Ebook Muscle contraction and cell motility: Part 2
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Ebook Muscle contraction and cell motility: Part 2
Chapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences an Ebook Muscle contraction and cell motility: Part 2nd Design, Japan Women’s University, Tokyo ì 12-ỈỈ6ỈH, Japan^Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-3902, Japansasakik@fc.jwu.ac.jp, ishii@idaten.c.u-tokvo.ac.jpRecently, an ultrasound-based elastographlc technique called supersonic shea Ebook Muscle contraction and cell motility: Part 2r imaging (SSI) has been developed and used to measure stiffness (shear modulus) of in vivo muscles. This review describes the theoretical backgroundEbook Muscle contraction and cell motility: Part 2
of SSI, summarizes some basic observations on the shear modulus of contracting human muscles, and presents the latest experimental findings. It is welChapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences an Ebook Muscle contraction and cell motility: Part 2shear modulus and motor unit activity assessed with surface electromyography. Moreover, we have demonstrated both the length-dependent changes in shearMuscle Contraction and Cell Motility Fundamentals and DevelopmentsEdited by Haruo SugiCopyright © 2017 Pan Stanford Publishing Pte. Ltd.ISBN 978-981- Ebook Muscle contraction and cell motility: Part 24745-16-1 (Hardcover), 978-981-4745-17-8 (eBook)www.panstanford.com210 I Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingEbook Muscle contraction and cell motility: Part 2
modulus and the association of shear modulus with contractile force, even when the motor unit activity is controlled by direct electric stimulation ofChapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences an Ebook Muscle contraction and cell motility: Part 2r contractile force in a variety of conditions. While the structures and mechanisms determining muscle stiffness in vivo are not fully understood, the result of our pilot study suggests that the shear modulus of contracting muscle may reflect both the single-fiber stiffness (cross-bridge kinetics) a Ebook Muscle contraction and cell motility: Part 2nd the motor unit recruitment, Ì.C., the number of activated muscle fibers.8.1 IntroductionIn studies of muscle mechanics, stiffness of contracting siEbook Muscle contraction and cell motility: Part 2
ngle fibers has been used as a measure of the number of attached cross-bridges at any instance. It has usually been quantified by measuring force respChapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences an Ebook Muscle contraction and cell motility: Part 2associated with crossbridge cycling, so that stiffness of contracting fibers is “dynamic” in nature and varies depending on the frequency of length oscillation. Sinusoidal analyses with skinned fibers from rabbit muscle have shown that the dynamic stiffness of contracting fibers involves three visco Ebook Muscle contraction and cell motility: Part 2us (exponential) components, and length oscillation at a frequency much higher than ~10() Hz (e.g., ~1 kHz) can be used to measure the series elasticiEbook Muscle contraction and cell motility: Part 2
ty representing the number of cross-bridges attached at either "rigor state” or “power stroke" in their cyclic reaction (Kawai, 1979).During both forcChapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences an Ebook Muscle contraction and cell motility: Part 2e (Fig. 8.1; Riiegg et al., 1979). In steady-state contractions, the stiffness decreases in a linear fashion with increasing sarcomere length beyond the optimal length for force generation (Lo), indicating that it is proportional to the amount of overlap between thick and thin filaments (Fig. 8.2; R Ebook Muscle contraction and cell motility: Part 2iiegg et al., 1979). For isotonic contractions, Tsuchiya et al. (1979) have shown that the stiffness linearly increases with force and reaches a maximEbook Muscle contraction and cell motility: Part 2
um under maximal isometric force (Fig. 8.3). Alternatively, the stiffness is inverselyIntroductionI211related to the shortening velocity, suggesting tChapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences an Ebook Muscle contraction and cell motility: Part 2 as proposed by Huxley (1957).Figure 8.1 Relations between contractile tension and stiffness in skinned frog muscle fibers, (a) Stiffness measured during the tension rising phase after “calcium jump." (b) Stiffness measured during steady-state tension in contractions at varied Ca2* concentrations (m Ebook Muscle contraction and cell motility: Part 2odified from Rticgg Ct al., 1979).Figure 8.2Dependence of active tension (filled circles) and stiffness (open circles) on sarcomere length in skinnedEbook Muscle contraction and cell motility: Part 2
frog muscle fibers, showing that both are proportional to the overlap between thick and thin filaments (modified from Ruegg etal., 1979).212 StiffnessChapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences an Ebook Muscle contraction and cell motility: Part 2city relation (b) obtained from the same preparation of frog single muscle fiber. Stiffness was determined by measuring length changes of fibers after quick changes in isotonic loading. Tension is expressed relative to the maximal isometric tension (Po). Negative velocity represents forced lengtheni Ebook Muscle contraction and cell motility: Part 2ng Linder the load >l\, (adapted from Tsuchiya el al., 1979).Measuring stiffness of contracting human muscles in vivo is also of great physiological sEbook Muscle contraction and cell motility: Part 2
ignificance, because it may provide us with information about the force-generating capacity of muscle fibers, which is determined by the relation betwChapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences an Ebook Muscle contraction and cell motility: Part 2aximal voluntary torques at varied joint angles. However, obtained relation between joint torque and joint angle may be considerably truncated from the original length-force relation of muscle, due mainly to changes in effective moment-Methods and MaterialsI asarm length with joint angles (Maganaris Ebook Muscle contraction and cell motility: Part 2, 2001; Sasaki et al., 2014). It can also be influenced by activation of synergistic and antagonistic muscle groups. Therefore, direct determination oEbook Muscle contraction and cell motility: Part 2
f the relation between muscle length and stiffness (length-stiffness relation) is regarded as highly effective to predict the lengthforce relations ofChapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences an Ebook Muscle contraction and cell motility: Part 2 frequency to muscles in vivo is substantially impossible, due to the presence of a large amount of series elasticity and intervening soft tissues. A recently developed ultrasound-based elastographic technique, "supersonic shear imaging" (SSI; Bercoff et al., 2004) can overcome this problem and pote Ebook Muscle contraction and cell motility: Part 2ntially be useful for in vivo measurements of stiffness in contracting muscle. Also, in place of its poor time resolution due to complicated image proEbook Muscle contraction and cell motility: Part 2
cessing, SSI can visualize changes in regional stiffness within muscle during steady-state contractions. Among other things, it may provide us with anChapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences an Ebook Muscle contraction and cell motility: Part 2el, during sustained exertion of small contractile force, during the course of muscle fatigue, etc.This review lists some recent studies on stiffness of contracting human muscles, with special reference to the effects of muscle activation level, muscle length, and contraction types.8.2 Methods and M Ebook Muscle contraction and cell motility: Part 2aterials8.2.1 Theoretical Basis of Supersonic Shear ImagingSSI is based on the B-mode ultrasound imaging that has widely been used in research and cliEbook Muscle contraction and cell motility: Part 2
nical diagnosis. In addition to usual scanning supersonic waves for image acquisition, SSI projects another strong supersonic beam that is focused on Chapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences an Ebook Muscle contraction and cell motility: Part 2 as shear wave. In a linearly elastic and transversely isotropic material, its shear elastic modulus (G) is a function of the propagation velocity of shear wave (K.) as described by the following equation: Ebook Muscle contraction and cell motility: Part 2Chapter 8Stiffness of Contracting Human Muscle Measured with Supersonic Shear ImagingKazushige Sasaki3 and Naokata Ishiib'Faculty of Human Sciences anGọi ngay
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