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首页> 外文学位 >Anisotropy of human muscle via non invasive impedance measurements. Frequency dependence of the impedance changes during isometric contractions.
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Anisotropy of human muscle via non invasive impedance measurements. Frequency dependence of the impedance changes during isometric contractions.

机译：通过非侵入式阻抗测量可得出人类肌肉的各向异性。等轴测收缩期间阻抗的频率依赖性变化。

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摘要

In this thesis we present non invasive muscle impedance measurements using rotatable probes extending the work done by Aaron et al. (1997) by measuring not only the real part of the impedance but the imaginary part as well. The results reveal orientations of underlying muscle fibers via minima in resistance and reactance versus angle curves, suggesting this method as potentially useful for studying muscle properties in clinical and physiological research.;Calculations of the current distribution for a slab of material with anisotropic conductivity show that the current distribution depends strongly on the separation of two current electrodes and as well as on its conducting anisotropy.;Forearm muscle impedance measurements at 50 kHz done by Shiffman et al. (2003) had shown that both resistance (R) and reactance (X) increase during isometric contraction. We have extended these measurements in the 3 to 100 kHz range and we found that resistance (R) and reactance (X) both increase and their changes increased or decreased at frequency dependent rates. Analysis based on circuit models of changes in R and X during the short contraction pulses showed that the extra cellular fluid resistance increased by 3.9 ± 1.4 %, while the capacitance increased by 5.6 ± 2 %. For long contraction pulses at very low frequencies: (1) there was practically no change in R during contraction, which implies that these changes are due to cellular membrane or intracellular effects with the extra cellular water component not participating, and (2) in post contraction stage there were no morphological changes which means that drifts in R can only be due to physiological changes.;Following Shiffman et al. (2003) we measured impedance changes of R and X during a triangular shaped pulse of force generated via isometric forearm muscle contraction at 50 kHz. We measured these changes in 3-100 kHz frequency range for a stair case pulse of forces and the results showed that they are frequency dependent. Analysis based on circuit models suggest that the increase of isometric forearm muscle contraction is accompanied with both extra and intra cellular effects. The decrease following it is accompanied with changes in the extra cellular components and with intracellular elements remaining at the values they have at the maximum contraction force.
机译：在本论文中，我们提出了使用可旋转探针的无创肌肉阻抗测量，这些测量扩展了Aaron等人的工作。 （1997年）不仅测量阻抗的实部，而且还测量虚部。结果通过电阻和电抗与角度曲线的极小关系揭示了基础肌肉纤维的取向，表明该方法对于研究临床和生理学研究中的肌肉特性具有潜在的实用价值;对具有各向异性电导率的材料的电流分布的计算表明：电流分布在很大程度上取决于两个电流电极的间隔及其导电各向异性。Shiffman等人在50 kHz下测量前臂肌肉的阻抗。 （2003年）表明，在等距收缩过程中，电阻（R）和电抗（X）均增加。我们将这些测量范围扩展到3至100 kHz，并且发现电阻（R）和电抗（X）均以频率相关的速率增加，并且其变化增加或减少。根据电路模型的分析，在短收缩脉冲期间R和X的变化表明，细胞外液的电阻增加3.9±1.4％，而电容增加5.6±2％。对于极低频的长收缩脉冲：（1）收缩过程中R几乎没有变化，这意味着这些变化是由于细胞膜或细胞内效应引起的，而多余的细胞水成分未参与其中;（2）收缩期没有形态学变化，这意味着R的漂移只能是由于生理变化引起的。 （2003年），我们测量了通过等距前臂肌肉在50 kHz下产生的三角形力脉冲期间R和X的阻抗变化。我们在阶梯力作用下的3-100 kHz频率范围内测量了这些变化，结果表明它们与频率有关。基于回路模型的分析表明，等距前臂肌肉收缩的增加同时伴有细胞内和细胞外效应。随之而来的减少伴随着细胞外成分的变化以及细胞内元素保持在最大收缩力时的值。

著录项

  • 作者

    Kashuri, Hektor.;

  • 作者单位

    Northeastern University.;

  • 授予单位 Northeastern University.;
  • 学科 Physics General.;Biophysics General.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 125 p.
  • 总页数 125
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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