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  • 1
    ISSN: 1432-0932
    Keywords: Muscles paravertébraux ; Muscle multifide ; Anthropométrie ; Lombalgie ; Paraspinal muscles ; Multifidus ; Anthropometry ; Low back pain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary This study of 52 patients (27 men) with recent (18 months) or chronic (〉18 months) low back and unilateral radicular pain symptoms was undertaken to investigate whether wasting of the paraspinal muscle components is generalised or selective. During the patients' routine computed tomographic lumbar spinal scans a standardised transaxial view was obtained along the upper end-plate of the L4 vertebra, and the cross-sectional areas of the paraspinal muscles and their components, multifidus and erector spinae, estimated. Irrespective of whether the symptoms were recent or chronic, multifidus dimensions were significantly greater on the side ipsilateral to the radicular pain symptoms. The results indicate selective changes of multifidus in these patients and possibly reflect an adaptive response by this muscle, such as to an increased role in stabilising the lumbar spine in the face of overall paraspinal muscle atrophy.
    Notes: Résumé Cette étude a été réalisée chez cinquante deux patients (27 hommes, 25 femmes), présentant une lombalgie soit récente (depuis moins de 18 mois), soit chronique (depuis plus de 18 mois) associée à une radiculalgie unilatérale. Le but de la recherche était de déterminer si l'atrophie des muscles paravertébraux était globale ou élective. Lors de l'examen scannographique de routine pratiqué chez ces patients, une coupe transversale a été pratiquée le long du plateau supérieur de la 4e vertèbre lombaire, permettant d'évaluer l'étendue de la surface occupée par ces muscles paravertébraux et leurs composants, plus particulièrement le muscle multifide et le muscle érecteur du rachis. Les résultats indiquent des modifications électives du muscle multifide chez les patients porteurs de lombalgies, et réflètent vraisemblablement une réponse adaptative de ce muscle qui semble jouer un rôle accru dans la stabilisation du rachis lombaire face à l'atrophie globale des muscles paravertébraux.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report in this letter the observation of folded acoustic phonons in hydrogenated nanocrystalline silicon/amorphous silicon multilayers with visible emission, which are prepared in a plasma enhanced chemical vapor deposition system. In the low-frequency range of 10–100 cm−1, the obtained Raman spectra clearly show some folded doublets from longitudinal acoustic phonons. Using the elastic continuum model, we calculated their frequencies and the obtained results were in agreement with the experimental ones. In addition, some broad folded doublets and additional peaks were clearly observed in the sample with thin nancorystalline sublayers. We attributed them to the mixing of longitudinal and transverse acoustic phonons due to the layered structure. A confined acoustic mode was also proposed to be responsible for the strongly folded longitudinal acoustic phonon peak at 61 cm−1. © 1996 American Institute of Physics.
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  • 3
    ISSN: 1439-6327
    Keywords: Ultrasound imaging ; Muscle size ; Anterior tibial muscle group
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cross-sectional images of the anterior tibial muscle group were obtained using real-time ultrasound scanning in 17 normal women. From photographs taken of the images, the cross-sectional area (CSA) and two linear measurements of muscle cross-section were determined. A measurement of the shortest distance of the muscle depth was termed DS, and a measurement of the longest distance through the muscle group was termed DL. Both linear dimensions showed a positive correlation with CSA and the best correlations were obtained when the dimensions were squared or combined (DS × DL). The correlation values were: CSA vs DS2, r=0.9; CSA vs DL2, r=0.75 and CSA vs DS × DL, r=0.88. An approximate value for CSA could be calculated from DS2 by the equation 2 × DS2 + 1. A shape ratio, obtained by dividing DL by DS, was consistent within the group [mean 2.1 (SD 0.2)] and characterised the muscle geometrically. The CSA of repeated scans was assessed for repeatability between-days and between-scans by analysis of variance and the coefficient of variation (CV) calculated. Areas were repeatable between-days (CV 6.5%) and between-scans (CV 3.6%). Linear dimensions of the anterior tibial muscle group reflected CSA and their potential for assessing changes in muscle size with atrophy and hypertrophy have yet to be established.
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  • 4
    ISSN: 1439-6327
    Keywords: Acoustic myography ; Electromyography ; Eccentric contractions ; Concentric contractions ; Biceps brachii muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The relationship between acoustic myography (AMG), electromyography (EMG) and force during submaximal dynamic contractions was examined in the biceps brachii muscles of eight healthy males (aged 17–26 years). Different weights were lifted and lowered at a constant speed, using a wall pulley system, to perform concentric and eccentric contractions, respectively. Integrated AMG (iAMG) and integrated EMG (iEMG) activity both increased linearly with force during concentric (iAMGr=0.94; iEMGr=0.99) and eccentric (iAMGr=0.90; iEMGr=0.94) contractions. The slopes of the concentric regression lines were significantly different from the eccentric slopes (P〈0.01) for both iAMG and iEMG with concentric contractions showing greater levels of activity. The results indicated that AMG can be used to detect changes in force during dynamic contractions which has important implications for the use of AMG in rehabilitation. The differences in iAMG activity between concentric and eccentric contractions are discussed in relationship to the origin of the AMG signal.
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  • 5
    ISSN: 1439-6327
    Keywords: Twitch potentiation ; Contraction-induced potentiation ; Force enhancement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of stimulation frequency on twitch force potentiation was examined in the adductor pollicis muscle of ten normal subjects. The ulnar nerve was supramaximally stimulated at the wrist and isometric twitch force was measured from a 3-Hz train lasting 1 s. Test stimulation frequencies of 5, 10, 20, 25, 30, 40, 50 and 100 Hz were applied for 5 s each in random order (5 min apart) and the twitches (3 Hz) were applied immediately before and after (1 s) the test freuqency and at intervals up to 5 min afterwards (10 s, and 1, 2 and 5 min). Poststimulation twitches were expressed as a percentage of the prestimulation twitch. Low frequency fatigue was not induced by the protocol since the 20: 50 Hz ratio did not alter within each session. The degree of twitch potentiation was frequency dependent, with potentiation increasing up to 50 Hz [mean 173 (SD 16)%] but the effect was markedly less at 100 Hz [mean 133 (SD 25)%,P〈0.011 for all subjects. The reduced potentiation at 100 Hz may have occurred due to high frequency fatigue produced by the 100-Hz test stimulation train. The optimal frequency of those examined in the experimental group was 50 Hz but this only produced maximal potentiation in six of the ten subjects and 100 Hz always produced less potentiation. These findings have implications for electrical stimulation of muscle in the clinical setting.
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  • 6
    ISSN: 1439-6327
    Keywords: Muscle weakness ; Muscle fatigue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fatiguing contractions of the adductor pollicis muscle were produced by intermittent supramaximal stimulation of the ulnar nerve in a set frequency pattern, in six normal subjects. At the end of an initial fatiguing contraction series, low frequency fatigue (LFF) had been induced and persisted at 15 min of recovery. Stimulated fatiguing activity was then repeated in an identical fashion to the initial series. At high frequencies, declines in force were similar for both series. At low frequencies, declines in force were greater during the second series despite similar changes in compound muscle action potential amplitude. This confirmation that LFF persists during subsequent stimulated activity, and reduces low but not high frequency fatigue resistance, suggests that the impaired endurance of fatigued muscle during voluntary activity primarily results from peripheral changes at low frequency. These findings also have implications for therapeutic electrical stimulation of muscle.
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