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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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.
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.
Exploring the Exercise and Physical Activity Experiences of Adults with X-Linked Hypophosphatemia
(University of Waterloo, 2025-08-20) Morgante, Emmett
Background: X-linked hypophosphatemia (XLH) is a rare hereditary phosphate-wasting disorder, marked by mutations in the PHEX gene on the X chromosome. Mutations result in renal phosphate wasting and decreased 1,25-dihydroxyvitamin D, leading to rickets in children and osteomalacia in adults. XLH contributes to significant physical impairments including lower limb deformities, reduced height, bone pain, stiffness, early osteoarthritis, and fractures, which collectively hinder mobility, physical functioning, and quality of life. Despite pharmaceutical treatments, mobility and physical functioning deficits remain inadequately addressed. Currently, there is not a strong understanding of how physical activity and exercise can affect health outcomes for people with XLH. XLH brings unique challenges to mobility and physical functioning which could bring its own barriers to exercise making it an important topic to explore to create interventions for the XLH population. Objective: The objective of the study was to understand the experiences of people with XLH when participating in physical activity and exercise. I looked to identify how having XLH affects participation in physical activity and exercise, the barriers to and facilitators of exercise and physical activity, and the health outcomes that are most important for people with XLH when making treatment decisions with medications, and exercise. Methods: Using a phenomenological approach from a post-positivism point of view, semi-structured interviews were conducted with adults diagnosed with XLH. The interview guide was designed using the COM-B model of behavior to reveal how capability, motivation and opportunity affects people with XLH’s exercise and physical activity behaviors. Data was analyzed using reflexive thematic analysis to understand the experiences during exercise and physical activity, the barriers to and facilitators of exercise, and the outcomes prioritized by participants. A content analysis was done to understand the most frequent modes of exercise being completed, and the patient important outcomes most prioritized to participants. Results: Semi-structured qualitative interviews, and two content analyses with 17 adults who have XLH were conducted. Pain, stiffness, and fatigue were identified as major barriers to both a person with XLH’s capability and motivation to participate in exercise and physical activity. Pain and stiffness created mobility limitations challenging a person’s capability. Fatigue and overexertion led to increases in pain and stiffness. The exacerbation of pain and stiffness from fatigue led to a fear of worsening symptoms affecting people’s reflective motivation to exercise. While fatigue worsens symptoms and discourages activity, participants described that when they were able to find the right balance of physical activity and exercise with rest they found improvements in pain, stiffness, mobility and overall physical functioning. Walking, stretching, swimming/water aerobics and strength training were completed most frequently by participants. Key facilitators to exercising were strategizing movement to manage fatigue, and tailoring exercise for mobility impairments. The study also highlights the importance of identifying patient important outcomes. Similar outcomes were identified for treatment with medications and exercise (pain, fatigue, strength mobility and physical functioning). But physical functioning and its individual components, such as strength, were more highly prioritized for exercise, versus pain for treatment with medications. Regardless of the context, improving functional outcomes and progression of the disease in the long-term was of the highest priority. Conclusion: While pain, stiffness, and fatigue pose substantial barriers to motivation and capability to participation in physical activity and exercise, the findings reveal that appropriately tailored and balanced exercise can lead to improvements in physical functioning, mobility, and symptom management. Participants emphasized the need for tailored approaches that account for their unique physical limitations, and for the management of fatigue. Crucially, the study underscores the significance of centering interventions around patient-prioritized outcomes which are often underrepresented in current clinical approaches. The findings lay the foundation for developing informed, person-centered physical activity guidance and exercise interventions that address both the physical and psychological challenges of living with XLH, ultimately aiming to improve quality of life and long-term health outcomes.
Investigating and promoting lifestyle factors to improve sleep in people at risk for and with dementia
(University of Waterloo, 2025-08-20) Kuhn, Tara
Introduction: Sleep disturbance is not only associated with increased risk of dementia but is common after dementia onset and is a noted stressor for care partners. Physical activity may reduce dementia risk, as well as promote sleep for people with dementia. However, it is unclear whether physical activity and sleep interact to mitigate dementia risk or promote quality of life in people with dementia. This thesis aims to: 1A) understand the relationship between sleep, physical activity and cognitive function in people without dementia, and 1B) understand how sleep and physical activity relate to cognitive function and functional abilities among people with dementia, and 2) adapt a lifestyle-focused sleep intervention for Canadians with dementia. Aim 1: Data from the Rush Memory and Aging Project —which utilized accelerometers, a cognitive battery, and clinical expertise— was used to examine: how sleep and physical activity were associated with cognitive decline and dementia risk in people without cognitive impairment (Study 1); and how sleep and physical activity were associated with cognitive and physical function in people with dementia (Study 2). In Study 1, greater physical activity was associated with slower cognitive decline and reduced dementia risk. Additionally, more fragmented sleep was associated with worse baseline global cognition, but not cognitive trajectory or dementia incidence. In Study 2, physical activity was associated with better functional abilities, but not with cognitive trajectory or sleep fragmentation in people with dementia. Sleep fragmentation was not associated with global cognition or functional abilities among people with dementia. Aim 2: A lifestyle intervention for sleep (NITE-AD) that included sleep education, physical activity, and light therapy was adapted to be s appropriate for use in Canada (NITE-CAD). Based on the Knowledge to Action cycle, we approached this program adaptation in three steps. Step 1: identify the knowledge gap and determine availability of sleep programs for people with dementia in Canada. Step 2: assess the barriers and facilitators to knowledge use (Study 3) and determine which aspects of the program required requires modification. Using a qualitative descriptive design, semi-structured interviews were carried out with people with dementia and their care partners. Interviews were coded with a deductive content analysis, using the Behaviour Change Wheel as the guiding framework. Findings indicated winter conditions exacerbated previous challenging circumstances for people with dementia and winter physical activity participation was facilitated when people with dementia had appropriate equipment, access to facilities or cleared trails, and had their preferences met (e.g. indoor vs. outdoor activities, risk tolerance). Step 3 (Study 4) tailored the NITE-AD program with an advisory team using the results from Study 3 to create the NITE-CAD program. Changes included flexible physical activity options to support participation of people with dementia with diverse needs, contexts, and preferences, and minor wording and formatting changes. Conclusion: Sleep and physical activity were independently associated with cognitive functioning, with physical activity reducing cognitive decline and dementia risk in adults without dementia. However, the positive effect to cognitive function was not evident after dementia onset, although physical activity benefited functional abilities. Several barriers and facilitators for engaging in winter physical activity were identified for people with dementia, which should be kept in mind for future dementia interventions utilizing physical activity. Flexible options may be needed to accommodate the diverse preferences, abilities, and resources of people with dementia and care partners.
The Effect of Acute Intermittent Hypercapnia and Exercise on Ventilatory Chemosensitivity and Cardiovascular Function
(University of Waterloo, 2025-05-27) Rynne, Paige
Ventilatory long-term facilitation (vLTF) is a form of respiratory plasticity triggered by intermittent hypoxia (IH) in the presence of CO2 (1,2,4,34). The manifestation of vLTF following intermittent hypercapnia (IHc) without concurrent hypoxia – particularly in combination with exercise- remains unclear. This study evaluated the physiological effects of IHc and moderate-intensity exercise on cardiovascular function and ventilatory control in the resting and exercising states. Twenty healthy participants (10F) completed a three-visit protocol, including two experimental exposures to either IHc (PETCO2 +5mmHg for 40s, intersped with 20s normocapnic normoxia) or continuous room air (control), each followed by an exercising and resting observational period (~45 minutes in total). At rest, the cardiovascular response to IHc was not found to be different from control. During exercise, heart rate (HR) increased following IHc and mean arterial pressure (MAP) significantly decreased (HR: +12bpm, p < 0.001; MAP: -8mmHg, p = 0.006), while both appeared stable in the time-matched control. Exercising peripheral hypercapnic chemosensitivity (PHC) appeared constant over time with IHc (+14 ± 25%), contradicting the significant decrease observed with control (-8 ± 20%, p = 0.017). While ventilation (V̇E) increased across both states following IHc relative to control, only resting V̇E was disproportionate to metabolic demand, as reflected by a lower %ΔV̇E/%ΔV̇CO2 ratio relative to control. These findings suggest the presence of exercise with IHc may have a modulatory role in the development or expression of cardiorespiratory plasticity, as well as implicating sensory long-term facilitation (LTF) as a contributor to vLTF. Finally, a progressive amplification in V̇E over the course of IHc, independent of CO2 stimulus intensity, is consistent with early-stage chemosensory gain. Collectively, these findings demonstrate that IHc without hypoxia can elicit key indicators of vLTF.
Dual energy CT for more accurate diagnosis and monitoring of early osteoarthritis-related shoulder injuries
(University of Waterloo, 2025-05-08) Quayyum, Sarah
The rapid acceleration of population aging has led to a growing prevalence of age-related musculoskeletal (MSK) conditions, such as osteoarthritis (OA). Dual-energy computed tomography (DECT) is an advanced imaging modality that shows promise in enhancing the diagnosis and characterization of MSK disorders by providing improved visualization of joint and tissue changes after injury. These advancements may support more effective treatment planning and better patient outcomes. The primary aim of this study was to refine input parameters used in DECT imaging and apply them to better understand the relationship between shoulder injury and early osteoarthritic changes over a six month period. This knowledge is expected to improve therapeutic outcomes and support early screening for individuals at high risk of developing OA. DECT was employed to quantify volumetric bone mineral density (vBMD) and to model bone stiffness and loading using finite element modeling (FEM) in both cadaveric specimens and participants. Three anatomical regions of the proximal humerus were assessed: the humeral shaft diaphysis, the articular surface of the humerus (humeral head), and the anatomical neck. Cadaveric scans were performed using both dipotassium phosphate (K2HPO4) and hydroxyapatite (HA) calibration phantoms while participants were scanned using only the HA phantom. Imaging was conducted using both BONE and Standard (STD) reconstruction kernels at three energy pair combinations: 40/90, 90/140, and 40/140 keV. These combinations were chosen to evaluate whether higher energy pairs could help mitigate attenuation issues commonly encountered at lower energy pair combinations. The BONE kernel was selected for its superior bone edge sharpening and contrast, whereas the STD kernel was used to enhance visualization of surrounding soft tissues. Participant imaging occurred at baseline (within six weeks of injury) and again at six-month follow-up. Results of this study demonstrated that both vBMD and FEM-derived stiffness values were significantly higher in the diaphysis when scanned using the BONE kernel at the highest energy pair combination (90/140 keV). In contrast, the anatomical neck consistently showed the lowest vBMD and stiffness values, with no significant differences in vBMD or FEM-derived stiffness values observed within the anatomical neck or humeral head regions under the same parameters. By developing patient-specific, image-based computational models, this study contributes to a deeper understanding of both biomechanical and imaging characteristics of early shoulder OA, potentially informing future diagnostic and therapeutic strategies.
Evaluation of Visual Function, Eye-Hand Coordination and Motor Ability in Typically Developing Children
(University of Waterloo, 2025-01-24) McKee, Elena; Niechwiej-Szwedo, Ewa
Many aspects of a child’s development contribute to thriving in everyday activities. For example, motor ability and visual function play a crucial role impacting social, physical and emotional development. While it is expected that better visual function would be associated with better motor performance, this association has not been directly assessed in school-aged, typically developing children. Thus, this study aims to characterize the visual function, motor ability, and hand-eye coordination in a typically developing cohort of children and to determine if there is any association between measures of visual function and motor performance. A cohort of 35 children aged 7-14 years (9.7 SD 2.1 years, 19 males) were tested during a one-time visit which included three standardized clinical tests, an assessment of vision and binocular function, and an experimental hand-eye coordination task. The clinical tests consisted of the Movement Assessment Battery for Children (MABC-2) to assess overall motor development with subtests including fine and gross motor skills, the Beery Butkenica Developmental Test of Visual-Motor Integration (Beery-VMI) to assess visuomotor integration, and the Test of Word Reading Efficiency – 2nd Edition (TOWRE-2) to assess reading and pronunciation ability. The optometric assessment included visual acuity, stereoacuity, fixation disparity, phoria, fusional vergence, vergence facility, accommodative facility, and amplitude of accommodation. Eye-hand coordination was assessed using eye tracking and hand motion tracking while children performed a bead threading task. Results from the optometric tests fell within expected ranges with the exception of vergence facility (13.5 SD 3.9) and binocular accommodative facility (9.2 SD 3.1). Performance on the TOWRE-2 subtests and the Beery-VMI aligned with the expected norms as well. The overall score for the MABC-2 was within the expected range (8.9 SD 2.1), however the manual dexterity subtest fell below the expected range (7.8 SD 2.8). A correlation analysis was performed revealing a relationship between the total MABC-2 score and vergence facility (ρ = -0.38, p = 0.04, 95% CI -0.65, -0.02) as well as accommodative facility (r = -0.48, p = 0.007, 95% CI -0.71, -0.05). The MABC-2 manual dexterity subtest score was associated with accommodative facility (r = -0.38 p = 0.037, 95% CI -0.71, -0.05). In addition, the amplitude of accommodation was associated with three kinematic measures from the bead threading task: the grasping interval (ρ = 0.63, p = <.001, 95% CI 0.35, 0.81), bead threading interval (ρ = 0.38, p = 0.041, 95% CI 0.02, 0.65), and total movement time (ρ = 0.42, p = 0.021, 95% CI 0.07, 0.67). The findings from this study provide preliminary information about visual and motor function measures obtained from the same cohort of typically developing children. In contrast to the hypothesis, a negative moderate association was found between the MABC scores and accommodative and vergence facility. Similarly, the association between accommodation amplitude and bead threading task measures was in the opposite direction to the hypothesis. A larger study is necessary to determine whether the associations found in this small cohort are reliable. An important contribution of this study is the creation of a normative database that includes both the visual and motor scores. These normative values will be used when comparing the performance of children with a coordination disorder in a subsequent study.
The influence of sex and the human serum environment on fuel storage, skeletal muscle metabolism, and insulin sensitivity
(University of Waterloo, 2025-01-23) Wilkinson, Jennifer; Devries-Aboud, Michaela
Type 2 diabetes (T2D) is a growing global health concern with notable sex-based differences in its pathology. Despite having lower muscle mass and greater fat mass, pre-menopausal females are more insulin sensitive and have a lower prevalence of T2D than males. These discrepancies may be the result of incomplete understanding of the molecular mechanisms underlying glycemic control, insulin resistance and the relationship between sex and insulin sensitivity. As skeletal muscle is the predominate tissue responsible for peripheral insulin sensitivity, the overall purpose of this thesis was to delineate the contribution of sex on factors that affect skeletal muscle insulin sensitivity. The primary aims of this thesis were to determine if 1) sex differences existed in mitochondrial or lipid storage characteristics in aerobically matched participants, 2) sex hormones correlate with metabolic changes in skeletal muscle, and 3) the human serum environment influences proteins associated with metabolism and insulin signaling in mouse skeletal muscle cells (C2C12). In study 1 and 2, muscle biopsies were taken for the determination of mitochondrial and intramyocellular (IMCL) content using electron microscopy and content and activity of proteins related to mitochondrial function and lipid metabolism using western blot and activity assays. Both mitochondrial and IMCL storage characteristics were similar between females and males. However, females have a greater number of mitochondria interacting with IMCL in the subsarcolemmal region (SS) of muscle (p=0.05). For studies 3, 4, and 5, blood was collected from females in the follicular phase and luteal phase of the menstrual cycle and males. Samples were analyzed for estradiol, progesterone, testosterone, insulin, and glucose using commercially available assays. Differentiated C2C12 cells were incubated in 2% human serum for 24 hours and mRNA expression (RT-qPCR), glucose uptake (2-NBDG assay), and protein expression and activation (WB) were measured. We determined that human serum altered mRNA expression, such that estrogen receptor alpha (ERα) expression correlated with estradiol in male serum (Pearson’s r=0.64, p=0.05), but not in female follicular or female luteal serum in C2C12 cells relative to cells incubated with horse serum. Myosin heavy chain I (MHCI) gene expression correlated with estradiol in female follicular (Pearson’s r=0.71, p=0.05) and male serums (Pearson’s r=0.67, p=0.02), but not in female luteal serum in C2C12 cells. Interestingly, the ratio between testosterone and estradiol was positively correlated with ERα gene expression in female follicular serum (Pearson’s r=0.82, p=0.03), but not in female luteal or male serums in C2C12 cells. Further, in C2C12 cells, the activation of protein kinase B (AKT) sans insulin was greater following treatment with female luteal serum than males (p=0.02), but not than female follicular serum, with no difference between female follicular compared to male serums despite similarities in fasting insulin concentrations. Similarly, in C2C12 cells, the activation of phosphatase and tensin homolog (PTEN) without insulin stimulation was lower with female luteal serum when compared to female follicular serum (p=0.05), but not when compared with male serum, with no difference between female follicular and male serum. Finally, glucose uptake with insulin stimulation was increased in female follicular serum (p=0.006), but not in C2C12 cells treated with female luteal or male serums. These findings suggest that insulin sensitivity of skeletal muscle is likely, at least in part, controlled by the hormonal environment in which it is surrounded. Overall, the findings of this thesis found that: 1) aerobically matched females and males have similar mitochondrial characteristics, 2) aerobically matched females and males have similar lipid storage characteristics, 3) sex hormone environment correlates with changes in mRNA, 4) human serum did influence the activation status of proteins associated with insulin-stimulated glucose uptake, and 5) human serum alters insulin-dependent glucose uptake in a similar pattern as seen in whole body trials. These findings provide new insights into the distinct roles of skeletal muscle morphology and serum composition in regulating insulin sensitivity, helping to clarify the interplay between sex, metabolism, and insulin resistance.
Understanding the Importance of Fear of Movement on Physical Activity and Physical Function in People with Knee Osteoarthritis
(University of Waterloo, 2025-01-16) Liu, Huaning; Maly, Monica
Pain is the main reason why people with knee osteoarthritis (KOA) consult a healthcare provider (Jackson et al., 2020). The benefits of physical activity (PA) for KOA symptoms, including pain, are clear (Verhagen et al., 2019). However, people with KOA face numerous barriers to exercise. For example, fear of movement (FOM) is highly prevalent in KOA (58% to 86%) (Aykut Selçuk & Karakorum, 2020; Gunn et al., 2017; Tan et al., 2022) and is associated with lower levels of PA. It is likely that FOM affects the relationships between pain intensity and PA, but it is currently unclear if FOM is a covariate, a mediator, or a moderator in this relationship. The purpose of this study was to investigate how FOM affects the relationship between pain intensity or pain sensitization with the weekly level of PA in a sample of KOA. Additionally, this study investigated how FOM affects the relationships between pain intensity, physical function, and muscle impairments (including walking speed and quadriceps muscle power) in a sample of KOA. Participants who met the clinical criteria for KOA set forth by the American College of Rheumatology were included. PA was measured using a commercial 3-axis accelerometer (wGT3X-BT, Actigraph, USA). Pain intensity was measured via a validated, self-report questionnaire, the pain subscale of the Knee Injury and Osteoarthritis Outcome Score (KOOS-Pain). Pressure-pain threshold was determined using an algometer (FPX 25, Wagner, USA). FOM was self-reported by participants on the Brief Fear of Movement Scale (BFMS). Walking speed was measured from the 6-minute walk test. Quadriceps muscle power was obtained with a commercial dynamometer (System 4, Biodex, USA). Multiple linear regression was used to test the relationships between PA and pain (pain intensity and pain sensitization in separate analyses), after adjusting for age and body mass index (BMI). Then, the regression model was repeated, adding FOM and its interactions with the covariates. Thirty-one participants completed this study. After adjusting for the covariates (age and BMI), pain was not associated with PA levels (pain intensity: R2 = 0.199, p = 0.107; pain sensitization: R2 = 0.233, p = 0.072). After adding the moderator variable FOM and its interactions, our results showed a significant moderation effect of the BMI x FOM interaction (pain intensity: p = 0.003; pain sensitization: p = 0.002) in explaining variance in PA. The covariates, pain, and FOM (moderator) explained variance in PA in people with KOA (pain intensity: R2 = 0.525, p = 0.009; pain sensitization: R2 = 0.567, p = 0.005). FOM did not significantly moderate the relationship between pain intensity with either walking speed nor quadriceps muscle power (p > 0.05). Our results have important clinical implications. Our results suggest that those with higher levels of FOM combined with higher levels of BMI are less physically active compared to their counterparts. Rehabilitation clinicians should provide education on the benefits of PA and exercise in all people with KOA, but especially to those with higher BMI and higher FOM levels. Additionally, clinicians should use simple self-report tools such as the BFMS to screen for the level of FOM and provide additional education on safety of PA in KOA.
Advancing Clinical Gait Assessment Methods with Low-Cost Triaxial Accelerometers: Applications for Individuals with Neurodegenerative Diseases
(University of Waterloo, 2025-01-06) Cornish, Benjamin; McIlroy, William
Clinical gait assessment provides objective measurement of a person’s locomotor and dynamic balance control. Applications of wearable sensors for gait assessment have gained popularity over the past decade as a feasible tool to objectively measure gait in clinical settings. Commonly, clinical assessments and research studies limit a focus to steady-state walking relying on static thresholds to remove intra-bout phases, such as gait initiation and termination. Despite this historical focus on steady-state gait, the use of wearable technology affords the ability to provide insight into the variability of walking that occurs not only within (intra-stride) and between strides (stride-to-stride) but also variability of phases within a walking bout (intra-bout), measures that potentially have clinical importance. To achieve necessary details of intra-stride, stride-stride and intra-bout characteristics there continues to be a need to advance algorithm development to accurately detect gait characteristics specifically when applying across range of ages, task conditions, and gait control ability. The purpose of this thesis was to advance the analytical approaches of gait assessments performed in clinical environments with cost-effective wearable sensors in two meaningful ways: (1) advancing stride segmentation methods beyond standard stride or stance-swing segmentation using ankle-worn accelerometry and describe these metrics across tasks of varying difficulty, (2) identifying groups of strides that are representative of intra-bout phases and how these metrics change with task and understand their relation to gait-specific clinical metrics of mobility in older adults and neurodegenerative disease. Using accelerometry data collected as part of the Ontario Neurodegenerative Disease Research Initiative (ONDRI) allowed for the development of a Finite State Machine (FSM) algorithm to segment gait cycles into unique intra-stride phases. The FSM algorithm was tested for stride detection accuracy, across cognitively intact young adults and people living with neurodegenerative disease (NDD) or cerebrovascular disease (CbVD), and during walking with varying speeds and secondary cognitive tasks. Temporal and accelerometry-based kinematic outcomes from the algorithm were evaluated across dual-task walking conditions to identify compensatory gait strategies to secondary cognitive demands. These same FSM outcomes were used to quantify intra-bout phases using stride clustering approaches and examine how intra-bout phases and accelerometry-based kinematics might contribute to stride-to-stride variability within the dual task paradigm. In addition, the relationship between conventionally reported metrics, stride clustering outcomes, and gait-specific clinical markers was assessed to understand the interaction between mobility outcomes. In general, FSM stride detection performed well across tasks of varying difficulty and speed in young healthy adults during long treadmill walking and in people with NDD or CbVD during short overground walking tasks. Algorithm performance was also considered in the context of defining long periods of walking for implications in free-living environment; where depending on the parameters used to define a walking bout, the algorithm performance influenced the identification of the start and stop of walking. This approach to segment walking into stride-to-stride and intra-stride phases proves to be an accurate method using minimal data inputs with clinically feasible tools. Temporal and accelerometry-based kinematics (e.g., cycle time, accelerometer magnitudes) derived from the FSM methods were different between clinical walking tasks, such that cycle time gradually increased during dual task walking and across task difficulties and accelerometry kinematics decreased during dual task walking. Of particular interest was the significant differences between preferred walking tasks; the first preferred trial was typically different from the subsequent trials with the same conditions for conventionally reported and accelerometry based gait outcomes. In addition, when these outcomes were used to characterize intra-bout phases there were significant differences between preferred and dual task conditions across all cluster-based outcomes (e.g., initiation length). These outcomes suggest that the FSM can detect previously reported and novel kinematic outcomes to describe compensatory strategies selected by NDD and CbVD persons in response to secondary dual task walking. Clinically, these FSM or cluster-based outcomes can distinguish between groups that are stratified by commonly reported gait-specific markers of mobility, such as walking speed, dual task cost magnitude, or the Unified Parkinson’s Disease Rating Scale gait score. This work advances the detection of stepping with an adaptable algorithm that requires minimal data input, performs well across young and older adults including those with NDD, and can characterize compensatory strategies under dual task conditions. In addition to algorithm advancements, the present thesis expands stride clustering methodology to identify and characterize intra-bout phases across different dual-task conditions and understand how these representations of stride variability are related to clinical gait outcomes. Results from this study highlight the need to examine the contribution of intra-bout phases to gait variability and emphasizes the opportunity to expand our analytical approaches to gait assessment in and outside the clinic for optimal rehabilitative and therapeutic interventions.
Exploring Biomechanical and Metabolic Determinants of Lifting Movement Strategy
(University of Waterloo, 2024-12-11) Zhao, William; Fischer, Steven
Background: Poorly designed manual materials handling (MMH) work, such as lifting, lowering, pushing, pulling, and carrying, can increase the risk of developing musculoskeletal disorders (MSD). To ensure MMH work is safely designed, digital human models (DHMs) can be deployed. A DHM enables a designer to simulate and understand the interactions between a worker and the work in a virtual environment, without the risk or expense of physical prototyping. However, our current understanding of how humans select movement strategies during MMH tasks limits our ability to accurately predict human postures in digitally simulated MMH environments. To address this limitation in our current understanding, more fundamental research is needed to uncover how biomechanics and energetics influence movement strategies during MMH work. Optimal Feedback Control (OFC) theory provides a comprehensive framework for explaining why individuals choose specific movement strategies. OFC proposes that people move in ways optimized for task-specific and situation-specific performance criteria, such as minimizing low back moments or metabolic cost. Currently, we lack a thorough understanding of the relevant performance criteria for MMH tasks like lifting, lowering, pushing, pulling, or carrying. By leveraging optimal feedback control theory as a framework to uncover biologically relevant performance criteria, in the future we can improve our ability to predict and simulate MMH movements. Purpose: The study was designed to determine the effect task parameters including load mass and lift frequency and time (pre- and post-exploration) have on the biomechanical exposures and metabolic costs of lifting. A research paradigm designed to study optimal control of gait was adapted to investigate the biomechanical and metabolic determinants of lifting movement strategy. Methods: Using a repeated-measures experimental design, participants performed four 7-minute bouts of repetitive lifting in two different sessions, a high load low frequency (HLLF) session and a low load high frequency (LLHF) session. Within sessions, participants completed lifting bouts under 4-different technique conditions, where the first and fourth bouts allowed participants to self-select their technique (SS1, SS2) and the 2nd and 3rd bouts required lifters to adopt squat (SQ) or stoop (ST) techniques, respectively. High and low loads were defined as 15% and 5% of maximum voluntary lifting capacity in a semi-squat posture. High and low frequency were defined as 12 lifts per minute and 4 lifts per minute, respectively. Full body kinematics and VO2 consumption were collected during all trials. Using a whole-body top-down rigid link modeling approach, the peak sagittal L4/L5 moment was calculated. Two-way repeated measures ANOVAs tested for significant differences in biomechanical exposure and metabolic cost between the SS1 and SS2 lifting bouts. Results: The group mean peak sagittal L4/L5 moment was 211 ± 7 Nm in the HLLF condition, and 149 ± 2 Nm in the LLHF condition. This task condition main effect was significant (F = 91.89; p < 0.001) where the HLLF condition resulted in significantly greater peak sagittal L4/L5 moments (64.6 ± 6.74 Nm; p<0.001). However, no main effect of time (F = 1.22 ; p = 0.28) or interaction effect was found (F = 0.46 ; p = 0.50). Significant main effects of task (F = 30.06; p < 0.001), and time (F =5.54; p < 0.05) were found for mean VO2 consumption, but no interaction effect (F = 2.81 ; p = 0.10) was found. Post-hoc analysis revealed that the LLHF condition resulted in significantly greater VO2 consumption (4.69 ± 0.86 mL.kg.min; p < 0.001), and that the SS2 technique had significantly greater VO2 consumption (0.95 ± 0.403 mL.kg.min; p < 0.05). An increase in VO2 consumption in SS2 was unexpected, so a secondary analysis was conducted to explore movement specific adaptations characterized using the Squat Stoop Index (SqStI). The SqStI analysis revealed that the mean for the last ten lifts across all lifting bouts was on average 13% greater in the LLHF condition relative to the HLLF condition (i.e. closer to a stoop lift). However, the change in SqStI between the SS1 and SS2 lifting techniques was 0.4 within the HLLF condition, and 1.3 within the LLHF condition. Discussion: The magnitudes of the peak sagittal L4/L5 moments and relative VO2 consumption experienced by the participants were primarily affected by task parameters such as load mass and lifting frequency, which was expected by design. The biomechanical exposure and metabolic cost of participants did not significantly decrease following exploration of different lifting movement strategies. This was contrary to the hypothesis, where it was expected that VO2 consumption would decrease following exploration in the LLHF condition (i.e., learn to optimize for metabolic cost when the metabolic system is more challenged), and peak sagittal L4/L5 moments would decrease following exploration, but only in the HFLF condition (i.e., learn to optimize for biomechanical cost when the biomechanical system is more challenged). Instead, a significant increase in metabolic cost from SS1 to SS2 was observed across both task conditions. This could suggest a willingness to sustain a lifting movement strategy that increases metabolic cost over time in order to avoid increasing the biomechanical exposure experienced. Ultimately, participants were either unwilling or unable to significantly adapt their lifting movement strategy within the constraints of each task in order to reduce metabolic cost. A secondary analysis of lifting postures revealed that the initial and final preferred lifting movement strategy may have been modulated by the task parameters, where participants overall preferred a more stoop-like lift in the LLHF condition compared to the HLLF condition. In addition, it was seen that participants did not reach similar end ranges within the squat and stoop lifting bouts. Assuming that an SqStI value of 0% is a full squat lift, and an SqStI value of 100% is a full stoop lift, then participants were 31.6% away from a full squat but only 17.1% from a full stoop. This highlights a potential limiting factor of functional capacity, where participants may require additional relative strength, ankle range of motion, or aerobic fitness to explore a similar range of lifting movement strategies within the squat lift as compared to the stoop lift. Therefore, the results of this study did not support the hypothesis that an exploration of different lifting movement strategies would elicit movement strategy adaptation to optimize for certain task relevant performance criteria, however this may have been due to limiting factors such as the functional capacity of participants. However, the results of this study do demonstrate how varying task parameters can significantly modulate the biomechanics and energetics of occupational lifting, and thus the resulting preferred lifting technique. Although this study may not have uncovered how an individual’s optimal feedback control law may change during occupational lifting when exposed to different movement strategies, it does provide insight into how an individual’s preferred lifting movement strategy can be affected by the biomechanical and metabolic exposures experienced due to varying task parameters.
The Feasibility and Perceived Impact of the DEmentia Lifestyle Intervention for Getting Healthy Together (DELIGHT) Program for People Living with Dementia and their Care Partners
(University of Waterloo, 2024-10-30) Tupling, Olivia; Middleton, Laura
Improving supports to enhance quality of life for people living with dementia is a priority of research and practice. Multimodal lifestyle interventions that include components such as physical activity, nutrition, and social activity may help support quality of life and function for people living with dementia and their care partners. The DEmentia Lifestyle Intervention Program for Getting Healthy Together (DELIGHT) was co-designed by people with dementia, care partners, community stakeholders, and researchers with the goal of promoting ‘living well’ with dementia. The DELIGHT program incorporates exercise and shared learning on topics related to health and wellbeing (healthy eating, physical activity, social support, mental wellbeing, sleep). The aim here was to assess the feasibility and perceived impact of the 8-week in-person DELIGHT program. Feasibility was evaluated through recruitment rate (target: 6 per month), attendance (target: 75% of sessions), retention (target: 80% of participants who started the program complete post-program assessments), and program acceptability. Perceived impact and challenges and were also assessed through semi-structured interviews with participants, study leaders, and volunteers. Interview transcripts were analyzed using inductive thematic analysis to identify and describe experience with, and impact of, the DELIGHT program. A separate deductive content analysis was used to identify issues related to feasibility (challenges and recommendations). Exploratory effectiveness outcomes included quality of life, physical activity, balance confidence, exercise self-efficacy, nutrition risk, social connectedness, social isolation, balance, strength, and fitness. Quantitative and qualitative results were compared to support a richer interpretation of the programs impact on participants. Seventeen participants completed the DELIGHT program, recruited at an average of 4.25 participants/month, which was lower than our feasibility target. All participants completed the program with an average attendance of 89.7% and 16 (94%) completed post-program evaluation. All (100%) of participants (n=16) and volunteers/study personnel (n=7) described enjoying their participation in the DELIGHT program and reported that they would be interested in participating again. Four themes related to the impact of and satisfaction with the DELIGHT program were identified from interviews. Making the most of today for tomorrow describes the immediate and lasting emotional and physical benefits of the program and the empowerment participants felt over their health, inspiring lifestyle changes. These aligned with group average improvement on assessments of physical function and physical activity. Broadening perspectives and taking action describes how participants and volunteers challenged stigma, providing hope and inspiring action to continue the conversation. Connecting and caring describes the feelings of comfort and belonging among participants and volunteers, inspiring participants to engage and go outside their comfort zone. These aligned with the group average improvement of social connection and maintained low levels of loneliness. Learning together and sharing knowledge describes how participants and volunteers learned from each other’s unique knowledge and perspectives, and the paramount value of learning from experience. All themes generally suggest that DELIGHT supported participants in improving wellbeing however, quantitative measures of quality of life showed a decrease of one point in average scores. Results indicate DELIGHT is a feasible lifestyle intervention for people living with dementia and their care partners with promise for supporting wellbeing but more time may be required to recruit to the program. Further large-scale evaluation is warranted to examine the effectiveness of DELIGHT. In addition, adaptation of DELIGHT for specific ethno-cultural groups should be explored.
Understanding the Role of Mitochondrial Remodeling during Myogenesis, Postnatal Muscle Growth, and Disuse Atrophy
(University of Waterloo, 2024-09-23) Rahman, Fasih; Quadrilatero, Joe
Mitochondria are characterized as the chemical factory of cells. This organelle is fundamental to life and death, by generating chemical energy (i.e., ATP) and regulating cellular stress responses. Importantly, mitochondria have evolved elegant mechanisms to respond to numerous stressors/stimuli. These stressors/stimuli including metabolic and oxidative stress elicit differential responses at the mitochondria level, which is accompanied by a change in its structure and function. Collectively, the change in mitochondrial structure and function is termed mitochondrial remodeling. At the organelle level, the dynamic balance of mitochondrial morphology (i.e., fission/fusion balance) coupled with mitochondrial turnover (i.e., biogenesis and mitophagy) is required for appropriate mitochondrial remodeling. These remodeling processes must occur in a controlled manner to prevent excessive activation of downstream mitochondrial apoptotic signaling events. Although the primary function of mitochondria is to produce energy; their behaviour and response to stressors/stimuli can vary between different tissues. This is particularly relevant in tissues with high metabolic demand, such as skeletal muscle. Within skeletal muscle, there are phenotypically distinct myofibers (e.g., slow-twitch and fast-twitch), and within each myofiber, there are distinct pools of mitochondria (e.g., subsarcolemmal and intermyofibrillar). Given the uniqueness and complexity of skeletal muscle mitochondria, there are several unknowns with respect to mitochondrial remodeling in skeletal muscle. Therefore, the studies in this thesis were designed to better understand mitochondrial remodeling during three important stages: skeletal muscle formation (myogenesis), postnatal muscle growth, and disuse muscle atrophy. Chapter 1 provides a literature review of mitochondria, mitochondrial quality control, skeletal muscle mitochondria and mitochondrial remodeling during myogenesis, postnatal muscle growth, and disuse atrophy. Chapter 2 is focused on understanding the interaction between mitochondrial dynamics and turnover during myogenesis in vitro. Enhancing mitochondrial fission increased mitochondrial network fragmentation and mitophagic flux during myogenic differentiation of C2C12 cells, resulting in smaller myotubes without impairing the myogenesis. Despite these morphological changes, higher fission did not affect the levels of mitochondrial turnover proteins. In contrast, greater mitochondrial fusion reduced mitophagic flux, significantly impairing myogenesis and increasing mitochondrial apoptotic signaling. Cells with hyperfused mitochondria also display diminished mitochondrial biogenesis and mitophagy signaling. Enhancing mitophagy in fission-deficient cells reduced mitochondrial apoptotic signaling and biogenesis signaling without impacting myogenesis. Finally, upregulation of mitochondrial biogenesis worsened myogenic defects in fission-deficient cells, independent of changes in mitophagy or mitochondrial protein levels. These findings demonstrate that optimal mitochondrial fission is crucial for regulating both mitophagy and biogenesis during myogenesis. Chapter 3 then explored the role of mitochondrial remodeling on postnatal skeletal muscle growth. RNA sequencing analyses identified several differentially expressed genes during postnatal development, including upregulation of metabolic genes and a downregulation of genes involved in cell growth and differentiation. In vivo experiments revealed significant increases in body mass, muscle mass, and myofiber cross-sectional area. Mitochondrial maturation during this period was evidenced by increased mitochondrial function, and elevated mitophagic flux, along with increased mitochondrial localization of autophagy and mitophagy proteins. Cellular signaling revealed an increase in anabolic signaling, which was accompanied by enhanced mitophagy and fusion signaling and a simultaneous decrease in mitochondrial biogenesis signaling. In skeletal muscle-specific autophagy-deficient mice, there were no changes in body or muscle mass, nor in mitochondrial function despite ablated mitophagic flux. These mice exhibited compensatory activation of alternative degradative enzymes, including mitochondrial apoptotic signaling and ubiquitin-proteasome signaling, suggesting a shift in degradative pathways to preserve muscle mass and function in young mice. These findings demonstrate that postnatal development is marked by increased mitochondrial activity and mitophagy. Furthermore, while constitutive autophagy deficiency abolishes mitophagic flux, it does not impair muscle growth in young mice. Chapter 4 examined the role of mitochondrial remodeling with an emphasis on mitophagy during disuse atrophy of mature skeletal muscle. RNA sequencing analyses reveal an upregulation of genes associated with protein degradation, particularly those linked to the ubiquitin-proteasome system and apoptosis, while downregulating genes involved in muscle development and mitochondrial components. Immobilization-induced muscle atrophy affected the large muscles of the hindlimb, with partial recovery following remobilization. Immobilization increased mitophagic flux, which remained elevated following remobilization, alongside a reduction in mitochondrial function. Mitochondrial translocation of mitophagy receptors were identified in immobilization and remobilization muscles. Immobilization also enhanced mitochondrial apoptotic signaling, with increased mitophagy and suppressed mitochondrial biogenesis signaling. Antioxidant during immobilization suppressed mitophagy flux but exacerbated atrophy in fast/glycolytic myofibers without significantly altering markers of mitochondrial remodeling or the localization of autophagy/mitophagy-related proteins. Autophagy inhibition during immobilization also led to atrophy in fast/glycolytic myofibers, inhibiting mitophagic flux without affecting mitochondrial tagging with mitophagy or apoptosis-related molecules. Together, these findings suggest that mitophagy protects against excessive atrophy is muscle due to immobilization. Finally, Chapter 5 integrates and summarizes the findings from all the studies and highlights the physiological implications. Overall, these insights suggest that targeted therapeutic strategies aimed at enhancing the coordination of mitochondrial remodeling processes could optimize skeletal muscle function. Such strategies would focus on stabilizing the balance between mitochondrial fission and fusion, ensuring efficient mitophagic clearance of damaged or dysfunctional mitochondria, and promoting mitochondrial biogenesis to maintain a healthy mitochondrial network in skeletal muscle cells and tissues.
Examining the effects of computer mouse sensitivity on upper extremity muscle activity and kinematics in video game players
(University of Waterloo, 2024-09-23) Russell-Bertucci, Kayla; Dickerson, Clark
Computer mice are a primary component of human-computer interfaces in both office and video game settings, with video game players adjusting their mouse sensitivity to optimize performance. Limited data exists on how mouse sensitivity affects muscle activity and kinematic during video gaming. Differing movement strategies are associated with changes in mouse sensitivity, as lower sensitivity requires larger mouse movements for the same cursor movements. Therefore, the purpose of this investigation was to assess mouse sensitivity’s effects on muscle activity, arm kinematics, while investigating skill level and game difficulty effects. Thirty-four participants, classified as experienced or casual players, played a rhythm-based target acquisition game called osu! (ppy Pty Ltd), while using a mouse set at three sensitivities. Mouse sensitivity was set at low (400 DPI), high (1600 DPI) and preferred (mean=921 DPI). Participants played 7 trials per mouse sensitivity; 3 with the closest accuracy were analyzed. Experienced participants completed both easy- and hard-difficulty beatmaps. Kinematics and EMG data from the right upper limb and torso were compared across mouse sensitivities and between participant skill level or game difficulty. Main effects of sensitivity revealed a consistent relationship in muscle activity levels, where muscle activation was 40+% higher in the upper trapezius, supraspinatus, infraspinatus, and extensor carpi ulnaris while using the mouse at a low sensitivity compared to high or preferred. Mean muscle activity was within ranges of 1-6 %MVC across sensitivities, while peaking up to 23 %MVC in extensor carpi ulnaris, which combined with long play times may result in signs of muscle fatigue (Jørgensen et al., 1987, Jonsson et al., 1978). Sensitivity effects in kinematics only emerged in wrist radial deviation across mouse sensitivities, with low sensitivity revealing 6° more wrist deviation than high sensitivity. Shoulder kinematics differed between skill groups, as experienced players demonstrated more shoulder abduction and internal rotation, with mean postures differing by 10° and 4°, respectively. Lastly, more difficult gameplay resulted in significantly higher muscle activation across most muscles. This thesis offers novel insights into how the effects of mouse sensitivity on muscle activity and posture, which can assist clinicians with further understanding potential causes of injury prevalence in computer mouse users.
Competing effects of arterial pressure and carbon dioxide on cerebrovascular regulation during exercise and orthostatic stress
(University of Waterloo, 2024-09-20) Hedge, Eric Thomas; Hughson, Richard
The human brain is highly sensitive to changes in cerebral blood flow. There are multiple integrated and redundant regulatory mechanisms acting simultaneously to ensure adequate cerebral perfusion and removal of waste products. However, the contribution of different cerebrovascular control mechanisms to the increase in cerebral blood flow during exercise or the reduction in flow during orthostatic stress are controversial, especially for the competing roles of arterial pressure and CO2. Therefore, the purpose of this thesis was to identify which regulatory factors play prominent roles in modulating cerebral blood flow during and following transitions in exercise intensity or posture change. This was accomplished through a series of experiments that evaluated cerebrovascular responses to moderate- and high-intensity interval exercise, bed rest, and orthostatic stress tests to pre-syncope. Through causal time-series modeling, it was identified that cerebral autoregulation effectively minimized the effects of exercise-induced increases in mean arterial pressure (MAP) on middle cerebral artery blood velocity (MCAv), and that changes in estimated arterial partial pressure of CO2 (PaCO2) largely dictated MCAv dynamics in response to step changes in work rate. These findings sharply contrast with recent attempts to characterize the increase in MCAv at the onset of exercise as a mono-exponential response. Sex-specific effects of MAP and end-tidal PCO2 on MCAv were identified while standing following two weeks of bed rest in post-menopausal women and similar-aged men, with reduced end-tidal PCO2 contributing to reductions in men and lower MAP contributing to reductions in women. Vertebral artery blood flow was also identified as an important factor potentially mediating cerebrovascular-respiratory interactions during orthostatic stress in the progression to syncope. Overall, the results of these experiments demonstrate important connections between the cerebral vasculature and respiratory control during exercise and orthostatic stress, enhancing our fundamental understanding of cerebrovascular control and the integrative cerebrovascular cascade leading to syncope.
Knee Kinematics and Kinetics During a Dynamic Balance Task and Gait in Those With and Without Generalized Joint Hypermobility
(University of Waterloo, 2024-09-19) Grad, Dalia; Maly, Monica
Symptomatic generalized joint hypermobility (GJH) is a life-long condition characterized by a predisposition to joint dislocations and subluxations, disturbed proprioception, chronic pain and fatigue, degenerative joint disease, and disability. Disease burden is amplified by delayed diagnosis which is, in part, due the current reliance on an invalidated diagnostic measure of symptomatic GJH, the Beighton Score. Biomechanics has the potential to improve the identification of GJH. While no patterns have emerged that appear specific to GJH in gait, stair climbing or vertical jumping, biomechanical characteristics of postural stability appear distinct in GJH. The overall purpose of this study was to test whether performance of a dynamic balance test, the modified Star Excursion Balance Test (mSEBT), on stable and unstable surfaces, distinguishes between GJH and non-GJH in age and sex matched adults. A secondary objective was to determine the associations of performance on dynamic balance tasks with (i) the current diagnostic criteria and (ii) a measure of disease impact. It was hypothesized that maximum reach distance (MRDcomp) and maximum knee flexion angle (MKAcomp) would be smaller, and centre of pressure total excursion (COPTEcomp), dynamic knee stiffness (DKS) would be greater in those with GJH versus those without GJH. It was also hypothesized that disease impact would share a stronger association with MRDcomp than the current diagnostic criteria. This cross-sectional study design compared two age (24.6 ±4.1 years) and sex (26 females, 2 males) matched, non-athlete groups with and without GJH. From the entire sample, one participant met the criteria for symptomatic GJH. Kinematic and kinetic data were captured synchronously with research-grade motion capture (Optotrak Certus, Northern Digital Inc., Waterloo, ON, CA) and an in-ground force plate (OR6-7, Advanced Mechanical Technologies Inc., Watertown, MA, USA). First, participants performed a dynamic balance task, the mSEBT, in three conditions: stable (no foam surface), unstable (foam surface) and stable and timed. Performance on the mSEBT was measured. MKAcomp and COPTEcomp were also measured during the mSEBT. Second, DKS was averaged over five gait trials at a standardized speed (1.0 m/s). A two-way mixed analysis of variance was used to model the main effects of group and condition on for MRDcomp and MKAcomp and COPTEcomp. A Mann-Whitney U test was used to compare DKS in the non-dominant leg of both groups. Two hierarchical multiple regressions were used to determine if there is an association between (i) the current diagnostic criteria and MRDcomp, (ii) disease impact and MRDcomp, with physical activity (International Physical Activity Questionnaire) as a covariate. No significant main effect was found between MRDcomp and group (p = 0.26), showing there was no difference between GJH and non-GJH groups in MRDcomp. No significant main effect was found between COPTEcomp and group (p = 0.99), showing there was no difference between GJH and non-GJH groups in COPTEcomp. No significant main effect was found in MKAcomp between groups (p = 0.45), showing there was no difference between the amount of maximum knee flexion between non-GJH and GJH groups during the mSEBT. No significant difference was found between GJH and non-GJH groups for DKS in the timed condition (p = 0.22). The regression models identified that the diagnostic criteria (Beighton Score) (R2 = 0.07; p = 0.90) and disease impact (Bristol Impact of Hypermobility Questionnaire) (R2 = 0.08; p = 0.95) were not associated with MRDcomp. The results of this study indicate performance on the mSEBT and DKS are not different in GJH than non-GJH groups in this sample of non-athlete university graduate and undergraduate students. Additionally, a measure of disease impact does not better associate with performance on the mSEBT than the current diagnostic criteria in this study’s sample. Strengths of study include using a combination of novel clinical and biomechanical methods and measures in those with GJH. Future work on the clinical use of the mSEBT and DKS may consider recruiting those with symptomatic GJH and/or older participants with GJH.
The relative contributions of different sensory afferent and corticocortical projections on the motor cortex during skilled motor behaviour
(University of Waterloo, 2024-09-18) Graham, Kylee; Meehan, Sean
The motor system is required to perform an endless number of movements. To do this, general motor plans are created for similar groups of movements that can be adjusted for specific iterations of each movement. To ensure that the motor plan is accurate to the specific iteration of the movement, sensory information from a variety of modalities is integrated into the plan via corticocortical connections to the motor cortex. Shorter sensorimotor loops will also project to various cortical areas involved in generating the motor plan to modulate this process with updated sensory afference. However, it is still unclear exactly how these circuits interact with each other during the planning and execution of skilled motor behaviour. The current study used two transcranial magnetic stimulation paradigms to investigate these interactions. Short-interval intracortical inhibition (SICI) probes the longer corticocortical loops, while short-latency afferent inhibition (SAI) probes the shorter sensory afferent circuits. Performing both techniques during a waveform tracking task involving a planning phase and movement execution phase, the current study could investigate interactions between corticocortical and sensory afferent projections during skilled motor behaviour. Twenty-three healthy individuals completed two sessions where SICI and SAI were quantified in the first dorsal interosseous muscle during a waveform tracking task. SICI was assessed using an unbalanced transcranial magnetic stimulus that induced a posterior-anterior current in the underlying tissue with a positive phase lasting 70 µs (PA70). SAI was assessed using a stimulus that induced a posterior-anterior current in the underlying tissue with a positive phase lasting 120 µs (PA120) or a stimulus that induced an anterior-posterior current in the underlying tissue with a positive phase lasting 30 µs (AP30). TMS stimuli were delivered at seven different time points during the task: one baseline time point where the waveform was hidden from participants, two planning time points (-0.5s and -0.25s from movement onset), a time point at the onset of the movement, and three time points during the movement (1s, 2s, 3s after movement onset). Results showed that the effect of the conditioning stimulus was stronger for SICI than SAI across each of the time points during the task. We also found that the magnitude of difference in the weighting of SICI and SAI changed across the time point. These findings suggest that a variety of sensorimotor loops converge on the corticospinal neuron in the primary motor cortex to shape motor output. The corticocortical connections probed by SICI play a dominant role consistent with setting the initial motor plan. In contrast, the sensory afferent projections probed by SAI play a modulatory role updating the initial plan to reflect current sensory states and providing feedback. The interactions between corticocortical and sensory afferent circuits are important for healthy motor control and explain how the motor system is able to perform a seemingly endless number of movements.
Attentional effects on visual-tactile crossmodal enhancement at early stages of cortical processing
(University of Waterloo, 2024-09-12) Salazar, Esteban; Staines, Rich
Sensory processing can be facilitated through bimodal interactions between relevant visual-tactile sensory inputs in order to achieve goal-oriented behaviours. While the specific neural mechanisms contributing to this modulation remain unclear, the dorsolateral prefrontal cortex (DLPFC) may have a role in regulating the observed processing facilitation seen in the somatosensory cortex (S1), though the extent is not yet clear. We used electroencephalography (EEG) to observe the temporal contributions of visual priming to the enhancement of S1 responses. We hypothesized that inhibiting DLPFC cortical activity would result in a diminished facilitation of tactile processing in S1 (represented by the P50), observed by a visual-tactile stimuli onset with a 200-300 ms time delay. Somatosensory modulation was inferred through amplitude and latency shifts in tactile event-related potentials (ERPs) recorded while participants performed a sensory integration task that required scaled motor responses dependent on the amplitudes of tactile and visual stimuli. Tactile stimuli were discrete vibrations (25 Hz) presented to the left index finger, visual stimuli were presented as a central horizontal bar on a computer screen at varying heights, and graded motor responses were made by squeezing a pressure-sensitive rubber bulb. Healthy adults completed a training session to become familiar with the stimulus-response relationships for both visual and tactile stimuli prior to completing a task where pairs of discrete stimuli with random amplitudes were presented: Tactile-tactile (TT, 500 ms each, 30 ms ISI), visual-tactile with a 200-300 ms delay (vTd 200-300 ms), and visual-tactile with a 300-400 ms delay (vTd 300-400 ms). Stimuli pairs were administered in a block setting, where each block contained 60 trials, with 20 trials for each of the discrete stimuli presented in a randomized order. The study design consisted of 10 blocks, with a short transcranial magnetic stimulation (TMS) intervention at the halfway mark. Participants were randomly assigned to either an intervention group (n=16) or control group (n=16) where TMS modalities of theta burst stimulation (TBS); continuous TBS (cTBS) was given to the intervention group and intermittent TBS (iTBS) was given to the control group, both applied to the right DLPFC. Results revealed that P50 upregulation observed in condition vTd (200- 300 ms) is significantly lower following cTBS on the right DLPFC but still greater than unimodal TT stimulation. Following iTBS, bimodal facilitation was observed in condition vTd (300-400 ms) for P50 and N70. These findings improve our understanding of the role right DLPFC plays regarding crossmodal facilitation observed in visual-tactile processing.
SYMMETRY OF HIP, KNEE AND ANKLE JOINT POWER DURING CYCLING WITH AND WITHOUT PAIN FROM KNEE OSTEOARTHRITIS
(University of Waterloo, 2024-09-10) Currie, Daniel; Maly, Monica
Knee osteoarthritis (OA) is one of the most common chronic conditions in Canada (Bombardier et al., 2011). Commonly, the pain caused by knee OA is unequal between knees, which can lead to asymmetry of movement and joint power in daily activities. With hip and knee extensors generating the greatest proportion of power during cycling, it is unclear how the body will compensate if there is a painful knee (Elmer et al., 2011). The purpose of this study was to investigate if seat height, workload and, any difference in knee pain, affected asymmetry of power between hips, knees and ankles during cycling. Asymmetry was defined as the difference between the dominant versus non-dominant leg. It was hypothesized that bilateral joint power would become more symmetrical as seat height increased, workload decreased and any difference in knee pain decreased. Twenty-six participants aged 45-75 years, with and without knee OA completed six cycling bouts at three seat heights (20°, 30°, 40° minimum knee flexion angle) and two workloads (40W and 75W) on a commercial fit-bike (Pro 1, Purely Custom, USA). Self-reported knee pain on the Numeric Pain Rating Scale (NPRS) was recorded for each knee before the first bout and after each bout. Three-dimensional kinematics were collected with a commercial motion capture system (Optotrak Certus, NDI, Canada) and synchronized three-dimensional kinetics were collected with commercial instrumented 3-axis pedals (Science to Practice, Slovenia). Joint angles and power were calculated in Visual3D (HAS-Motion, Germantown, USA) for the full bout. From that full bout, a one-minute portion was selected. Then revolutions in that one-minute were averaged to one pedal cycle using custom Python code. Seat height and workload did not have a significant effect on symmetry of joint power. A significant relationship was found between hip, knee and ankle joint power difference and knee pain difference. The leg with the more painful knee produced less power than the opposite leg (p < 0.001, both workloads). Evaluating asymmetry for each joint revealed an interesting pattern. The more painful knee produced more joint power than the less painful knee (p = 0.003, 75W workload). The hip and ankle in the leg with the more painful knee produced less power than the contralateral joints (p < 0.001, both workloads). These results demonstrated the relationship between lower limb joint power and knee pain during cycling and in turn, how these joints could contribute power in the presence of knee pain. These findings are also relevant to rehabilitation clinicians, because they show rehabilitation could aim to boost the power produced by healthy joints to offload a symptomatic joint.
On the utility of a rotating swim bench as a freestyle swimming emulator
(University of Waterloo, 2024-08-30) Webster, Kathryn Frances; Dickerson, Clark
The swim bench is an isokinetic ergometer intended to aid competitive swimming training by replicating the underwater pull of the freestyle stroke. Yet limited literature addresses the biomechanical fidelity of the swim bench relative to in-water swimming (Olbrecht & Clarys, 1983; Piovezan et al., 2019). Further, the lack of body roll on the swim bench may limit simulation fidelity. Accordingly, the Kayak Pro SwimFast swim bench includes a rotating bench setting. Specific changes to a competitive swimmer’s kinematics and muscle activation patterns with a rotating setting is unknown. The purposes of this study were assessment of the influences of swim bench settings on kinematics and muscle recruitment, and exploration of the similarity of kinematic data between swim bench and in-water data sets. Fifteen collegiate and/or national level, male, competitive swimmers completed 8 sets (4 rotating and 4 fixed) of 30 second continuous freestyle stroke pulling on a Kayak Pro SwimFast swim bench. Surface electromyography of 12 right upper limb muscles and bilateral upper limb and torso kinematics were collected. Time-series swim bench kinematic and electromyographic data were compared using statistical parametric mapping, enabling holistic evaluation. The swim bench kinematics were compared to existing in-water data from McCabe (2008). Few kinematic and electromyographic differences existed between the rotating and fixed swim bench settings. Briefly, left shoulder elevation was higher on the rotating swim bench setting nearing the end of the push leading into the recovery phases of the freestyle swimming stroke (p = 0.08). The left shoulder axial rotation approached significance at during the push phase, with a higher internal rotation angle on the rotating setting. Right wrist radial deviation was greater on the fixed setting during the recovery phase (p = 0.024). Infraspinatus achieved greater activations on the fixed bench than the rotating during the late pull to early push phases (p = 0.012). Despite the device’s roll design, no differences existed in shoulder roll between the rotating or fixed setting and, regardless of bench setting, participants laterally flexed the torso, potentially as compensation for the overall lack of roll allowance. The similarities between settings indicated that the rotating setting may not substantially augment the realism of stroke mechanics on the swim bench. Compared to in-water swimming, the swim bench produced similar elbow flexion angles and maximum vertical depth at the third distal phalanx. However, entry phase duration phase decreased on the swim bench, while the pull, push, and recovery phases increased (p < 0.0001). Additionally, the stroke length, mediolateral stroke width range, and vertical stroke depth range, and total shoulder roll decreased (p = 0.0002, p < 0.0001, p < 0.0001, p < 0.0001). The differences between the stroke mechanics, lack of entry phase, and addition of the lateral torso flexion on the swim bench are notable considerations for swim bench use in training and research. Swimmers could develop associated habits that reduce swimming economy, and the results suggest that using the swim bench in training may not extrapolate to in-water swimming.

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