Kinesiology and Health Sciences

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This is the collection for the University of Waterloo's Department of Kinesiology and Health Sciences. It was known as the Department of Kinesiology until January 2021.

Research outputs are organized by type (eg. Master Thesis, Article, Conference Paper).

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Advancing the measurement and use of daily life heart rate using wearable technology: applications to Parkinson's disease
(University of Waterloo, 2026-01-19) Godkin, Florence Elizabeth
Measures of heart rate (HR), including those conducted during resting conditions and in response to physical activity, have been shown to relate to risk of adverse health outcomes and can provide insight into the function of the autonomic nervous system (ANS). However, HR measures have conventionally been conducted at a single point in time and in controlled settings, such as during clinical or laboratory visits. Alternatively, when HR has been measured in uncontrolled, free-living settings, there has been a lack of standardization in the methods used and most have not provided sufficient behavioral context to support the interpretation of HR in daily life. Use of wearable technology, and specifically, a multi-sensor and -device approach, presents a unique opportunity to measure HR continuously in the context of daily life behaviors, and advance understanding of ANS function and context-dependent HR responses. This may be particularly relevant to individuals living with Parkinson’s disease (PD), who can experience ANS dysfunction that may manifest with altered diurnal HR profiles and who can have diverse movement characteristics that may affect the HR response to physical activity. The overarching goals of this thesis work were to 1) advance the development of standard approaches to assess HR from continuously collected data over multiple days and behavioral contexts, and 2) apply these approaches to advance understanding of ANS function and characterization of daily life physical activity profiles among individuals with PD. All studies were based on a collection protocol that instrumented participants with a portable, chest-worn electrocardiography device and two limb-worn inertial measurement units (wrist and ankle) that continuously collected data across a week-long period in daily life. In the first study, HR was measured across accumulated periods of sedentary behavior and sleep within a cohort of adults without PD (“control”), and the high levels of within-participant variability in HR that were observed within a given resting condition led to recommendations being put forth for standardizing the measurement of HR outcomes during resting conditions in daily life. In the second study, standards suggested in Study 1 were applied and extended upon in a cohort of adults with and without PD, and revealed no differences between cohorts in resting condition-specific HR outcomes (e.g., minimum HR during sleep) or in measures of nocturnal HR dipping in daily life. However, a significant association was observed between nocturnal HR dipping and a clinical measure of ANS dysfunction in PD. In the third study, resting HR was used as a reference when quantifying the relative intensity of the HR response to daily life walking across the same cohort of adults with and without PD. While no between-cohort differences were observed in the average relative intensity of daily life walking, there was considerable variability in the between- and within-participant HR response to continuous, longer walking bouts (≥ 30 seconds), which were not consistently associated with walking cadence or bout duration. This dissertation provides recommendations for, and illustrates the importance of, adopting standardized approaches to measure resting and activity-dependent HR in daily life. Findings from the studies in this thesis suggest that context-based ambulatory HR monitoring has the potential to improve characterization of daily life behaviors and provide insight into clinically relevant outcomes in individuals with and without PD. Continued research in larger, more heterogenous populations, which includes robust clinical profiling and continues to attend to the importance of high data quality, is necessary to determine generalizability and advance understanding of within- and between-participant drivers of variability in context-dependent HR measures. This type of future work is required before context-dependent HR monitoring can be integrated and evaluated as a tool to support self-management or clinical health care decision making.
Exploring the association between muscle mass and strength measures and hip geometry in males and postmenopausal females aged 50 and older with low bone mass.
(University of Waterloo, 2026-01-16) Graham, Connor
Background: Dual-energy X-ray absorptiometry (DXA) scans and hip structural analysis (HSA) software allow for the analysis of bone geometry in the proximal femur. Bone architecture is influenced by muscle, as described by the Utah paradigm, yet the specific muscle-bone geometry relationship remains poorly understood, thereby revealing a knowledge gap. Therefore, the investigation aimed to examine the relationship between lower limb muscle or strength measures and hip geometry, as measured by DXA scans, in a population of males and post-menopausal females aged 50 and above with low bone mass. Methods: We led a cross-sectional, exploratory secondary analysis of the baseline data from the Finding the Optimal Resistance Training Intensity For Your (FORTIFY) Bones trial. Statistical analysis was completed using R Studio (Version 4.4.2), wherein 24 multivariable linear regressions were developed using section modulus and buckling ratio of the femoral neck, intertrochanteric region and femoral shaft as dependent variables. Lower left limb lean soft tissue (LLLLST), muscle quality index (MQI), 30-second chair stand test and normalized knee extension strength were examined as independent variables in separate models for each dependent variable. All models were controlled for age, while only models using normalized knee extension strength or 30-second chair stand test were controlled for BMI. Results: In a sample of 324 participants (93% female, 83% Caucasian) descriptive statistics as mean (SD) were as follows: BMI 24.59 (4.33) kg/m2, normalized knee extension strength 85.91 (31.51) Nm, LLLLST 6.183 (1.2325) kg, MQI 13.68 (3.95) Nm/kg, 30-second chair stand test score 15.80 (4.33), femoral neck section modulus 1.187 (0.280) cm3, femoral neck buckling ratio 13.434 (2.948), intertrochanteric region section modulus 3.734 (0.936) cm3 , intertrochanteric region buckling ratio 9.612 (1.834), femoral shaft section modulus 2.091 (0.444) cm3, femoral shaft buckling ratio 3.149 (0.846). Models using LLLLST explained the greatest amount of variance of section modulus at the femoral shaft (Unstandardized ß=0.272, 95%CI [0.247 to 0.298]; R2=0.5840, p<0.001), intertrochanteric region (Unstandardized ß=0.520, 95%CI [0.460 to 0.581]; R2=0.4686, p<0.001) and femoral neck (Unstandardized ß=0.126, 95%CI [0.105 to 0.146]; R2=0.3147, p<0.001). Models using knee extension strength explained the second greatest amount of variance of section modulus at their respective sites. Specifically, models using normalized knee extensor strength explained 38.26% of section modulus variance at the femoral shaft (Unstandardized ß=0.00560, 95%CI [0.00434 to 0.00687]; R2=0.3826, p<0.001), 35.11% of section modulus variance at the intertrochanteric region (Unstandardized ß=0.0111, 95%CI [0.00832 to 0.01391]; R2=0.3511, p<0.001) and 18.22% of section modulus variance at the femoral neck (Unstandardized ß=0.00366, 95%CI [0.00273 to 0.00460]; R2=0.1822, p<0.001). Conclusion: Our findings indicate that the models using LLLLST and normalized knee extension strength moderately or strongly explain section modulus depending on the region of interest. The relationships illustrated here add to our understanding of the muscle-bone relationship, specifically by highlighting the muscle-bone geometry relationship. Future investigations should determine whether changes in lean soft tissue or strength result in changes in bone geometry within participants over time.
Development of a 7-item Dietary Screener Questionnaire for Determining Intakes of Eicosapentaenoic and Docosahexaenoic Acid in Canadians
(University of Waterloo, 2026-01-08) Liu, Ming Rong
The intakes of the omega-3 polyunsaturated acids, eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) are associated with various health benefits. The main dietary sources of EPA and DHA are seafood, but there are non-seafood sources that contain significant amounts of EPA and DHA. Determining the dietary intake of EPA and DHA can be challenging due to the sporadic nature of seafood intake. An online 7-item dietary screener has been used to estimate the DHA intake of pregnant women from both seafood and non-seafood sources in the United States. Using this screener as a template, a Canadian screener for estimating EPA and DHA intakes was developed. In Project 1, EPA values were added and DHA values revised to match those in the Canadian Nutrient File, the questions were reordered to focus on seafood commonly consumed, questions about eggs were expanded to include options for size and omega-3 enrichment, and a French version of the screener was developed. In Project 2, fatty acid quantitation analyses were completed on screener items when the Canadian Nutrient File EPA and DHA data was either missing or not consistent with literature. This included eggs (medium, large, extra-large, omega-3, and omega-3 plus), liver (beef, pork, and chicken), and chicken (regular and organic). For Project 3, the “Canadianized” screener was evaluated for errors using mock. To do this, intake information from the 24-hour dietary recalls in the 2015 Canadian Community Health Survey (CCHS) were extrapolated to bimonthly intakes and entered into the screener. The EPA and DHA intakes estimates from the screener agreed with those from the CCHS 2015 Nutrition, indicating that the Canadian screener is ready for a proper validation study in the future. Once validated, this online tool should be able to improve our ability to estimate the intakes of EPA and DHA by Canadians. In addition, the process that was used to “Canadianize” the screener can be used as a template top adapt the screener for different countries.
Intra- and Inter-Rater Reliability of Features of Movement Commonly Associated with Movement Competency
(University of Waterloo, 2026-01-07) Sen, Dilara
Movement screening tools, such as the Functional Movement ScreenTM and the Movement Competency Screen, are commonly used to assess fundamental movement patterns. These movement patterns, such as squatting and lunging, serve as the foundation for human movement, essential for daily living and athletic performance. By assessing an individual’s ability to control their joints during fundamental movements, screens help identify potential areas for improving performance and reducing injury risk. However, existing screens are limited. They do not adequately assess movement competency, the ability to move competently, without limitation or impairment, under different task demands (e.g., varying loads or speeds). The Physical Literacy ScreenTM (PLS) was developed to more comprehensively assess movement competency. Unlike previous screens, the PLS considers how different task demands (e.g., varying load or speed) influence how movers control key movement features, to inform exercise, education, and coaching recommendations based on a more thorough understanding of an individual’s movement abilities. Because PLS feature scoring relies entirely on visual observation, the reliability of judging these features must be established before the framework can be applied with confidence. Therefore, the purpose of this study is to determine the intra-rater and inter-rater reliability of visually assessing key movement features commonly associated with movement competency. This study examined the reliability of raters visually judging three key movement features, knee control, back control, and shoulder control, using standardized video recordings of athletes performing PLS-derived tasks. Twenty-two kinesiology students independently assessed pre-recorded videos of varsity volleyball athletes and re-scored the same videos at least 14 days later. Intra-rater reliability was measured using Cohen’s Kappa, and inter-rater reliability using Fleiss’ Kappa. Results showed moderate intra-rater reliability for Knee (κ = 0.42) and Back (κ = 0.47) features and fair reliability for Shoulder (κ = 0.28). Inter-rater was poor across all features, with Fleiss’ Kappa values below zero. The study provides initial reliability evidence for the visual judgment of key movement features using PLS-derived tasks. These findings highlight the importance of refining feature definitions, improving rater training and calibration procedures, and clarifying scoring criteria to enhance consistency. Strengthening these elements may support more reliable use of visual movement assessments in sport, education, and health contexts.
Advanced venous flow dynamics and return mechanisms during physiological stress and aging
(University of Waterloo, 2025-12-22) Cohen, Jeremy
Human veins are dynamic vessels responsible for managing return of blood to the heart. Unlike arteries, veins are structurally limited, creating exceptional hemodynamic susceptibility to hydrostatic forces and pressure generating forces. The precise extent of venous flow regulating mechanisms to these forces have implication for disease pathogenesis yet have been historically limited by technological tools. Thus, the purpose of this thesis is addressing the responses to hydrostatic volume stress, muscle pump activation and healthy aging through the piezoelectric lens of vector flow imaging ultrasound through a series of projects. First, progressive hydrostatic volume stress is applied to the internal jugular vein to address regional flow complexity and volume expansion behaviour. The internal jugular vein presented step-wise volume expansion in a trapezoidal shape and increasing flow complexity, increasing the risk for flow stasis and thrombus formation. Second, hydrostatic volume stress is used to compare artery-adjacent and non-adjacent veins to probe the existence of an arterial pump. During relevant hydrostatic driving forces, artery-adjacent veins demonstrated a preservation of venous flow, suggestive of a newly described mechanism of venous and an elegant conservation of mechanical energy within the cardiovascular system. Third, a comparison of younger and older adults leveraged differences in venous compliance to investigate flow complexity features during muscle pump activation during hydrostatic volume stress. Older adults were found to utilize their lower compliance to maintain venous ejection efficiency, whereas younger adults experienced great turbulence and vorticity flow features for the same venous outflow. Finally, venous valves were explicitly investigated during progressive hydrostatic volume stress and muscle pump activation to describe flow complexity features. Healthy valves generated efficient forward jets with downstream disturbed, low-shear zones, and volume stress amplified regional differences, underscoring the role of valve geometry in venous hemodynamics. Together, these studies establish new mechanistic links between venous structure, hydrostatic and muscle pump forces, and aging, advancing understanding of venous flow regulation and its implications for thrombotic risk and cardiovascular health.
Examining the influence of attentional distraction and emotional distress on gait behaviour in Functional Gait Disorders
(University of Waterloo, 2025-12-17) Girlea, Alexandra Laura
Functional Gait Disorders (FGD) are a subgroup of Functional Neurological Disorders (FND) that are characterized by the presence of abnormal postures and movements whose appearance and severity fluctuate, or are inconsistent, over time. These movements appear voluntary but are reported to be involuntary by the patient. FGD symptoms may arise from abnormalities in attentional and emotional regulation, and these dysfunctions lead to loss of agency (control) over movement. These movements may mimic those of other neurological disorders, however sensory and motor testing reveals normal function. This preservation of function despite symptom presentation is referred to as symptom incongruency. Due to the inconsistency and incongruency FGD symptoms, as well as the heterogeneity in phenomenology across individuals with FGD, diagnosis proves a challenge. Individuals with FGD often face delays and excessive costs when pursuing an appropriate diagnosis, ultimately prolonging their disability and delaying access to adequate treatment. A majority of previous work has utilized qualitative approaches to phenotype FGD and aid in diagnosis. While these approaches provided key foundational information about FGD, they do not capture all aspects of FGD. Therefore, quantitative methods of FGD may provide more insight into its phenomenology. However, there is a lack of work utilizing quantitative approaches in FGD. Existing work has primarily focused on the influence of attentional distraction on symptom presentation and severity during gait, providing mixed evidence addressing the influence of attention on functional gait. Similar to qualitative descriptions, some quantitative evidence shows an improvement in symptom presentation and severity while completing a secondary task. To date, there have been no studies investigating the effect of emotional distress on gait in FGD, and this area would be important to investigate given that emotional dysregulation is a key component of FGD phenomenology. While anxiety during gait has been manipulated with postural threat paradigms, the threat of shock paradigm has also been shown to elicit anxiety in laboratory settings. However, the threat of shock has not yet been utilized in gait research. Investigating its validity for use in gait may provide more insight into how this paradigm provokes anxiety during walking, and how walking may change during this scenario. As such, the present thesis aims to address several gaps in the literature. The first is that there are few quantitative descriptors of FGD phenomenology, therefore identifying descriptors may complement and augment qualitative observation and subsequent diagnosis. The second is that while the influence of attention has been investigated in FGD, there has been limited work done investigating the influence of emotional distress on gait in this population, despite its self-reported influence on symptom provocation. Understanding or characterizing the influence of emotional distress on gait in this group may provide novel insights for clinical diagnosis. The use of the novel threat of shock paradigm may also provide more insight into the influence of anxiety on walking in FGD. Together, the present study aimed to address these gaps by utilizing the novel threat of shock paradigm to investigate the influence of attentional distraction and emotional distress on gait behavior and symptom severity in individuals with FGD. It was expected that the threat of shock paradigm would elicit anxiety in all participants. Additionally, it was expected that the dual task would lead to normalized gait in the FGD group, and that the threat of shock would yield a worsening of gait in the FGD group. Finally, it was anticipated that greater levels of movement reinvestment in FGD patients would be associated with a greater dual-task effect on gait in this group, meaning that greater reinvesters would show a greater degree of movement normalization when completing a dual task compared to walking in the absence of a dual task. Eleven FGD patients and 17 age- and sex-matched controls completed 11 walking trials that spanned 4 conditions (neutral, dual task, shock, dual task + shock). All participants self-reported their level of anxiety after each trial, and at the end of the study, completed a battery of questionnaires addressing their movement reinvestment and anxious tendencies. The present study confirmed the utility of the threat of shock during gait, as participants reported greater anxiety when the shock was present. Interestingly, the dual task did not lead to gait normalization in FGD patients. Rather, both patients and matched controls showed worsened gait in the presence of the dual task. Additionally, the threat of shock only impacted step length variability in FGD patients, wherein patients showed greater variability compared to controls in both the presence and absence of shock. Finally, the present study revealed insights into the relationship between reinvestment and symptomology in FGD, wherein patients with a greater degree of reinvestment showed improved gait while dual tasking compared to their baseline gait. Taken together, the present study not only illustrates the utility of the threat of shock paradigm in gait assessments, but also shows nuances in the relationship between attentional distraction and FGD symptomology. Findings from the present study set the stage for future use of the threat of shock during gait, as well point to the importance of movement reinvestment in the presentation and potential resolution of symptoms in FGD. Future work should continue to investigate reinvestment in the context of FGD and should take a more nuanced and individualistic approach to better encapsulate the heterogeneity inherent in functional gait disorders. Doing so may provide a more complete picture of these disorders and may improve characterization, diagnosis, and treatment of these patients.
Real-Time Assessment of Pain and Physical Activity in Knee Osteoarthritis: The Moderating Roles of Self-Efficacy, Fear of Movement, and Locus of Control
(University of Waterloo, 2025-12-09) Almaw, Rachel
Knee osteoarthritis (OA) is a highly prevalent chronic musculoskeletal condition and growing health concern in Canada. Characterized by loss of articular cartilage in the joint and fluctuating pain, knee OA is a leading contributor to physical and psychosocial disability (Steinmetz et al., 2023). By 2041, knee OA will affect over 10 million Canadians, driven by an aging and obese population (Sharif et al., 2017). Physical activity (PA) is recommended for knee OA management to reduce pain; but pain is commonly cited as a barrier to engagement (Bannuru et al., 2019). The links between PA exposure and pain are unclear. Current assessment tools cannot capture the temporal relationship between pain and PA in knee OA, as each dynamically influences the other throughout the day. This dynamic relationship is further complicated by psychosocial factors, including fear of movement, self-efficacy, and locus of control, which are associated with altered pain perception and PA behaviour in knee OA (Bayrak & Alkan, 2025). Yet, their roles in shaping the temporal relationship between pain and PA remain unclear in real-world contexts. Objectives and Hypothesis The primary objective of this study was to determine whether psychosocial factors (fear of movement, self-efficacy, and locus of control) moderate the temporal relationship between pain and subsequent PA in knee OA. The secondary objective examined the reverse temporal association: whether these psychological factors moderated the effect of PA on subsequent pain. It was hypothesized that (1) pain would reduce subsequent PA, with higher self-efficacy and internal locus of control weakening this negative effect and higher fear of movement strengthening the association; and (2) PA would increase subsequent pain, with higher self-efficacy and internal locus of control weakening this positive effect and higher fear of movement strengthening the association. Methods This prospective cohort study used ecological momentary assessment (EMA) over nine days. Fifty community-dwelling adults who had symptomatic knee OA consistent with American College of Rheumatology clinical criteria participated. Exclusion criteria included other forms of arthritis, neurological conditions, active cancer treatment, non-nociceptive pain, or lack of a compatible smartphone for EMA.Participants reported knee pain intensity, duration, and analgesic use four times daily using an EMA approach, via scheduled prompts delivered using a smartphone application (m-Path). Participant could also initiate prompts, unscheduled, to report pain flares. A pain composite score was calculated using z-score standardization of pain intensity and duration with participant-specific means and standard deviations, providing a novel within-person approach to characterizing knee OA pain. PA was continuously tracked using accelerometers (Actigraph wGT3X-BT) during waking hours. Psychosocial factors including fear of movement, self-efficacy, and locus of control were assessed through validated questionnaires at baseline. The primary objective examined whether the pain composite score influenced subsequent step count in the 90 minutes after EMA prompts, and whether this association was moderated by psychosocial factors (fear of movement, self-efficacy, locus of control). Generalized linear mixed models with Tweedie distributions and random intercepts examined these relationships, adjusting for age, gender, analgesic use, study day, prompt number, and prompt type. The secondary objective examined whether step count in the 90 minutes before EMA prompts influenced subsequent pain intensity, and whether this association was moderated by the same psychosocial factors. Linear mixed-effects models with random intercepts examined these relationships, adjusting for the same covariates. Results Complete data were available for 49 participants (64.8±7.2 years, 77% women) (1 accelerometer failure). These 49 participants reported moderate pain (KOOS Pain: 65.3±15.6), high daily activity (mean 11,661 steps/day), and mixed pain patterns (92% experienced both constant and intermittent pain). Average EMA compliance was 90%, with participants completing an average of 32 prompts over the study period. Valid accelerometer data was available for 96.6% of monitoring days. Fear of movement moderated the association between within-person pain composite score and subsequent step count (β = -0.0144, 95% CI [-0.0277, -0.0010], p = 0.035). Individuals with higher fear of movement showed a 4.9% greater step reduction per 1-SD increase (3.4 points on a 24-point scale) in fear of movement score. Self-efficacy for pain management also moderated this association (β = 0.0059, 95% CI [0.0018, 0.0100], p = 0.005). Individuals with higher self-efficacy showed a 6.8% smaller step count reduction per 1-SD increase (11.9 points on a 50-point scale) in self-efficacy score. Locus of control showed no moderation effect. In the reverse temporal direction, internal locus of control demonstrated a weak positive interaction with within-person step count on subsequent pain intensity (β = 0.000012, 95% CI [0.000002, 0.000022], p = 0.014). Individuals with higher internal locus of control experienced slightly greater pain intensity following higher step counts compared to those with lower internal locus of control. Self-efficacy for pain management demonstrated a significant main effect on subsequent pain intensity (β = -0.028740, 95% CI [-0.052042, -0.005439], p = 0.019). Individuals with higher self-efficacy reported lower pain intensity regardless of step count. Fear of movement showed no moderation or main effect. Discussion This study, using EMA and objective accelerometry, provides preliminary evidence that psychosocial factors moderate the temporal pain-PA relationship in adults with symptomatic knee OA. Those with higher self-efficacy for managing pain showed 6.8% smaller step reductions following greater pain; while those with higher fear of movement showed 4.9% greater reductions in step count after experiencing greater pain. In the reverse temporal direction, higher step counts were associated with increased subsequent pain intensity. Internal locus of control statistically moderated this association, though the interaction was very small and of uncertain clinical significance. Real-time assessment captured substantial within-person variability in pain and physical activity, including participant-initiated reporting of pain flares (77.6% of participants). The small interactions likely reflect considerable heterogeneity due to unmeasured contextual environmental factors. These findings suggest that self-efficacy, fear of movement, and locus of control may influence how individuals with knee OA respond to pain in daily life. While larger and more diverse samples are needed to establish clinical significance, these results suggest that self-management interventions targeting these factors and personalized pacing strategies during pain-free periods may help individuals with knee OA maintain activity despite pain fluctuations.
Quantifying Endplate Deflection in Response to Cyclic Load Exposures Using a Porcine Cervical Spine Model
(University of Waterloo, 2025-11-27) Watson, Michael
The vertebral endplate is a thin layer of cartilage and bone that separates the intervertebral disc from adjacent vertebral bodies and facilitates the transmission of compressive force through the spine. Despite this essential function, it remains the weakest component of the vertebra-disc unit and is highly susceptible to mechanical failure. Endplate failure typically arises from localized tensile strains that manifest as deflection, defined as the out-of-plane displacement of the surface under load. While prior work has demonstrated inferior endplates of intervertebral joints exhibiting greater deflection and higher incidence of failure than their superior counterpart, current techniques for quantifying endplate deflection face notable limitations. Early studies using metallic markers or displacement transducers required drilling channels into the vertebral body, potentially exaggerating deformation by weakening subchondral bone support. Imaging-based approaches, particularly micro-CT, offer high spatial resolution but are limited to static or stepwise loading due to temporal constraints. These static conditions do not capture the cyclic loading patterns experienced by the spine during daily activity, where repeated deformation can cause fatigue-induced microdamage and eventual failure. Additionally, static loading promotes excess fluid loss from the nucleus pulposus, altering endplate deflections in ways that do not reflect physiological motion. Consequently, existing measurement techniques may misrepresent true endplate behavior and are unable to evaluate changes in deflection as a function of cyclic load exposure. This study addresses these limitations by developing a unique method to assess endplate deflection during cyclic loading without requiring prolonged stepwise protocols or causing damage to the vertebral bone. By comparing superior and inferior endplates across different load magnitudes and cyclic durations, this work aims to clarify the mechanisms underlying endplate vulnerability and further validate the porcine cervical spine as an experimental model for human lumbar spine deflection. Eighteen porcine cervical spine functional units (C3C4, C4C5, and C5C6; n = 6 per level) were dissected to yield 36 individual vertebrae. High-resolution laser profilometry was then used to capture the topography of the caudal endplates of C3, C4, and C5 and the cranial endplates of C4, C5, and C6. Custom indenters, designed as negative molds of the nucleus-occupying endplate region, were created from the resulting surface scans and fabricated via 3D printing. Specimens were then oriented such that the tested endplate was in a neutral position and subjected to a normalized haversine waveform, ranging from 0.3 kN to 30% of the predicted ultimate compressive strength using a servohydraulic materials testing system. The cycle-dependent changes in endplate deflection were measured at 0, 1000, 3000, and 5000 total cycles. At each time point, endplate deflection measurements were captured via the indenter’s displacement while specimens were exposed to a brief static force of 0.3 kN, 1 kN, and 3 kN, totaling 12 measurements per vertebra. Three separate linear mixed effects models were used to evaluate the impact of loading magnitude, loading cycles, endplate level and the proportion of the nucleus occupying endplate area on superior and inferior endplate deflection within each joint. A fourth linear mixed effects model was used to evaluate the impact of loading magnitude, loading cycles, and joint level on the magnitude of the differences between superior and inferior endplate deflection. Utilizing this novel methodology, this study was the first to quantify endplate deflection under cyclic loading conditions, observing greater deflection of the inferior endplate across all spinal levels, except at baseline (0.3 kN, 0 cycles). This method also enabled comparison of deflection rates between endplates, with the C4C5 and C5C6 inferior endplates showing a significantly greater rate of deflection during the first 1000 cycles. Among joints, C4C5 exhibited the largest difference in superior and inferior endplate deflection compared to C3C4 and C5C6. Endplate deflection was not influenced by the proportion of the nucleus occupying endplate area at any spinal level. Lastly, as the first study to examine endplate deflection in porcine cervical vertebrae, the observation of greater inferior endplate deflection being consistent with human cadaveric studies further supports the validity of this model. Overall, this study demonstrates the utility of a novel methodology for measuring and comparing superior and inferior endplate deflection under cyclic loading.
Effects of Phospholipase A/Acyltransferase-1 (Plaat1) gene deletion on brain molecular and biochemical measures and memory
(University of Waterloo, 2025-10-30) Cocco, Alex
Phospholipase A1/2 and Acyltransferase-1 (PLAAT1) is a small lipid metabolizing enzyme that possesses transacylase activity and is expressed highly in the rodent heart and brain. Recently, our lab has found that in vitro, PLAAT1 is capable of acylating monolysocardiolipin with an acyl chain donated from phosphatidylcholine acyl donors to produce cardiolipin. Cardiolipin is a glycerophospholipid that is essentially exclusive to the mitochondria and is vital for trans-membrane protein stability, inner mitochondrial membrane structure, apoptosis, and more. The de novo synthesis and acyl chain alterations (‘remodeling’) of cardiolipin are important for the health and proper functioning of cells. Previous work in our lab has demonstrated that mice deficient in Plaat1 (Plaat1-/-) had significant deficiencies in cardiac cardiolipin content, suggesting an in vivo role of PLAAT1 in cardiolipin metabolism. However, Plaat1-/- mice are poorly characterized, especially with regards to the brain, and study of this tissue, and phenotypic changes related to brain function, could help to delineate the role that PLAAT1 may serve there. Thus, the purpose of this thesis project was to explore the effects of Plaat1-deficiency on mouse brain cardiolipin metabolism and related functions. Lipid analyses of cardiolipin, monolysocardiolipin and phosphatidylcholine revealed small, sex-specific alterations in composition but not content, while analyses of gene expression for relevant biosynthetic and remodeling enzymes exhibited significant transcriptional downregulation in female but not male Plaat1-/- brains. Immunoblotting for mitochondrial protein markers suggested changes to mitochondrial shape in female Plaat1-/- brains, while both male and female Plaat1-/- brains experienced perturbations in subunit content for complexes of the electron transport chain. Lastly, mouse anxiety and short-term memory behaviour was tested, revealing that female Plaat1-/- mice are relatively anxiolytic (relaxed), while neither male nor female Plaat1-/- mice had altered short-term memory. Taken altogether, the data collected in this project suggests that PLAAT1 acts in a tissue- and sex-specific manner for reasons that were unable to explored within the scope of this thesis project. The present thesis project demonstrates both a cellular and physiological role of PLAAT1 in the female brain, and provides a foundation from which further work on PLAAT1 can be explored. These results have implications for the interaction of sex and cardiolipin metabolism in the function of brain mitochondria and resultant behavioural outcomes.
Cybersickness: Linking Postural Control to User Discomfort in a Virtual Roller Coaster
(University of Waterloo, 2025-10-23) Gulifeire, Alimu
Cybersickness (CS) remains a major obstacle to the widespread use of Virtual Reality (VR), with leading explanations emphasizing sensory conflict, sensory reweighting, and postural instability. Prior research has shown that individuals who flexibly reweight visual, vestibular, and body cues report lower CS, particularly in interactive VR tasks where users can move freely. Whether this relationship generalizes to more passive, visually intense VR experiences is less clear. This thesis examined sensory cue reweighting and postural control as predictors of CS during an immersive roller coaster simulation. Nineteen younger adults completed the Oriented Character Recognition Task (OCHART) before and after VR exposure to estimate perceptual upright and quantify cue weightings. During VR exposure, postural movement was recorded using markerless motion capture, and participants reported symptoms using the Fast Motion Sickness (FMS) scale after each trial. Contrary to findings from interactive VR contexts, sensory reweighting was not significantly associated with CS in this passive roller coaster environment. In contrast, measures of postural control, particularly total path length, were robust predictors of sickness severity, with greater displacement linked to higher FMS scores. These findings suggest that in visually dominant VR tasks with limited bodily engagement, postural instability provides a more reliable marker of CS than sensory reweighting. This work clarifies that the predictive value of sensory reweighting is context dependent, emerging more clearly in interactive than passive VR tasks. It further points toward movement-based strategies for mitigating discomfort in VR experiences where movement is restricted but visual conflict is high.
The Role of Binocular Vision in Visuomotor Control during Discrete Pointing and Reciprocal Tapping
(University of Waterloo, 2025-09-22) Wang, Shirley
Visual information is integral for executing movements in most daily activities. The accuracy and precision of upper limb movements towards targets are highly dependent on movement planning and the online monitoring of visual feedback. Investigating the effects of amblyopia and strabismus could provide insight into the neuroplasticity of visuomotor control. This study had two objectives: (1) to assess the role of binocular vision in two types of tasks, and (2) to investigate the impact of amblyopia and strabismus on visuomotor control. Two groups of participants were recruited: visually normal adults (n = 40) and patients with amblyopia and strabismus (n = 8). Participants were asked to perform two visuomotor tasks: discrete pointing and reciprocal tapping. For the discrete pointing task, participants pointed to a visual target at either 5º or 10⁰ along the horizontal meridian. For the reciprocal tapping task, participants repeatedly tapped between two targets of various sizes as fast and accurately as possible. For visually normal adults, binocular viewing resulted in faster movements compared to viewing with one eye, demonstrating a binocular advantage for motor efficiency for both discrete and reciprocal tasks. Patients with amblyopia and strabismus executed slower, more cautious movements when viewing with their amblyopic (non-dominant) eye compared to binocular and fellow (dominant) eye viewing. The patients also had significantly better movement performance when using binocular viewing compared to fellow eye viewing for the discrete task, suggesting there was some binocular advantage. The patient group tended to execute their movements faster but was less precise than the control group, suggesting a speed–accuracy trade-off. It is important to acknowledge that the current patient cohort was small and the results should be considered with caution. Nonetheless, the findings demonstrate that binocular vision plays an important role in facilitating the accuracy and precision of upper limb goal-directed movements.
The Effects of Chronic Psilocybin Administration on Physiological, Metabolic and Behavioural Outcomes in Control and High-Fat Diet-Fed Male and Female C57BL/6J Mice
(University of Waterloo, 2025-09-22) Diaguarachchige De Silva, Kalsha
Psilocybin, the prodrug, and psilocin, the psychoactive compound and serotonin receptor agonist found in Psilocybe mushrooms has been used by Mesoamerican communities for thousands of years for spiritual and medicinal purposes. In Canada, psilocybin is designated as a Schedule III substance prohibiting its use recreationally and in research. However, in 2018, psilocybin received “Breakthrough Therapy” status from the United States Food and Drug Administration, due to its impressive safety profile, and clinical evidence in the treatment of several psychiatric disorders, including substance-related and addictive disorders, when used in conjunction with psychotherapy. While obesity, which affects 1 in 4 Canadians, can be associated with a number of contributing factors; for those affected by overeating, obesity shares neurobiological and environmental parallels with other addictive disorders. For this reason, psilocybin is of interest as a potential treatment for obesity. To date, only three pre-clinical studies have examined psilocybin in diet-induced obesity models, and none have studied its chronic effects in female animals or effects on metabolic parameters, glucose tolerance and insulin sensitivity. Therefore, this thesis investigated the expression of serotonin (5-HT) receptors in 3T3-L1 adipocyte differentiation, in addition to the physiological, metabolic and behavioural effects of chronic psilocybin administration in female and male mice fed control diet (CD) or high-fat diet (HFD). In doing so, the expression of 5-HT receptors involved in regulating feeding behaviour and satiety (i.e., 5-HTR1B, 5-HTR2A-C, 5-HTR3 and 5-HTR7) were examined in 3T3-L1 adipocytes over 16 days of differentiation. Interestingly, only the expression of 5Htr2a significantly changed during differentiation, further signifying its vital role in regulating lipogenesis. Other than 5-HTR1B, which was expressed but did not vary during differentiation, all other 5-HT receptors showed minimal or no expression in differentiating and mature adipocytes indicating their rather dispensable role in these cells. In subsequent studies, eight-week-old male and female C57BL/6J mice were randomized to receive a 45 kcal% HFD or 10 kcal% CD for 17-weeks to induce divergent body masses, then they were further randomized to also receive weekly i.p. injections of 1 mg/kg psilocybin or vehicle (isotonic saline) for an additional 19-weeks. Towards the end of the injection period, mice were subjected to a test battery consisting of behavioural and metabolic tests: open field testing and elevated plus maze to monitor the movement of mice and to assess for anxiolytic behaviour; the Oxymax Comprehensive Lab Animal Monitoring System by Columbus Instruments® to assess respiratory gas exchange and ambulatory, rearing and total locomotion over a 24-h period; the Low-Profile Wireless Running Wheels by Med Associates® to assess voluntary running; glucose tolerance and insulin sensitivity testing to evaluate glucose response; and food intakes and body weights were measured on a weekly basis for the duration of the study, while organ weights were collected at study termination. Collectively, all studies showed no differences in body weight, food intake, respiratory gas exchange, organ weight, glucoregulation, anxiolytic behaviour or spontaneous movement following chronic psilocybin treatment in HFD-fed male and female mice when compared to the CD-fed mice. Although there were no differences due to drug treatment, differences due to diet were present in nearly all the measures evaluated. Contrary to my hypotheses, psilocybin was unable to correct and restore the physiological, metabolic and behavioural alterations caused by HFD feeding to CD-fed levels. Nonetheless, CD-fed male mice treated with psilocybin had improved insulin sensitivity compared to all other groups. This novel finding leads us to speculate a role for psilocybin in glucose regulation, which may be elucidated in future studies. Therefore, this thesis, through its proposed studies, answered a vital question – chronic psilocybin treatment does not affect satiety or feeding behaviour in mice.
Understanding the relationship between gait and cognition in mild cognitive impairment subtypes and probable REM sleep behaviour disorder
(University of Waterloo, 2025-09-22) Elasfar, Salma
Introduction: Mild cognitive impairment (MCI) represents a transition state between normal cognition and dementia. Individuals with amnestic MCI (aMCI) are more likely to develop Alzheimer’s disease (AD), whereas individuals with non-amnestic MCI (naMCI) are more likely to progress to non-AD dementias. Individuals with multi-domain (MD-) MCI are more likely to develop dementia than individuals with single-domain (SD-) MCI. Previous research has demonstrated that individuals with MCI have slower gait compared to cognitively unimpaired (CU) older adults, but limited research has characterized gait differences across MCI subtypes over time in these groups. There is also growing evidence that specific gait characteristics are selectively associated with specific cognitive domains, but few studies have investigated these associations longitudinally in MCI. REM sleep behavior disorder (RBD) is a prodromal biomarker of α-synucleinopathies, particularly Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). Individuals with RBD are more likely to develop MCI than healthy controls, and the presence of MCI in RBD is associated with greater risk for early phenoconversion. Recently, research has highlighted that individuals with isolated RBD exhibit subtle changes in gait. Despite this, no studies to date have explored how the presence of RBD influences gait characteristics in people with MCI. Therefore, this study aimed to a) characterize baseline and longitudinal gait characteristics across MCI subtypes, b) explore how the presence of RBD impacts gait characteristics in MCI, and c) assess whether baseline gait characteristics can predict future decline in specific cognitive domains in MCI. Methods: This study involved secondary data analysis of data from the Mayo Clinic Study of Aging. 382 individuals with MCI (180 SD-aMCI, 48 SD-naMCI, 134 MD-aMCI, 20 MD-naMCI), and 382 age-, sex- and education-matched CU individuals were included. Mean follow-up duration for the entire sample was 16.8 months. Participants completed gait assessment using an instrumented gait walkway. Informants completed the Mayo Sleep Questionnaire, which was used to determine probable RBD (pRBD) status. Cognition was measured using domain-specific z-scores for attention, memory, language, visuospatial function, as well as global cognition. Linear mixed effects models were used to compare gait outcomes over time between groups and by pRBD status. Principal component analysis and linear mixed effects models were used to derive gait components and assess if they predict change in cognitive domains from baseline to follow-up visits. Results: All individuals with MCI walked slower, with shorter steps, longer step time, and increased double support (%) compared to CU individuals. Variability of step length, stride velocity and swing time were increased in MD-aMCI compared to CU individuals. Over time, stride velocity and step length decreased, and step time increased in MD-aMCI. The presence of pRBD was associated with decreased stride velocity and step length, and increased stride width and double support (%), particularly in MD-naMCI. Swing time increased over time in people with MD-naMCI and pRBD. Principal component analysis identified three gait factors: pace and stability, timing and rhythm, and variability. The pace and stability factor was negatively associated with global cognition and attention. Surprisingly, the rhythm and timing factor was positively associated with memory. Variability was negatively associated with global cognition and visuospatial function, but this association weakened at follow-up. Conclusions: Gait analysis may be a helpful tool to distinguish MCI from normal aging. Gait variability and slowing of gait may be specific markers of multi-domain impairment. Gait is impacted by comorbid pRBD in MCI, particularly in MD-naMCI. These findings provide further support for the notion of selective associations between specific gait and cognitive domains in people with MCI. Importantly, further investigation with longer follow-up duration, larger sample sizes, and integration of neuroimaging and fluid biomarkers is needed to better understand the role of gait in predicting future progression to dementia in individuals at risk.
Accumulation and Recovery of Prolonged Low-Frequency Force Depression at Different Intensities of Repetitive Isometric Contractions
(University of Waterloo, 2025-09-19) Friedel, Jared
Prolonged Low Frequency Force Depression (PLFFD) may impact performance in the workplace by influencing musculoskeletal disorder (MSD) risk or reducing force stability. PLFFD is a reduction in low-frequency stimulated force with little change in high-frequency stimulated force for long period after contraction. The objective of this research was to measure changes in PLFFD over exposure and recovery from a half-shift of an isometric contraction task at two intensities on separate visits, and to determine whether there is a relationship between PLFFD and force stability. Participants repetitively supported a weight with their elbow flexors for 4 consecutive 1-hour work-segments. Participants performed a low-force high-duty cycle and a high-force low-duty cycle workload-matched protocol on two different days. PLFFD and force stability were measured in the biceps brachii muscle throughout task exposure and recovery. PLFFD was measured as the ratio of elbow flexion force produced at low (10 Hz) and high (100 Hz) frequency transcutaneous stimulations on both the left (non-intervention) and right (intervention) arms. A repeated measures ANOVA detected a progression of PLFFD in the intervention arm through intervention and recovery, but no protocol-effects were detected. Force stability metrics of variability (normalized standard deviation) and unsteadiness (average rate of change) of force during an isometric elbow flexion force matching task were poorly predicted by PLFFD and better predicted by changes in Maximum Voluntary Force (MVF). This research expanded on incidental findings of PLFFD from past research, and reinforced relationships between muscle fatigue and force stability. PLFFD did not recover at different rates depending on exertion intensity, nor impact force stability metrics, therefore likely not affecting worker performance. Muscle fatigue was shown to impact force unsteadiness to a greater extent than force variability, leading to the suggestion that force stability changes caused by muscle fatigue should be considered when designing a workplace.
The Effect of Jaw Clenching on Extracranial and Intracranial Blood Flow
(University of Waterloo, 2025-09-19) Zafiris, Eudoxia
The internal carotid artery (ICA) and external carotid artery (ECA) facilitate perfusion to the intracranial and extracranial regions, respectively. Under current dogma, the ICA is tightly regulated to ensure stable cerebral perfusion, while the ECA remains more pressure-passive, compensating for fluctuations in blood flow to the brain by redirecting blood flow to protect the cerebrovascular network during physiological stressors. While previous research has attempted to influence ECA flow through indirect stimuli such as facial cooling and exercise, direct experimental manipulation of ECA flow has rarely been tested. It remains unclear how ICA and ECA branches reallocate flow in response to changing demands in the facial vasculature. The purpose of this research is to determine whether the ECA can directly control carotid flow redistribution via jaw clenching by increased facial flow resistance and a post-exercise hyperemic response. 26 healthy adults (24±4 years; 15 female) performed isometric (25% maximum voluntary jaw clench (MVJC); 60 sec) and dynamic (50% duty cycle 3 seconds ON/OFF, for 60 sec at 75% MVJC) jaw clenching exercises. Additionally, a facial cooling mask was placed on each participants face to elicit a non-metabolic vasoconstrictor response. Blood velocity in the CCA, ECA and ICA was measured with conventional Doppler ultrasound before, during, and post clenching periods, and before and during facial cooling. Transcranial Doppler ultrasound continuously recorded middle cerebral artery velocity (MCAv), and vector flow imaging (VFI) was used to scan the carotid bifurcation before and post jaw clenching to determine changes in blood flow patterns. During both isometric and dynamic jaw clenching protocols, CCA and ECA blood flow increased from baseline, during, and post clenching, accompanied by a decrease in the pulsatility index (PI) (p < 0.05), indicating that jaw clenching actively increases extracranial blood flow via the ECA. In contrast, no changes were observed in ICA blood flow and PI throughout isometric jaw clenching, however, during dynamic jaw clenching, blood flow increased during the post clench phase compared to the ON phase (p < 0.05) and the PI decreased throughout (p < 0.05). MCAv increased during dynamic clenching (p < 0.05). The resistance index decreased during clenching and rebounded post clench for both jaw clenching conditions (p < 0.05), suggesting that intracranial responses depend on the clenching modality. VFI revealed that isometric jaw clenching increased flow and uniformity at the carotid bifurcation, reflecting laminar redistribution between the ECA and ICA. These findings provide novel evidence that jaw clenching can modulate carotid hemodynamics at both extracranial and intracranial levels and reshape local flow patterns at the carotid bifurcation. This has potential implications for understanding vascular contributions to temporomandibular disorders and the broader cerebrovascular impact of chronic jaw muscle activity.
The Association Between Physical Activity and Sleep Quality on Risk of Anxiety and Depression across Cognitive Statuses in Older Adults
(University of Waterloo, 2025-09-17) Ghodsi Boushehri, Maral
Introduction: Anxiety and depression are prevalent neuropsychiatric issues among older adults with cognitive impairment. They are associated with accelerated cognitive decline, increased caregiver burden, and reduced quality of life. Given the noticeable side effects of pharmacological treatments, there is growing interest in non-pharmacological approaches to tackle anxiety and depression. Physical activity and sleep quality have shown promise in reducing anxiety and depression in the general population, but their potential benefits remain largely underexplored in older adults with cognitive impairment. The objectives of this thesis were to: 1) examine the associations between physical activity and sleep quality with odds of having anxiety and depression among older adults with different cognitive statuses; 2) investigate whether physical activity moderates the association between sleep quality with anxiety and depression; and 3) explore whether the associations between sleep, physical activity, and anxiety and depression vary by dementia subtype. Methods: This was a secondary analysis of data from the Comprehensive Assessment of Neurodegeneration and Dementia study. Physical activity was assessed using the Physical Activity Scale for the Elderly (PASE) and sleep quality with the Pittsburgh Sleep Quality Index (PSQI). Anxiety and depression symptoms were assessed using the Generalized Anxiety Disorder 7–item (GAD-7) and the Geriatric Depression Scale (GDS). Cutoff scores of GAD-7 ≥ 5 and GDS ≥ 10 were used to identify participants who are likely to have at least mild anxiety or depression. Logistic regression models with a backward selection of covariates were used to evaluate associations. Results: The study sample included 956 older adults: 150 with no cognitive impairment, 116 with subjective cognitive impairment, 460 with mild cognitive impairment, and 230 with dementia. Poor sleep quality was strongly associated with increased odds of both anxiety (OR = 1.138, CI = 1.09–1.19, p < 0.001) and depression (OR = 1.355, CI = 1.137–1.646, p = 0.001). Increased physical activity was associated with lower odds of depression (OR = 0.996, CI = 0.994–0.999, p = 0.038), but higher odds of anxiety (OR = 1.003, CI = 1.000–1.006, p = 0.007). The relationship between physical activity and outcomes was consistent across cognitive groups, whereas the association between sleep quality and depression was weaker among people with dementia. Moreover, no significant interaction between sleep quality and physical activity was found, suggesting that there is no moderating effect in their relationship with anxiety and depression. Additionally, none of the associations varied by dementia type, indicating consistent relationships across different types of dementia. Conclusion: The consistent association between poor sleep quality and higher odds of anxiety and depression emphasizes the need to prioritize sleep interventions among older adults with various cognitive statuses. Physical activity may be beneficial in reducing depressive symptoms, but its unexpected positive association with anxiety highlights the need for further investigation.
Determining the maximum feasible box dimensions and box masses for one-handed box transfers from varying heights
(University of Waterloo, 2025-09-10) Li, Julia Xinyi
Background: To address continued prevalence of musculoskeletal disorders (MSD) related to manual materials handling (MMH) in logistics and warehousing industries, more effort is being devoted to proactive ergonomics when (re)designing the workspace through the use of digital human models (DHM). However, effectively using a DHM requires the user to estimate how a worker will interact with an object. One example includes guessing when a worker might use one hand versus two when lifting and transferring a box. To avoid guessing we need a better understanding of the determinants for performing one-handed lifts and transfers to inform DHM users on when human-object interactions should be modeled with one-hand verses two. Purpose: The aim of this work was to determine the maximum feasible box dimensions and masses that would permit a one-handed box lift and transfer from three shelf heights. Methods: Two sex-balanced samples of 20 participants completed a series of box transfer tasks from varying shelf heights (ankle, greater trochanter (GT), shoulder height) to a table with their dominant hand. For Study One, participants were instructed to grab a minimally weighed retractable box from either front or top and expand/collapse its dimension until they perceived that they could no longer transfer it with only one hand. For Study Two, participants were instructed to grab the box from either front or top (using the maximum acceptable dimensions from Study One) and to adjust the mass of the box until they perceived that they could no longer transfer it with only one hand. Within-subject repeated measure ANOVA with an alpha value of 0.05 were used for both studies to detect for shelf height or grip orientation differences. Results: The perceived maximum acceptable box width ranged from 70-73% of participant’s hand length. Perceived maximum width decreased with higher shelf height when grasping the box from the top, while staying consistent when grabbing the box from the front regardless of shelf height. Perceived maximum mass was lower when grasping the box from the top regardless of shelf height and was lower when grasping the box from shoulder height compared to ankle height regardless of grip orientation. Discussion: When the box width exceeded 124mm of the person’s hand length and required more than 36.7% wrist strength, people may be more likely to use two hands. The discrepancy in perceived maximum acceptable box width and box mass when grasping from the top at shoulder height was potentially due to awkward hand/wrists posture or line of sight issues. The effects between grip orientation and shelf height on the perceived maximum lifting capacity for one-handed transfers should be considered when proactively designing stock-picking tasks to optimize safety. Additionally, an understanding of the maximum determinants helped set manual material handling limits for one-handed box transfers. Findings from the current investigations provided psychophysical insights into the one-handed lifting capacity of standard cardboard boxes with no handles.
Exploring the use of the RCRA equation as an MSD risk assessment tool to evaluate electrical harness installation tasks.
(University of Waterloo, 2025-08-29) Nestor, Hailey Michelle
Intro: Electrical wire harnessing on an automotive line consists of routing a harness through a car’s engine, securing electrical connections, and successfully securing retention clips to keep the harness in place. The wire harnessing task is complex in nature and installation involves many hand forces and repetitive motions. Additionally, wire harnessing is highly repetitive, with workers having to install up to 500 engine harnesses per shift. Anecdotal evidence is emerging that some wiring harnessing work can lead to workplace musculoskeletal disorders of the hand and wrist. Due to the complex nature of the task, and difficultly in measuring internal exposures in-field by using tools such as electromyography, there is a lack of quantification and analysis of biomechanical demands of the task. The Recommended Cumulative Rest Allowance (RCRA) tool, developed by Potvin & Gibson (2016), aims to characterize exposures by assessing isolated subtasks in conjunction with other subtasks to assess the risk of a complete job. The RCRA is informed by percent efforts (%Efforts) that can vary and result in different outcomes based on inputs. Thus, there is a need to quantify and analyze biomechanical demands of wire harnessing using both high-fidelity in-laboratory equipment and potential lower-fidelity in- field equipment to compare and validate a cumulative tool to be used on the line. This study aimed to evaluate the usability of the RCRA tool for estimating required rest necessary to prevent undue fatigue during harness installation. Methods: Using a mock-engine setup in a controlled laboratory environment, 26 participants completed repeated installations of two harness types while surface electromyography (EMG) and force data were collected for wrist flexors, extensors, and applied hand force. RCRA ratios were calculated across subtasks and input types including muscle activity as a percent of maximum voluntary contraction of the wrist flexors and extensors and applied force as a percent maximum voluntary force to assess fatigue accumulation. Results: Findings revealed that input selection significantly influenced RCRA outputs, with applied force and wrist flexor EMG producing consistent and interpretable estimates of required rest allowances. In contrast, peak wrist extensor inputs often resulted in unrealistically high RCRA ratios due to the extensor muscle’s sustained activation patterns and the equation’s sensitivity to frequency and duration. No significant differences were found between the two harness types, likely due to their similar physical characteristics. Conclusion: Overall, this study supports that the RCRA tool yields similar outputs when driven with peak force or peak wrist flexor EMG, but not when driven with peak extensor EMG. It also underlines the need for careful input selection and complementary assessment strategies when evaluating different muscles. These insights provide a foundation for developing validated, in-field fatigue assessment protocols to help prevent overuse injuries in automotive manufacturing.
Investigating fiberglass casting materials and cross-system modality measurements in DXA and X-ray forearm imaging
(University of Waterloo, 2025-08-28) Ying, Tsz Yui
Falls on an outstretched hand (FOOSH) injuries often lead to distal radius fractures (DRFs). X-ray imaging is used to visualize fracture morphology and provide qualitative information; however, quantitative information is not readily available without more advanced imaging modalities. This study investigated the impact of fibreglass cast thickness on the accuracy of areal bone mineral density (aBMD) and bone mineral content (BMC) measurements obtained through Dual-Energy X-ray Absorptiometry (DXA). It evaluated the potential of a novel dual-energy spectral X-ray detector (Reveal 35C) as a point-of-care alternative. Eight cadaveric forearm specimens were scanned under baseline, two-roll, and four-roll cast conditions using both imaging modalities. Simulated DRFs were induced via quasi-static loading, followed by post-fracture imaging to assess structural integrity and imaging fidelity. Results showed that DXA-derived aBMD and BMC significantly decrease with increasing cast thickness. The mid-distal subregion of interest (MD-sROI) shows the most consistent attenuation trend. In contrast, the ultra distal (UD-sROI) and one-third distal (OTD-sROI) subregions of interest showed greater variability, particularly in specimens with lower density. The Reveal 35C detector showed a strong correlation with the DXA system under uncasted conditions (R2 = 0.82-0.89), but correlations are markedly lower in casted scans (R2 = 0.29-0.63). This discrepancy highlights cast-induced imaging distortions. Through fracture testing, it is shown that specimens with higher aBMD and BMC generally sustained greater loads prior to fracture. Findings from this study indicate that DXA-derived aBMD and BMC are susceptible to errors caused by fiberglass medical casts and variations in positioning during imaging. Meanwhile, the Reveal 35C system shows promise as a viable alternative for bedside fracture monitoring through calibration, but limited in enabling virtual cast removal and longitudinal assessment.
Validating Internal Density Calibration in The Proximal Humerus to Estimate Bone Stiffness Using Finite Element Analysis for Stemless Shoulder Arthroplasty
(University of Waterloo, 2025-08-26) Stiles, Chloë Karrie Anne
Stemless humeral head components are a popular choice for patients undergoing shoulder arthroplasty for end-stage osteoarthritis (OA). OA is known to alter bone density in the humeral head, which can compromise implant stability and increase the need for surgical revisions. Current pre-operative clinical assessments are limited in evaluating bone mineral density (BMD) and fail to consider the mechanical properties of bone in the region directly supporting the stemless component, leaving a critical gap in understanding the structural integrity of the bone supporting the stemless component. Traditionally, in-scan phantom calibration determines volumetric bone mineral density (vBMD) from greyscale intensity in computed tomography (CT) images, but this method is rarely used in clinical practice due to limited time and resources. As a result, alternative density measures for determining accurate vBMD from clinical CT images are needed. Internal density calibration using internal tissues as references has been validated in the spine and hip, however, it has yet to be validated in the proximal humerus. Additionally, vBMD derived from internal density calibrated images has yet to be linked to finite element model (FEM) apparent stiffness in the context of stemless shoulder arthroplasty. Establishing stiffness as a measure of bone mechanical properties is a first step in accurately predicting bone strength in clinical CT images. The purpose of this thesis was to 1) determine the correlation between phantom and internal density calibration in the proximal humerus using three different tissue combinations, 2) compare vBMD in an end-stage OA patient group to a non-pathologic group, and 3) determine the correlation between vBMD and apparent stiffness. Non-pathologic cadaveric single-energy CT images containing a dipotassium phosphate (K2HPO4) phantom were used to analyze a 10 mm thick volume of interest (VOI) directly below the anatomic neck. Phantom and internal density calibration was performed on each phantom-containing cadaveric specimen. vBMD was extracted and FEMs were generated from the VOI. The internal calibration with the lowest bias was used to calibrate images for all end-stage OA patient specimens. VOIs were created for cortical, trabecular, and combined (integral) bone compartments across specimens and vBMD was extracted for each compartment. FEMs were generated using the integral VOI to estimate apparent stiffness. Statistical analysis revealed a strong correlation between internal and phantom density calibration, establishing internal calibration as a valid metric for determining vBMD (AAdC R2 = 0.80; AAdCM R2 = 0.88; ACM R2 = 0.90). The ACM (Air, Cortical Bone, Skeletal Muscle) tissue combination had the lowest error (Mean: 13.08 mgK2HPO4/cm3). The end-stage OA patient group had significantly lower integral (Patient: 119 mg K₂HPO₄/cm³; Cadaver: 159 mg K₂HPO₄/cm³), cortical (Patient: 518 mg K₂HPO₄/cm³; Cadaver: 643 mg K₂HPO₄/cm³), and trabecular (Patient: 79.8 mg K₂HPO₄/cm³; Cadaver: 110 mg K₂HPO₄/cm³) vBMD than the non-pathologic cadaveric group (p<0.001), highlighting the biological relevance of vBMD. Mean apparent stiffness was found to be significantly lower in the end-stage OA group (672 MPa) relative to the non-pathologic cadaveric group (1261 MPa) (p < 0.001), however stiffness was not correlated with cortical vBMD in either group (Patient: R² = -0.018, p = 0.73; Cadaver: R² = -0.018, p = 0.71), suggesting the need for a multi-factorial approach when quantifying mechanical properties using FEMs.

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