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 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.
Sex Differences in the Physiological Response to the Modern Fire Environment
(University of Waterloo, 2024-08-30) Pulford-Thorpe, Alexis; Devries-Aboud, Michaela
Due to recent changes in building design and materials, modern structural fires tend towards a ‘ventilation-limited’ fire environment, resulting in globally low levels of oxygen (O2) and increased amounts of carbon monoxide (CO) and smoke. It is unknown how the dynamic hypoxic and hypercapnic environment as a result of the fire impacts an occupant’s physiological and cognitive ability to evacuate. Moreover, it is unknown if physiological sex differences in males and females may further impact egress abilities. This work explored the effects of this dynamic hypoxic and hypercapnic environment on the ability to egress by exposing males and females to sub-incapacitating levels of hypoxic and hypercapnic gases measured in large-scale ventilation-limited fires. Thirty participants (n=15 females) completed three testing days. Day 1 was a familiarization day, intended for participants to familiarize themselves with the experimental protocol of the egress scenario in ambient conditions. Day 2 consisted of five trials of the simulated evacuation scenario wherein real-time changes to O2 and CO2 were administered with CO saturations (%COHb) of 4% and 7%. Day 3 consisted of four trials of the simulated egress scenario wherein changes to O2 and CO2 were carried out in tandem and in isolation. The egress scenario consisted of the following 12.5 minute sequence: 1 min seated pre-test baseline, 5 mins seated, 3.5 mins walking, 4 mins walking carrying a 20lb weight and 2.5 mins seated post-test baseline. This scenario was intended to simulate a realistic evacuation of an occupant from a residential structure, however did not include the more dangerous fire elements (increased temperature, smoke and particulate matter). End-tidal gases, ventilation, heart rate and oxygen saturation were measured continuously. Response (decision, answer and reaction) time was assessed by participants answering a prompt every 15s throughout each trial. The prompts consisted of a directional EXIT sign in which participants had to select the arrow corresponding to the direction of the EXIT sign, as well as a modified Stroop Colour Test. Results demonstrate that females elicited a greater percent change within a condition compared to males for heart rate (p=0.04), tidal volume (p=0.03) and fraction of hemoglobin bound to oxygen (p=0.02). Physiological changes in responses for all participants were significantly greater during the hypercapnia egressing trials compared to hypoxia and control trials (Ventilation: 72±20 L/min, 34±8.9 L/min, 33±6.4 L/min, p< 0.05; tidal volume: 2.3±0.6L, 1.5±0.4, 1.4±0.3, p <0.05). Physiological responses during 4% COHb and 7% COHb trials did not differ other than the fraction of hemoglobin bound to oxygen during pre and post baselines (p<0.05). Overall, the presence of CO2 resulted in the greatest physiological response and coincided with a decrement in ability to complete the egress protocol. Smaller females appeared to be more affected by fire conditions during egress than males. These results indicate that the modern ventilation-limited fire environment results in physiological responses that could negatively impact an occupant’s ability to effectively evacuate.
Effects of posture and trunk muscle coordination on multi-joint isometric lifting strength: Implications for individualised movement assessment and intervention
(University of Waterloo, 2024-08-30) Pinto, Brendan Luke; Callaghan, Jack
The manner in which movement is executed can influence biomechanical demand and consequently the development of musculoskeletal disorders. Although modifying movement execution can help regulate biomechanical demand by influencing tissue loading and tolerance, it can also influence physical performance by influencing the ability to exert force. Movement-based interventions to regulate biomechanical demand that hinder physical performance can limit acceptability, sustainability, and effectiveness of the intervention. Conversely, interventions to enhance physical performance that modify movement execution in a way that imposes higher than necessary biomechanical demand, can hinder physical development and long-term performance. However, the development of comprehensive movement assessments and interventions that consider both the impact on biomechanical demand as well as physical performance is challenged by a scarcity of knowledge of how movement execution can influence physical performance in multi-joint tasks. The global aim of this thesis was to investigate how modifying posture and trunk muscle coordination can influence the ability to exert force during isometric lifting. Four studies were conducted to address the global thesis aim. Study 1 investigated the effects of modifying trunk inclination and low back curvature on isometric lifting strength as previous research has yet to clearly dissociate how these distinct postural characteristics could influence the ability to exert force in multi-joint tasks such as lifting from the ground. Results showed that modifying trunk inclination and low back curvature can influence strength in multi-joint tasks substantially and to a similar extent. However, the effect of modifying these postural characteristics interact and vary greatly across individuals in magnitude (up to 620N of isometric lifting force) and direction (increase/decrease). Thus, a single postural profile cannot be generalized as the strongest for every individual and the ability to exert force in multi-joint tasks cannot be inferred solely from posture. Additionally, the individually varying effects of posture on strength suggests that individuals can adapt through movement training to be stronger in postures that are favourable for tissue loading and tolerance. Assessing the L4/L5 joint contact forces of the observed postures suggested that the effect of posture on biomechanical loading is more consistent, and the biomechanical demand imposed by flexing the low back outweighs any potential acute gain in isometric lifting strength. Together this supports the recommendation to avoid highly flexed low back postures during demanding physical activities. Study 2 compared the immediate effects of a simple verbal directive and detailed trunk muscle bracing coaching on isometric lifting strength, low back postural displacement and trunk muscle co-contraction. Prior research has suggested that cueing co-contraction of all the trunk muscles can enhance the ability to exert force in multi-joint tasks but has not yet isolated the effect of modifying trunk muscle coordination on the ability to exert force which may potentially depend on the approach used to cue trunk muscle coordination. Detailed coaching which included a combination of verbal and physical cues was more effective than the simple verbal directive at increasing trunk muscle co-contraction (group mean co-contraction for the baseline, directive and coached condition was 10.1%, 11.0% and 13.5% respectively) and decreasing low back postural displacement (group mean change in low back flexion angle normalized to each individual’s maximum flexion range-of-motion for the baseline, directive and coached condition was 21.4%, 19.5% and 17.2% respectively). However, both cueing approaches immediately reduced isometric lifting strength to a similar extent (group mean peak isometric lifting force for the baseline, directive and coached condition was 1194 N, 1109 N and 1096 N respectively). Results indicate that detailed coaching is more effective than simple verbal directives at modifying trunk muscle coordination to restrict low back postural displacement but cautions cueing trunk muscle coordination for the first time in situations where peak force production is desired. Results also suggest that future research should confirm acquisition and transfer of the targeted trunk muscle coordination patterns as the full potential impact of modifying trunk muscle coordination may not be completely apparent from observing the immediate responses to cues. Motivated by the individually varying effects of posture on the ability to exert force observed in Study 1, Study 3 evaluated the extent to which proxies for leverage derived from kinematic quantities can statistically explain the individual variation in the effects of posture on the ability to exert isometric lifting force. Prior research has used kinematic-based proxies to describe and make inferences about how posture can influence leverage in multi-joint tasks. However, these approaches do not capture all the mechanics involved in multi-joint kinetics and the extent to which they may explain the individually varying effects of posture on the ability to exert force in a multi-joint task has not yet been tested. As expected, based on fundamental biomechanical principles, the kinematic-based proxies for leverage that were investigated (joint-to-external force moment arms and predicted joint-angle-dependent torque-generating capacities) explained a very low proportion of variation (<17%) in the effects of posture on isometric lifting force. In contrast, variables derived from both kinematic and kinetic measurements such as the net joint reaction moments calculated using a rigid linked segment model and inverse dynamics explained a higher proportion of variation in the effects of posture on the ability to exert isometric lifting force (approximately 80%). These results indicate that simplified kinematic-based approaches cannot be used to assess the effects of posture on leverage in multi-joint tasks on an individual basis. Instead, variables derived from both kinematic and kinetic measurements such as the net joint reaction moments show promise for being used in development of quantitative assessments of multi-joint leverage. Study 4 investigated whether individuals maintain their potential for physical performance when given instruction to avoid rounding the low back during light mass lifting. Compared to prior movement-based interventions such as the squat lift technique that vaguely describes whole body posture, targeting a key postural feature such as low back flexion is theoretically expected to afford greater flexibility to self-organize the rest of the body linkage to regulate biomechanical demand, without hindering physical performance. However, using simple verbal directives to cue specific movement features during low demand tasks may not acutely prompt individuals to prioritize physical performance as they self-organize, rendering the intervention ineffective. Although aggregate group level results indicated that low back postural instruction targeting biomechanical demand decreased low back flexion during crate lifting and increased isometric lifting strength in postures replicating those exhibited during crate lifting, there was high heterogeneity in responses. Among the 37 of 40 participants classified as individuals who could potentially benefit from decreasing their low back flexion, 15 and 22 participants were respectively classified as successful and unsuccessful in decreasing low back flexion in response to the instruction, to be within a range that minimizes passive tissue strain. Though replicating the crate lifting posture to assess isometric strength emerged to be challenging, there were individuals who increased (n=8), decreased (n=9) and did not change (n=23) isometric strength, independent of their low back postural response. Hence, although most participants appeared to maintain physical performance potential when given simple verbal directives that target low back flexion to regulate biomechanical demand, some participants responded in a manner that decreased performance potential and many did not successfully decrease their low back flexion within a range that minimizes passive tissue strain. This suggests a need for more detailed movement coaching and training in research and practice to effectively modify movement behaviour without hindering physical performance potential. Overall, the results from this thesis indicate that the effects of modifying posture and trunk muscle coordination on the ability to exert force in multi-joint tasks is complex and can greatly vary across individuals. Additionally, modifying movement execution may need to go beyond simple verbal directives to provide detailed movement coaching. The findings support that considering the effects of movement execution on physical performance has the potential to advance movement assessment and intervention strategies. Yet, there is a need to develop approaches to capture the individually varying effects of movement features such as posture on the ability to exert force in multi-joint tasks to develop strategies that can effectively regulate biomechanical demand without hindering physical performance as well as enhance physical performance without imposing unnecessary biomechanical demands.
The Effects of Single- and Dual-Energy Quantitative Computed Tomography on Volumetric Bone Mineral Density Assessment and Strain Analysis in the Proximal Humerus
(University of Waterloo, 2024-08-30) Beshay, Daniel; Knowles, Nikolas
A common and difficult orthopedic injury, proximal humerus fractures frequently require surgery to restore functional shoulder motion. For optimal patient outcomes and to inform treatment choices, accurate evaluation of fracture stability and healing progress is essential. A thorough combination of the use of computational loads through finite element modeling (FEM) with innovative imaging methods to evaluate proximal humerus fractures was used to predict their fracture locations based on volumetric bone mineral density (vBMD). To quantify fracture characteristics, vBMD, and morphological changes related to proximal humerus fractures, 2 different imaging modalities were used. The effectiveness of single energy quantitative (SEQCT) and dual-energy quantitative computed tomography (DEQCT) was compared. BONE and STD reconstruction kernels, an algorithmic procedure, were parameters that were changed post-processing to alter the frequency content of images obtained from the SEQCT and DEQCT scanners. These imaging techniques enable a multidimensional study, giving rise to a deeper comprehension of fracture locations, bone quality, and provide preliminary steps to inform risk factors. To achieve this objective, fourteen cadaveric shoulders (n = 7 left, n = 7 right) were scanned under each scanning modality and post-processed into both BONE and STD reconstruction kernel, respectively. Four different images were created per shoulder scan: SEQCT BONE/STD and DEQCT BONE/STD, creating a total of 56 different possible images. Density in volumetric bone mineral density (vBMD) was calculated in the humeral head, metaphysis, and diaphysis regions, for each imaging modality. Image processing software was utilized to create 3D models of the humerus and highlighting the selected regions. Specimen-specific slope/intercept was used to convert from native Hounsfield Units (HU) to equivalent vBMD [mgK2HPO4/cm3]. Strain measurements were calculated using FEMs derived from each proximal humerus model and are reported as maximum and minimum principal strain through visual representations and histograms according to each region, showcasing differences in them between BONE and STD reconstruction kernel. BONE reconstruction kernel showcased higher values in both HU and vBMD measures than STD reconstruction kernel in SEQCT with significant differences seen respectively between reconstruction kernels in HU and vBMD (p < 0.05) in all three regions. Strong correlations (R2 = 0.99) between BONE and STD image-based density (HU and vBMD) by bone region (Humeral Head, Metaphysis, and Diaphysis) was observed in SEQCT. On the other hand, BONE reconstruction kernel vBMD was not higher than STD reconstruction kernel in all regions when looking at individual cadavers in DEQCT. Only the metaphysis showcased this whereas the diaphysis had four models that didn’t follow this trend and one model in the humeral head. vBMD differences arise from anatomical differences while scanning such either as a full torso or an isolated shoulder. Strong correlations (R2 = 0.99 & 0.98) between BONE and STD image-based density (vBMD) in the humeral head and metaphysis, respectively. The r-squared was lower in the diaphysis region (0.86). Fracture location predictions are possible from the FEM visual representation in both maximum/minimum principal strain with the aid of the figure showcasing strain levels in the three regions. These qualitative and respective quantitative data are cadaver dependent as each cadaver was influenced according to anatomical differences such as bone quality, comorbidities, age, patient activity levels and more. The FE models generated showcased that 7 out of the 7 models generated from SEQCT predict fracture location in the metaphysis region and 7 out of the 7 models generated from DEQCT also predict fracture location in the metaphysis region. As they clarify the significance of fracture morphology, bone quality, and loading circumstances on fracture location, the study's findings shed light on the relationship between imaging parameters and biomechanics of proximal humerus fractures. This research also seeks to assist physicians in choosing the best imaging approach for precise fracture characterization and treatment planning by comparing the performance of several imaging modalities. Ultimately, the combination of innovative imaging methods with finite element modeling can increase our ability to understand proximal humerus fractures by providing us knowledge on the optimal imaging modality, with the long-term objective of enabling better clinical outcomes for patients with these injuries through improved diagnostic and treatment options.
The Role of Low Back Capacities on Loaded and Unloaded Functional Movements: Squat and Lunge
(University of Waterloo, 2024-08-29) Zafar, Elizabeth; Callaghan, Jack
Variability of movement patterns across individuals have been well documented in healthy young adults. Large heterogeneity of movement patterns within seemingly homogenous populations suggests the possible presence of subgrouping of individuals. This variability makes it difficult to study and draw conclusions based on group effects, since group means may not be representative of individuals within the group, and especially when subgroups respond differently to interventions. It is also well established that certain movements and movement characteristics are relevant to movement efficiency, tissue exposure, and injury risk, however, it is not fully understood why individuals utilize certain movement patterns over others. It is plausible that physical capacity related differences between subgroups of individuals can help explain differences in movement. As such, this thesis aimed to cluster individuals according to their lumbar movement profiles during functional movements, and then relate characteristic profiles of each subgroup to the low back capacities of strength, muscular endurance, proprioception, and motor control. Additionally, this thesis investigated the effects of introducing a moderate challenge (i.e., loading) to the lumbar movement profiles during functional movements. Thirty-two healthy young adults (16 M, 16 F) performed two sets of ten repetitions each of squat (SQT) and lunge (LNG) in both unloaded (UL) and loaded (LD) conditions. Additionally, lumbar capacity tests of strength (S), endurance (E), joint position accuracy (P-A), joint position sensitivity (P-S), and motor control (MC) were assessed. State spaces of lumbar angle dynamics for each condition of movement were constructed, then discretized into 48 bins and averaged across repetitions. State spaces were then analyzed using spectral clustering with the number of subgroups selected based on the strongest silhouette score. Analyses of variance (ANOVAs) testing the effect of sex and group on each capacity test’s scores were conducted. The results of the clustering produced two groups with weak clustering strength in each condition. In both the SQT UL and SQT LD conditions, a significant interaction between sex and group in P-S (p = 0.01), and a significant effect of sex in E (p = 0.04)were found. In the LNG UL condition, a significant interaction between sex and group in P-A (p = 0.04), and a significant effect of sex in E (p = 0.04) were found. Significant interactions between group and sex were found in both P-S (p = 0.04) and MC (p = 0.03) for the LNG LD condition. Differences in lumbar capacities between groups were related to features of the state spaces, including shape, diffuseness, and intensity of attractors. This thesis highlighted the importance of physical capacities on movement patterns and affirmed the necessity of characterizing subgroups of individuals within a heterogeneous sample population. This thesis provides a framework for more comprehensive investigations into the relationships between specific capacities and movement profiles.

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