The purpose of the present study was to investigate the acute effects of local vibration on muscle performance at different durations and frequencies. Fifteen male handball players participated in the study voluntarily. University&rsquo / s Ethics Committee approved the study and the informed consent forms were filled by all participants. Different vibration durations, (10 sec, 1 min, 10 min), different frequencies (40 and 80 Hz), dominancy (dominant and non-dominant) and conditions (vibration and no-vibration) were independent variables of study. Dependent variables were maximum isometric strength measures under different situations. One way Repeated measures ANOVA, Bonferoni adjusted paired sample t-tests and Two way Repeated ANOVA was used for statistical analyses. Result of this study demonstrated that local vibration (LV) induced significantly higher muscle activity than no vibration (NV) condition. Strength improvements were obtained in quadriceps muscles of dominant and non-dominant legs for 40 Hz and 80 Hz. When 40 Hz vibration was applied to dominant leg with different durations (10 sec, 1 min, 10 min), significantly higher strength measures were found than no vibration. When 80 Hz vibration was applied to dominant leg with different durations (10 sec, 1 min, 10 min), only 10-sec vibration duration revealed significant increase in strength measures. When 40 Hz vibration was applied to non-dominant leg with different durations, (10 sec, 1 min, 10 min) significantly higher strength measures were found than no vibration. When 80 Hz vibration was applied to non-dominant leg with different durations (10 sec, 1 min, 10 min), 10-sec and 1 min vibration durations revealed significant increase in strength measures. However, no significant difference was obtained when the different vibration durations were compared between 40 Hz and 80 Hz.

<p>Is it possible for a minimal model of anaerobic muscle contraction to describe measured data? There have been many models trying to describe separate parts of the human body with various results. In this thesis a model has been created to describe all the essential biochemical reactions of anaerobic muscle metabolism during contraction but with as few states and parameters as possible. A toolbox in Matlab was used for simulation and also for parameter estimation. The best model eventually got validated to see statistically how well it can describe the measured data. During the simulations an unnecessary assumption got revealed which helped us to understand the system better. The vision of a whole-body model may not be so far into the future as many think and the first step is to understand smaller biochemical systems like muscle contraction.</p>

Thesis (Ph. D. in Pharmacology)--Vanderbilt University, Dec. 2009. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri--Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 122-137). Also available on the Internet.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2009. / Härtill 5 uppsatser.

published_or_final_version / Pharmacology and Pharmacy / Doctoral / Doctor of Philosophy

The State of Texas has the most extensive network of surface-treated pavements in the nation. This network has suffered from the detrimental effects of expansive soils in the subgrade for decades. Longitudinal cracking on the Farm-to-Market (FM) network is one of the most prevalent pavement distresses caused by volumetric changes of expansive subgrades. Engineering practice has shown that geogrid reinforcement and lime treatment can effectively reduce the reflection of longitudinal cracking on the pavement over shrinking subgrade. However, little is known about the mechanism leading to the propagation of the shrinkage cracks to the surface of the pavement. The use of geogrid reinforcement and lime treatment is mostly based on empirical engineering experience and has not been addressed in depth. This dissertation research evaluates the stress field and constitutive models of the subgrade soil subjected to matric suction change. The non-uniform matric suction change in the subgrade is simulated by a thermal expansion model in a finite element program, ABAQUS, to determine the shrinkage stresses in the subgrade soil and pavement structure. Numerical solution by the finite element analysis shows that the most likely location of shrinkage crack initiation in the subgrade is close to the pavement shoulder and close to the interface of the base and subgrade. Linear elastic fracture mechanics theory is used to analyze the crack propagation in the pavement. Compared to the fracture toughness of the pavement materials, the stress concentration at the initial shrinkage crack tip is large enough to drive the crack to propagate further. When the shrinkage crack propagates through the whole pavement structure, a longitudinal crack develops at the pavement surface close to the pavement shoulder. Based on the analysis of shrinkage crack propagation, this dissertation investigates the mechanism of geogrid reinforcement and lime treatment. The geogrid can significantly reduce the stress concentration at the crack tip if the geogrid is placed at the bottom of the base. A geogrid with a higher stiffness further reduces the stress intensity factor at the upper tip of the shrinkage crack. The lime treatment can improve the mechanical properties of the expansive soil in several ways. The lime-treated soil has lower plasticity index, higher tensile strength and higher fracture toughness. The possible location of the shrinkage crack initiation is not in the lime-stabilized soil but in the untreated natural soil close to the bottom of the lime-treated layer, where tensile stresses exceed the tensile strength of the untreated soil. The shrinkage crack is less likely to develop through lime-treated soil, which has increased fracture toughness. The combination of geogrid reinforcement and lime treatment offers the most benefit for the control of dry-land longitudinal cracking. In a pavement with a lime-treated layer, the best place to install the geogrid is at the interface between the lime-stabilized layer and the untreated natural soil. If using a geogrid with high stiffness, the Mode I stress intensity factor may be reduced to a certain level that is lower than the fracture toughness of the pavement material.

Is it possible for a minimal model of anaerobic muscle contraction to describe measured data? There have been many models trying to describe separate parts of the human body with various results. In this thesis a model has been created to describe all the essential biochemical reactions of anaerobic muscle metabolism during contraction but with as few states and parameters as possible. A toolbox in Matlab was used for simulation and also for parameter estimation. The best model eventually got validated to see statistically how well it can describe the measured data. During the simulations an unnecessary assumption got revealed which helped us to understand the system better. The vision of a whole-body model may not be so far into the future as many think and the first step is to understand smaller biochemical systems like muscle contraction.

No description available.

This thesis investigates the origin of spontaneous activity in the uterus. This organ does not show any activity until shortly before delivery, where fast and efficient contractions are generated. The aim of this work is to provide insight into the origin of spontaneous oscillations and into the transition from asynchronous to synchronized activity in the pregnant uterus. One intriguing aspect in the uterus is the absence of any pacemaker cell. The organ is composed of muscular cells, which are excitable, and connective cells, whose behavior is purely passive; None of these cells, taken in isolation, spontaneously oscillates. We develop an hypothesis based on the observed strong increase in the electrical coupling between cells in the last days of pregnancy. The study is based on a mathematical model of excitable cells, coupled to each other on a regular lattice, and to a fluctuating number of passive cells, consistent with the known structure of the uterus. The two parameters of the model, the coupling between excitable cells, and between excitable and passive cells, grow during pregnancy.Using both a model based on measured electrophysiological properties, and a generic model of excitable cell, we demonstrate that spontaneous oscillations can appear when increasing the coupling coefficients, ultimately leading to coherent oscillations over the entire tissue. We study the transition towards a coherent regime, both numerically and semi-analytically, using the simple model of excitable cells. Last, we demonstrate that, the realistic model reproduces irregular action potential propagation patterns as well as the bursting behavior, observed in the in-vitro experiments.