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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Now showing 1 - 14 of 14

Analysis of high and low physical functioning breast cancer survivors within two years of treatment
(University of Waterloo, 2017-08-29) Maciukiewicz, Jacquelyn; Dickerson, Clark
The five year survivorship rate of females diagnosed with breast cancer is 88% across Canada (Canadian Cancer Society, 2015). Often, treatments can cause damage to the tissue which may lead to impairment of upper limb function, specifically range of motion and strength. There have been several attempts to quantify these changes, but to inconclusive extents. This study investigated differences between breast cancer survivors with low and high self-reported physical functioning scores, differences between affected and unaffected limbs, as well as differences after 4 months of usual care. Ten female breast cancer survivors (between 3 months and 2 years post treatment) completed six maximal strength trials (flexion, extension, abduction, adduction, internal and external rotation) per limb and six maximal range of motion trials (flexion, extension, abduction, scapular plane abduction, and internal and external rotation), along with three questionnaires. Groups were split based on scores from the disability of arm, shoulder and hand (DASH) questionnaire. Maximal strength was compared for strength trials, and glenohumeral elevation was compared for range of motion trials. For both sets of trials, peak, median and static muscular activity was compared for high and low physical function scores as well as between affected and unaffected limbs. No differences were found between affected and unaffected limbs for either strength or range of motion. However, flexion, extension, abduction, and adduction strength were 32-52% higher in the group with higher self-reported physical functioning scores compared to the group with lower self-reported physical function scores. Correspondingly, internal rotation range of motion was 1.92 times higher in the group with higher physical function scores (effect size =1.98). The other five range of motion tasks (abduction, flexion, extension, scapular plane abduction and external rotation) were not statistically different between groups of high and low physical function scores but had moderate to large effect sizes (0.42-0.94). Several measures were correlated with DASH scores, indicating that increased strength and range of motion relate to self-reported physical functioning in breast cancer survivors. Between baseline and follow up, none of the six measured strengths changed, with only one of the six range of motion measures increased over the four month period. Extension range of motion increased by 112% during this period of usual care. Overall, this thesis provides insight into the period of time immediately following treatment. These variables had not been evaluated within the first two years of survivorship. Additionally, this work suggests breast cancer survivors are not a homogeneous group, and that function (range of motion and strength) differ. In previous literature, all outcomes are reported from one group and have been inconclusive. However this work shows that there may be a difference in survivors’ function. This can help refine future rehabilitation strategies as the deficits for these individuals can be quantified more accurately.
Breast cancer survivor functional changes immediately following treatment: quantifying mechanisms of strength deficits and compensatory kinematic and muscular strategy adaptations
(University of Waterloo, 2021-11-04) Maciukiewicz, Jacquelyn; Dickerson, Clark
Breast cancer is prevalent among Canadian women, but treatments may cause functional impairments among survivors. Over 22,000 Canadian women join the survivor population yearly (Brenner et al., 2020). Despite this substantial number, minimal research has approached the challenges faced by this population after primary treatment. Particularly, decreases in strength, range of motion and shoulder-related quality of life are widely reported (Harrington, Padua, Battaglini, & Michener, 2013; Lee, Kilbreath, Refshauge, Herbert, & Beith, 2008; Rietman et al., 2004). These factors, linked with changes in kinematics and muscular activation may result in further complications (Brookham, Cudlip, & Dickerson, 2018a, 2018b). Variability in previous studies, in both the population sampled and results make it difficult to isolate potential mechanism disrupting function. Further, this complicates the determination of key deficits to target in the early years of survivorship. Therefore, the purpose of this dissertation was to determine which factors affect breast cancer survivors in the first two years following the conclusion of treatment, if these factors translate to differences during low load functional tasks, and to investigate the feasibility of increasing strength (as a surrogate for function) to help mitigate these factors and increase function. Study 1 and 2 shared an in vivo experimental collection, with Study 3 using input from the collection in an in-silico approach. Briefly, 35 breast cancer survivors within two years since the conclusion of their treatment participated in the experiment. Participants completed a general questionnaire about their diagnosis, three shoulder-related quality of life questionnaires, and a Godin-Shephard leisure-time physical activity questionnaire, followed by a dual energy x-ray absorptiometry (DXA) scan. Eight muscles were monitored on the affected limb (pectoralis major (sternal and clavicular), deltoids (anterior, middle and posterior), infraspinatus, supraspinatus, and latissimus dorsi). Six maximal isometric strength trials were completed (flexion, extension, abduction, adduction, internal rotation and external rotation). Kinematics of the affected limb were collected for the remaining trials. These consisted of 6 maximal range of motion trials (flexion, extension, abduction, scapular abduction, internal rotation and external rotation), as well as 8 activities of daily living. Study 1 clustered participants into two distinct groups, the low score cluster (LSC) and high score cluster (HSC). The variance in treatment, force production, range of motion, body composition and shoulder-related quality of life is well documented in literature, however there is no distinguishing characteristics that separate survivors who may need rehabilitation following treatment. This study determined, through feature reduction, that internal rotation force production, active extension range of motion and 3 shoulder related quality of life variables (energy/fatigue, social functioning and pain) separated survivors within 2 years of treatment into two clusters (LSC and HSC). The LSC participants had higher self-reported disability, role limitations (health and emotion), fatigue, and lower self reported physical well-being, along with lower abduction, adduction, extension and flexion force production (p<0.001). Several other factors differed between groups (p<0.05); the HSC group had more lean mass of the affected arm, internal and external force production and active flexion range of motion. These factors highlight potentially important factors to address in a rehabilitation program, as survivors finish treatment, specifically that lower force production likely corresponds to lower self-reported shoulder-related quality of life. Study 2 contrasted the muscular activation and kinematics of the LSC and HSC during various activities of daily living. The selected low load functional tasks can indicate survivors’ ability to complete daily tasks and return to work. The LSC used lower range of angles, and increased muscular activation. Range of angles differed 6.5-16.1° across elevation angle, axial rotation and plane of elevation during the shelf reach, forward reach, pitcher pour and tray transfer tasks. Additionally, the LSC had 0.89-12.73% MVC more muscular activation than the HSC across all muscles and tasks. At least one muscle differed between groups during each of the 8 tasks investigated. Finally, study 3 simulated various treatment scenarios to find a maximal producible force and the internal muscle forces required to produce that force in a compromised system with an in-silico approach. Beginning with the force from the LSC, and increasing capacity of muscles based on given treatment scenarios (permanent damage of a subset of muscles from radiation, or overall reduction in capacity due to chemotherapy, or a combination of both), 70-80% of strength in adduction and internal rotation is recoverable if retraining of muscles can be achieved. Specifically, for adduction rhomboid (major and minor), upper trapezius, subscapularis (lower), and triceps (long), latissimus dorsi (upper and lower), pectoralis minor, middle deltoid, middle trapezius and biceps (short) increased during the various simulations to increase force output compared to the LSC group. During internal rotation, latissimus dorsi, rhomboid (major and minor), upper trapezius, posterior deltoid, subscapularis (middle and lower), triceps (long), pectoralis minor, middle deltoid, and middle trapezius estimation increased from the LSC group levels in each of the simulations. Although no scenario reached reference control population force levels, achieving 70-80% of force would be meaningful for enabling daily task performance, returning to work and enhancing physical self-efficacy. Taken together, these studies point towards novel strategies and valuable considerations in creating rehabilitation foci that enable improved arm function for breast cancer survivors.
A combined in vivo and in vitro approach to assess supraspinatus activation and tissue responses to arm elevation demands
(University of Waterloo, 2020-01-22) Cudlip, Alan Christian; Dickerson, Clark
Rotator cuff degeneration affects a large portion of the human population, yet knowledge surrounding which loading scenarios allow transition from healthy to diseased states remains largely unresolved. Mechanistic progression of rotator cuff pathology often originates in the supraspinatus before cascading to other tissues, leading to substantial degeneration. Posture, loading and repetitive motions are known risk factors that exacerbate shoulder injury progression. This suggests a causal relationship between specific upper extremity task scenarios and degenerative rotator cuff loading. This thesis intentionally explored regional activations of the supraspinatus and accompanying tendon loading across a range of postures. The global objective was to evaluate how postural and task intensity differences alter tissue-level mechanical parameters in both in vivo muscular activation and in vitro tangent stiffness, hysteresis and optical stretch ratios. These findings combine in vivo muscular activation and physiologically relevant in vitro mechanical testing results through novel methods to better understand supraspinatus loading. Three experimental studies provided the means to achieve this global objective. In Vivo Examination of Supraspinatus Activation: The purposes of this study were 1) to document the interplay of anterior and posterior supraspinatus activations and 2) to describe the influences of posture and hand loads on anterior and posterior supraspinatus activations. Forty participants completed arm elevations in seven planes of elevation with three hand loads that were normalized to the individual’s maximal elevation force. Indwelling electromyography was collected from the anterior and posterior regions of supraspinatus. Hand load and elevation angle interacted to affect the anterior region activation in most planes of elevation by up to 41% of maximal activation, but these changes were less influential for the posterior portion. Activation patterns between the two regions suggest different functional roles of the supraspinatus portions; consistent levels of activation in the posterior supraspinatus may indicate this region is primarily a glenohumeral stabilizer, while the larger anterior region acts to achieve glenohumeral motion. This work represents the most comprehensive concurrent evaluation of these supraspinatus regions over a large set of planes of elevation, hand loads and humeral elevations, providing more holistic descriptions of supraspinatus activation in a critical arm movement. Comparing Surface Electromyography of Supraspinatus to Anterior and Posterior Indwelling Recordings: The purpose of this study was to compare anterior and posterior supraspinatus indwelling electromyography responses to a surface supraspinatus signal across a range of arm postures in order to develop relationships between these two recording methods. Forty participants completed arm elevations with altering hand loads and planes of elevation at a fixed cadence. Indwelling electromyography of the anterior and posterior supraspinatus as well as a surface recording of supraspinatus were collected. Bivariate regressions of anterior and posterior indwelling electrodes relative to the bipolar surface electrodes were used to determine relationships between these signals throughout the range of these humeral elevations. Differences between these predictions were modulated by plane of elevation, elevation angle, load intensity and sex of the participant, but no interactions existed. Surface signals underestimated indwelling activation recordings at low elevation angles, then overestimated as humeral elevation angle increased. Surface recordings underestimated indwelling signals by up to 15% in unloaded conditions, while overestimating the posterior region by up to 17% at the highest hand load intensity. In addition, surface signals overestimated posterior supraspinatus indwelling activity by 21%. This work greatly expands current knowledge surrounding relationships between these indwelling and surface signals, both in the inclusion of the indwelling posterior supraspinatus recordings and the expansion of arm postures examined. These findings indicate that relationships between the surface and indwelling signals are altered by plane of elevation, load and elevation angle, and the surface signal more closely predicts anterior region activity. Examining Changes of In Vitro Supraspinatus Mechanical Properties in a Rat Model: The purposes of this study were 1) to complete in vitro mechanical tissue testing in scenarios emulative of empirical muscular activation and postural conditions in an animal model, and 2) to determine the relative influences of arm posture and external loading levels on tissue responses. Forty-eight shoulders harvested from Sprague-Dawley rats were affixed into custom 3D printed mounting pots and placed into one of eight testing groups combining glenohumeral posture and load magnitude. Orientations represented four different postures observed in vivo, and applied tensile load within the animal model was scaled from human activation of the two supraspinatus regions collected from in vivo research for 1500 cycles. A three-way interaction between elevation angle, load magnitude and cycle number occurred for tangent stiffness within specific cycles, with increasing angles, loads and cycles increasing stiffness by up to 49% in some scenarios; differences in maximum and minimum displacement indicated elevated tissue responses in higher elevation angles. Interactions between elevation angle, load intensity and cycle number altered stretch ratio characteristics, with increased elevation angles, loads and cycles increasing stretch ratios, as well as differentiating articular and bursal side responses. Complex interactions between angle, load and cycle number suggest higher abduction angles, increased load magnitude and subsequent cycles generated increased tendon response characteristics. Novel thesis contributions: Multiple novel findings and contributions originated from this work. This dissertation has combined in vivo and in vitro methodologies to advance understanding of rotator cuff mechanics. This dissertation supports the notion that supraspinatus loading varies throughout the range of motion, and postural and external load variations alter tissue-level supraspinatus responses. Activations of the anterior and posterior regions of the supraspinatus were collected from the largest collection of postures to date and described activation differences between these regions. These EMG activations were used to assist in determining applied force load levels for mechanical testing, representing the first known attempt to generate force-controlled tensile loading using physiologically derived exposure levels for the supraspinatus. This work is also the first to maintain a functional glenohumeral unit to complete mechanical testing using postures representative of those observed in vivo to examine supraspinatus responses. General conclusions: Posture and load magnitude have distinct and noteworthy effects on supraspinatus, both in muscular activation and tendon responses. This research combined in vivo muscular activation with in vitro mechanical tissue testing to generate novel findings for rotator cuff loading; further work should continue to pair in vivo responses with mechanical tendon loading to generate physiologically relevant research scenarios throughout the range of humeral postures. This work has established that the supraspinatus is sensitive to scenario conditions, but continued expansion of our understanding of exposure aspects would help diagnose or anticipate overexposure.
Comparing occupational musculoskeletal exposures during common materials handling tasks between non-obese and obese adults
(University of Waterloo, 2017-12-08) Liang, Carmen; Dickerson, Clark
Higher body mass is associated with increased risk of musculoskeletal injury, a greater number of insurance claims, and higher direct and indirect costs due to decreased productivity during manual materials handling. Over one billion adults are overweight and at least 400 million are obese worldwide. Obese individuals may experience higher musculoskeletal exposures during work performance due to excess body mass. With greater segmental masses and higher distance of these masses from joint centers of rotation, larger joint moments could be generated for obese persons in similar postures to non-obese persons. This consequently would make tasks that require farther reaches relatively more demanding for obese persons. It is crucial to assess this potentially vulnerable cohort to reduce risk of musculoskeletal injuries during manual materials handling (MMH) tasks, particularly as many current workspace designs are based on normal weight anthropometric charateristics. The purpose of this research was to determine differences in joint loading and modified motion patterns between non-obese (normal weight & overweight) and obese adults during common manual materials handling tasks. Thirty participants (15 male & 15 female) performed the following four manual materials handling tasks: load transfer (0.5kg, 1.5kg, 2.5kg), lift & lower (2.5kg, 5kg, 10kg), push (40N, 60N, 80N), and pull (40N, 60N, 80N). Upper extremity kinematics were collected during the four MMH tasks with 29 reflective markers. Joint kinematic profiles of amplitude probabilty distribution functions (APDF) were created for the low back, shoulder, and elbow, while joint moments of APDF were created for the low back, shoulder, elbow, and wrist. Isometric and maximal functional strength tests evaluated low back and shoulder strength. Worktables and handle heights were adjusted to each participant according to NIOSH and Liberty Mutual Table recommendations. Participants were categorized into two groups: those obese with BMI>30kg/m2 or non-obese with BMI≤30kg/m2. Body discomfort and exertion were recorded for each task combination. Statistical comparisons between the obese and non-obese individuals were performed for isometric and maximal functional strength tests, kinematic and kinetic profiles for APDFs. Results showed that obese individuals have higher absolute strength unless normalized to body mass, and they experiece higher moments at the low back and shoulder for specific task parameters. On average, obese individuals had greater absolute strength for isometric tests, low back flexion (495N), low back extension (453N), shoulder flexion (86N), shoulder internal rotation (128N), and for maximal functional strength tests push (216N) and down (148N) exertions. Absolute isometric joint and maximal functional strength had positve corrleations with increases in BMI. When strenght tests were normalized to body mass, there was a negative correlation with increase in BMI. Interactions between distance and groups during the 90th percentile level of exposures resulted in increases to low back resultant moments by 39% at the 30cm reach, 31% at 50cm, and 21% at 70cm reach during the load transfer task compared to the non-obese group. Lift combinations from knuckle to shoulder (KS) resulted in higher low back moments with hand loads of 2.5kg and 10kg by 20%, 5kg and 10kg increased by 29%, and 2.5kg and 5kg increased by 43% for obese participants. Height combinations of floor to shoulder (FS) resulted in higher low back moments with hand loads of 2.5kg and 5kg by 25%, 5kg and 10kg by 27%, and 2.5kg and 5kg by 46% for obese participants when compared to the non-obese group. Interactions between distance and groups for shoulder moments were higher at exposure levels of 90th percentile where height combination of FK, KS and FS were greater by 30%, 19%, and 21% respectively, for obese participants when compared to the non-obese group. Obese individuals experienced more exertion when executing the push and pull tasks, but did not exemplify significant differences from the non-obese groups. Future recommendations for manual materials handling tasks for obese individuals, particularly for the upper extremity during load transfer tasks, should consider closer work distances and lighter hand loads. This would minimize low back and shoulder moments as they were higher compared to non-obese individuals for all distance and load combinations. To minimize the amount of work performed, lifts requiring floor-to-shoulder heights should have lighter hand loads to minimize high exposures. Workspaces should allow individuals to move freely as movement compensations may occur to potentially avoid overload at certain joints or segments.
Compensatory movement simulation of subacromial impingement syndrome kinematics using an asymptomatic group for rehabilitative shoulder exercises
(University of Waterloo, 2021-01-27) Fournier, Daniel; Dickerson, Clark; McLachlin, Stewart
Rotator cuff tears are a common source of shoulder pain that requires conservative management or surgical intervention to heal and regain proper function. During both interventions, prescribed exercise programs are given to patients as they increase range of motion (ROM) and improve patient outcome scores. However, when tasked with completing exercises in the home, patient adherence usually decreases and is subjectively monitored by the patient themselves. Wearable sensor devices, such as smartwatches, demonstrate feasibility to objectively track shoulder exercise adherence using machine learning, but these algorithms require a broad range of training data in order to accurately classify exercise type. Further, to monitor shoulder exercise rehabilitation, sensor training data should include compensatory exercise performance associated with symptomatic individuals. However, capturing this movement data from a symptomatic population presents a number of challenges. To address this problem, the objective of this study was to determine if asymptomatic individuals can simulate compensatory movement cues associated with subacromial impingement during various rehabilitative shoulder exercises. Seventeen participants (10 asymptomatic and 7 symptomatic for subacromial impingement) performed twenty repetitions of six evidence-based shoulder exercises following standard and compensatory movement cues based on their group classification. Kinematics of the torso and upper limbs were collected to identify changes in maximum angle and ROM for torso, thoracohumeral and elbow joint angles. Time-series joint angle data were compared for the standard and compensatory conditions performed by the asymptomatic group using statistical parametric mapping (SPM). Symptomatic and asymptomatic (compensatory) were compared using maximum angle and ROM measures. Asymptomatic participants were successful in simulating compensatory movement cues based on changes in their time-series data. Differences occurred in the middle portion of the thoracohumeral elevation time-series profile during the flexion (p < 0.05), scaption (p < 0.05), and abduction (p < 0.05) exercises. Further, these simulated compensatory movements were similar to the movement patterns of some symptomatic participants. Overall, these results suggest that asymptomatic individuals can execute both standard and compensatory movement cues. The variability of the data collected represents a spectrum between worst-case compensatory and best-case proper movement for the six shoulder exercises performed. Further research is needed to better understand the range of symptomatic exercise performance in order to refine the movement cue instructions for asymptomatic individual performance. Data and findings from this work provide crucial groundwork towards the development of improved machine learning algorithms for sensor-based tracking of rehabilitative shoulder exercise program adherence and progression.
Dependency of shoulder muscle activation on simulated labral conditions during isometric and functional tasks
(University of Waterloo, 2023-08-14) Lam, Fergus; Dickerson, Clark
Glenohumeral (GH) joint stability depends on a combination of shoulder muscular action and the glenoid labrum. Labral injuries and degenerations can affect glenohumeral joint reaction forces and potentially modify shoulder muscular efforts. However, the relationship between shoulder labral condition and muscle demands lacked clarity as compensatory muscle strategies accompanying labral compromise were unidentified. Targeted analysis was required to determine each muscle’s activation, as traditional non-invasive biomechanical physical measurements could not readily assess the influence of labral damage. This study aimed to determine how simulated labral statuses influenced shoulder muscle activations using a customized mathematical biomechanical shoulder model. Secondarily, this study investigated potential links between observed variations in muscle recruitment and potential muscle overuse. Six isometric and six functional movement tasks kinematic data were collected using a passive 3D motion capture system to generate necessary geometric inputs for the musculoskeletal model from a single male participant. A total of 13 labral conditions were simulated for each isometric and functional movement task by altering the glenoid stability constraints within an existing computational shoulder model. The percentage of maximal predicted muscle group capability (%MMGC) of the rotator cuff (RC) muscles and glenohumeral articulating (GA) muscles and glenohumeral joint contact forces were predicted by the shoulder model to illustrate the potential responses from the shoulder (i.e., changes in muscle demand and the relationship of joint contact-shear force) to changes in the stability of the GH joint between simulated conditions. Task performance and potential for muscle fatigue were ranked and evaluated by comparing the changes in muscle group recruitment, the percentage changes in %MMGC and glenohumeral shear forces, and the directional changes in glenohumeral shear forces among simulated labral conditions. RC muscles showed a substantial increase in muscular activation level of 5%–41% in activities when engaging in more physically demanding tasks, such as isometric external rotation, isometric abduction and weight relief lifting, compared to the intact condition. These large increases particularly occurred in simulated conditions with no labrum and a degenerated labrum in older age groups (ages over 60). This illustrated the aging impacts on GH joint stability and muscle recruitment strategies. Further, the high RC muscle activity contributed to a decrease in joint shear forces by further stabilizing the GH joint through the compression mechanism which is consistent with reduced humeral translation. Simulated surgical repairs effectively lowered the activation level of muscle groups, and the level of muscle activation was further decreased by surgical bone augmentations, such as posterior bone blocks, which further stabilized the GH joint. This study provided insight into the muscle strategies that may arise to compensate for directional shoulder instabilities. This information can be used as a guideline for secondary injury prevention by identifying connections between tissue overload during certain tasks and previously reported potential shoulder pathologies. In conclusion, this study can help raise awareness and inform considerations relative to compromised labral management and mechanistic bases for functional capacity.
Development of a Probabilistic Chimpanzee Glenohumeral Model: Implications for Human Function
(University of Waterloo, 2018-08-17) MacLean, Kathleen; Dickerson, Clark
Modern human shoulder function is affected by the evolutionary adaptations that have occurred to ensure survival and prosperity of the species. Robust examination of behavioral shoulder performance and injury risk can be holistically improved through an interdisciplinary approach that integrates anthropology and biomechanics. Anthropological research methods have attempted to resolve gaps in human shoulder evolution, while biomechanics research has attempted to explain the musculoskeletal function of the modern human shoulder. Coordination of these two fields can allow different perspectives to contribute to a more complete interpretation of, not only how the modern human shoulder is susceptible to specific injuries, but also why. How the modern human shoulder arose from a, likely, weight-bearing, arboreal past to its modern form, and what this has meant for modern behaviors, is not well understood. Despite a weight-bearing, locomotor ancestral usage, the modern human upper extremity is highly fatigable in repetitive, low to moderate force tasks, such as overhead reaching. The closest living human relative, modern chimpanzees, has retained an arboreal, locomotor upper extremity. Interdisciplinary comparative research on humans and chimpanzees could lead to greater insight on modern human shoulder function. The purpose of this research was to explore the modern human capacity for ancestral, brachiating behaviors and resultant injury mechanisms through comparative experimental, computational modeling and probabilistic modeling approaches with chimpanzees. The first study experimentally explored the modern human ability to perform a horizontal bimanual arm-suspensory climbing task. EMG of 12 upper extremity muscles and motion capture of the arm and thorax were monitored in experienced and inexperienced climbers. Results were also compared to previously published or collected data on chimpanzees performing an analogous task. While all human climbers used a high proportion of their muscular reserve to perform the task, experienced climbers had moderately reduced muscle activity in most muscles, particularly during phasic shifts of the climb cycle and moderately more efficient kinematics. Climbing kinematics and muscle activity were very similar between humans and chimpanzees. However, chimpanzees appear to have a different utility of the posterior deltoid, suggesting an influence of their habitual arboreal behaviors. The second and third studies describe the development of a deterministic chimpanzee musculoskeletal glenohumeral model. Study 2 developed geometric parameters of chimpanzee shoulder rhythm and glenoid stability ratios for the construction of a chimpanzee glenohumeral model. The chimpanzee glenohumeral model of Study 3 was designed to parallel an existing human glenohumeral model, enabling comparative analyses. The chimpanzee glenohumeral model consists of three modules – an external torque module, musculoskeletal geometric module, and an internal muscle force prediction module. Together, these modules use postural kinematics, subject specific anthropometrics and hand forces to estimate joint reaction forces and moments, subacromial space dimensions, and muscle and tissue forces. Using static postural data from Study 1, predicted muscle forces and subacromial space were compared between chimpanzees and humans during an overhead, weight-bearing climbing task. Compared to chimpanzees, the human model predicted a 2mm narrower subacromial space, deltoid muscle forces that were often double those of chimpanzees and a strong reliance on infraspinatus and teres minor (60-100% maximal force) over other rotator cuff muscles. Finally, the deterministic chimpanzee and human glenohumeral models were expanded in Study 4 to a probabilistic analysis of rotator cuff function between species. Using probabilistic software and the same postural climbing inputs, both models had anthropologically relevant musculoskeletal features perturbed in a series of Monte Carlo simulations – muscle origins and insertions, glenoid inclination and glenoid stability – to determine if rotator cuff muscle force prediction distributions would converge between species. Human rotator cuff muscle behavior did not converge with chimpanzees using probabilistic simulation. The human model continued to predict strong dependence on infraspinatus and teres minor, with 99% confidence intervals of [0-100]% maximal force, over supraspinatus and subscapularis, with confidence intervals of [0-5]% maximal force. Chimpanzee rotator cuff confidence intervals were typically between [0-40]% maximal force, with median force for all four rotator cuff muscles typically 5-20% maximal force. While perturbation of muscle origins and insertions had the greatest effect on muscle force output distributions, no musculoskeletal variation notably modified human climbing performance. Structural musculoskeletal differences between species dictated differences in glenohumeral function. The results from all studies indicate susceptibility for the fatigue-induced initiation of subacromial impingement syndrome and rotator cuff pathology in modern humans during overhead and repetitive tasks. Lower muscle absolute PCSA in humans, combined with a laterally oriented glenohumeral joint and laterally projecting acromion reduced the capacity for overhead postures and weight-bearing postures. These evolutionary differences may have been vestigial consequences, concurrent with necessary adaptions for important, evolutionary human-centric behaviors such as throwing. However, they have influenced the high rates of rotator cuff pathology in humans compared to closely related primates. The present work represents an important first step toward a broad scope of future research. Interdisciplinary computational modeling offers an evolving and improving alternative to traditional methods to study human evolution and function. Computational and probabilistic simulations can be expanded to numerous other biomechanical and evolutionary queries. The results of this thesis are a promising initial step to examining the evolutionary structural connection to biomechanical human function through comparative computational modeling.
Examination of Healthy Neuromusculoskeletal Control of the Pectoralis Major Muscle
(University of Waterloo, 2020-10-29) Lulic, Tea; Dickerson, Clark
The pectoralis major, a large, multipennate muscle, assists in shoulder complex mobility and stability. Although its highly intricate architectural properties allow it to contribute to many upper extremity tasks, its exact role in typical shoulder function is ambiguous. Due to this, the pectoralis major is typically classified as an ‘exercise’ muscle; its functional relevance to daily and occupational tasks dismissed, and its purpose in arm movements diminished. However, mounting evidence associates direct or indirect injury to this muscle to debilitating long-term arm disability. A more deliberate investigation of its role in typical shoulder function is paramount for developing targeted treatments, exercises, and rehabilitation protocols. Therefore, this dissertation aimed to establish critical foundational knowledge on regional pectoralis major neuromusculoskeletal control in males and females. Study 1 demonstrates that current electromyographic (EMG) methods misrepresent pectoralis major activation in several tasks and effort levels in healthy males. It proposes a holistic framework, combining high-density surface electromyography (HD-sEMG) and neural decoding. This framework allows for an investigation of the spatial distribution of whole pectoralis major activation, with in-depth insights into its neural and neuromuscular control. In study 2, methodological challenges in EMG acquisition from pectoralis major in females are addressed, demonstrating that HD-sEMG signals in the array overlaying the breast have low amplitudes and high mean power frequency. However, the acquisition of HD-sEMG signals from the top regions of the pectoralis major in females is achievable. Studies 3 and 4 evaluated the activity of the pectoralis major in healthy females. These studies showed predominantly middle sternocostal region involvement in adduction, internal rotation, and extension, while clavicular regions specifically contributed to flexion and horizontal adduction. Further, characterization of pectoralis major activation in males (Study 5 and 6) revealed lower sternocostal region involvement in tasks requiring adduction, internal rotation, and extension. All three regions assisted in flexion and horizontal adduction. Lastly, study 7 revealed high discharge rates of motor units at low effort levels and reliance on motor unit recruitment to increase force. Findings from this dissertation have broad implications in fundamental and clinical sciences. First, the scope of this work represents the first transformative step in understanding the role of pectoralis major in typical shoulder function. Second, it addresses several methodological limitations and challenges that currently limit the ability to investigate its intricate control. Lastly, current findings inform surgical procedures involving pectoralis major resection or disinsertion, rehabilitation or exercise protocols aimed at regional pectoralis major recovery, and fundamental studies, aimed at understanding the complexities of shoulder function. This dissertation’s outcomes collectively highlight the utility of examining the neuromusculoskeletal control of the pectoralis major and its significance in numerous tasks.
Examining the effects of a passive upper extremity exoskeleton on shoulder fatigue during a simulated automotive overhead weld inspection task
(University of Waterloo, 2024-04-26) Kurt, Jacklyn; Dickerson, Clark
Exoskeletons are emerging as occupational assistive devices, and in particular passive upper extremity exoskeletons have been implemented in workplaces in situations where it is not possible to remove overhead work job elements. Previous studies have commonly reported the effects of exoskeleton usage on the deltoid muscles during short duration tasks, but these data incompletely characterized how exoskeletons may influence shoulder fatigue development and subsequent injury risk. The main purpose of this thesis was to quantify the exoskeleton’s impact on psychophysical, localized muscle, and strength measures of fatigue in the shoulder throughout a two-hour simulated welding task. Ten male participants completed two in-lab sessions of the same task with and without the exoskeleton. Psychophysical measures of exertion, shoulder, elbow, and wrist discomfort were recorded along with surface electromyography (EMG) from bilateral supraspinatus, infraspinatus, upper trapezius, anterior and middle deltoids using a posture-controlled weighted reference task to calculate changes in mean power frequency (MPF) every 10 minutes throughout the 2-hour protocol. Maximum voluntary strength efforts (abduction and external rotation) were completed every 20 minutes to monitor changes in strength. The left and right sides were compared over time to assess potential changes in strategy throughout the task progression. The absence of significant hand by time interactions indicated there was no systematic change in strategy throughout the task protocol. The overhead weld inspection task caused increased markers of fatigue (decreased MPF) in the supraspinatus, infraspinatus, and upper trapezius over the 2-hour protocol. Wearing the exoskeleton resulted in significantly higher MPF compared to no exoskeleton in the supraspinatus (p<0.001), infraspinatus (p<0.001), and upper trapezius (p<0.001), with measures remaining at baseline in the EXO group, indicating a lack of fatigue development. Shoulder discomfort was reduced by 0.67 points (EXO = 1.97, NE = 2.64) when wearing the exoskeleton. Additionally, wrist discomfort was 0.4 points lower without the exoskeleton (EXO = 1.06, NE = 0.66), suggesting that the wrist and other body regions that are not targeted by the exoskeleton should be monitored if these devices are implemented. External rotation force was also lower with the exoskeleton than without, driven by a decrease in force output at the start of the collection period that returned to baseline values by the end of the 2-hour protocol. This could indicate that the exoskeleton may have affected cognitive fatigue in these non-expert users; however, cognitive fatigue was not directly measured in this thesis and should be investigated further in future work. Overall, this thesis provides novel findings regarding the effects of a passive upper extremity exoskeleton on muscular fatigue, particularly in the glenohumeral stabilizing muscles (supraspinatus, infraspinatus, and upper trapezius). This had not been previously explored during an extended duration task representative of the workplace.
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.
Multifaceted Approaches to Enhancing Shoulder Health in Breast Cancer Patients undergoing Radiation Therapy: quantification of treatment effects and rib fracture prediction assessment
(University of Waterloo, 2024-04-11) Herrera Valerio, Maria Cristina; Dickerson, Clark
Radiotherapy is a highly effective treatment for breast cancer, but it is also associated with several complications that can impact patients’ quality of life and overall survival. This dissertation addressed the lack of research examining the influence of radiation therapy on shoulder health indicators during the treatment window. Additionally, it investigated the effectiveness of an intervention program focused on shoulder strength to compensate for potential shoulder health impairments. Finally, it assessed the feasibility of using quantitative ultrasound for more accessible evaluations of rib fragility fractures, which may arise as a long-term consequence of radiation therapy. Study 1 and 2 shared an in vivo experimental collection. Shoulder health indicators of the affected limb of 27 breast cancer patients were tracked at baseline, midpoint, and endpoint assessments within the radiation therapy window. The activation of latissimus dorsi, teres major, pectoralis major, and serratus anterior, were quantified using a wearable electromyography (EMG) device during two shoulder flexion-extension, two shoulder abduction-adduction, and two shoulder external-internal rotation submaximal tasks. The kinematics of the shoulder complex were measured using an Inertial Measurement Unit (IMU) during six maximal range of motion trials involving flexion, abduction, and external rotation. Additionally, arm strength was evaluated using a hand-held dynamometer during flexion, extension, abduction, adduction, external rotation, and internal rotation maximal exertions. Finally, the arm circumference was determined using a measuring tape. Study 1 showed significant changes (p<0.05) in the latissimus dorsi and teres major muscles during all evaluated shoulder movement tasks. There was also a significant reduction (p<0.05) in shoulder abduction at the end of treatment compared to baseline. No changes were noted in pectoralis major and serratus anterior muscles, nor in arm strength. Radiation dose was negatively correlated with shoulder abduction range of motion. Study 2 evaluated and compared a control group with a shoulder strength intervention group throughout the radiation treatment. The intervention group exhibited higher activation of teres major and serratus anterior compared with control group (p < 0.05) in external- internal rotation and flexion-extension movement tasks. This group also exhibited significantly greater (p<0.05) arm strength and negative correlations between radiation fractions and arm strength for all the evaluated movements. No significant differences were noted in pectoralis major and latissimus dorsi activation, nor shoulder complex range of motion between the groups. Study 3 employed an in-silico approach to simulate oncological treatments and demonstrated that Quantitative Ultrasound Imaging of Bone (QUSIB) is sensitive to the structural changes induced by these therapies. Specifically, two sets of ribs were created to simulate the effects of 5 years of radiation and bisphosphonate treatments. Acoustic attenuation and backscatter coefficient parameters were examined to assess their ability to detect changes in trabecular structure. The results revealed significant correlations (p<0.05) between the observed and predicted values of Bone Volume Fraction (BV/TV). Furthermore, significant differences (p<0.05) were observed in trabecular thickness between the base and simulated radiation and bisphosphonate models. This dissertation provides valuable insights into the effects of radiation therapy on shoulder functionality. It aims to help patients minimize the potential side effects of this treatment and assist health providers in finding more accessible solutions for managing these long-term consequences.
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.
Quantifying regional pectoralis major fatigue and its influence on performance of activities of daily living
(University of Waterloo, 2020-01-24) Luciani, Bhillie; Dickerson, Clark
Extensive research reports on healthy shoulder function in the context of motion and muscular activity. However, less is known regarding how the shoulder complex and in particular its muscular components respond to disruptions, including musculoskeletal disorders, iatrogenic damage, or fatigue. The pectoralis major is a multipennate fan-shaped muscle, composed of three regions, and contributes to many upper extremity actions such as internal rotation, adduction, and horizontal adduction. Despite contentions that the pectoralis major may not be necessary for normal shoulder function, when damaged, shoulder function changes. The objective of this study was to examine differential fatigue in the pectoralis major as well as the effects of pectoralis major fatigue on shoulder muscle activation and shoulder kinematics in the context of daily activities. Twenty, young healthy male participants performed baseline activities of daily living, then performed a fatiguing protocol targeting the pectoralis major. Following the fatigue protocol, participants performed the same activities of daily living at 0, 1, 3, 7, and 15-minutes post-fatigue. Electromyography (EMG) was collected from the three regions of the pectoralis major and surrounding shoulder musculature of the dominant upper extremity were collected to assess muscle contributions to the activities of daily living (mean EMG). Kinematics of the dominant upper extremity were also collected to identify changes to joint angle range of motion changes (torso, thoracohumeral, and elbow). Fatigue was quantified in the three regions of the pectoralis major in order to determine differential fatigue. Fatigue, EMG, and kinematic data from post-fatigue time points were compared to pre-fatigue. All participants experienced fatigue in the pectoralis major as a result of the fatiguing protocol. More specifically, differential fatigue occurred between regions of the pectoralis major, with participants fatiguing in one, two, or all three regions. Further, changes in kinematics and muscle activity during the activities of daily living occurred, indicating changes in muscle activation patterns and joint angle ranges of motion due to fatigue. Joint angle ranges of motion changed (~6˚) as a result of the fatigue protocol, while there were small changes (less than 2% maximum voluntary contraction) in muscle activity. Overall, this thesis suggests that the pectoralis major muscle is complex and focused investigation of its regional contributions is necessary to understand how the muscle variously contributes to shoulder function. These initial findings can inform future research on the pectoralis major while informing on the utility of fatigue as a muscle knock-out or knock-down model.
Upper extremity kinematic changes and shoulder muscle fatigue during a repetitive goal directed task
(University of Waterloo, 2017-01-20) Whittaker, Rachel; Dickerson, Clark
Repetitive workplace tasks are associated with fatigue induced changes to shoulder muscular behavior, which can alter glenohumeral joint kinematics and lead to chronic injury. However, accessible and reliable methods to detect shoulder muscle fatigue in the workplace are scarce. The overall purpose of this thesis was twofold. First to determine if changes in upper extremity joint angle across individuals during a workplace emulative repetitive task exhibit features that may be visually identifiable, and second, to characterize the relationship between potentially visually identifiable changes in thoracohumeral elevation and traditional indicators of shoulder muscle fatigue. Twenty-seven, young healthy individuals performed a seated repetitive manuals materials handling task requiring them to lift and lower a weighted bottle between two target locations to exhaustion. During the last five lift motions of each 2-minute interval during the repetitive task, a symbolic motion structure representation (SMSR) algorithm was used to identify the basic spatial-temporal structure of the time series upper extremity joint angle data (i.e. torso, thoracohumeral, elbow and wrist), followed by measures of selected shoulder muscle electromyography (EMG) mean power frequency (MPF) and ratings of perceived fatigue and discomfort (RPF/RPD). Joint angle SMSRs characterize motion as a sequence of directional changes in joint angle time series data, which are easier to visually identify by ergonomists, in comparison to joint angle magnitudes. Changes in joint angle SMSRs occurred across upper extremity joints for most participants (at least 24 of 27) in this repetitive task. A weak positive linear relationship existed between the onset of changes in thoracohumeral elevation SMSR and the onset of shoulder muscle fatigue (as identified by a decline in the EMG MPF from the infraspinatus muscle) (R2 = 0.275, p = 0.02). Participants who varied the thoracohumeral elevation SMSR, in comparison to those who did not, exhibited a 7.45% greater decrease in anterior deltoid EMG MPF (p = 0.304), indicative of higher levels of muscle fatigue, throughout the repetitive task. In principle, the results of this thesis indicate that upper extremity kinematic changes in a repetitive task may be visually identifiable as directional changes in joint motion identified by the SMSR algorithm. The relationship between anterior deltoid muscle fatigue and variability in thoracohumeral elevation SMSRs throughout the repetitive task provide a link between potentially visually identifiable directional changes in thoracohumeral elevation joint motion (SMSR) and shoulder muscle fatigue accumulation. These initial findings can inform future research endeavors aimed at developing heuristic guidelines for visually identifying variations in thoracohumeral joint angles as a more accessible method to identify local shoulder muscle fatigue in ergonomics assessments.

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