The study aimed to assess whether a short-term, high-intensity cold acclimation protocol would modulate finger vasomotor [i.e., finger temperature (TF), cold induced vasodilation (CIVD)] responses and regional thermo-perception to localized cooling. Six men performed a hand cold provocation (consisting of a 30-min immersion in 8°C water), while being whole-body immersed, once, in 21°C water (i.e., cold trial; HYPO), and, the following day, in 35.5°C water (i.e., normothermic trial; NORM). The local cold provocations were repeated, in the same order, after 10 days. In the intervening period, the subjects undertook a whole-body cold acclimation pro-tocol, consisting of daily whole-body 14°C-water immersions for 5 consecutive days, for a maximum of 2 h, while the skin temperature of the right hand was maintained at 35.6 (0.1)°C. Thermal (rectal temperature, skin temperature, finger temperature) cardiorespiratory (mean arterial pressure (MAP), heart rate and oxygen uptake), and perceptual responses (thermal sensation and comfort, pain, affective valence) were monitored throughout the trials. The acclimation protocol resulted in hypothermic adaptation (i.e., habituation), which was characterized by a modest reduction in shivering and an attenuation of whole-body thermal discomfort. The main finding of the study was that, regardless of subjects’ thermal status, the 5-day whole-body cold acclimation protocol did not alter TF (P > 0.1) and CIVD responses (P > 0.2) during local cold stress. Yet, after the acclimation, the cold-induced increase in MAP was reduced and tended to be reduced during the HYPO (P = 0.05) and NORM (P = 0.14) local cold provocation trials, respectively. Furthermore, the perceived thermal discomfort and pain in the immersed hand appeared to be alleviated in all post-acclimation trials.

An adequate vascular perfusion status is essential not only to maintain life, but to ensure the proper physiology of the different systems that form the animal’s body. Due to its role in the transport of oxygen and nutrients toward, and the removal of cellular waste products away from the body’s tissues, the circulatory system is responsible for the maintenance of body homeostasis. Production related functions in farm animals are not an exception, and directly depend on sufficient vascular physiology. In the past, the study of blood flow in large domestic species was restricted to highly invasive techniques. However, even when such techniques are the foundation for the actual understanding of vascular dynamics in these animals, their limited feasibility and potential impact over the normal vascular physiology represent significant limitations to these approaches. Recently, the development and application of non-invasive technologies (i.e., Doppler and B- mode ultrasound) to the area of animal sciences has provided the potential for the study of vascular dynamics while, the negative implications aforementioned are avoided. In our studies, these technologies were applied to assess the role of the circulatory system on different production related variables such as: temperament, reproduction, and milk production in the bovine. A tendency toward differences in jugular blood flow was associated with the temperament in beef calves in this study. Also, a significant increase in vasodilation in the uterine arteries of beef cows was found to be associated with a numerically higher reproductive efficiency (i.e., pregnancy rates). Moreover, an increase in blood flow towards the mammary gland in dairy cows was associated with administration of bovine somatotropin. In conclusion, B- mode and Doppler ultrasound resulted in tools able to reflect the essential role of an adequate vascular perfusion in the normal physiology and productive performance in the bovine. However, in real farm scenarios the feasibility of these techniques in large domestic species is limited. Therefore, further specialization of this instrument to the conditions existent in such farm scenarios are recommended to improve its feasibility and to significantly accelerate the rate of knowledge acquisition in this area.

Data from the McMaster Occupational Biomechanics Laboratory were consolidated to evaluate overall trends relating to tissue motion and blood flow in the carpal tunnel. Regarding tissue motion, displacements of the flexor digitorum superficialis (FDS) tendon and its subsynovial connective tissue (SSCT) were found to decrease with greater movement speed and a flexed wrist posture. Notably, changes to shear outcomes including relative tendon-SSCT displacement, the shear strain index (SSI), and maximum velocity ratio (MVR) demonstrate that greater movement speed contributes to SSCT damage according to the shear strain mechanism of injury theorised to promote carpal tunnel syndrome (CTS). Median nerve blood flow was also found to be implicated by wrist flexion, and appeared to decrease with greater CTS severity status. Finally, induced blood flow alteration of the carpal tunnel was found to elicit a median nerve blood flow response similar to the level found in CTS subjects, confirming its effectiveness as an intervention to study tissue motion in a CTS-like state. The influence of altered blood flow on tissue motion was differential, where the higher supradiastolic condition altered FDS displacement, and the lower subdiastolic condition affected SSCT displacement and SSI. These findings provide valuable evidence for changes in median nerve blood flow—and by extension, the local fluid environment within the carpal tunnel—not only being a consequence of SSCT fibrosis characteristic of CTS, but potentially also acting as a cause for said changes in carpal tunnel tissue motion. / Thesis / Master of Science in Kinesiology / This thesis aimed to evaluate and summarize key findings from the McMaster Occupational Biomechanics Laboratory relating to tissue motion and blood flow in the carpal tunnel. Performing repetitive finger movements faster and with a flexed wrist posture were found to decrease the distance travelled of the underlying finger tendon. Blood flow of the median nerve, which is implicated in carpal tunnel syndrome (CTS), is higher with forceful exertion and flexed wrist posture, and lower with greater severity of CTS. Finally, altering blood flow to the carpal tunnel was found to create a CTS-like environment, affected tissue motion in the carpal tunnel, and promoted movement disparity between these tissues that is associated with injury. This suggests that fluid/blood flow changes affecting the carpal tunnel is a plausible mechanism for increasing the likelihood of developing CTS.

Inledning: Den optimala intensiteten för styrkeökning vid styrketräning anses vara 60–70% av 1RM (repetitions maximum). Ocklusionsträning innebär träning i samband med delvis strypning av det arteriella blodflödet via ett yttre tryck proximalt på extremiteten. Vid ocklusionsträning används oftast en yttre belastning som endast motsvarar 20–40% av 1RM. Syftet med den här litteraturöversikten var att undersöka effekten av lågintensiv ocklusionsträning i övre extremitet avseende styrka och hypertrofi i muskler proximalt och distalt om ocklusionen jämfört med hög- och/eller lågintensiv styrketräning. Metod: En systematisk litteratursökning genomfördes 2023-03-01. Databaserna som söktes var PubMed, SPORTDiscus och CINAHL. Sökningen kompletterades genom granskning av inkluderade studiers referenslistor. En kvalitetsgranskning av det sammanvägda resultatet utfördes enligt the Grading of Recommendations, Assessment, Development and Evaluation (GRADE).Resultat: Sökningen genererade 151 enskilda artiklar varav 15 artiklar inkluderades i studien. Kvalitetsgranskningen av underlaget visade på låg (⨁⨁◯◯) evidensgrad enligt GRADE. Två studier visade något större styrkeökning för ocklusionsträning jämfört med lågintensiv styrketräning på distal muskulatur, en visade ingen skillnad. Två studier visade större hypertrofi i ocklusionsgruppen jämfört med lågintensiv styrketräning på distal muskulatur, en visade ingen skillnad. Jämfört med högintensiv styrketräning på distal muskulatur var resultaten motsägelsefulla gällande styrka och hypertrofi. För proximal muskulatur gav ocklusionsträning större styrkeökningoch hypertrofi jämfört med lågintensiv styrketräning enligt majoriteten av studierna men verkade ge lägre styrkeökning och hypertrofi än högintensiv styrketräning. Konklusion: Ocklusionsträning i övre extremitet hos friska vuxna ger med låg säkerhet större styrkeökning och hypertrofi i muskulatur distalt och proximalt om ocklusionen jämfört med lågintensiv styrketräning. Jämfört med högintensiv styrketräning verkar ocklusionsträning ge relativt likvärdiga resultat för muskulatur distalt om ocklusionen men lägre styrkeökning och hypertrofi för proximal muskulatur. Dock bör dessa resultat tolkas med försiktighet på grund av de stora diskrepanserna mellan studierna när det kommer till träningsprotokoll, ocklusionsprotokoll och utvärderingsmetoder. / Introduction: The optimal intensity for strength gain during resistance training is thought to be 60-70% of 1RM (repetition maximum). Blood flow restriction training (BFRT) is when the arterial blood flow is partially occluded by a cuff placed proximally on the extremity during training. Usually during BFRT an external load equal to only 20-40% of 1RM is used. The aim of this study was to examine the effect of low intensity BFRT in the upper extremity regarding strength and hypertrophy in muscles proximally and distally to the occlusion site compared to high intensity resistance training (HI-RT) and/or low intensity resistance training (LI-RT). Method: A systematic search was conducted 2023-03-01. The databases that were searched wasPubMed, SPORTDiscus and CINAHL. The original search was supplemented by exploring the reference lists from the included studies. A quality assessment of the overall result was conducted according to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE).Results: Of 151 identified articles, 15 were included in the study. The quality assessment showed low (⨁⨁◯◯) quality evidence according to GRADE. Two studies showed slightly higher strength gain after BFRT compared to LI-RT in distal muscles, one study showed no difference between groups. Two studies showed higher hypertrophy after BFRT compared to LI-RT in distal muscles, one study showed no difference between groups. Compared to HI-RT on distal muscles the results were contradictory regarding strength and hypertrophy. BFRT on proximal muscles produced higherstrength gain and hypertrophy than LI-RT according to most studies but seemed to provide lower strength gain and hypertrophy than HI-RT. Conclusion: BFRT in the upper extremity generates, with low certainty, higher strength andhypertrophy in muscles distally and proximally to the occlusion site compared to LI-RT. Compared to HI-RT, BFRT produces equivalent results in distal muscles but lower strength gain and hypertrophy in muscles proximally to the occlusion site. These results should be interpreted with caution due to the large discrepancy between the included studies regarding training protocols, occlusion protocols and assessment methods.

Umbilical flow velocity waveforms (FVW' s) can be measured non-invasively using Doppler ultrasound. Changes in the FVW's occur long before the warning signs from other conventional monitoring methods. Correct interpretation of the changes in the FVW has the potential of providing the clinician with an early warning of foetal distress. A number of indices have been described in the literature to characterise the FVW including the Pulsatility Index (PI), the Resistance Index (RI) and more recently, the High Resistance State Index (HRSI). Researchers have shown a dependence of the FVW, and thus the indices which describe it, on factors such as the placental resistance (Muijsers et al 1990a) blood pressure pulsatility (Mulders et al 1986), and the foetal heart rate (Downing et al 1991). In order to model the foetal circulation, the dimensions of the foetal vessels were required. These were taken from the literature when available, but had to be supplemented by measurements on post mortem specimens. This information, together with blood pressures and flow rates taken from the literature, was used to design electrical analogous models of the foetal arterial circulation (model 1 and model 2), which were implemented using PSpice, which is an electronic circuit simulator package. The Flow Velocity Waveforms (FVW's) simulated were stored and then analyzed using MATLAB, which is a mathematical package to calculate the waveform indices and both the blood pressure and percentage blood flow to the different anatomical regions of the foetus. Model 1 is a simple model of the umbilical placental unit only, which assumes a rectified sine wave with a D.C. offset as an input waveform while Model 2 is a distributed element model of the complete foetal arterial system, including a realistic representation of the foetal heart. AIM: Simulations of the FVW were used to examine the effects of placental obliteration (raised placental resistance), placental size, foetal heart rate (FHR), blood pressure pulsatility (BPPI), mean blood pressure (BP), and site of measurement of the FVW along the umbilical artery and thus on the waveform indices which are used to describe it (RI, PI and HRSI). RESULTS/ DISCUSSION: The investigations using models 1 and 2 showed that the indices were significantly dependent on the placental resistance, the size of the placenta and the type of placental obliteration. Model 1 was also used to investigate the effect of FHR variations on the indices under the original assumption that the input waveform to the umbilical/placental unit was a rectified sinusoid offset by a constant voltage (D.C.) (Thompson and Trudinger 1990). The result obtained, that is, the FHR does not affect the indices (in particular the PI) needed further investigation because the assumption for the input waveform is not true under all conditions. For this reason, the simulations were repeated using model 2, with the interesting result that there is a difference between short term FHR variations and long-term FHR variation. Short term FHR variations had a pronounced effect on the indices. The blood pressure pulsatility and the indices concerned varied by large amounts in this case, which indicated a link between the blood pressure pulsatility and all the indices. Long term FHR variations had an inconsistent but small effect on the blood pressure pulsatility and in turn had a small effect on the RI and PI. The mean blood pressure in these simulations decreased with increasing FHR which resulted in a pronounced increase in the HRSI which indicated the dependency of this index on the mean blood pressure rather than on the blood pressure pulsatility. It was found that the HRSI is a good index of placental resistance and may be particularly useful in evaluating high placental resistance in cases of absent flow during diastole, since, in these cases it is only slightly affected by the FHR. A value of greater than 34 percent is the recommended HRSI value to indicate severe foetal distress. The results also indicate that the FVW shape varies along the umbilical artery and is far more pulsatile at the aortic (proximal) end than the placental end. This is reflected in the indices which thus have worst case values at the placental end. It is thus recommended that, where possible, the indices are measured at the placental end of the umbilical artery.

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Background: Vascular dysfunction due to hyperglycemia in individuals with diabetes is a factor contributing to distal symmetric polyneuropathy (DSP). Reactive oxygen species (ROS) reduce the bioavailability of nitric oxide (NO), a powerful vasodilator, resulting in reduced circulation and nerve ischemia. Increases in blood NO concentrations and circulation have been attributed to whole body vibration (WBV). The purpose of this study was to the determine the effects of low frequency, low amplitude WBV on whole blood NO concentration and skin blood flow (SBF) in individuals with symptoms of DSP. Research Design and Methods: Ten subjects with diabetes and impaired sensory perception in the lower limbs participated in this cross-over study. Each submitted to two treatment conditions, WBV and sham, with a one week washout period between. Blood draws for NO analysis and Doppler laser image scans of SBF were performed before, immediately after and following a 5 minute recovery of each the treatments. Results: Low frequency, low amplitude WBV vibration significantly increased skin blood flow compared to the sham condition (p=0.0115). Whole blood nitric oxide concentrations did not differ between the WBV and sham condition immediately or 5 minutes post-treatment ( p=0.1813) Conclusions: These findings demonstrate that subjects with diabetes respond to whole body vibration with increased skin blood flow compared to sham condition. The implication is that WBV is a potential non-pharmacological therapy for neurovascular complications of diabetes.

BACKGROUND: Age-related declines in endothelial function have been well documented with larger declines observed in middle-aged. Passive heat exposure has been shown to be a promising method to improve vascular endothelial health, with sauna specifically being linked to reduced risk of cardiovascular disease. Increases in blood flow and shear rates associated with heat exposure are often considered to have a major influence on the observed improved endothelial function following heat exposure. The magnitude of these changes in response to sauna have not yet been defined. Therefore, the purpose of this study is to quantify and compare the vascular response to an acute bout of sauna heating in young and middle-aged individuals. METHODS: 10 young (24.9 ± 4.2 years, 6 males and 4 females) and 8 middle-aged adults (55.6 ± 3.9 years 4 males and 4 females) underwent 40 min of sauna exposure at 80 oC. Esophageal and intramuscular temperatures were recorded throughout the duration of the experiment. Brachial and superficial femoral artery blood flow, artery diameter, and shear rates were recorded at baseline and following heat exposure. Brachial artery flow-mediated dilation (FMD) was measured at baseline and following 90 min of recovery. RESULTS: Core and muscle temperatures significantly increased by 1.5 ± 0.53 and 1.95 ± 0.70 °C, respectively (P < 0.05) and the magnitude of increase did not differ between young and middle-aged participants (P0.867 and 0.488, respectively). Shear rate increased by 170– 200% (P < 0.001), while blood flow increased by 180–390% (P < 0.001) in the superficial femoral and brachial artery, respectively, in both groups. Importantly, the changes in shear and flow did not significantly differ between young and middle-aged subjects for either artery (P = 0.190–0.899.) Systolic blood pressure (SBP) was significantly reduced from 135.25 ± 17.50 to 122.38 ± 19.7 mmHg (P = 0.017) only in middle-aged participants and a decrease in diastolic blood pressure was observed from 81.6 ± 13.0 mmHg at baseline to 69.8 ± 8.4 mmHg (P < .001). Heat-induced dilation was strongly correlated to baseline endothelial function in the young (R = 0.86, P = 0.006), but not the old (R = 0.22, P = 0.631). CONCLUSIONS: These results indicate that young and middle-aged adults have similar shear-rate and blood flow responses to acute sauna heating, which significantly reduces blood pressure in middle-aged, but not young individuals. Future heat therapy studies may elicit meaningful cardiovascular benefits from lower magnitudes of chronic passive heat stress.

Carotid artery wall stiffness has been widely considered as an index of vascular health, and has been associated with occurrence of cardiovascular events, such as stroke. In addition, the blood flow patterns in the carotid artery can yield crucial information on atherosclerosis progression and cerebrovascular impairment. Pulse wave imaging (PWI) is a non-invasive ultrasound imaging technique that tracks the propagation of the arterial pulse wave, providing thus regional arterial wall stiffness mapping. Moreover, towards enabling accurate visualization of blood flow patterns, ultrasound-based vector flow imaging (VFI) modalities have been developed. Building upon PWI and VFI techniques, the overall goal of this dissertation is to develop ultrasound-based methodologies that can provide simultaneous imaging of the carotid artery wall mechanics and blood flow dynamics at high temporal and spatial resolutions. The developed techniques are validated through vessel phantom experiments and simulations. Furthermore, their potential to diagnose pre-clinical stages of carotid artery disease and provide additional insights in risk for stroke assessment, is demonstrated in an atherosclerotic swine study and human subjects in vivo. More specifically: A method is presented that analyzes the pattern of arterial wall motion derived by PWI, in order to detect spatial mechanical inhomogeneity across an imaged artery, and provide piecewise arterial wall stiffness estimates. The proposed technique is validated in a phantom consisting of a soft and a stiff segment, while its feasibility is demonstrated to identify inhomogeneous wall properties in atherosclerotic human carotid arteries, as well as provide atherosclerotic plaque mechanical characterization in vivo. Subsequently, PWI is integrated with VFI techniques in the same ultrasound acquisition sequence, in order to enable simultaneous and co-localized imaging of arterial wall stiffness and blood vector flow velocity. The performance of the technique is investigated through experiments and FSI simulations. Moreover, its feasibility was shown to investigate associations between carotid artery Pulse Wave Velocity and blood flow patterns, in vivo. Based on the previously developed PWI and VFI modalities, a novel ultrasound-based technique is developed that combines high frame rate vector flow imaging with a data clustering approach, in order to enable direct and robust wall shear stress measurements. The performance of the proposed method is evaluated through vessel phantom experiments and simulations, while its feasibility is shown to detect pre-clinical stages of carotid artery disease in a swine model in vivo. In addition, a pilot clinical study is presented involving application of the developed modality in normal and atherosclerotic human carotid arteries in-vivo. Moving forward, the developed imaging modalities are used to implement novel clinical biomarkers based on carotid artery arterial wall mechanics and blood flow dynamics, that can potentially assist in risk for stroke assessment. The patterns of those biomarkers are investigated in the common carotid arteries of subjects with low degree of stenosis and medical history of stroke, against subjects without history of stroke. The same biomarkers are also analyzed with respect to stroke symptomatology in atherosclerotic patients with moderate to high degree of stenosis. Moreover, the developed techniques are used to identify vulnerable plaque components in subjects with fully developed plaques, as compared with CTA scans. Finally, a deep learning-based approach for motion tracking of the arterial wall throughout the cardiac cycle is proposed. A neural network is trained to learn the motion patterns of the carotid artery and potentially improve the quality of PWI. The performance of the technique is assessed in vessel phantom experiments and its feasibility is demonstrated in healthy human carotid arteries in-vivo.

Heart disease is the main cause of death today, and studying causes and treatments are of great interest. Blood flow simulations using computational fluid dynamics shows promise in providing insight into this area. This study builds upon previous work by Larsson et al. and Kronborg et al. who have developed a program for simulating the blood flow through patient specific left ventricles. More specifically we aimed to improve the accuracy of their blood flow simulation by accounting for the protruding structure of the endocardial wall, previously disregarded in the model due to the limitations in spacial accuracy of echocardiography. These structures, consisting of trabeculae carneae and papillary muscles, have been shown to have a significant impact on the blood flow. In a recent study, Sacco et al. proposed a solution were a porous layer could mimic the effects on the blood flow from these structures in a rigid heart model. Our study aimed to apply this modification to the left ventricle of the dynamic model using the Navier-Stokes-Brinkman flow equation and a subdomain defining the porous region. This study has been working towards the end goal of fully implementing the porous layer into the heart simulation. The equations needed have been formulated and simulations have been run on flow in a more simple setting to verify the model. The simulations show promise in being able to recreate the results from Sacco et al. but further development is needed before the porous model can be tested in the dynamic left ventricle model, most notably defining the porous subdomain in the dynamic model. We conclude that the porous domain will affect the flow, possibly breaking up vortices and reducing the wall shear stress. Confirming this requires additional studies, but the implementation of a porous domain would likely result in a more accurate simulation.