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A review of concepts regarding the origin of respiratory muscle fatigue

100%
Kuraszkiewicz B., Piotrkiewicz M.
Polish Journal of Medical Physics And Engineering
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2011
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vol. 17
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issue 1
27-34
EN
In this review, the classification of respiratory muscle fatigue from the perspective of its origin is presented. The fatigue is classified as central or peripheral, and the latter further subdivided into high- and low-frequency fatigue. However, muscle fatigue is a complex process and all three types of fatigue probably occur simultaneously in the overloaded respiratory muscles. The relative importance of each type depends on the duration of respiratory loading and other physiological variables. However, central and high-frequency fatigue resolve rapidly once muscle overload is removed, whereas low-frequency fatigue persists over long time.
2
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MU firing characteristics in human dystrophic muscle

81%
Piotrkiewicz M., Filipiuk M., Hausmanowa-Petrusewicz I.
Acta Neurobiologiae Experimentalis
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1993
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vol. 53
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issue 1
313-318
EN
During isometric contractions of constant force surface EMG as well as intramuscular MU potentials from extensor digitorum communis and biceps brachii muscles were recorded on magnetic tape for furthr off-line analysis. Surface EMG power spectra were computed and transformed so as to reveal low-frequency peaks which might correspond to MU firing rates. From intramuscular recordings, single MU action potentials were identified with an aid of semi-automatic recognition program. For each single MU action potential train (MUAPT) statistical parameteres of interspike intervals (ISIs) were determined and related to the measured muscle force level. Sixty four MUAPTs from 9 patients and 55 MUAPTs from 4 normals were analysed so far. The estimates of MU firing rate from surface and needle EMG corresponded well to each other. The MU firing rates were higher in muscular dystrophy and this difference was more pronounced for higher levels of muscle force. The tendency towards mean MU firing rate increase is stronger for the patients with more advanced disease. The typical dependency of standard deviation of ISIs on their mean value may be axpproximated by two lines of different slope. There were reported experimental data indicating that the breaking point of this dependency may be an estimate of AHP duration in motoneurones. Our results for dystrophic muscle showed a shift of this point towards shorter ISIs, as compared to normals.This suggests that inmuscular dystrophy also motoneurones may be altered, either by the disease itself or as a compensation for changes in muscular part of a MU.
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