Bileaflet mechanical heart valves (BMHVs), though a life-saving tool in treating heart valve disease, are often associated with serious complications, including a high risk of hemolysis, platelet activation, and thromboembolism. One likely cause of this hyper-coagulative state is the nonphysiologic levels of stress experienced by the erythrocytes and platelets flowing through the BMHVs. Research has shown that the combination of shear stress magnitude and exposure time found in the highly transient leakage jet emanating from the b-datum gap during valve closure is sufficient to cause hemolysis and platelet activation. Regions of flow stasis in the valve vicinity may also allow activated platelets to aggregate and form thrombus. This thesis addresses the hypothesis that passive flow control may have the potential to reduce flow-induced thrombogenicity by altering the fluid mechanics of bileaflet mechanical heart valves. To test this hypothesis, a steady model of the regurgitant b-datum line jet was developed and studied. This model served as a test bed for various vortex generator array designs. The fluid mechanics of the b-datum line jet model was investigated with flow visualization and particle image velocimetry. In vitro tests with whole human blood were performed with and without the vortex generators in order to determine how the presence of the passive flow control affected the propensity of the blood to form thrombus. An effort was then made to correlate the fluid mechanics of the jet model with the procoagulant potential results from the blood experiments. The effect of the vortex generators on the fluid mechanics of the valve under physiologic pulsatile conditions was also investigated via flow visualization in the Georgia Tech Left Heart Simulator. By studying a steady model of the regurgitant b-datum line jet, it was found, using an in vitro system with whole human blood, that the presence of vortex generators significantly decreased the blood's propensity for thrombus formation. The potential of applying passive flow control to cardiovascular hardware in order to mitigate the injurious effects of shear-induced platelet activation is thus demonstrated. The investigation into the effect of vortex generators on the fluid mechanics of the b-datum line jet showed that the jet oscillated aperiodically and that the effect of the applied flow control was played out at both the scale of the chamber (large-scale) and on the scale of the vortex generator fins (small-scale). On the large scale, the presence of vortex generators appeared to decrease the magnitude or frequency of jet oscillation, thereby stabilizing the jet. After removing the effect of the large-scale oscillations via phase averaging, the effect of the vortex generators on the small scale was examined. On the small scale, the jet without flow control was found to have higher levels of velocity RMS, particularly on the jet periphery, and higher levels of Reynolds shear stress. It is proposed that the vortex generators effect this change by generating vorticity in the plane of the jet. This vorticity is theorized to stabilize the jet, delaying roll-up of the jet shear layer which occurs via the Kelvin-Helmholtz instability. The method by which the vortex generators acted on the fluid mechanics of the steady jet system to decrease the blood's procoagulant potential was investigated via flow visualization and DPIV. The results from these studies implicate two possible mechanisms by which the vortex generators may act. First, the peak turbulent shear stresses in the jet were reduced by 10-20% with the application of vortex generators. Even if only a few platelets were activated in each passage through the valve, the cumulative effect of this difference in peak stresses after many passes would be greatly magnified. Thus, this reduction in turbulent shear stresses may be sufficient to explain the change seen in the blood's procoagulant potential with the application of passive flow control. It is suspected, though, that the second mechanism is dominant. The flow fields revealed that the presence of the vortex generators delayed or prevented the roll-up of the Kelvin-Helmholtz instability in the b-datum jet's shear layers into discrete vortices. By doing so, it is thought that opportunities for the interaction of activated and unactivated platelets entrained in these vortices were prevented, thereby inhibiting further propagation of the coagulation cascade. Even if the rate at which platelets were activated was similar for cases with and without flow control, it seems that the flow fields experienced by the platelets subsequent to activation can determine the level of procoagulant potential. Under the steady conditions observed in this experiment, the jet influenced by vortex generators was thus shown to induce significantly lower levels of procoagulant potential.

MRI can provide anatomical, functional, and physiological images at relatively high spatial resolution and is non-invasive and does not have depth limitation. However, the application of MRI to study the retina is difficult due to the very small size of the retina. This thesis details the development of MRI methods to image blood flow (BF), anatomy, and function of the retina and choroid, and their application to two diseases of the retina: diabetic retinopathy and retinal degeneration. A unique continuous arterial spin labeling technique was developed to image BF in mice and tested by imaging cerebral BF. This method was then applied to image layer-specific BF of the retina and choroid in mice, and to acquire BF functional MRI of the retina and choroid in response to hypoxic challenge. Additionally blood oxygen level dependent functional MRI of the mouse retina and choroid in response to hypoxic challenge was obtained using a balanced steady state free precession sequence which provides fast acquisition, has high signal to noise ratio, and does not have geometric distortion or signal dropout artifacts. In a mouse model of diabetic retinopathy, MRI detected reduced retinal BF in diabetic animals. Visual function in the diabetic mice, as determined by psychophysical tests, was also reduced. Finally, in a mouse model of retinal degeneration, BF and anatomical MRI detected reductions of retinal BF and the thickness of the retina. The studies detailed in this thesis demonstrate the feasibility of layer-specific MRI to study BF, anatomy, and function, in the mouse retina. Further, these methods were shown to provide a novel means of studying animal models of retinal disease in vivo.

The human foot has been accepted over the years as an important source of afferent input, used not only in the recognition of the surrounding environment (e.g. hard and soft surfaces), but also in the fine regulation of common daily-live movements (e.g. gait and balance control). The performance of these movements is usually accompanied by fluctuations in foot skin temperature as well as reciprocal blood flow changes at the foot area. Moreover, both variables are likely to be affected by footwear usage. Although these three factors are constantly present during the performance of daily live movements, only little and partially controversial information regarding the effects of foot skin temperature, blood flow at the foot area and footwear on foot sensitivity can be found in the literature. Therefore, the goal of the thesis was to investigate the effects of foot skin temperature, blood flow at the foot area and footwear on plantar foot vibration sensitivity of healthy young subjects. Three single studies were performed in order to investigate each variable separately. The first study investigated the influence of foot sole skin temperature on plantar foot sensitivity of 40 healthy subjects. Vibration thresholds were measured at 200Hz at a initial baseline temperature and after cooling/warming the foot skin 5-6 °C. The second study investigated the influence of short-time lower leg ischemia on plantar foot vibration sensitivity of 39 young adults. Lower leg ischemia was evoked with a pneumatic tourniquet, placed about 10cm above the popliteus cavity. Vibration thresholds were measured at 200 Hz in three different cuff pressure conditions: baseline (0 mmHg), low (50 mmHg) and high (150 mmHg). Finally, the influence of footwear on foot sensitivity was investigated in the third study, using specific Formula 1 shoes. Twenty-five male subjects participated in the study. Plantar foot vibration thresholds were measured at 30 and 200 Hz in five different foot/shoe conditions (barefoot and four shoe conditions). In all studies, vibration thresholds were measured at three anatomical locations of the plantar foot: heel, first metatarsal head (MET I) and hallux. The main results of the three studies show that the analysed variables significantly influence plantar foot vibration sensitivity. Data from the first study show that 5-6 °C alterations in foot skin temperature significantly influence the foot sensitivity of healthy young adults, whereby skin cooling results in reduced foot sensitivity, whereas skin warming improves plantar foot vibration sensitivity. The results of the second study indicate that short-time lower leg ischemia; especially regarding the high cuff pressure condition (150 mmhg), significantly reduces plantar foot sensitivity. Data from the third study show that the footwear effects on foot sensitivity are frequency-dependent. While barefoot sensitivity is better than shod sensitivity at 30Hz, shod sensitivity is better than barefoot sensitivity when measured at 200Hz. In conclusion, foot sole skin temperature, blood flow at the foot area and footwear significantly influence the plantar foot vibration sensitivity of healthy young adults. The alterations in foot sensitivity caused by these variables have important consequences for future clinical as well as movement-related research. Future clinical applications of quantitative sensory testing should consider the influence of these three factors during the assessment of sensory data, in order to standardize the measurement procedures as well as to enhance the quality of the collected data. Regarding the movement-related research, further studies should try to identify the importance of foot sensitivity for the performance of different types of movements (including sport-related activities). Additionally, the combined effects of movement-related changes in foot skin temperature and blood flow should be analysed and integrated in the development process of functional footwear, which is able to fulffill the foot sensitivity requirements of different movements. / Die Rolle des menschlichen Fußes als wichtiger „Mediator“ sensorischer Reize wird zunehmen in der Literatur akzeptiert. Die vom Fuß aufgenommenen afferenten Informationen werden im Zentralen Nervensystem integriert und weitergeleitet, um die Regulation typischer Bewegungsmuster (z.B. Gang und Gleichgewichtskontrolle) mitzusteuern. Während der Durchführung derartiger Bewegungen werden oftmals Änderungen der Hauttemperatur oder auch des Blutflusses im Fußbereich provoziert. Diese werden wiederum durch das Tragen von Schuhen beeinflusst. Obwohl Hauttemperatur, Blutfluss im Fußbereich und Schuhwerk wichtige Faktoren bei der Bewegungsdurchführung darstellen, können nur wenige und teilweise konträre Informationen über den Einfluss dieser Faktoren auf die Fußsensibilität in der Literatur gefunden werden. Somit hat diese Dissertation zum Ziel, den Einfluss der Temperatur der Fußsohle, des Blutflusses am Fußbereich sowie des Schuhwerkes auf die Vibrationssensibilität des plantaren Fußes gesunder Probanden zu untersuchen. Um den Einfluss der einzelnen Parameter auf die Fußsensibilität untersuchen zu können, wurden drei Studien durchgeführt. Die erste Studie hatte zum Ziel, den Einfluss der Temperatur der Fußsohle auf die Vibrationssensibilität von 40 Probanden zu untersuchen. Dabei wurden die Vibrationsschwellen, - mit einer Frequenz von 200 Hz -, bei einer Ausgangsmessung sowie nach einer 5-6 °C Abkühlung/Erwärmung der Haut der Fußsohle gemessen. In der zweiten Studie wurde der Einfluss einer Kurzzeitischämie des Unterschenkels auf die plantare Fußsensibilität von 39 Probanden getestet. Die Ischämie im Unterschenkel wurde mit Hilfe eines im Bereich der fossa popliteal platzierten pneumatischen Tourniquets hervorgerufen. Die plantaren Vibrationsschwellen wurden mit einer Frequenz von 200Hz in drei verschiedenen Druckbedingungen ermittelt: Ausgang (0 mmHg), niedrig (50 mmHg) und hoch (150 mmHg). Schließlich beschäftigt sich die dritte Studie mit dem Einfluss vom Schuhwerk auf die Fußsensibilität. Fünfundzwanzig Probanden haben an der Studie teilgenommen. Die Vibrationsschwellen wurden mit Frequenzen von 30 und 200 Hz bei fünf verschiedenen Bedingungen gemessen (eine Barfuss- und vier Schuhbedingungen). In allen Studien wurden die Vibrationsschwellen im plantaren Fußbereich unter der Ferse, dem Metatarsalkopf I sowie unter dem Hallux ermittelt. Die Ergebnisse der drei Studien zeigen, dass die analysierten Parameter einen signifikanten Einfluss auf die plantare Vibrationssensibilität der Probanden haben. Die erste Studie zeigt, dass eine 5-6° C - Schwankung der Hauttemperatur der Fußsohle die Fußsensibilität signifikant beeinflusst, wobei die Erwärmung der Haut eine Zunahme der Fußsensibilität verursacht und die Abkühlung eine Abnahme der Fußsensibilität hervorruft. Die Ergebnisse der zweiten Studie demonstrieren, dass die im Unterschenkel hervorgerufene Ischämie eine Verschlechterung der Fußsensibilität verursacht, insbesondere bei den Messungen der Hochdruckbedingung (150 mmHG). Die Daten der dritten Studie weisen darauf hin, dass der Einfluss vom Schuhwerk auf die Vibrationssensibilität des plantaren Fußes frequenzabhängig ist. Bei einer Vibrationsfrequenz von 30Hz ist die Sensibilität barfuss besser als die mit Schuhen gemessene Vibrationssensibilität. Hingegen ist bei einer Frequenz von 200 Hz die mit Schuhen gemessenen Sensibilität besser als die Sensibilität barfuss. Anhand der Ergebnisse der drei Studien konnte festgestellt werden, dass die Temperatur der Fußsohle, Blutfluss im Fußbereich und Schuhwerk einen signifikanten Einfluss auf die plantare Vibrationssensibilität gesunder Probanden haben. Daraus folgen wichtige Hinweise für zukünftige klinische- sowie bewegungsorientierte Forschung. Der Einfluss der drei analysierten Parameter sollte künftig bei der Beurteilung sensorischer Daten mit einbezogen werden. Dies würde zum einem eine Standardisierung der Messverfahren gewährleisten, zum anderen die Qualität der im klinischen Bereich gemessenen Daten erhöhen. Im Rahmen bewegungsorientierter Forschung soll die Wichtigkeit der Fußsensibilität bei der Durchführung unterschiedlicher Bewegungsformen, auch sportlicher Bewegung, näher untersucht werden. Weiterhin sollte eine gemeinsame Analyse der bewegungsbezogenen Änderungen der Hauttemperatur bzw. des Blutflusses im Fußbereich in künftiger Forschung angestrebt werden. Folglich können diese Änderungen in die Entwicklung funktionellen Schuhwerkes eingesetzt werden, um den Anforderungen der Fußsensibilität bei unterschiedlichen Bewegungsformen möglichst gerecht zu werden.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 162-176).

Hemodynamic monitoring is extremely important in the accurate measurement of vital parameters. Current methods are highly invasive or noncontinuous, and require direct access to the patient’s skin. This study intends to explore the modulated magnetic signature of blood method (MMSB) to attain blood flow information. This method uses an applied magnetic field to magnetize the iron in the red blood cells and measures the disturbance to the field with a magnetic sensor [1]. Exploration will be done by experimentally studying in-vitro, as well as simulating in COMSOL the alteration of magnetic fields induced by the flow of a magnetic solution. It was found that the variation in magnetic field is due to a high magnetization of blood during slow flow and low magnetization during rapid flow. The understanding of this phenomenon can be used in order to create a portable, non-invasive, continuous, and accurate sensor to monitor the cardiovascular system.

During each cardiac cycle pulsatile arterial blood inflates the vascular bed of the brain, forcing cerebrospinal fluid (CSF) and venous blood out of the cranium. Excessive arterial pulsatility may be part of a harmful mechanism causing cognitive decline among elderly. Additionally, restricted venous flow from the brain is suggested as the cause of multiple sclerosis. Addressing hypotheses derived from these observations requires accurate and reliable investigational methods. This work focused on assessing the pulsatile waveform of cerebral arterial, venous and CSF flows. The overall aim of this dissertation was to explore cerebral blood flow and intracranial pulsatility using MRI, with respect to measurement, physiological and pathophysiological aspects. Two-dimensional phase contrast magnetic resonance imaging (2D PCMRI) was used to assess the pulsatile waveforms of cerebral arterial, venous and CSF flow. The repeatability was assessed in healthy young subjects. The 2D PCMRI measurements of cerebral arterial, venous and CSF pulsatility were generally repeatable but the pulsatility decreased systematically during the investigation. A method combining 2D PCMRI measurements with invasive CSF infusion tests to determine the magnitude and distribution of compliance within the craniospinal system was developed and applied in a group of healthy elderly. The intracranial space contained approximately two thirds of the total craniospinal compliance. The magnitude of craniospinal compliance was less than suggested in previous studies. The vascular hypothesis for multiple sclerosis was tested. Venous drainage in the internal jugular veins was compared between healthy controls and multiple sclerosis patients using 2D PCMRI. For both groups, a great variability in the internal jugular flow was observed but no pattern specific to multiple sclerosis could be found. Relationships between regional brain volumes and potential biomarkers of intracranial cardiac-related pulsatile stress were assessed in healthy elderly. The biomarkers were extracted from invasive CSF pressure measurements as well as 2D PCMRI acquisitions. The volumes of temporal cortex, frontal cortex and hippocampus were negatively related to the magnitude of cardiac-related intracranial pulsatility. Finally, a potentially improved workflow to assess the volume of arterial pulsatility using time resolved, four-dimensional phase contrast MRI measurements (4D PCMRI) was evaluated. The measurements showed good agreement with 2D PCMRI acquisitions. In conclusion, this work showed that 2D PCMRI is a feasible tool to study the pulsatile waveforms of cerebral blood and CSF flow. Conventional views regarding the magnitude and distribution of craniospinal compliance was challenged, with important implications regarding the understanding of how intracranial vascular pulsatility is absorbed. A first counterpoint to previous near-uniform observations of obstructions in the internal jugular veins in multiple sclerosis was provided. It was demonstrated that large cardiac- related intracranial pulsatility were related to smaller volumes of brain regions that are important in neurodegenerative diseases among elderly. This represents a strong rationale to further investigate the role of excessive intracranial pulsatility in cognitive impairment and dementia. For that work, 4D PCMRI will facilitate an effective analysis of cerebral blood flow and pulsatility.

This dissertation presents the development and use of a novel optical imaging system capable of monitoring changes in blood flow, oxygenated hemoglobin, deoxygenated hemoglobin, and absolute pO₂ in the brain. There are several imaging modalities capable of monitoring these parameters separately. Laser speckle contrast imaging (LSCI) and multi-spectral reflectance imaging (MSRI) have been used to monitor relative blood flow and hemoglobin changes respectively. Phosphorescence quenching, while not typically used for imaging, is capable of noninvasive measurements of pO₂. Combining these three techniques has led to the development of an imaging system that could ultimately lead to a better understanding of brain physiology. By combining techniques such as LSCI and MSRI, it becomes possible to estimate the cerebral metabolic rate of oxygen (CMRO₂), an important indicator of neuronal function. It is equally important to understand absolute pO₂ levels so that oxygen metabolism can be examined in context. Integrating phosphorescence quenching and a spatial light modulator into the imaging system allowed absolute pO₂ to be simultaneously measured in distinct regions. This new combined system was used to investigate pathophysiological conditions such as cortical spreading depression (CSD) and ischemia. The observed hemodynamic changes associated with these events were largely dictated by baseline oxygen levels and varied significantly in different regions. This finding highlighted the importance of having a system capable of monitoring hemodynamic changes and absolute pO₂ simultaneously while maintaining enough spatial resolution to distinguish the changes in different regions. It was found that animals with low baseline pO₂ were unable to deliver enough oxygen to the brain during events like CSD because of the high metabolic demand. In order for this technique to become more prevalent among researchers, it is essential to make it cost effective and simple to use. This was accomplished by replacing the expensive excitation sources with cheaper light emitting diodes (LEDs) and redesigning the software interface so that it was easier to control the entire device. The final system shows the potential to become a key tool for researchers studying the role of absolute pO₂ and other hemodynamic parameters during pathophysiological conditions such as CSD and ischemia. / text

No description available.

Στην παρούσα διατριβή μελετάται η ροή βιομαγνητικών ρευστών υπό την επίδραση μαγνητικού πεδίου. Ως βιομαγνητικό ορίζεται ένα ρευστό το οποίο υπάρχει σε έναν έμβιο οργανισμό και η ροή του επηρεάζεται πάντοτε από την παρουσία μαγνητικού πεδίου. Χαρακτηριστικό βιομαγνητικό ρευστό θεωρείται το αίμα και αυτό χρησιμοποιείται για να δωθούν τιμές στις παραμέτρους που εμφανίζονται στα προβλήματα που μελετώνται.... / - / The flow of biomagnetic fluids in the presence of an applied magnetic field is studied in the present thesis. As biomagnetic is defined a fluid that exists in a living creature (biofluid) and its flow is affected by the presence of a magnetic field. The most characteristic biofluid is the blood. The Newtonian viscous laminar incompressible blood flow is considered in the present thesis for the estimation of the parameters appearing in the problems under consideration. An introduction is made at the first chapter of the thesis concerning fundamental concepts of the magnetic fluids such as the magnetization and equilibrium flow. Experimental applications in the biomedicine are also given as well as the mathematical model describing the flow of biological fluids under the influence of an applied magnetic field. In order to investigate the effect of the magnetic field in the next three chapters basic flow problems of biomagnetic fluid (blood) are studied. In the second chapter the flow over a stretching sheet under the influence of an applied magnetic field is studied. The physical problem is described by a coupled system of non linear partial differential equations (pdes) with their appropriate boundary conditions. For the variation of the magnetization with the temperature and/or the magnetic field intensity two cases are considered (I and II). The arising system describing the physical problem is transformed into corresponding coupled systems of non linear ordinary differential equations (ods) after the introduction of proper non dimensional variables. For the numerical solution, finite differences are used for the case I, whereas a spectral method with Chebyshev polynomials is also used for the case II. It is apparent that the application of the magnetic field increases the skin friction and the pressure on the surface, whereas the heat transfer is reducing. A comparison is also made between the two numerical methods used in the case II. The efficiency and the accuracy of the spectral method over against the finite differences method are demonstrated. The superiority of the spectral method is apparent especially when high accuracy solution is desired. In the third chapter the fundamental problem of the biomagnetic fluid flow taking place in a rectangular duct under the influence of an applied magnetic field is studied. For the numerical solution of the problem, which is described by a coupled and non linear system of PDEs, with their appropriate boundary conditions, the stream function-vorticity formulation is adopted and the solution is obtained developing an efficient numerical technique based on the upwind finite differences joint with a line by line implicit method. Results concerning the velocity and temperature field, skin friction and rate of heat transfer indicate that the presence of magnetic field appreciable influence the flow field. The three dimensional, fully developed flow of a biomagnetic fluid in an impermeable rectangular duct under the influence of an applied magnetic field is numerically studied in the fourth chapter. The system of the partial differential equations, resulting after the introduction of appropriate non-dimensional variables, is solved applying an efficient numerical technique based on a pressure-linked pseudotransient method on a collocated grid. Results concerning the existence and the uniqueness of the solution are also given. The obtained results, for different values for the parameters entering into the problem under consideration, show that the flow is appreciably influenced by the presence of the magnetic field in the sense of reduction of the axial velocity and the formation of two vortices at the transverse plane. These first results indicate that the magnetic field significantly influences the blood flow and encourage further study in more complex geometries, oscillatory flow or including the non-Newtonian behaviour of blood in order to demonstrate applications in biomechanics and biomedicine.

Temos aktualumas: Sportinėje praktikoje taikomi įvairaus intensyvumo statiniai ir dinaminiai fiziniai pratimai. Statinė ir dinaminė ištvermė yra kaip darbingumo rodiklis, priklausantis nuo maksimalių tiriamojo pastangų. Statinė ir dinaminė raumenų ištvermė fiziniuose krūviuose 50 proc. arba 75 proc. MVJ yra savarankiški fiziologiniai funkciniai mėginiai, rodantys judėjimo aparato funkcines galimybes. Svarbu žinoti skirtingo intensyvumo 50 proc. MVJ ir 75 proc. MVJ, ir rėžimo fizinių krūvių poveikį funkcinei raumenų būsenai, širdies ir kraujagyslių sistemos veiklai. Tikslas: Įvertinti ištvermės sporto šakų sportininkų, kai kurių ŠKS parametrų ir arterinės kraujotakos kaitą blauzdos raumenyse atliekant 50 proc. ir 75 proc. MVJ statinius ir dinaminius fizinius krūvius. Uždaviniai: 1. Nustatyti statinių ir dinaminių fizinių krūvių 50 proc. ir 75 proc. MVJ poveikį pėdos lenkiamųjų raumenų darbingumui. 2. Nustatyti statinių ir dinaminių fizinių krūvių 50 proc. ir 75 proc. MVJ iki visiško nuovargio poveikį arterinės kraujotakos kaitai blauzdos raumenyse. 3. Nustatyti statinių ir dinaminių fizinių krūvių 50 proc. ir 75 proc. MVJ iki visiško nuovargio poveikį AKS ir ŠSD kaitai. Hipotezė: Ištvermės sporto šakų sportininkams daugiau priimtinas funkcinis mėginys 75 proc. MVJ tiek statiniam, tiek dinaminiam fiziniam darbingumui įvertinti negu 50 proc. MVJ. Tyrimo metodai: Dinamometrija, ergometrija, veninė okliuzinė pletizmografija, arterinio kraujo spaudimo matavimas, pulsometrija... [toliau žr. visą tekstą] / Research background and hypothesis. In sport activity different intensity static and dynamic exercises are used. Static and dynamic endurance is an activity rate dependent on maximum voluntary contraction. Static and dynamic muscles endurance in sport activity 50 per cent or 75 per cent MVC are a physiological functional test, which shows locomotor functional abilities. It is important to know different intensity 50 per cent and 75 per cent MVC physical activities influence functional muscular and cardiovascular systems. Hypothesis: endurance sports athletes accept more functional test of 75 perc ent MVC both static and dynamic physical activity nor 50 per cent. Research aim. Analyze endurance athletes some of the heart vascular systems parameters and arterial blood flow changes of the intensity in the calf muscle in different intensities 50 per cent and 75 per cent MVC static and dynamic exercises. Objectives of the study. 1. Identifying static and dynamic physical loads 50 and 75 per cent. MVC influence of foot flexion muscles working capacity. 2. Identifying static and dynamic physical loads 50 and 75 per cent. MVC until exhaustion, arterial blood flow changes of the calf muscles. 3. Identifying static and dynamic physical loads 50 and 75 per cent MVC until exhaustion blood preassure and heart rate changes. Research methods. Dynamometry, ergometry, venous occlusive plethysmography, arterial blood preassure measurement, pulsometry, statistical analysis. Research... [to full text]