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

Receive updates for this collection

The role of cardiorespiratory fitness and the effectiveness of exercise in altering visceral adipose tissue and cardio-metabolic risk factors in post-menopausal South Asian women

Author: 
Date created: 
2015-11-20
Abstract: 

Background: South Asians have higher rates of type 2 Diabetes and cardiovascular disease (CVD) than Europeans with earlier disease onset. South Asians have been shown to have a unique obesity phenotype of greater visceral adipose tissue (VAT) at a given body size which may explain the higher cardio-metabolic risk factors compared to Europeans. Exercise has been shown to reduce VAT in Europeans but it is unknown if it is also effective in South Asians given their unique obesity phenotype.Objectives: The objectives of this thesis were threefold; 1) to explore the association between cardiorespiratory fitness (CRF) and VAT; 2) to assess the role of standard exercise and Bhangra dance in altering VAT and 3) to assess the association between exercise-induced change in VAT and change in cardio-metabolic risk in post-menopausal South Asian women.Methods: Multi-slice computed tomography was used to assess VAT, aerobic fitness via metabolic testing and cardio-metabolic risk factors through a 12-hour fasting sample. Seventy-five post-menopausal South Asian women were randomized into either three weekly sessions for 12-weeks of standard exercise, Bhangra dance or a non-exercise control group. One-way ANOVA was used to compare VAT across tertiles of CRF. General linear models were used to assess whether VAT was reduced in exercise compared to the referent control group. Bivariate correlations were used to assess the associations between change in VAT with change in cardio-metabolic risk factors. Results: Physically inactive post-menopausal South Asian women with higher levels of CRF were shown to have lower levels of VAT. There was a non-significant reduction in VAT after 12-weeks of aerobic exercise compared to the referent control group while the Bhangra dance group exhibited a significant improvement in CRF. The change in VAT was significantly associated with change in markers of glucose regulation.Discussion: Cardiorespiratory fitness is associated with VAT; however, a 12-week aerobic exercise program did not significantly reduce VAT in South Asian women. Nevertheless, those who reduced VAT saw improvements in cardio-metabolic risk factors. There may be a South Asian VAT “resistant” phenotype; however, Bhangra dance appears to be an effective physical activity option for increasing CRF.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dr. Scott Lear
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Dissertation) Ph.D.

Timing estimations of cardiovascular events; applications to seismocardiography, microneurography, and blood pressure.

Author: 
Date created: 
2015-09-25
Abstract: 

There is a wealth of untapped information within commonly acquired cardiovascular signals. Electric, vibration, and pressure measurements in this system allow us to obtain precise timings of events that can inform us about its ability to maintain health. In particular, this thesis applies new data analysis methods to continuous blood pressure, muscle sympathetic nerve activity, and seismocardiography. Three phase estimation techniques, including one of our own design, were compared in terms of accuracy. The three techniques were based on wavelet analysis, Hilbert analysis, and a new peak detection method, respectively. They were applied to modelled in-silico data, as well as a set of four pairs of in-vivo data. The results showed that the wavelet method should be selected for data with signal-to-noise ratio above −5 of unknown or varying frequency. Otherwise, all three techniques performed with equivalent accuracy, with the wavelet technique being computationally slower. The new peak detection technique was applied to blood pressure and muscle sympathetic nerve activity data on participants undergoing lower body negative pressure. In this sit- uation, the peak detection method offered better time resolution, and did not make the assumption that the signals were composed of a sum of sine waves. New indices were developed to identify timings within each time series, and quantify the relationship between the two signals. The indices returned values analogous to those obtained from traditional methods. One index differentiated between the participants that completed the lower body negative pressure protocol without exhibiting symptoms of pre-syncope, and those participants who did not complete the protocol. A third study considered seismocardiography, which measures thoracic vibration caused by the beating heart, and contains unique information about cardiac mechanics. Starting from a wavelet analysis basis, an algorithm capable of obtaining precise timings in seismocardiogram signals without the use of any other concurrent signal was developed. The algorithm included a new model of seismocardiogram systolic vibrations, fitted by minimizing an original distance function. At levels of lower body negative pressure of intensity below −30 mmHg, the algorithm was 95% accurate, and the heart rate variability indices were not statistically different from those obtained with electrocardiography.Cardiac timings that are represented in seismocardiogram peaks include isovolumic mo- ment, aortic valve opening, and aortic valve closure. It is known that the valve opening and closing peaks are not caused by the movement of the valve itself. Furthermore, the isovolumic moment peak, defined as the seismocardiogram minimum that occurs during the isovolumic contraction, does not correspond to any known, precisely timed event. In fact, the mechanical processes that cause seismocardiogram fiducial points have not been identified. Two 3D meshes were developed to study the propagation of vibrations in the thoracic cage. The first mesh was created from basic geometrical shapes and the second was adapted from a life-like full-body human mesh. By modelling the viscoelastic proper- ties of materials therein, we applied a previously developed solving algorithm to simulate seismocardiograms caused by a heart-like force applied to the sternum. Both simulations contained peaks analogous to all in-vivo seismocardiogram fiducial points.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Andrew Blaber
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Dissertation) Ph.D.

Effect of Mild Hypercapnia and Skin Temperature on Physiological Responses during Face Immersion

Author: 
Date created: 
2014-09-19
Abstract: 

The studies in this thesis were to assess if face cooling and CO2 combine in their influences on pulmonary ventilation and cardiovascular responses in humans. It was hypothesized that mild hypercapnia enhances these ventilatory and cardiovascular response to cold water face immersion. The first study resulted in significant elevations in pulmonary ventilation (p = 0.014), tidal volume (p = 0.008), inspiratory duty cycle (p = 0.013) and reductions in inspiratory flow (p = 0.051) during face immersions. The second study resulted in significant graded elevations in mean arterial blood pressure (p < 0.001), and reductions in the index of cerebral conductance in the middle cerebral artery (MCA) (p = 0.045) during face immersion. In conclusion, cold face immersion during mild hypercapnia increases ventilatory gasping and the blood pressure response while decreasing the conductance for cerebral blood flow to cerebral tissues supplied by the MCA.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Matthew White
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Structural mechanics of skeletal muscle contractions: mechanistic findings using a finite element model

Author: 
Date created: 
2015-04-21
Abstract: 

This thesis examines relations between skeletal muscle structure, function and mechanical output. Specifically, this thesis considers the effect of regionalization of muscle activity, changes in connective tissue properties and the inclusion of intramuscular fat on the mechanical output from the muscle. These phenomena are typically hard to measure experimentally, and so in order to study these effects a modelling framework was developed to allow manipulations of the structural and functional parameters of the in silica muscles and observe the predicted outcome of the simulations. The tissues within the muscle-tendon unit were modelled as transversely isotropic and nearly incompressible biomaterials. The material properties of the tissues were based on those of previously measured for the human gastrocnemius muscle. The model was tested mathematically and physiologically. Muscle fibre curvatures, along and cross fibre strains and muscle belly force-length predictions were validated against published experimental values. The validated model of human gastrocnemius was used to predict muscle forces for different muscle properties, architectures and contraction conditions. A change in the activity levels between different regions of the muscle resulted in substantial differences in the magnitude and direction of the force vector from the muscle. The stiffness of the aponeuroses highly influenced the magnitude of the force transferred to the tendon at the muscle-tendon junction. The higher the stiffness, the greater the force. This indicates the importance of understanding the differences in the structure and material properties between aponeurosis and tendon with regard to their functions. The increase in adipose tissue (fat) in the skeletal muscles (characteristic of elderly and obese muscle) was simulated by describing the fat distribution in six different ways. The results showed that fatty muscles generate lower force and stress, and the distribution of the fat also impacts the muscle force.

Document type: 
Thesis
Senior supervisor: 
James Wakeling
Nilima Nigam
Department: 
Science:
Thesis type: 
(Dissertation) Ph.D.

Nonshivering thermogenesis: responses to acute cold exposure in obese males

Date created: 
2015-05-13
Abstract: 

The studies in this thesis were to assess whether obese relative to non-obese individuals have blunted metabolic and non-shivering thermogenic responses in acute mild cold exposure, possibly established by a higher capacity to activate brown adipose tissue in the non-obese, resulting in greater energy expenditure. It was hypothesised that the obese would demonstrate a reduced non-shivering thermogenesis during acute mild cold exposure despite having lower skin temperatures and the same core temperature. The first study resulted in obese individuals having lower mean rate of oxygen consumption (p < 0.05), lower mean skin temperatures (p < 0.05), and lower mean heat flux (p < 0.05) during a 19°C exposure. There was no difference, however, in carbohydrate (p = 0.14) or lipid (p = 0.46) oxidation rates. The second study resulted in obese having lower mean supraclavicular skin temperatures (p < 0.001), lower mean supraclavicular heat flux (p < 0.05), lower mean surface temperatures from FLIR thermography (p < 0.05) and a lower mean metabolic response (p < 0.05). Non- shivering thermogenesis was achieved as there was minimal and no significantly different skeletal muscle activity between the two groups (p = 0.94). In conclusion, during acute mild cold exposure, obese individuals displayed a significantly lower non- shivering thermogenesis despite having lower skin temperatures and the same core temperatures relative to non-obese individuals. This possibly originates from a decreased capacity to activate brown adipose tissue depots in the obese that contributes to their lower energy expenditure in these conditions.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Matthew White
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

The Effect of Glaucoma on Gaze Behaviour and Mobility While Walking in Cluttered Environments

Date created: 
2015-08-14
Abstract: 

Glaucoma causes loss of peripheral vision and is a leading cause of blindness worldwide. It primarily affects older adults, limiting their mobility and increasing their risk for falls. This thesis investigated the effects of visual field loss from glaucoma on gaze behaviour and mobility during two visually demanding walking tasks while multitasking; stepping to targets, and navigating around obstacles. Older adults with glaucoma had less precise foot placement, looked to the same target more often, and looked toward future targets sooner, compared to healthy older adults. Subjects with glaucoma also collided with obstacles more frequently, looked to obstacles more often, and looked more frequently toward their feet. Dual tasking also disrupted mobility and gaze during the walking tasks. For this population these findings provide the framework to design future walking and gaze training programs for people with glaucoma to improve their quality of life.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dr. Daniel Marigold
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

KeyLabel Algorithms for Keyword Search in Large Graphs

Author: 
Date created: 
2015-08-24
Abstract: 

Graph keyword search is the process of extracting small subgraphs that contain a set of query keywords from a graph. This problem is challenging because there are many constraints, including distance constraint, keyword constraint, search time constraint, index size constraint, and memory constraint, while the size of data is inflating at a very high speed nowadays. Existing greedy algorithms guarantee good performance by sacrificing accuracy to generate approximate answers, and exact algorithms promise exact answers but require huge memory consumption for loading indices and advanced knowledge about the maximum distance constraint. We propose a new keyword search algorithm that finds exact answers with low memory consumption and without pre-defined maximum distance constraint. This algorithm builds a compact index structure offline based on a recent labeling index for shortest path queries. At the query time, it finds answers efficiently by examining a small portion of the index related to a query.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Ke Wang
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

Internephron synchronization of renal blood flow autoregulation

Date created: 
2015-07-21
Abstract: 

Renal autoregulation is the system that maintains a constant renal blood flow when arterial pressure fluctuates. Failure of autoregulation leads to renal damage and subsequent failure. There are two mechanisms of autoregulation. First is the myogenic response, which is common to almost all microvascular beds. Second is tubuloglomerular feedback, which is a slower system that fine-tunes the delivery of solutes to each nephorn. Autoregulation is well studied. However, limitations in measurement techniques, and simplifying assumption, previously forced us to assume that all nephrons in the kidney act independently in response to local changes in blood pressure. The goal of this dissertation was to determine the presence, extent, and mechanism of network behaviour in renal autoregulation. In this dissertation I show that the mechanisms of renal autoregulation are synchronized over macroscopic regions of the renal surface, and that the spatial distribution of synchronization can be modulated by nitric oxide. Then I show that the patterns of synchronization of autoregulation on the surface of the kidney are governed by the underlying arterial anatomy. We show that the mechanism of internephron synchronization is chiefly dependent on gap junctional intercellular communication, and that removal of this communication pathway reduces the efficiency of autoregulation overall. Finally, impaired autoregulation in early diabetes is shown to coincide with a reduction in spatial smoothing of autoregulation. By the end, I have shown that internephron synchronization is present in the kidney, and 1) synchronization is modulated by an important hormonal modulator, nitric oxide, 2) that arterial anatomy determines divisions between synchronized clusters, 3) gap junctions mediate synchronization and contribute to autoregulation effectiveness, and 4) that network behaviour of autoregulation is reduced in early diabetes, linked with impaired autoregulation. Overall, this shows that internephron synchronization is an important aspect of renal autoregulation, and it must be considered in the future when studying this field.

Document type: 
Thesis
File(s): 
Senior supervisor: 
William Cupples
Department: 
Science:
Thesis type: 
(Dissertation) Ph.D.

Cardiovascular and cerebrovascular consequences of spinal cord injury

Date created: 
2015-06-08
Abstract: 

Spinal cord injury (SCI) has profound effects on motor, sensory, and autonomic function. The autonomic repercussions of SCI are widespread and demand life-long management and care. Cardiovascular problems are particularly common after high-level SCI that disrupts spinal sympathetic pathways to the heart and blood vessels. In this thesis I investigated the effect of damage to autonomic pathways on cardiovascular control during routine activities of daily living. In Chapter 2, I showed that moderate changes in wheelchair seating positions could challenge or bolster blood pressure and cerebral blood flow in individuals with damage to autonomic pathways. This shows that positional changes can be used as physical manoeuvres to maintain blood pressure. Chapter 3 documented the progression of autonomic function over time in the acute post-injury period, demonstrating the wide range of trajectories of cardiovascular function after injury. This work also highlighted how motor, sensory and autonomic function can be affected differently by SCI; damage to motor and sensory pathways cannot always predict autonomic deficits. Next, in Chapter 4, I examined cerebrovascular control, and found that individuals with damage to autonomic pathways have a reduced cerebral blood flow response to low oxygen. While the aetiology of this difference is unclear, the results suggest that exposure to low oxygen, for example during sleep apnea, may be particularly detrimental in this population. Finally, in Chapter 5, I conducted a survey examining bowel care and cardiovascular function after SCI that identified a significant need for ongoing support to improve bowel management. It also revealed the major limitations that bowel care can have on social participation and employment. A knowledge gap was also identified regarding blood pressure control and cardiovascular symptoms triggered by bowel care. This work reiterates the importance of autonomic assessment after SCI and the value of combining physiological recording with symptom assessments. Autonomic dysfunctions have significant ramifications for blood pressure control, cerebrovascular control, and quality of life after SCI. The integrity of the autonomic nervous system should be incorporated into research outcomes and stratification and be used to help guide clinical decision-making and self-management.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Victoria Claydon
Department: 
Science: Biomedical Physiology and Kinesiology
Thesis type: 
(Dissertation) Ph.D.

Diaphragm Pacing during Mechanical Ventilation: Development of a Control Algorithm and Analysis of Respiratory Mechanics

Date created: 
2013-04-23
Abstract: 

Prolonged totally controlled mechanical ventilation results in the complete absence of mechanical activity of the diaphragm leading to rapid loses in diaphragmatic function, a syndrome known as Ventilator-Induced Diaphragmatic Dysfunction VIDD. Electrical activation of the diaphragm by phrenic nerve stimulation may prevent diaphragm atrophy in sedated patients undergoing Controlled Mechanical Ventilation CMV. The aims of this thesis were to develop a control algorithm to pace the diaphragm in-synchrony with a ventilator during controlled mechanical ventilation in critically-ill patients and analyze the respiratory mechanics resulting from such co-ordinated inspiratory action of the diaphragm and the mechanical ventilator. The algorithm was verified through bench tests and evaluated in an animal model. In the animal study, the respiratory mechanics were also analyzed to better understand the effects of synchronous diaphragm pacing during mechanical ventilation and to identify an optimal level of pacing support during mechanical ventilation for clinical applications.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Andy Hoffer
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.