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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Accuracy of self-reported intake of signature foods in a school meal intervention study: comparison between control and intervention period
(Cambridge University Press, 2015-08-28) Biltoft-Jensen, Anja; Damsgaard, Camilla T.; Andersen, Rikke; Ygil, Karin Hess; Andersen, Elisabeth Wreford; Ege, Majken; Christensen, Tue; Sorensen, Louise Bergmann; Stark, Ken; Tetens, Inge; Thorsen, Anne-Vibeke
Bias in self-reported dietary intake is important when evaluating the effect of dietary interventions, particularly for intervention foods. However, few have investigated this in children, and none have investigated the reporting accuracy of fish intake in children using biomarkers. In a Danish school meal study, 8- to 11-year-old children (n 834) were served the New Nordic Diet (NND) for lunch. The present study examined the accuracy of self-reported intake of signature foods (berries, cabbage, root vegetables, legumes, herbs, potatoes, wild plants, mushrooms, nuts and fish) characterising the NND. Children, assisted by parents, self-reported their diet in a Web-based Dietary Assessment Software for Children during the intervention and control (packed lunch) periods. The reported fish intake by children was compared with their ranking according to fasting whole-blood EPA and DHA concentration and weight percentage using the Spearman correlations and cross-classification. Direct observation of school lunch intake (n 193) was used to score the accuracy of food-reporting as matches, intrusions, omissions and faults. The reporting of all lunch foods had higher percentage of matches compared with the reporting of signature foods in both periods, and the accuracy was higher during the control period compared with the intervention period. Both Spearman's rank correlations and linear mixed models demonstrated positive associations between EPA + DHA and reported fish intake. The direct observations showed that both reported and real intake of signature foods did increase during the intervention period. In conclusion, the self-reported data represented a true increase in the intake of signature foods and can be used to examine dietary intervention effects.
ACL Injury Mechanisms and the Kinetic Chain Linkage: The effect of proximal joint stiffness on ACL injury risk.
(University of Waterloo, 2016-08-30) Cannon, Jordan
Recent literature has suggested that core and gluteal neuromuscular deficits are involved in the mechanism of non-contact ACL injury. Several research groups have identified dynamic valgus of the lower extremity to be an injurious posture that is predictive of future non-contact ACL injury risk. Aberrant kinematics of segments proximally in the kinetic chain, namely the trunk and hip, have also been observed to drive dynamic valgus during dynamic activities. Comprehensive investigation of the neuromuscular deficits postulated as the mechanism of injurious mechanics are lacking in the literature. Given that certain motions can be created by infinite muscle activation combinations, and that muscle activation contributes both force and controlling stiffness, this work aims to characterise any such deficits by examining the ability to modulate proximal joint stiffness to dynamically control distal segments of the kinetic chain. Three-dimensional lumbar spine stiffness and hip stiffness were quantified in participants deemed as ‘high valgus’ and ‘low valgus’ based on their frontal plane knee displacement during each task. The risk of non-contact ACL damage is highest among active females, justifying their choice to study. Eighteen female participants completed drop vertical jump (DVJ), stop jump (SJ), single leg drop (SLD) and single leg crossover drop (SLCD) tasks in order to measure medial knee displacement and associated proximal joint stiffness values. It was hypothesized that those with high valgus would not generate sufficient joint rotational stiffness at the lumbar spine, hip, or both, and thus aberrant kinematics and the injurious dynamic valgus motion would result. Those who were able to develop sufficient stiffness at the lumbar spine and hip had greater control over the kinetic chain and in doing so reduced dynamic valgus and likely their risk of future ACL injury. However, variance within subjects was found, specifically the same person would show a valgus landing on one trial, but not on another. This necessitated a change in analysis to one considering the landings as case studies, and groupings of landings by whether valgus occurred or not, rather than by subjects. This was an unexpected, and therefore exciting part of the thesis journey. The results here provide insight into the motor control component of avoiding dynamic valgus and is the first work to confirm, and specifically characterize, a neuromuscular deficit at the core or hip. That deficit appears to be an inability to generate sufficient joint rotational stiffness in order to control the linkage. Given this insight, appropriate interventions and training programs may be designed to reduce one’s risk of ACL injury.
Acute Cardiac Responses to Respiratory Muscle Unloading at Different Exercise Intensities
(University of Waterloo, 2022-08-29) Angus, Sarah
Respiration is accomplished by alterations in intrathoracic pressure (ITP) and has physiological implications on the heart. For example, the negative ITP during inspiration is transmitted to the right atrium, which augments venous return, preload, stroke volume (SV), and cardiac output (Q). We sought to determine the impact of respiration on Q during semi-supine cycle exercise by using a proportional assist ventilator to attenuate ITP changes and the work of breathing (Wb). Thirteen healthy participants (6 females) completed three discrete exercise trials at 30%, 60% and 80% peak power (Wmax) with unloaded and spontaneous breathing. Intrathoracic and intraabdominal pressure were measured with balloon catheters placed in the esophagus and stomach. Stroke volume was determined via echocardiography and the Simpson’s biplane method. An electrocardiogram measured heart rate (HR) and a customized metabolic cart measured ventilatory and mixed expired variables such as ventilation and oxygen consumption (V̇O2). Mean esophageal pressure was greater during unloaded relative to spontaneous breathing at all exercise intensities (p<0.0001). Esophageal pressure swings per breath (between spontaneous and unloaded breathing) were different at 30%, 60% and 80%; (-3.5±3.4 vs. -6.8±6.4 vs. -11.9±7.9 cmH2O, respectively (p=0.01). However, the decrease in Wb was not different between exercise intensities (39±22 vs. 46±14 vs. 51±14% from spontaneous breathing for 30%, 60%, and 80%Wmax, respectively, all p>0.05). Cardiac output decreased during unloaded breathing by -1.2±1.3 vs. -1.7±1.4 vs. -1.8±2.0 L min-1 from spontaneous breathing at 30%, 60% and 80%Wmax, respectively (all p<0.05). Heart rate decreased during unloaded breathing by -2±3 vs. -6±4 bpm at 60% and 80%Wmax, respectively (both p<0.05), with no change at 30%Wmax (p=0.2). Stroke volume decreased during unloaded breathing by -10.7±11.2 vs. -10.1±10.2 vs. -8.0±12.3 mL from spontaneous breathing at 30%, 60% and 80%Wmax, respectively (all p<0.05). Oxygen consumption decreased during unloaded compared to spontaneous breathing at 80%Wmax (2.5±0.6 vs. 2.6±0.7 L min-1, p=0.002) with no change at 30% and 60%Wmax (both p>0.05). In summary, attenuating ITP swings resulted in a reduction in Q at all exercise intensities. At 30%Wmax, the decrease in Q may be due to a reduction in SV. At 60%Wmax, Q decreases likely because of a reduction in SV and HR. At 80%Wmax, Q may decrease due reductions in SV, HR and V̇O2. In conclusion, the normally occurring swings in ITP developed during spontaneous breathing is helpful for maintaining cardiac function during exercise.
The Acute Effect of Exercise Intensity on Cognitive Function
(University of Waterloo, 2016-08-30) Wikkerink, Spencer
Recent research has found that regular exercise has a positive effect on cognitive function. Some studies indicate that even an acute session of exercise has a slight positive effect on cognitive function, though factors moderating this effect have not been thoroughly examined. Exercise intensity and timing of cognitive assessment may have an interactive effect on cognitive changes after exercise. Previous research suggests that moderate intensity exercise has the most consistent benefit to cognitive function. In contrast, studies find positive, negative, or null effects to cognitive function after high intensity exercise, where the timing of the post-exercise assessments may account for the observed differences. Since high-intensity interval training (HIIT) is an increasingly popular form of exercise due to equal or greater cardiovascular adaptation for reduced exercise time, understanding its cognitive effects is of interest. The primary objective of the study was to compare the cognitive effects of an acute bout of HIIT to both moderate intensity continuous training (MCT) and rest. The secondary objective was to compare the timeline of the cognitive effects between these three sessions. Twenty-two participants performed 28.5min of HIIT, MCT, and rest on three separate days, each 2 weeks apart. The rest session was performed first and the subsequent exercise sessions were randomized. Cognitive function was assessed using a modified Flanker task with concurrent electroencephalography (EEG) before and 0, 15, 30, and 45min post-intervention. The hypothesis that cognitive function would improve after MCT and HIIT was not supported. Though there was some variability in cognitive function post-exercise, cognitive function was not significantly different before to after exercise or in comparison to the rest session. However, measures of cognitive function were often better prior to the exercise sessions than before exercise, possibly due to an anticipatory effect prior to exercise or learning carry-over after the rest session, which complicated interpretation of results. Of note, only a small number of prior studies included a baseline assessment of cognitive function in each session. Future research should examine the influence of the anticipation of exercise on cognitive function to better understand whether it is the psychological or physical stress imposed by exercise that enhances cognitive function.
Acute effects of aerobic exercise on cognitive function in individuals with Parkinson’s disease
(Elsevier, 2018-04-03) Silveira, Carolina R. A.; Roy, Eric A.; Almeida, Quincy J.
Deficits in executive functions are highly prevalent in Parkinson’s disease (PD). Although chronic physical exercise has been shown to improve executive functions in PD, evidence of acute exercise effects is limited. This study aimed to evaluate the effects of an acute bout of exercise on cognitive processes underlying executive functions in PD. Twenty individuals with PD were assessed in both a Control and an Exercise conditions. In each condition, individuals started performing a simple and a choice reaction time (RT) task. Subsequently, participants were asked to sit on a cycle ergometer (Control) or cycle (Exercise) for 20 min in counterbalanced order. Participants were asked to repeat both reaction time tasks after 15-min rest period in both conditions. While no differences were found in simple RT, participants showed faster choice RT post Exercise as well as Control conditions (p = .012). Participants had slower choice RT for target stimulus compared to non-target stimuli irrespective of time or experimental condition (p < .001). There was no change in accuracy following experimental conditions. Results suggest that individuals with PD may not respond behaviourally to a single bout of exercise. The lack of selective effects of exercise on cognition suggests that practice effects may have influenced previous research. Future studies should assess whether neurophysiological changes might occur after an acute bout of exercise in PD.
Acute Regulation of Na+-K+-ATPase Activity in Skeletal Muscles of Different Fibre Type Composition in Response to Insulin Exposure
(University of Waterloo, 2008-01-09T19:00:18Z) Foley, Kevin Patrick
The Na+-K+-ATPase (pump) is a transmembrane, multi-subunit (α and β) protein that is expressed in all cells, and particularly in skeletal muscle cells. In one cycle, it pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell at the expense of 1 ATP molecule. This enzyme is responsible for maintaining muscle cell excitability. This is of particular importance during contractile activity, when the flux of Na+ and K+ across the cell membrane is high. The activity of the Na+-K+-ATPase is highly regulated and very responsive to hormonal stimuli. Previous research has shown that 20-30 min insulin exposure in vivo induces the translocation of pumps from intracellular stores to the plasma membrane. However, no study has examined the catalytic properties of this enzyme in response to short insulin exposures. The objective of this study was to investigate the response of the Na+-K+-ATPase to short insulin incubation in vitro in muscles of different fibre type. It was hypothesized that the short insulin treatment would result in an increase in pump activity, not only through translocation but also increased intrinsic activity. Using an in vitro model, rat soleus (Sol), red gastrocnemius (RG), and white gastrocnemius (WG) muscle homogenates were incubated at 37°C for 5 min with and without 75μM insulin (Ins). Next, in order to separate mechanisms of translocation and intrinsic activation, the plasma (SLP) and endosomal (EN) membranes were separated through a fractionation procedure. This allowed the investigation of insulin-induced increases in intrinsic activity in SLP and EN fractions of Na+-K+-ATPase; SLP and EN (non-treated) membranes were incubated at 37°C for 5 min with and without 75μM insulin. Lastly, muscle homogenates were insulin-treated for 5 min at 37°C with 625μM insulin prior to fractionation. These SLP and EN fractions (insulin-treated) were then incubated at 37°C for 5 min with and without 75μM insulin. Na+-K+-ATPase maximal activity (Vmax, mmol•mg prot-1•h-1) and km (substrate affinity), α2 content, and tyrosine phosphorylation (Tyr-P) were probed. It was found that insulin increased Vmax (P<0.05) in Sol and RG, but not WG, homogenates (Con vs Ins, Sol=221±17 vs 256±21; RG=190±14 vs 256±18; WG=104±4.6 vs 99±1.8). In non-treated fractions, insulin increased Vmax (P<0.05) in Sol and RG SLP fractions (Con vs Ins, Sol=1710±186 vs 1970±231; RG=1476±128 vs 1655±139). A main effect, Con
Acute Regulation of Vascular Tone by AMP-activated Protein Kinase in Arteries of Healthy, Hypertensive and Aged Rats
(University of Waterloo, 2011-12-21T16:15:00Z) Ford, Rebecca Jill
Background, Rationale and General Purpose: Several seminal observations suggest that AMPK mediates vascular tone: 1) in endothelial cell culture and in vitro isolated protein experiments, activation of AMPK stimulates nitric oxide (NO) production via phosphorylation of endothelial nitric oxide synthase (eNOS), 2) stimuli associated with AMPK activation relax isolated vascular smooth muscle preparations from healthy animals, and 3) acute activation of AMPK in vivo induces hypotension in normotensive animals, an effect that could be indicative of reduced vascular tone. Together these findings prompt the logical hypothesis that acute activation of AMPK induces relaxation that is both endothelium-, NO-dependent and also vascular smooth muscle dependent; however the direct effects of AMPK activation on the regulation of vascular tone in the context of intact healthy arteries in vitro or in situ have not been tested. AMPK activation is dysregulated in essential hypertension and aging, conditions both characterized by vasomotor dysfunction. The integrity of AMPK-mediated vasomotor effects has not been evaluated in any model of vascular dysfunction or in the presence of AMPK dysregulation, and so it is unknown if or to what extent, activation of AMPK alters vascular tone in vessels with these impairments. The mechanisms of AMPK-mediated vasomotor effects have also not been delineating in healthy or dysfunctional arteries. Studying basic vascular signalling mechanisms in both healthy and dysfunctional models is important for understanding physiological function and regulation of vascular tissue, as well as to understand vascular pathology and aid in the development of therapeutic interventions. Collectively these considerations present compelling reasons to investigate the role of AMPK in vasomotor function in health and disease. The unifying purpose of this thesis was therefore to investigate the role of AMP-activated protein kinase in regulating vascular tone in arteries of healthy, hypertensive and aged rats. Experimental Approach and Main Findings: The global objective of the thesis is satisfied by four main studies that utilize a combination of in vitro isolated artery preparations to assess vasomotor function, biochemical analyses and in vivo hemodynamic assessments. In Study 1, we characterize the basic nature of the vasomotor response generated acutely by the pharmacological AMPK activator AICAR in vitro in isolated aorta of normotensive (Wistar-Kyoto rats; WKY) and hypertensive rats (Spontaneously Hypertensive rats; SHR), and the mechanisms mediating these responses. In these experiments, acute activation of AMPK using AICAR induced dose-dependent relaxation of isolated, precontracted arteries from WKY and SHR that was dependent in part on both the endothelium and vascular smooth muscle, and vasorelaxation to AICAR was enhanced in aortic rings of SHR versus those of WKY. In WKY, the endothelium-dependent component of relaxation to AICAR was solely NO-mediated, while in SHR it was dependent on both elevated NO-bioactivity and blunted COX-dependent contraction. In Study 2, we investigate the mechanisms responsible for AMPK-mediated inhibition of endothelium- and cyclooxygenase-dependent vasocontraction in aorta from WKY and SHR (a response enhanced in arteries of hypertensive rats that contributes to vasomotor dysfunction). Pre-activation of AMPK blunted endothelium-dependent contractions to acetylcholine in isolated, non-precontracted WKY and SHR aortic rings. The mechanisms accounting for this effect of AICAR were endothelium-specific, occurring via inhibition of the ACh-stimulated production/release of 6-keto-prostaglandin F1α, the major product of prostacyclin, which is the key prostanoid responsible for endothelium-dependent contractions in aorta of WKY and SHR. AMPK activation had no effect on vascular smooth muscle responsiveness to TP-receptor agonists, ruling out a contribution of vascular smooth muscle mechanisms. In Study 3, we examine responses and mechanisms associated with acute pharmacological AMPK activation on vascular tone of isolated mesenteric resistance arteries in vitro, and on in vivo hemodynamics in WKY and SHR. These experiments revealed that administration of AICAR acutely in vivo acutely reduced blood pressure by ~70mmHg in SHR and this effect was partly NO-dependent. In contrast, AICAR had no effect on blood pressure in WKY. Activation of AMPK also produced vasodilation of isolated, precontracted WKY and SHR resistance mesenteric arteries in vitro, and this was dependent on NO to a greater extent in SHR than in WKY. Together, the parallel reductions in blood pressure in vivo and relaxation of isolated arteries in vitro support reduced vascular resistance as a potential explanation for the in vivo blood pressure effects. Finally, Study 4 characterizes the basic vasodilatory responses to acute AMPK activation and mechanisms associated with these responses in aorta from aged animals and their young counterparts (male Sprague Dawley rats) to glean insight using an additional model of vasomotor dysfunction. In this study, acute activation of AMPK using AICAR generates relaxation in a dose-dependent manner that is partly endothelium-, NO-dependent and partly reliant on vascular smooth muscle in precontracted aorta of both young and aged rats. Similar to the findings of Study 1 in SHR versus WKY, vasodilatory response to AICAR were also enhanced in dysfunctional aorta of aged rats versus healthy aorta of young animals. Other agents shown to activate AMPK in other tissues and models, the anti-diabetic drug metformin and the polyphenol resveratrol, generated varying amounts of relaxation in vascular smooth muscle of young and aged aortic rings. These effects were only associated with AMPK activation in rings treated with metformin but not resveratrol. Conclusions and Perspectives: These findings are the first to characterize the vasomotor responses generated by acutely activating AMPK in intact arteries of any hypertensive or aging model, and to delineate mechanisms mediating these responses in healthy and dysfunctional vessels. Despite vasomotor dysfunction and dysregulated AMPK activity in arteries of hypertensive and aged rats, acute AMPK activation still generates robust relaxation responses via endothelium- and NO-dependent relaxation, inhibition of enhanced endothelium-dependent contractions in SHR, and direct relaxation of the vascular smooth muscle; effects that would aid in reversing the dysfunctional characteristics of arteries from these animals, and may recommend AMPK as a useful therapeutic target for interventions aimed at improving vasomotor function. Future studies will be necessary to reveal whether AMPK plays a role in generating acute changes in vessel tone induced by AMPK-activating physiological stimuli in situ (i.e. such as shear stress during exercise). Together these data continue to support AMPK as a novel regulator of vascular tone, yield valuable, novel, mechanistic insight into AMPK-mediated regulation of vasomotor function in arteries during health, disease and aging, and highlight the need for continued investigation into a vasoregulatory function for AMPK in health and disease.
Age-related changes in the control of mediolateral dynamic stability during volitional and reactive stepping
(University of Waterloo, 2012-04-23T20:10:34Z) Singer, Jonathan Craig
The high incidence of falls and fall-related injuries among Canadians over the age of 65 continues to be a key public health issue. As the current proportion of individuals within this cohort of the population is predicted to double by the year 2031, the absolute number of individuals experiencing falls, fall-related injuries and subsequent hospitalization will increase dramatically. While a fall in any direction can lead to injury and reduced quality of life, lateral falls have been shown to be prevalent and can be particularly devastating because of the increased probability of hip fracture. Forward stepping tasks, whether initiated volitionally or by external perturbation, pose a challenge to stability, as they require the precise regulation of the spatial and temporal characteristics of the whole body centre of mass (COM) in relation to a changing base of support (BOS). Despite our understanding of both proactive and reactive mechanisms for balance control at movement initiation during such stepping tasks, there appears to be little understanding or consensus regarding the origins of age-related decline in mediolateral stability, which can manifest during the restabilisation phase, at movement termination. From this, the global objective of this thesis was to develop further understanding regarding such age-related differences in mediolateral dynamic stability control during the restabilisation phase of forward stepping. Notwithstanding the well documented differences between volitional and perturbation-evoked stepping until the time of foot-contact, we have proposed the control of the COM during the restabilisation phase of such stepping tasks to be a central determinant of age-related differences in mediolateral dynamic stability, common to both forms of stepping. We quantified the COM kinematics during the restabilisation phase and calculated the magnitude of incongruity between the peak and final, stable, COM position, in addition to the intertrial variability of this incongruity. Further, we analysed the orientation of the net ground reaction force (GRF) with respect to the COM, which allowed us to draw conclusions regarding the mechanisms that may be responsible for the age-related differences in the COM kinematics. To vary the challenge to control, we included conditions in which individuals were required to step with altered step width. In addition, we attempted to probe the extent and means by which individuals could alter the dynamics of stepping over time, with trial repetition. In general, we found that overshoots of the final COM position were common to all forms of stepping and may serve the functional role of simplifying reactive control during the restabilisation phase. The magnitude and intertrial variability of incongruity, however, were greater among the older adults during all forms of stepping. We believe such increased COM incongruity is likely indicative of greater instability within this group, which may be associated with the increased time required to reorient the net GRF in a manner necessary to oppose the total body angular momentum that developed during the swing phase. Particularly interesting was the use of proactive strategies by older adults, which may have the potential to offset instability that arises due to difficulty with reactive control during the restabilisation phase. The present work provides support for previous studies, which have suggested that the control of mediolateral stability may be particularly challenging for older adults. Further, our work provides evidence that the challenges associated with mediolateral stability control have important links to the restabilisation phase and are common to both volitional and reactive stepping. This work highlights the need to further explore the control of mediolateral stability and develop therapeutic interventions to reduce such incidence of instability among older adults.
The aging spine: The effect of cyclic loading, simulated degeneration and prolonged sitting on joint stiffness across age
(University of Waterloo, 2018-08-22) Gruevski, Kristina May
Background: Low back pain is estimated to have a lifetime prevalence as high as 84%, and both the severity and frequency of low back pain reporting have a dependency on age. The nucleus pulposus and annulus fibrosis of the intervertebral disc undergo significant structural and compositional changes with increases in age. As the Canadian working population ages, an understanding of mechanical properties of spine tissue across age is needed to understand pain generating pathways and functional changes. The aim of this thesis was to determine if spine stiffness changes with age and to determine how the mechanical properties of the osteo-ligamentous spine and the annulus contribute to these changes in different loading scenarios. The thesis implemented both in-vitro (Studies I and II) and in-vivo (Studies III and IV) approaches to meet the objectives of the global thesis question. Study I: The effect of age and a cyclic loading protocol on the stiffness in porcine functional spine units (FSUs) was explored in study I. A total of 40 FSU specimens, with 21 young (aged 6-8 months) and 19 mature (aged 1.5-8 years) were cyclically loaded at 1 Hz to a range of motion of 8.5 degrees in flexion and extension around the midpoint of each specimen’s neutral zone for 3000 cycles with 1400 N of compression. Neutral zone stiffness was reduced in all specimens following the cyclic loading protocol, indicating no significant differences in temporal responses to repetitive loading across age. However, mature specimens were found to have greater neutral zone stiffness at both the C34 and C56 levels compared to younger specimens. This baseline differences between older and younger spines may alter load distributions in the disc and predispose mature discs to different types of injuries compared to younger specimens. Study II: The aim of study II was to isolate stiffness changes in isolated samples of the annulus in response to simulated aging. Low pH in the disc caused by lactic acid has been linked with cell death in the nucleus, discogenic pain and is a hypothesized initiator of disc degeneration. A total of 79 multilayer samples of porcine annulus fibrosis tissue obtained from young (aged 6-8months) spines were immersed in one of four pH and concentration controlled solutions of lactic acid in phosphate buffered saline (PBS) for a duration of 6 hours. The solutions included; (i) pH 7.2 PBS, (ii) pH 3.5 Lactic acid in PBS (15 mmol/L), (iii) pH 6 Lactic acid in PBS (15 mmol/L) or (iv) pH 7 Lactic acid in PBS (15 mmol/L). Following immersion, Specimens were biaxially loaded in tension in both the circumferential and axial directions to 20% strain at a rate of 2%/cycle for 100 cycles. The results of the study showed that circumferential peak stress was significantly higher in C56 specimens immersed in pH 3.5 solution compared to other solution groups. Circumferential stiffness was higher in the C56 specimens in a low pH 3.5 environment compared to the other solution groups. Exposure to a low pH environment altered the mechanical properties of the annulus fibrosis, including higher peak stress and increased stiffness. These changes demonstrate that the annulus is a contributor to increased spine stiffness changes with age. Furthermore, discs with accumulated lactic acid also have an altered mechanical environment that could put older discs at greater risk of annulus damage, such as delamination or fissures in the tissue. Study III: The purpose of study III was to determine the effect of age on lumped passive trunk stiffness, postures and discomfort responses during prolonged seated exposures. Participants in Studies III and IV were collected in the same session and shared a common cohort of 34 participants across younger and older age groups, with average (standard deviation) ages of 23.8 (5.0) years and 63.7 (3.9) years, respectively. Passive torso stiffness was measured in flexion before and after sitting continuously (90 minutes) while completing a controlled task on a desktop computer. Discomfort was reported to be higher among older adults in the neck, right shoulder and middle back regions during the prolonged sitting protocol compared to younger adults. There were no significant differences in passive torso stiffness between older and younger adults in flexion postures representing 10%, 20% and 30% of maximum. However, during the sitting protocol, younger adults adopted 19 degrees more flexion compared to older adults. Differences in seated postures across age may be explained by changes to passive tissues in older adults that affect the end range of functional motion, which may have implications for acute pain development during sitting. Study IV: The aim of study IV was to determine the effect of participant age, prolonged sitting and lift type on peak thoracic, lumbar, hip and knee postures and ratings of perceived effort. A secondary purpose was to quantify the effect of age on baseline lumbar range of motion about the mediolateral axis. All lifting tasks were floor to knuckle lifts and included, (i) 7 kg symmetrical, (ii) 4.5 kg symmetrical and (iii) 4.5 kg asymmetrical (box located 45 degrees to participant right). Lifting tasks were completed before and after the prolonged sitting protocol. The results of the study demonstrated lower peak lumbar flexion angles following 90 minutes of continuous sitting compared to prior to sitting. While there was no age-related difference noted in response to the prolonged sitting protocol, reduced peak flexion during the lifting tasks following sitting could represent swelling of the intervertebral disc in response to static sitting. Older adults adopted 12 degrees less lumbar flexion during the performance of all lifting tasks compared to younger adults. Older adults had reduced maximum range of motion about the mediolateral axis in the flexion direction compared to younger adults. However, when peak lumbar angles during lifting were expressed as a percentage of maximum flexion, angles were similar between groups with an average 71% and 65% among young and mature participants respectively. This could indicate that functional range of motion in the spine is reduced in older adults, with high flexion tasks entering a zone of higher stiffness. General Conclusions: Together, the findings from this thesis indicate that osteo-ligamentous functional spine units and the annulus increase in stiffness with age providing a mechanistic understanding of age-related mechanical changes to disc tissue. These changes may partially contribute to the reduction in maximum range of low back motion observed in older adults. Lumped passive stiffness was not significantly different at low flexion postures, but, maximum range of spine motion and peak flexion angles during high flexion tasks were reduced with increasing age. Higher stress in the posterior annulus of aged specimens could predispose older adults to greater risk of annulus disruption and could be a potential source of discogenic low back pain.
Agpat4/Lpaat delta deficiency highlights the molecular heterogeneity of epididymal and perirenal white adipose depots
(American Society for Biochemistry and Molecular Biology, 2017-10-01) Mardian, Emily B.; Bradley, Ryan M.; Henao, Juan J. Aristizabal; Marvyn, Phillip M.; Moes, Katherine A.; Bombardier, Eric; Tupling, A. Russell; Stark, Ken; Duncan, Robin E.
Acylglycerophosphate acyltransferase 4 (AGPAT4)/lysophosphatidic acid acyltransferase delta catalyzes the formation of phosphatidic acid (PA), a precursor of triacylglycerol (TAG). We investigated the effect of Agpat4 gene ablation on white adipose tissue (WAT) after finding consistent expression across depots. Epididymal WAT mass was 40% larger in male Agpat4(-/-) mice than wild-type littermates, but unchanged in perirenal, retroperitoneal, and inguinal WAT and subscapular brown adipose tissue. Metabolic changes were identified in epididymal WAT that were not evident in perirenal WAT, which was analyzed for comparison. The total epididymal TAG content doubled, increasing adipocyte cell size without changing markers of differentiation. Enzymes involved in de novo lipogenesis and complex lipid synthesis downstream of phosphatidic acid production were also unchanged. However, total epididymal TAG hydrolase activity was reduced, and there were significant decreases in total ATGL and reduced phosphorylation of hormone-sensitive lipase at the S563 and S660 PKA-activation sites. Analysis of Agpats 1, 2, 3, and 5, as well as Gpats 1, 2, 3, and 4, demonstrated compensatory upregulation in perirenal WAT that did not occur in epididymal WAT. Our findings therefore indicate depot-specific differences in the redundancy of Agpat4 and highlight the molecular and metabolic heterogeneity of individual visceral depots.
Analysis of high and low physical functioning breast cancer survivors within two years of treatment
(University of Waterloo, 2017-08-29) Maciukiewicz, Jacquelyn
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.
Analysis of the effect of rotator cuff impingements on upper limb kinematics in an elderly population during activities of daily living
(University of Waterloo, 2010-02-18T14:47:31Z) Hall, Laurie Cathryn
Despite a large prevalence of rotator cuff impingements or tears in the elderly population, little research has focused on understanding how this population adapts to perform tasks of daily living. Past research has focused on the analysis of upper limb kinematics of young healthy individuals while performing these essential tasks (Magermans, 2004, Murray and Johnson., 2004). The purpose of this thesis was to identify kinematic and shoulder loading differences between elderly mobile individuals and elderly individuals with rotator cuff impingements during specific activities of daily living. Motion capture techniques were used in combination with the Shoulder Loading Analysis Modules (Dickerson, 2005, Dickerson et al., 2007) to estimate thoracohumeral kinematics and calculate external joint moments. Two-tailed t-tests with injury status as the factor determined that differences in active range of motion in flexion/extension and humeral rotations existed between the two populations. Results of the ADL analysis showed that the impinged population tended to have decreased plane of elevation and humeral rotations during ADLs. Task was also a main factor for most variables examined. Perineal care, hair-combing and reaching tasks were the most demanding in terms of range of motion necessary to complete the task. The reaching tasks resulted in the highest shoulder moment. K-means clustering techniques proved to be unsuccessful in identifying different motion strategies between the two study groups. This investigation showed that developing adaptations for perineal care, hair-combing and reaching tasks should be considered a priority when working with patients with rotator cuff impingements, as these tasks demanded the largest ranges of motion as well as high shoulder moments.
Analysis of Transcranial Doppler Ultrasound Waveform Morphology for the Assessment of Cerebrovascular Hemodynamics
(University of Waterloo, 2012-08-29T14:19:22Z) Zuj, Kathryn
The use of transcranial Doppler (TCD) ultrasound for the assessment of cerebral blood flow velocity (CBFV) provides an indication of cerebral blood flow assuming the diameter of the insonated vessel remains constant. Studies using TCD have traditionally described cerebrovascular hemodynamics with respect to CBFV and cerebrovascular resistance (CVRi); however, a more complete assessment of the cerebral circulation can be gleaned from the analysis of within beat characteristic of the TCD velocity waveform for the determination of cerebrovascular tone. Therefore, the general purpose of the presented studies was to assess CBFV responses and within beat characteristic for the description of cerebrovascular hemodynamics after long duration spaceflight, with sustained orthostasis, in response to changes in the partial pressure of end tidal carbon dioxide (PETCO2), and with NG stimulation. After long duration spaceflight, cerebrovascular autoregulation was found to be impaired along with a reduction in cerebrovascular CO2 reactivity (Study 1). Additionally, critical closing pressure (CrCP) was found to be increased suggesting potential remodelling of the cerebrovasculature contributing to an increase in cerebrovascular tone (Study 2). With sustained orthostasis, CBFV was found to progressively decrease and to be related to reductions in PETCO2 and increases in CrCP suggesting the contribution of changes in cerebrovascular tone leading to the development of syncope (Study 4). The CBFV reduction with the progression towards syncope was also associated with changes in waveform morphology such that the dicrotic notch point was less than the end diastolic value (Study 3). Mathematical modelling (RCKL) was used to further assess changes in cerebrovascular hemodynamics for physiological interpretation of changes in CBFV waveform morphology and found that the amplitude of the dicrotic notch and the calculation of the augmentation index were both significantly related to vascular compliance before and after stimulation with NG (Study 5). The use of quantitative assessments of common carotid artery (CCA) blood flow as an indicator of cerebral blood flow suggested the dilation of the middle cerebral artery (MCA) with NG (Study 5 and 6) and changes in MCA diameter with acute alterations in PETCO2 (Study 6). CCA and MCA velocity wave morphology were assessed showing that with changes in PETCO2, changes in CBFV velocity wave were not reflected in the CCA trace (Study 7). In addition, further assessment of the CBFV velocity trace and the calculation of CrCP and the augmentation index suggested that with changes in PETCO2 cerebrovascular compliance and cerebrovascular tension, both thought to be components of cerebrovascular tone, change independently (Study 7). Combined, the results of the presented studies suggest that changes in cerebrovascular hemodynamics can be determined from alterations in the CBFV velocity waveform morphology. However, further work is required to determine how these variations relate to specific components of cerebrovascular tone, including alterations in cerebrovascular compliance and vascular tension, and how these variables change with acute and chronic alterations in cerebrovascular hemodynamics.
Anticipatory planning in object manipulation: A cross-sectional investigation of children, young adults and older adults
(University of Waterloo, 2016-08-25) Scharoun, Sara Marie
Over a series of five studies, this work aimed to investigate anticipatory planning in object manipulation across the human lifespan. Main objectives were to: (a) understand the influence of the movement context; (b) delineate the role of handedness; (c) characterize the influence of familiarity with an object; (d) investigate independent and cooperative movements; and (e) outline similarities and differences across the lifespan. Chapter 2 established a foundation for the thesis with right and left handed young adults. Findings supported the hypothesis that manual asymmetries do not influence anticipatory planning. Furthermore, despite end-state comfort reaching ceiling, kinematic data provided evidence for an increase in cognitive demand in pantomime compared to actual object use. Chapter 2 therefore served as proof of concept for manipulating contextual information to alter the cognitive demands of the task. Chapter 3 compared data to a group of left and right handed older adults. Similar to Chapter 2, manual asymmetries were not influential. Evidence of end-state comfort did not differ in young and older adults; however, after separating older adults into two groups, those who did not display the effect spent a longer time in the final approach to the target in pure pantomime. This was attributed to the increased reliance on feedback-dependent corrective mechanisms with increasing age. To quantify similarities and differences among children, young and older adults, Chapters 4, 5 and 6 assessed anticipatory planning across the lifespan. The main findings of the thesis are highlighted in the results of Chapter 6. Object use involves the direct perception of affordances, and indirect selection of motor programs based on action intentions. The ability to interact with objects in the environment is thus rooted in learned knowledge. With cognitive development, improvements in multisensory integration, and familiarity with objects, children become more proficient in anticipatory planning. As such, behaviours emulate a gradual transition from a reliance on habitual actions executed successfully in the past, to the recognition of affordances and incorporation of intentions into actions. Likewise, with decline in cognitive and motor processes, the behaviour of older adults (ages 71+) reflects a gradual transition back to habitual behaviours. Actions thus reflect stimulus-driven responses, as opposed to those which consider affordances and intentions.
Aperture Crossing in Challenging Environments: An Examination of the Factors that Influence the Passability of Narrow Spaces
(University of Waterloo, 2016-04-13) Hackney, Amy
In order to get to where we need to go, locomotion often involves walking through narrow spaces. Whether an aperture affords passage is thought to be determined by the body size/aperture size relationship. For normal, ground-level aperture crossing, spaces 1.3x the shoulder width or smaller are considered impassible (requiring a shoulder rotation) and as such, 1.3x SW is said to be the critical point of aperture crossing. However, daily activities often involve navigating through apertures under more challenging circumstances, such as when walking through a busy airport while carrying luggage. As such, additional factors other than simply the body size and the aperture size may contribute to whether an aperture is deemed passable. Therefore, the purpose of this thesis was to investigate how the factors associated with challenging environments contribute to the way in which the body-environment relationship determines the affordance of aperture crossing. Through a series of experiments, participants walked through apertures: 1) while carrying a wide object, 2) under conditions of increased postural threat, 3) where the narrow spaces were created by other individuals, and 4) where there were multiple, misaligned apertures. In general, aperture crossing behaviour was monitored through the frequency and magnitude of shoulder rotations at time-of-crossing (TOC), the critical point, the amount of space between the shoulders and the obstacles at TOC (spatial margin), the position of the body relative to midline (M-L COM at TOC) and the walking speed leading up to and crossing through the aperture (approach velocity and velocity at TOC). The results from study one reveal that the passability of apertures adapts to objects being carried by rescaling the body-environment relationship to consider the new person-plus-object width and maintaining a critical point of 1.3x the widest dimension. However, this rescaling occurred at different rates across individuals. Studies two and three demonstrate that action capabilities (postural threat) and characteristics of the aperture (people instead of poles) alter the passability of apertures, as evident by more cautious crossing behaviours. Specifically, individuals maintained a larger critical point, a higher frequency and larger magnitude of rotation, as well as a slower approach velocity and velocity at TOC. Lastly in study four, rather than walk through the center of an aperture and equalize the size of the spatial margin of each shoulder (as observed in single aperture crossing), individuals walking through multiple misaligned apertures reduce the size of the spatial margin by walking closer to the object nearest midline. Furthermore, participants choose to rotate their shoulders at apertures that would not normally require a rotation, likely in an attempt to maintain the straightest possible walking path. Together, these studies suggest that additional factors other than the body size/aperture size ratio are considered when determining the affordance of aperture crossing. Specifically, in addition to supporting the idea that individual abilities are an important contributing factor to the identification of affordances, these results demonstrate that the affordance of aperture crossing is influenced by: 1) the level of postural threat, 2) characteristics of the aperture, and 3) the number and position of apertures. Understanding the typical behaviour for walking through narrow spaces and knowing what and how specific factors influence the passability of apertures provides the necessary groundwork for understanding how these behaviours are altered with age or disease and can provide insightful suggestions for the future design of cluttered environments.
Apoptotic signalling and structural alterations in autophagy-deficient murine skeletal muscle
(University of Waterloo, 2014-10-15) Paré, Marie-France
Autophagy is a catabolic process by which the cell targets and degrades cytoplasmic materials, such as proteins and organelles. Autophagy is required for the control of muscle mass under catabolic conditions, but is also active basally to maintain myofibre homeostasis. The purpose of this thesis was to characterize the role of autophagy in the maintenance of skeletal muscle morphology and cellular health. A conditional muscle- specific Atg7 knockdown mouse model was used to examine the morphological, apoptotic, proteolytic, and proteasomal response to autophagy deficiency in the glycolytic and oxidative skeletal muscle of 5-week and 15-week-old mice. While overt phenotypic differences were absent between the autophagy-deficient animals and the controls, structural alterations were observed at the fibre level indicating moderate damage. Atg7 knockdown resulted in significant age-dependent accumulation of the autophagic markers LC3I (p<0.001) and p62 (p<0.01) in both oxidative and glycolytic muscle. Evidence of the upregulation of apoptosis was observed in the autophagy-null animals, including Bax expression (p<0.05) and nuclear translocation of AIF to the nucleus (p<0.01). The proteolytic activities of caspase-8 (p=0.06) and calpain (p<0.05) were also increased with autophagy knockdown. Reactive oxygen species (ROS) generation was not affected by Atg7 knockdown, nor were markers of mitophagic degradation. Several of the apoptotic and mitophagic measures revealed differences between the observed age groups, highlighting a role for degradative and cell death processes in skeletal muscle growth and development. Together, these findings point towards moderate but accumulative damage in autophagy-ablated skeletal muscle. The present work contributes to the existing literature demonstrating the importance of autophagy in the maintenance of skeletal muscle health.
Arm posture influences on regional supraspinatus and infraspinatus activation in isometric arm elevation efforts
(Elsevier, 2019-02) Alenabi, Talia; Whittaker, Rachel; Kim, Soo Y.; Dickerson, Clark R.
This study aimed to evaluate the effect of arm posture on activation of the anterior and posterior regions of supraspinatus and the superior and middle regions of infraspinatus during resisted isometric arm elevations. Thirty-one healthy participants performed 18 isometric resistance exertions against a force cube in three elevation planes (flexion, scaption, abduction) and three elevation angles (30°, 90°, 150°) in maximal and sub-maximal resistance conditions. EMG data were obtained using four pairs of fine wire electrodes. The mean activation of each region and the activation ratios were compared across postures using ANOVAs. Supraspinatus anterior was significantly more active during abduction and scaption, and in higher elevation angles, while the posterior region showed similar activation levels across postures. Infraspinatus regions were more active during flexion with more relative activation of the infraspinatus superior at 90° flexion. The results suggest that regional activation of supraspinatus and infraspinatus should be considered for assessment and rehabilitation purposes. In any clinical setting where it is important to reduce the stress on the supraspinatus anterior, isometric flexion exercises performed with arm in low elevation angles could provide the opportunity to strengthen the posterior region of supraspinatus with limited stress on the anterior region. Beside external rotation exertions, resisted flexion tests may be useful for evaluation of infraspinatus regions.
Assessing pre-existing movement and muscular recruitment differences in prolonged standing, transient low back pain developers compared to non-pain developers
(University of Waterloo, 2018-09-26) Park, Jonathan
Epidemiological studies have reported occupational prolonged standing to be associated with low back pain (LBP). Studies that have conducted simulations of prolonged standing work in healthy individuals have demonstrated a proportion of them will develop transient LBP (termed pain developers or PDs), while others will not (termed non-pain developers or non-PDs). Investigations into differences between pain groups using low-demand tasks have predominantly reported neuromuscular differences involving the hip musculature and have shown capacity to distinguish pain groups. However, misclassification persists. There is little published data on pain groups in response to higher-demand challenges, which may elicit previously unseen or larger differences. Thus, the purpose of this study was to examine movement behavior and muscle recruitment patterns in healthy individuals that are non-PDs or PDs during a variety of tasks with increased functional demand and variety. It was hypothesized that the higher demand challenges will elicit previously unseen or enhanced differences in movement behavior and muscle recruitment in PDs relative to non-PDs. Healthy university students were recruited to participate in two sessions. The first session involved participants performing a prolonged standing work simulation to determine their pain status. The second session involved participants performing a movement screening protocol involving low and high demand variations of the following tasks: symmetric trunk flexion-extension, symmetric floor-to-knuckle lift, modified star excursion balance test, active hip abduction, and reverse side bridge. Participants were outfitted with 3D motion capture markers and surface electromyography prior to task performance. Depending on the task, the kinematic data of the trunk and lower limbs were characterized into the following dependent variables: thorax segment angular velocity, peak lumbar spine flexion angle, frontal plane knee excursion, limb length normalized reach distances, and movement arc length. Depending on the task, surface electromyography of the external obliques, lumbar erector spine, gluteus medius, and gluteus maximus muscles were processed into the following dependent variables: phase lags at maximum correlation between muscle pairs and regression slope of median power frequencies for assessment of muscle fatigue. A total of 39 participants were recruited and categorized, resulting in a subtotal of 22 non-PDs (12 females) and 17 PDs (8 females). Mixed-design analysis of variance analyses revealed no statistically significant main or interaction effects between pain status groups in most of the aforementioned kinematic and surface electromyography dependent variables. Interestingly, performance during the active hip abduction (AHA) revealed a pain status and task difficulty interaction effect (F(1,35) = 5.22, p < 0.05), with PDs exhibiting larger angular displacement arc length during AHA performance with an external weight relative to no external weight; not observed in non-PDs. The results of this investigation showed that although task demands demonstrated changes in various kinematic and muscle activation patterns across participants, it did not always coincide with an individual’s pain status. Nonetheless, a significant finding to emerge from this study is the potential interaction an external weight has on pain status with their performance during the AHA. Taken together, these results suggest that there is minimal evidence for tasks with increased functional demand and variety to elicit unseen or larger aberrant movement behavior and muscle activation patterns in PDs relative to non-PDs.
Assessing Workers’ Ability to Recognize Lifting Risk Factors for Low Back Pain: Investigating the Efficacy of a Simple Educational Message.
(University of Waterloo, 2015-12-21) Ngo, Binh
Introduction: Participatory ergonomic approaches have been shown to be an effective method for identifying work place hazards. Since in many workplaces, expertise in ergonomics is not available, simple educational messages to identify low back injury (LBI) hazards were developed. This thesis examined lifting risk perceptions of workers and the efficacy of a simple educational message on improving their ability to recognize key LBI hazards, in particular, lifting objects on or close to the ground. Methods: 178 participants from differing sectors were shown 44 different lifting videos (representing 36 lifting scenarios). These scenarios differed in terms of factors such as lifting height origin/destination, weight, and the amount of horizontal reach. Participants were asked to rate each video, from 0-10, on how likely they believed the lifting task they just saw could eventually lead to a low back injury. One of two educational messages was then shown to the participants. These messages were crafted with the help of academic experts and knowledge translation professionals in health and safety associations. One message was used as the intervention and spoke of the risk of lifting objects from close to the floor and the other as the control and spoke of the use of back belts in industry. After reading the message, participants were shown and asked to rate the same 44 lifting videos again, but in a different order. Participant’s ratings of risk were correlated to a biomechanically-based tool (3DMatch) that estimates low back loading. Results: As lifts deviated from a waist-to-waist height, light object lift (mean Likert score = 0.421 units), ratings of risk perception increased. The highest rated tasks were the floor-to-waist stoop lift, heavy floor-to-floor lift, and the heavy floor-to-waist lift (mean Likert scores = 7.73, 7.382, and 7.107 respectively). Pre-post score differences were used to assess message efficacy. Of the 36 types of tasks, 19 significantly changed in the Lifting Height Message receiving group compared to 3 in the Back Belt Message group. The 19 changes were mainly seen in the videos that had lift origins at floor height. Participant’ risk ratings correlated positively, albeit only moderately with 3DMatch (R-value = 0.495, p<0.05). Demographically stratified correlations were also positive but were weak to moderate in strength (R-value range = 0.357 to 0.674, p<0.05). Conclusion: The results support the use of a simple message to increase conceptual awareness of the important lifting hazard of lifting objects from near the ground. This increase in recognition is the first step in the injury prevention cycle of identifying hazards, assessing risks, and controlling hazards.
An Assessment of the Interplay between the Shoulders and the Low Back in Occupational Tasks: A Manual Patient Handling Example
(University of Waterloo, 2010-12-16T19:42:02Z) Belbeck, Alicia
Redundancy and variation are characteristics of humans. Many muscles contribute to producing a movement at a joint, allowing different strategies for task performance. Further, the shoulders and back are involved in many tasks, including manual materials handling, but flexibility as to their relative roles in performing a task exists. In nursing, where manual patient handling (MPH) occurs daily, a risk of injury exists resulting from interactions with patients that may require awkward postures or sudden shifts in hand forces. Although some recommended MPH techniques have been advocated, many focus on lowering the risk of low back injury, without considering the effect of these techniques on other body regions. This study aimed to identify differences in shoulder and back physical exposures between performing self-selected and recommended patient handling techniques designed to reduce low back exposures. Twenty female participants performed three repetitions of five manual patient handling tasks using a self selected technique, followed by three repetitions of the same tasks using techniques learned in an interposed training session. Peak, mean and cumulative muscle activity, peak resultant moment, and ratings of perceived exertion were compared for each of the tasks before and after training, as well as identifying meaningful changes between the joints in mean population strength using a static strength prediction program. Significant decreases occurred at both the left and right shoulders and the low back for most measures, generally supporting the recommended techniques. Important exceptions existed, however, for the Sit-to-Chair tasks and Turn Toward tasks, where increases in several individual shoulder muscle activities, along with peak resultant moment, existed. Future recommendations for patient handling techniques should take into account potential negative exposures at the shoulders that may result from a back-centric injury avoidance paradigm.

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