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

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The effect of shoulder pad design on head impact severity during shoulder checks in ice hockey

Author: 
Date created: 
2016-03-22
Abstract: 

Forty-two percent of concussions in ice hockey are caused by hits involving shoulder-to-head contact. The goal of this project was to determine how shoulder pad stiffness affects head impact severity when players delivered checks to an instrumented dummy. Fifteen participants administered “the hardest shoulder checks they were comfortable delivering” to the head of an instrumented dummy. Trials were conducted with participants wearing two common types of shoulder pads, with and without a 2 cm thick layer of polyurethane foam over the shoulder pad cap. The study found that a 2 cm thick foam layer overlying the shoulder cap reduced peak linear accelerations to the head by 21.6-27.7%, peak rotational velocities by 10.5-13.8%, while causing no significant increase in shoulder impact velocity. Therefore, integration of foam padding on top of plastic caps warrants further examination as a method for preventing brain injuries in ice hockey.

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

Integrative characterization of the molecular evolution and functional divergence of teleost troponin C paralogs

Date created: 
2016-03-30
Abstract: 

Gene duplication results in extra copies of genes that can be sub-functionalized on structural and/or regulatory levels. Multiple paralogs are expressed in teleosts for troponin (Tn) components of the contractile unit (TnC, TnI and TnT), likely to maximize survival in different environmental conditions. The evolution of Tn subunits can be used as a model for understanding the variation in contractile function in ectotherms. The studies in this dissertation integrate evolutionary analysis with structural information to expand upon the knowledge of Tn function across phylogeny. Multiple parameters of cardiac structure and function were determined in vivo in the adult zebrafish, using high-resolution echocardiography, to accurately characterize the responses of this teleost model to both acute and chronic temperature perturbations. Cardiac output was modulated primarily by heart rate in response to acute temperature changes. With cold acclimation, a decreased E/A ratio suggests an increased reliance on atrial contraction for ventricular filling.The evolutionary history and sub-functionalization of the cardiac-specific TnC1 genes were characterized on both regulatory and structural levels. Three paralogs of TnC exist in fish, two of which are homologous to mammalian TnC1/cTnC. The TnC1 paralogs are likely the result of a tandem gene duplication that occurred in the common ancestor of the teleosts. In both zebrafish and trout hearts, TnC1 paralogs display temperature and chamber specific patterns in their usage of mRNA transcripts. While the zebrafish TnC1 paralogs have minimal variation in structure based on homology models, TnC1b has a higher Ca2+ affinity relative to TnC1a as measured by isothermal titration calorimetry. Variation in the apparent affinity of zebrafish TnC1 paralogs for Ca2+ results from dynamic conformational flexibility changes rather than from the direct interaction of site II with Ca2+. Finally, the inter-related roles of regulatory and structural sub-functionalization that guide the co-evolution of interacting proteins in the Tn complex were explored. Transcriptional expression patterns predict various TnC/TnI complexes exist in the zebrafish heart with differential interaction strengths between the N-TnC and TnI switch region. Domain-specific divergent selection pressures and interaction energies suggest that substitutions in the TnI switch region are crucial to modifying TnI/TnC function to maintain cardiac contraction with temperature changes. Through these studies, the interacting proteins of the Tn complex have been established as an important model of the functional divergence of paralogs in the adaptive evolution of the teleost cardiac contractile element.

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

Development of a Stick-on Hip Protector for Older Adults in the Acute Care Environment

Author: 
Date created: 
2016-02-16
Abstract: 

Over 90% of hip fractures in older adults are due to falls. Wearable hip protectors have been shown in clinical trials to reduce the risk for hip fracture by up to 80% when worn, but user compliance with conventional garment-based hip protectors averages less than 50%. Improvements in product design may lead to enhanced compliance. This thesis describes the development and preliminary evaluation of usability in the acute care environment of a “stick-on” hip protector (secured over the hip with a skin-friendly adhesive). Through biomechanical testing, I developed a prototype that attenuates impact force by over 30% (higher than protectors currently used in Fraser Health). In a feasibility pilot trial, five of six patients wore the device for seven days. Additional input from 43 acute care providers during a Feedback Fair resulted in a 20 mm thick donut- shaped prototype of surface area 19x15.5 cm, that provided 36% force attenuation.

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

Biofeedback driven muscle coordination

Date created: 
2015-12-17
Abstract: 

Groups of muscles are recruited in various combinations to perform smooth, controlled limb movements. Within these muscle groups, the excitation of a single muscle is commonly the focus of manipulation when attempting to influence limb movement, but it is the coordinated excitation of multiple muscles (muscle coordination) that ultimately determines the limb movement and mechanics. Despite successes with single muscles, the capabilities of manipulating muscle coordination are unknown. Therefore the goal of this research was to develop a biofeedback tool to purposefully manipulate muscle coordination.This research is comprised of four studies, three studies facilitated the development of a biofeedback tool and a fourth study finalized the development and validated the capabilities of the tool to purposefully manipulate muscle coordination in real-time during movement. The first study established a physiologically relevant outcome to be used by the biofeedback tool. The study showed that muscle excitation provides good predictions of changes in metabolic power and could therefore be used to determine the relative mechanical efficiency of different muscle coordination strategies.The second and third studies established a muscle coordination reference frame, specific to the relative efficiency outcome ascertained in the first study, used to characterize the current and desired end states of muscle coordination. Specifically, muscle coordination patterns, and their associated relative efficiencies, were determined across a range of mechanical demands to distinguish the key features responsible for differences in relative efficiency that were subsequently used to guide the biofeedback tool.In the final study, a novel biofeedback tool for manipulating muscle coordination was developed and validated. The underlying algorithm used principal component decomposition of muscle excitation to characterize the changes in coordination between the muscles at different mechanical demands. The algorithm was modified to render it feasible for implementation in real-time and the tool was validated by having subjects cycle while receiving feedback comparing their muscle coordination to the reference frame. The results showed that the subjects were successfully able to manipulate muscle coordination to improve the relative efficiency of the movement. Taken together, this research provides a valuable tool for research into motor learning and could be applied to improve rehabilitation and sport performance.

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

Personality Genetics and Health in Super-Seniors

Date created: 
2015-12-17
Abstract: 

Healthy aging is a complex phenotype, and genetic factors that contribute to long term good health are not well understood. Longevity and health are associated with lifestyle choices. Behaviour is governed by personality; therefore, variation in personality-related genes may affect healthy aging. Five candidate genes involved in the physiology of personality and personality disorders were identified from the literature: COMT, DRD4, MAOA, SLC6A4, and TH. Single nucleotide polymorphisms and variable number of random repeat polymorphisms were genotyped in DNA from 493 European-ancestry healthy oldest-old and 431 European-ancestry middle-aged controls. Tests for allelic associations were conducted, with stratification by sex. No associations remained significant after correction for multiple tests. Variants tested in these candidate genes were not associated with long-term good health in this sample. Either genetic variation in these genes does not influence healthy aging, or true effects exist that are too small to be detected in this study.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Angela Brooks-Wilson
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

Walking energetics, optimization and control

Date created: 
2015-12-09
Abstract: 

To walk in the real world, we continually alter our gait to cope with changing terrains, goals, and constraints on the body. This is a nontrivial feat—individual muscle activities must be adjusted to produce a desired gait and that desired gait must be selected from a myriad of possible coordination patterns. How this is accomplished is poorly understood. One principle that could guide the control of legged locomotion is an optimization process that seeks to meet some objective. The main goal of my thesis is to investigate the role of optimization, and in particular energy optimization, in the control of human gait. To do so, I undertook four distinct studies. In the first study, I developed a control system for a lower limb exoskeleton that leverages the body’s internal control by tapping directly into the user’s muscle activity. The myoelectric controller accurately identifies the user’s desired motion, automatically gradates the actuation of an exoskeleton, and is adaptable to varying gaits and terrains. In my second study, I sought to understand how entire coordination patterns, rather than individual muscle activities, may be optimized. I hypothesized that humans continuously optimize their gait to minimize energy expenditure. To test this, I used exoskeletons to alter the energetic consequences of various gaits. I made abnormal ways of walking energetically optimal and found that when given broad experience with the novel energetic landscapes subjects discovered the optimal gaits and opted to walk at them, even when the energetic benefits were small. In a third study, I found that the nervous system can be primed to initiate this optimization when perturbed toward low cost gaits, or can spontaneously initiate optimization when natural gait variability is high enough to elucidate a clear energetic gradient. Once optimization is initiated, I found evidence that the nervous system employs a ‘local search’ strategy to gradually descend energetic gradients and converge on novel optima. Given that energetic cost plays a central role in continuously shaping movement, in my fourth and final study I developed a technique to estimate instantaneous muscle energy use during non-steady state walking. This technique now makes it possible to measure a physiological signal that likely plays a central role in the control and optimization of human movement.

Document type: 
Thesis
File(s): 
Senior supervisor: 
J. Maxwell Donelan
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) Ph.D.

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.