was to evaluate such potential for flavonoids using biochemical- and population-based analyses. Among 23 developed nations, negative correlations were found between rates of dementia and intake of all flavonoid groups, especially flavonols (p <0.05); these correlations were not significantly confounded by other relevant factors. The biochemical component helped elucidate possible mechanisms of flavonoid protection against heme-amyloidβ;-enhanced oxidative reactions with potential relevance to neurotoxicity. Overall, the evidence suggests that flavonoids, especially flavonols, and flavonoid-rich foods are part of a preventive dietary strategy, along with other health-promoting factors, towards decreasing rates of dementia.

Document type: 
Thesis
File(s): 
Senior supervisor: 
A
Department: 
School of Kinesiology - Simon Fraser University
Thesis type: 
(Kinesiology) Thesis (M.Sc.)