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Comparison of brain activation after sustained non-fatiguing and fatiguing muscle contraction: a positron emission tomography study.
Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Sports Medicine.
Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Sports Medicine.
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2005 (English)In: Experimental Brain Research, ISSN 0014-4819, Vol. 163, no 1, 65-74 p.Article in journal (Refereed) Published
Abstract [en]

The concept of fatigue refers to a class of acute effects that can impair motor performance, and not to a single mechanism. A great deal is known about the peripheral mechanisms underlying the process of fatigue, but our knowledge of the roles of the central structures in that process is still very limited. During fatigue, it has been shown that peripheral apparatus is capable of generating adequate force while central structures become insufficient/sub-optimal in driving them. This is known as central fatigue, and it can vary between muscles and different tasks. Fatigue induced by submaximal isometric contraction may have a greater central component than fatigue induced by prolonged maximal efforts. We studied the changes in regional cerebral blood flow (rCBF) of brain structures after sustained isometric muscle contractions of different submaximal force levels and of different durations, and compared them with the conditions observed when the sustained muscle contraction becomes fatiguing. Changes in cortical activity, as indicated by changes in rCBF, were measured using positron emission tomography (PET). Twelve subjects were studied under four conditions: (1) rest condition; (2) contraction of the m. biceps brachii at 30% of MVC, sustained for 60 s; (3) contraction at 30% of MVC, sustained for 120 s, and; (4) contraction at 50% of MVC, sustained for 120 s. The level of rCBF in the activated cortical areas gradually increased with the level and duration of muscle contraction. The fatiguing condition was associated with predominantly contralateral activation of the primary motor (MI) and the primary and secondary somatosensory areas (SI and SII), the somatosensory association area (SAA), and the temporal areas AA and AI. The supplementary motor area (SMA) and the cingula were activated bilaterally. The results show increased cortical activation, confirming that increased effort aimed at maintaining force in muscle fatigue is associated with increased activation of cortical neurons. At the same time, the activation spread to several cortical areas and probably reflects changes in both excitatory and inhibitory cortical circuits. It is suggested that further studies aimed at controlling afferent input from the muscle during fatigue may allow a more precise examination of the roles of each particular region involved in the processing of muscle fatigue.

Place, publisher, year, edition, pages
2005. Vol. 163, no 1, 65-74 p.
Keyword [en]
Adult, Brain/blood supply/*physiology/radionuclide imaging, Cerebrovascular Circulation/physiology, Electromyography, Humans, Male, Muscle Contraction/*physiology, Muscle Fatigue/*physiology, Positron-Emission Tomography
URN: urn:nbn:se:umu:diva-17015DOI: 10.1007/s00221-004-2141-5PubMedID: 15645226OAI: diva2:156688
Available from: 2007-10-25 Created: 2007-10-25 Last updated: 2009-11-18Bibliographically approved
In thesis
1. Brain processing of experimental muscle pain and its interrelation with proprioception and muscle fatigue: positron emission tomography study
Open this publication in new window or tab >>Brain processing of experimental muscle pain and its interrelation with proprioception and muscle fatigue: positron emission tomography study
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Chronic muscle pain is a significant medical and social problem and better understanding of the pathophysiological mechanisms involved is an important requirement for further development of diagnostics, treatment and rehabilitation methods. Experimental imaging studies have investigated functional neuroanatomy of different pain components. However, several aspects of brain mechanisms underlying brain processing of muscle pain remain unclear.

The general goal of the present thesis was to study functional brain anatomy of systems underlying perception of muscle pain, processing of proprioceptive information and maintenance of fatiguing muscle contractions with an emphasize on their possible interrelations.

Four series of experiment were carried out. Using an injection of hypertonic saline (HS) into the m. triceps to induce pain comparable with clinical muscle pain a significant activation of insula and putamen as well as decrease of activity in the temporal and occipital cortex in comparison with control stimulation were revealed. An advanced model of prolonged muscle pain were provided by the infusion of the HS during 20 minutes into m. erector spinae A complex dynamics of brain activity during the habituation to nociceptive stimulation was shown: initial activation of insula changed to decrease of activity in this and several other cortical areas. A conjunction analysis identified activations jointly significant in both experiments (despite localization of HS nociceptive stimulation) in the right insula, occipital and left parietal cortical areas. The study of brain activity in response to different modalities of prorioceptive inputs – passive movements, kinesthetic illusions and muscle vibration showed corresponding different patterns of activation in motor and somatosenory areas and temporal areas. Finally, the study of sustained isometric muscle contractions of various force levels and durations revealed that muscle fatigue is associated with contralateral activation of the motor and somatosensory areas and temporal areas and bilateral activation in the supplementary motor areas and cingular cortex, indicating that increased efforts needed to maintain required force and its eventual breakdown with fatigue might induce activation of additional cortical areas. Analysis of data obtained in all experimental series revealed that insula, secondary somatosensory and auditory areas are activated during both perception of muscle pain and processing of somatosensory afferentation.

In conclusion, this thesis has elucidated brain processing of muscle pain showing distributed, bilateral patterns comprised of activated structures predominantly attributed to the medial pain system and deactivated structures. Furthermore, initial and late phases of tonic muscle pain are associated with different brain reactions, namely initial activation of the insula followed by a significant bilateral decrease of activity at the late stage. Area of brain cortex located near lateral sulcus and comprised of secondary somatosensory cortex, posterior part of the insula and adjacent auditory cortex is engaged in the perception of muscle pain and processing of somatosensory afferentation as well as maintenance of fatiguing muscle contractions.

72 p.
Experimental muscle pain, Hypertonic saline, Kinesthesia, Proprioception, Movement, Vibration, Muscle fatigue, Brain, Imaging, Positron emission tomography, Regional cerebral blood flow
urn:nbn:se:umu:diva-570 (URN)
Public defence
2005-09-09, Stora föreläsningssalen, Arbetslivsinstitutet Umeå, 10:00 (English)
Available from: 2005-08-23 Created: 2005-08-23 Last updated: 2009-11-18Bibliographically approved

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