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Muscle Thixotropy: Implications for Human Motor Control
Uppsala universitet, Medicinska vetenskapsområdet, Medicinska fakulteten, Institutionen för neurovetenskap, Klinisk neurofysiologi.
2005 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Human skeletal muscles possess thixotropic, i.e. history-dependent mechanical properties. This means that the degree of passive muscle stiffness and resting tension is dependent on the immediately preceding history of contractions and length changes. Athletes, for instance, reduce passive muscle stiffness by various types of ‘limbering-up’ procedures, whereas muscle stiffness gradually increases during inactivity.

Passive resistance of antagonistic muscles may significantly add to the total load during voluntary muscle contractions. This resistance may vary from one moment to another, depending on immediately preceding events. This research was conducted to determine whether history-dependent variations in passive muscular forces influence motor control of voluntary joint movements and steady maintenance of joint positions in healthy subjects.

In study I, the EMG signal revealed motor compensations for history-dependent variations in passive stiffness of the antagonists during slow voluntary wrist joint movements. Studies II and III demonstrated that the voluntary muscle activity required to maintain a certain wrist joint position was highly influenced by previous changes in forearm muscle length and contractions. Study IV showed that rapid voluntary movements varied in speed and onset time depending on the prevailing degree of muscle resistance, and in addition that the central nervous reaction time required to execute rapid movements was highly influenced by immediately preceding muscle-conditioning procedures.

History-dependent variations in passive muscular forces seem to be effectively compensated by the motor control system. Presumably, voluntary motor commands to the muscles are automatically adjusted in strength to history-dependent changes in passive muscular forces. Such adjustments occur within the central nervous system, which receives information about the mechanical state of the muscles. Several issues in connection with muscle thixotropy remain unaddressed. For instance, do alterations in the normal thixotropic mechanical behaviour of the muscles impose a particular problem in patients with certain neuromuscular diseases?

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis , 2005. , s. 56
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 38
Nyckelord [en]
Neurosciences, Motor control, Skeletal muscle, Thixotropy, History-dependent, EMG, Voluntary contractions
Nyckelord [sv]
Neurovetenskap
Nationell ämneskategori
Neurologi
Identifikatorer
URN: urn:nbn:se:uu:diva-5791ISBN: 91-554-6246-4 (tryckt)OAI: oai:DiVA.org:uu-5791DiVA, id: diva2:166390
Disputation
2005-05-28, Rudbecksalen, Rudbecklaboratoriet, Uppsala, 13:15
Opponent
Handledare
Tillgänglig från: 2005-05-09 Skapad: 2005-05-09Bibliografiskt granskad
Delarbeten
1. Human motor control consequences of thixotropic changes in muscular short-range stiffness
Öppna denna publikation i ny flik eller fönster >>Human motor control consequences of thixotropic changes in muscular short-range stiffness
2001 Ingår i: J Physiol, Vol. Aug 15, nr 535, s. 279-88Artikel i tidskrift (Refereegranskat) Published
Identifikatorer
urn:nbn:se:uu:diva-93032 (URN)
Tillgänglig från: 2005-05-09 Skapad: 2005-05-09Bibliografiskt granskad
2. Human motor compensations for thixotropy-dependent changes in resting wrist joint position after large joint movements
Öppna denna publikation i ny flik eller fönster >>Human motor compensations for thixotropy-dependent changes in resting wrist joint position after large joint movements
2003 Ingår i: Acta Physiol Scand., Vol. Dec, nr 179(4), s. 389-98Artikel i tidskrift (Refereegranskat) Published
Identifikatorer
urn:nbn:se:uu:diva-93033 (URN)
Tillgänglig från: 2005-05-09 Skapad: 2005-05-09Bibliografiskt granskad
3. Human motor compensations for thixotropy-dependent changes in muscular resting tension after moderate joint movements
Öppna denna publikation i ny flik eller fönster >>Human motor compensations for thixotropy-dependent changes in muscular resting tension after moderate joint movements
2004 Ingår i: Acta Physiol Scand, Vol. Nov, nr 182(3), s. 295-304Artikel i tidskrift (Refereegranskat) Published
Identifikatorer
urn:nbn:se:uu:diva-93034 (URN)
Tillgänglig från: 2005-05-09 Skapad: 2005-05-09Bibliografiskt granskad
4. Signs of muscle thixotropy during human ballistic wrist joint movements
Öppna denna publikation i ny flik eller fönster >>Signs of muscle thixotropy during human ballistic wrist joint movements
Artikel i tidskrift (Refereegranskat) Submitted
Identifikatorer
urn:nbn:se:uu:diva-93035 (URN)
Tillgänglig från: 2005-05-09 Skapad: 2005-05-09Bibliografiskt granskad

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