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Firing rate and conduction velocity of single motor units in the trapezius muscle in fibromyalgia patients and healthy controls.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
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2008 (English)In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 18, no 5, 707-716 p.Article in journal (Refereed) Published
Abstract [en]

Fibromyalgia is a common chronic pain condition in the population (2-4%), which often is associated with prominent negative consequences with respect to participation in daily activities. There are several reports in the literature concerning the effects of acute experimental pain on motor control. However, a more heterogeneous picture exists in the literature with respect to whether chronic pain conditions affect motor control. This study compares firing rate and conduction velocity (CV) of single motor units (MUs) in the trapezius muscle of fibromyalgia patients (FM) and healthy controls (CON). Multi-channel surface electromyography was used to estimate both MU firing rate and CV because this technique allows simultaneous estimation of both these variables and the measurements are easy and non-invasive. In this study, 29 FM and 30 CON subjects participated and performed isometric shoulder elevations using weights up to 4 kg. No significant differences in the firing rate of MUs in the trapezius muscle were found between the FM and CON groups (95% confidence interval was -1.9 and 1.3 pulses per second). There were no significant differences in CV between the groups at 1 and 2 kg load. However, the FM group had significantly higher CV in contractions without external load (p=0.004). We were unable to confirm the pain-adaptation model since no differences in firing rate between the two groups were found. CV was significantly higher in FM than in healthy controls; this might be due to alterations in histopathology and microcirculation.

Place, publisher, year, edition, pages
2008. Vol. 18, no 5, 707-716 p.
Keyword [en]
Electromyography, EMG, fibromyalgia, firing rate, conduction velocity
URN: urn:nbn:se:umu:diva-10458DOI: doi:10.1016/j.jelekin.2007.02.016PubMedID: 17459728OAI: diva2:150129
Available from: 2008-09-12 Created: 2008-09-12 Last updated: 2011-08-23Bibliographically approved
In thesis
1. Adaptive signal processing of surface electromyogram signals
Open this publication in new window or tab >>Adaptive signal processing of surface electromyogram signals
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electromyography is the study of muscle function through the electrical signals from the muscles. In surface electromyography the electrical signal is detected on the skin. The signal arises from ion exchanges across the muscle fibres’ membranes. The ion exchange in a motor unit, which is the smallest unit of excitation, produces a waveform that is called an action potential (AP). When a sustained contraction is performed the motor units involved in the contraction will repeatedly produce APs, which result in AP trains. A surface electromyogram (EMG) signal consists of the superposition of many AP trains generated by a large number of active motor units. The aim of this dissertation was to introduce and evaluate new methods for analysis of surface EMG signals.

An important aspect is to consider where to place the electrodes during the recording so that the electrodes are not located over the zone where the neuromuscular junctions are located. A method that could estimate the location of this zone was presented in one study.

The mean frequency of the EMG signal is often used to estimate muscle fatigue. For signals with low signal-to-noise ratio it is important to limit the integration intervals in the mean frequency calculations. Therefore, a method that improved the maximum frequency estimation was introduced and evaluated in comparison with existing methods.

The main methodological work in this dissertation was concentrated on finding single motor unit AP trains from EMG signals recorded with several channels. In two studies single motor unit AP trains were enhanced by using filters that maximised the kurtosis of the output. The first of these studies used a spatial filter, and in the second study the technique was expanded to include filtration in time. The introduction of time filtration resulted in improved performance, and when the method was evaluated in comparison with other methods that use spatial and/or temporal filtration, it gave the best performance among them. In the last study of this dissertation this technique was used to compare AP firing rates and conduction velocities in fibromyalgia patients as compared with a control group of healthy subjects.

In conclusion, this dissertation has resulted in new methods that improve the analysis of EMG signals, and as a consequence the methods can simplify physiological research projects.

Place, publisher, year, edition, pages
Umeå: Strålningsvetenskaper, 2006. 52 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1009
Signalbehandling, electromyography, signal processing, Signalbehandling
Research subject
Biomedical Radiation Science
urn:nbn:se:umu:diva-743 (URN)91-7264-033-2 (ISBN)
Public defence
2006-04-28, 244, 7, Norrlands universitetssjukhus, Umeå, 13:00 (English)
Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2010-01-18Bibliographically approved

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