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kmoerman85
06-26-2008, 09:01 PM
Dear BIOMCH-L list, On the 26th of May I posted the following questions: 1 Has the resting stiffness induced in passive living muscle due to muscle tone been quantified in the literature (e.g. compared to freshly dead tissue)? 2. Does muscle tone (and therefore its induced stiffness component) instantly disappear after death? 3. Is a mild state of rigor mortis mechanically similar to stiffness induced by muscle tone?4. Mechanoreceptors in muscle e.g. muscle spindles are capable of measuring stretch/stretch rate. Muscle spindles are known to increase muscle stiffness as a certain stretch threshold/stretch rate threshold is exceeded. Is there any data known on threshold deformation/deformation rates that result in enhanced stiffness of muscle? 5. Is this stretch reflex only present in extension or is there any data known on stiffness increase/decrease due to a certain compression/compression rate (e.g. perpendicular to the muscle fibre direction)?6. In the biomechanical literature the words 'passive muscle' are sometimes used for freshly dead tissue (without muscle tone induced resting stiffness), however in literature on living tissue the words 'passive muscle' are also used to describe relaxed, un-stimulated muscle at rest (with muscle tone). Since living and freshly dead tissue are mechanically different (e.g. due to the lack of muscle tone) what is the correct use of the word 'passive'? To me passive is the opposite of active which implies the tissue is alive and therefore it seems like the word should be used solely as a property of living tissue in vivo (even though it may be physically possible to activate freshly excised tissue). Unfortunately the majority of replies to this e-mail can largely be summarized by: 'Interesting questions, I don't known the answers but can you forward any responds you get'
Other postings and suggested literature are shown below.

Kevin Moerman, PhD student Trinity College Dublin, Ireland



> Date: Tue, 27 May 2008 08:58:56 -0400> From: mjohnson@nsm.umass.edu> To: kevinmoerman@HOTMAIL.COM> Subject: Re: [BIOMCH-L] 'passive' human skeletal muscle> > Victor Gurfinkel has been a pioneer in the realm of muscle tone for many years.> I can't think of an article that directly addresses one of your questions, but> it would be worthwhile to explore some of his work, particularly this article:> > Gurfinkel et al., 2006 V. Gurfinkel, T.W. Cacciatore, P. Cordo, F. Horak, J.> Nutt and R. Skoss, Postural muscle tone in the body axis of healthy humans, J.> Neurophysiol. 96 (2006), pp. 26782687.



> Date: Tue, 27 May 2008 10:50:23 -0400> From: alan.dibb@duke.edu> To: kevinmoerman@HOTMAIL.COM> Subject: Re: [BIOMCH-L] 'passive' human skeletal muscle> > Kevin,> > One paper with results of postmortem muscle mechanical properties is:> Van Ee, C A,Chasse, A L, and Myers,B S. "Quantifying skeletal muscle > properties in cadaveric test specimens: effects of mechanical loading, > postmortem time, and freezer storage." Journal of biomechanical > engineering 122.1 (2000):9-14.> > Concerning the the usage of the term "passive" with respect to muscles, > in our field of injury biomechanics, passive muscle refers to live > muscle that is not being activated neurologically. Postmortem muscle > properties should be referred as such, postmortem.> > I'd be very interested in hearing the other responses you get from the > community. I would really appreciated it if you could post a summery.> > Thanks> Alan Dibb> Injury and Orthopaedic Biomechanics Lab> Department of Biomedical Engineering> Duke University


Date: Fri, 30 May 2008 02:47:13 +1000From: david.morgan@eng.monash.edu.auSubject: Muscle toneTo: kevinmoerman@HOTMAIL.COM


It seems to me Kevin, that you are really asking "What is muscle tone?"I have always assumed that muscle in a deeply anaesthetised animal is truly passive. Even better, cut the nerve or ventral roots, and ensure that there is no injury activity. Thus tone is a low level spontaneous activity in a conscious animal. It is generally highly reflexive, so more "stiffness" than tension. The spindle response is very dependent on the gamma innervation, and gamma activity in conscious animals is quite contentious and probably highly variable. (When I climb a ladder I become more reflexive, possibly due to gamma activity.) In an anaesthetised animal, with cut spinal roots, with strong gamma-d activation, virtually any stretch will cause high spindle firing rate, likely to lead to a reflex contraction in an intact conscious animal. So the tone in a conscious animal is very indeterminate.Rigor is quite different to activity. Spindles certainly respond to pressure directly over them, but it needs to be in exactly the right spot. Compressing a whole muscle will generally cause it to extend simply by constant volume behaviour, and so activate the spindles.David


Date: Mon, 16 Jun 2008 05:57:10 -0700From: isymeonidis@yahoo.comSubject: Re: [BIOMCH-L] 'passive' human skeletal muscleTo: kevinmoerman@HOTMAIL.COM



Hello Kevin,I am also a PhD student working on muscle modeling in the University of Munich. I have the same confussion as you regarding passive muscle and so I am interested in your findings. From discussions that I had with more experienced researchers. They explained me that passive muscle is the muscle that have only the passive mechanical properties without the muscle tone(minimal activation level). This properties are due to the mechanical properties of fibers and the surrounding tissue of the fibers, membranes etc This properites are specific to each muscle and depend on its internal structure, they are not refreing to influences from tissue outside the muscle.For in vivo experiments I am not sure that you can measure only the passive muscle properties without the muscle tone. But maybe you can do it with anesthesia, you can think the dentist. For in vitro experiments, I can send you a publication with findings that the properties change drasticly during time.kind regards,ioannis symeonidis
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