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Biomedical subjects

N P Schumann

Publications and source records attributed to N P Schumann.

At least 19 recordsLinked to original sources
PubMed2005

Improved evaluation of back muscle SEMG characteristics by modelling.

Surface EMG (SEMG) as non-invasive method is a valuable tool in functional studies of movement co-ordination. The interpolation of the SEMG power (EMG mapping) gives information about intra- and inter-muscular co-ordination. It has been shown that SEMG maps of low back pain patients and healthy subjects differ. The only major drawback to SEMG is that volume conduction of muscle tissue, fat, and skin decreases the spatial and temporal resolution of signals. To improve the interpretation of SEMG signals, we have applied high pass filtering of cross covariance functions, which has proved to be useful in increasing the spatial resolution, to SEMG data of the back region. Experimental data demonstrate that SEMG signals from the back extensors show only rarely signs of action potential propagation. This behaviour, also described in the literature, can be explained by a model assuming short, deep muscle fibres, having bipolar end effects, with overlapping positions parallel to the fibre direction. This condition is fulfilled by the mm. multifidii et rotatores which are part of the m. erector spinae. Although the model is simplistic, the agreement between simulations and experiments is good.

Journal Article↗
PubMed2003

Selective spatial information from surface EMG after temporal filtering: the application to interference EMG using cross-covariance analysis.

OBJECTIVE: An increased spatial resolution in multichannel surface EMG recordings would provide new possibilities for the investigation of intermuscular and intramuscular coordination. A known analytical solution for volume conduction allows the conclusion that a high pass filtered surface electromyography (SEMG) signal contains information from a smaller environment near the recording electrode and therefore provides a higher spatial resolution. METHODS: The present paper concerns experiments on 9 subjects to measure, from the human biceps brachii muscle during static isometric contraction, using multichannel surface EMG. Cross-correlation functions between bipolar SEMG channels were calculated and high pass filtered. RESULTS: The correlation peaks showed the signs of propagating action potentials. The spatial width in the direction perpendicular to the muscle fibres decreased with increasing cut-off frequency. There exists an optimal cut-off frequency, which provides the best spatial resolution. It correlates with the thickness of the subcutaneous fat layer which causes a minimum depth of the active muscle fibres measured. CONCLUSIONS: High pass filtered cross-covariance functions of bipolar SEMG channels have an increased spatial resolution perpendicular to the muscle fibre direction and the frequency content of the signals can potentially give an indication of the depth of the active muscle fibres.

Action Potentials↗
PubMed2001

Spatiotemporal surface EMG characteristics from rat triceps brachii muscle during treadmill locomotion indicate selective recruitment of functionally distinct muscle regions.

Multichannel surface EMG recordings of a multiheaded skeletal muscle during cyclic locomotion combined with cineradiography were analysed in a chronic experiment. The resulting detailed two-dimensional activation pattern from the long and lateral triceps brachii heads of the rat during treadmill locomotion were combined with gait characteristics and fibre typing of the muscle. Shortly before ground contact of the forelimb, maximum muscle activity was found in the proximal part of the long head of the muscle. During the stance phase maximum activity was observed in the proximal part of the lateral head. The frequency dependent behaviour of cross-covariance functions over both muscle heads confirmed this selective shift in activation. In the lateral triceps brachii head of the investigated rats, exclusively type II fibres were found. In the long head the frequency of type I fibres was the highest in the deep muscle layers, proximally more than distally, whereas type II fibres were dominant in more superficial muscle layers. A combination of physiological and histological findings supports an anticipating mechanism whereby fine-tuning of the vertical foot down manoeuvre is mainly achieved by the (type I fibre dominated) proximal deep compartment of the biarticular long triceps brachii head and force generation is predominantly executed by the monoarticular lateral triceps brachii head.

Animals↗
PubMed2000

Surface EMG-recordings using a miniaturised matrix electrode: a new technique for small animals.

A new method for multichannel surface-EMG measurements in small animals is presented. The underlying scientific aim is the characterisation of the spreading and the co-ordination of skeletal muscle activation between different muscles or muscle parts, depending on various motor tasks. The myoelectrical signals were recorded monopolarly by a 16-channel matrix electrode on the muscle surface directly under the skin on the fascia of the investigated muscle, without damaging the muscle. Surface-EMG's were recorded for at least 5 days after surgery without electrical interferences. During defined motor tasks, the projection of the myoelectrical activation of the different parts of the M. triceps brachii of rats (Rattus norvegicus), pikas (Ochotona rufescens) and cuis (Galea musteloides) or the M. anconeus of toads (Bufo marinus) on the muscle surface was mapped. The locomotion of the investigated animals was monitored by a three-dimensional kinematic analysis (video and/or high-speed cineradiography). There was no perceptible influence from application of EMG matrix electrode. The miniaturised matrix electrode seemed practicable in gaining insight into changes in myoelectrical activation patterns (EMG mapping). This allows a characterisation of the intramuscular co-ordination processes corresponding to the actual morphofunctional state of the investigated animals.

Anesthesia↗
PubMed2000

Surface EMG mapping of the human trapezius muscle: the topography of monopolar and bipolar surface EMG amplitude and spectrum parameters at varied forces and in fatigue.

OBJECTIVES: To investigate the factors affecting the topography of trapezius muscle EMG, multichannel recordings were made at different forces of isometric shoulder elevation and during fatiguing exercise. METHODS: Twenty-eight channels of monopolar EMG were recorded from an array of 4 x 7 electrodes placed on the upper trapezius muscle. From the monopolar EMG and the bipolar derivations the root mean square (RMS(monopolar), RMS(bipolar)) and power spectrum median frequency (MF(monopolar), MF(bipolar)) were calculated. RESULTS: The maximum RMS(monopolar) was located above the middle part of the trapezius muscle, where a minimum was found for RMS(bipolar). The cranial-caudal RMS distribution shifted upwards when the force was increased from 50 to 100% MVC and during fatigue. MF(bipolar) showed a peak above the endplate region, where the MF(monopolar) was low. During fatigue the normalized MF slope was independent of the cranial-caudal electrode position, but MF(monopolar) decreased most strongly at positions above the endplate region, where MF(bipolar) decreased less. CONCLUSIONS: While the changes in MF reflected metabolic properties and volume conduction phenomena in the muscle, changes in RMS reflected a compensation for the fatigue processes within the muscle. The RMS changes in fatigue can be explained by the direction of the fibres involved in shoulder elevation.

Adult↗
PubMed1999

Surface EMG of shoulder and back muscles and posture analysis in secretaries typing at visual display units.

OBJECTIVE: A study was carried out to investigate temporal changes of activation of shoulder and back muscles in workers at visual display units by means of surface EMG. Moreover, postural parameters were recorded to distinguish fatigue-related from posture-related changes of the myoelectrical activity. METHODS: Nine healthy female office workers typed texts spoken from tape during three 1-h-long sessions. After the first and again after the second hour there was a break of 15 min. Sixteen-channel surface EMG was bipolarly recorded from the erector spinae, trapezius, deltoid and sternocleidomastoid muscles. Root mean square (RMS) and power spectrum median frequency of the EMG were calculated. Sitting posture was assessed using an eight-channel movement analysis system with ultrasound markers. The position of the seventh cervical spinous process and the left and the right acromion were analysed synchronously with the EMG characteristics using regression analysis. RESULTS: The normalised RMS of the left and right trapezius muscle increased, while the median frequency did not change. The increase of the normalised RMS was significantly lower when the linear influence of posture was excluded. On average, the distance between C7 and the left and right acromion decreased within each working an hour. C7 became lower on average by 5.5 mm within an hour, whereas the acromions became lower by only 1.7 mm (left) and 3.3 mm (right). CONCLUSION: The increase in trapezius muscle activity was partly related to a lifting of the shoulders to compensate a slight slumping of the back. Another part of the EMG activity increase has to be attributed to fatigue, to attention-related activity or to the combination of both. Therefore, training of the back muscles and a varied organisation of work might have a preventive effect with respect to musculoskeletal complaints in VDU workers.

Adult↗
PubMed1997

[EMG surface polygraphy of the pelvic floor--description of functional changes after radical prostatectomy].

Urinary stress incontinence after radical prostatectomy could be cured by physiotherapy in a high percentage. The authors developed an investigation procedure for description of myoelectrical activity of pelvic floor with surface electrodes. 10 patients were studied 1 day before, 10 days and 6 months after radical prostatectomy. Significant changes of amplitude and frequency characteristics could not be found in rest and during the stationary intervals of maximal contraction. But after the operation in all patients changed the activation pattern within the interval of increasing muscle contraction. The mean and median frequency decreased significantly (Friedman-test, p < 0.001). This was interpreted as a problem of intramuscular coordination. After physiotherapy urinary incontinence was cured or improved. The typical activation pattern of dyscoordination was not more evident after 6 months.

Aged↗
PubMed1994

A topographical analysis of spectral electromyographic data of the human masseter muscle under different functional conditions in healthy subjects.

In 20 healthy subjects, 16-channel surface electromyograms (EMG) were recorded with the mandible in its postural position, during compensation for forces applied from ipsilateral, contralateral and frontal positions, and during force-constant biting on a unilaterally placed force transducer. After artefact elimination, EMG power spectra were calculated on the basis of the original EMG curves via fast Fourier transformation. Using spectral EMG characteristics, EMG maps were computed by means of an interpolation algorithm and an imaging procedure. Spectral EMG maps were demonstrated for all the test conditions. Significant differences of myoelectrical activity were verified between the 16 electrode positions. Moreover, the levels and/or the topographical distributions of spectral EMG powers differed significantly between the test conditions. During biting as well as with contralaterally and frontally applied forces, the highest EMG activity was found in the inferior third of the masseter and the lowest in the superior third. With ipsilaterally applied forces, the topographical distribution of the total EMG power was completely changed. The power maximum was frequently demonstrated in the superior, especially the posterosuperior, third of the muscle, the minimum in the inferior third. In the postural position of the mandible, EMG activity decreased from the anterior to the posterior regions of the masseter. If the bite force or the horizontally applied forces were enhanced, EMG activity increased significantly but the EMG map structures were only changed in some details. The topographical distribution of myoelectrical activity demonstrated by EMG maps characterizes the intramuscular activation patterns of distinct masseter functions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Quantitative topographic characterization of the myoelectric activity distribution of the masseter muscle: mapping of spectral EMG parameters].

A new method for quantitative characterization of myoelectrical masseter activity distribution by mapping of spectral EMG-parameters is described. The surface electromyograms of M. masseter were monopolarly recorded (16 channels). On the basis of registered EMG intervals (512 ms) the spectral EMG power of several frequency bands was calculated (Fast Fourier Transformation). The spectral EMG parameters between the 16 electrode positions were estimated by linear interpolation (4-nearest neighbours algorithm). Afterwards the spectral EMG parameters were fitted in a grey-tone or colour scale with 10 intervals. The so obtained EMG activity maps ("EMG-Maps") permit a quantitative-topographic characterization of myoelectrical masseter activity during different functional load procedures. The frequency range which is to consider in masseter surface-EMG investigations encloses frequencies between 15 and 500 Hz. The topography of EMG activation pattern of M. masseter is only described in a comprehensive manner when the electrode array consists of 16 electrodes and more. During defined motor tasks like clenching with controlled forces the reproducibility of EMG-Maps which respect to the topography of EMG activity pattern is very high. The absolute values of spectral EMG power as well as power changes of selected band ranges during clenching correlate to the extent of chewing forces.

Adult↗
PubMed1992

[Mapping spectral EMG parameters of the masseter muscle in normal probands under defined loads].

In 20 healthy volunteers 16-channel surface electromyograms were monopolarly recorded from the right and left masseter muscle during defined functional conditions (force-constant bite, right and left hand side, 196, 333, 530 N chewing force, during a compensation of a load directed from a frontal or a lateral position to the mandible (20, 49, 69 N), during rest position of the mandible). The EMG curves were quantified by the calculation of spectral EMG-parameters (FFT). With respect to the muscle a topographic oriented representation of the myoelectrical activity was realised by a mapping of spectral EMG-parameters. The monopolarly recorded EMG activities significantly differed between the 16 electrode positions (topographic EMG distribution pattern). During the several examination conditions of the masseter muscle different topographic distribution pattern of the myoelectrical activity were found. Moreover, the total EMG power between the muscle functions differed too. The level of the load influenced the spectral EMG power as well as, partly, the topographic EMG distribution pattern.

Adult↗
PubMed1992

[Control of isometric muscle contraction in muscle hypotonia of central origin: EMG mapping analysis].

Electromyographic and mechanographic investigations in patients with muscular hypotonia, which is, for instance, a side-effect after stereotactic treatment of tremor syndromes, permit the presumption that in this sensomotor open-loop situation the decreased muscular resistance to stretching during isometric contraction (initial stiffness) is caused by changes of muscular innervation pattern. Probably, the innervation pattern during tonic activity is changed by a shift of a more tonic motoneurone behaviour to motoneurone activities with predominantly phasic characteristics. In 17 controls and 4 patients with muscular hypotonia caused by stereotactic lesions of VIM area (treatment of tremor syndromes) the EMG of right and left side forearm flexors (especially the activity of the M. biceps brachii) was investigated by a sophisticated, topographically oriented 16-channel-surface-EMG-technique ("EMG-Mapping") during slight isometric contraction. EMG-Maps of forearm flexors (especially of M. biceps brachii) in patients with centrally evoked muscular hypotonia demonstrate that in these open-loop conditions the motor control is changed. For this the reason could be a shift of the activated motor units from a predominantly static to a more phasic functional behaviour. The latest results on muscular activation processes in cats support this presumption.

Adult↗
PubMed1991

[Quantification of artefacts in surface EMG by validating the lower frequency limit in clinico-physiologic studies].

The surface-EMG becomes more and more important because computer assisted analysing systems can be applied. The occurrence of artefacts makes it very difficult to compare several recorded EMG channels with each other. In this study a frequency related quantification of movement artefacts and ECG-related influences on the EMG is carried out to select a suitable lower cut-off frequency for surface-EMG investigations. In 764 monopolar surface-EMG-recordings of the neck and back muscles the solely artefact-caused part of EMG-segments was analysed and quantified by means of modelling methods.

Adult↗
PubMed1991

[Methodologic studies in dynamic EMG mapping based on the Hilbert transformation].

On the basis of Discrete Hilbert Transformation spectral parameters for dynamic EMG analysis can be introduced. Within analysis intervals which are used in the same manner as in spectral analysis, the momentary power of EMG frequency bands can be computed as time series of the same interval duration. A close connection exists between momentary power and the current phenomenology of power spectral analysis because the momentary power of a defined frequency band can be seen as the exact dynamic equivalent of the corresponding mean power value deduced from the power spectrum. A multichannel EMG recording (greater than or equal to 16 channels) makes the representation of the topographical distribution of the spectral parameter by a coloured map possible. Additionally, the momentary power can be used to calculate map sequences. In this way, changes of EMG activity can be quantified by map sequences of an arbitrary time resolution. By calculation of momentary frequency via DHT an artefact detection scheme for ECG interference can be suggested. A completion of this methodology can be carried out by applications of adaptive filtration procedures. Using this concept of EMG processing, a new and common methodical basis of EMG power spectral analysis can be introduced.

Brain Mapping↗
PubMed1990

Characteristics of heart rate fluctuations and respiratory movements during orienting, passive avoidance and flight-fight behaviour in rabbits.

In the present study different heart rate patterns were demonstrated to accompany flight-fight behaviour, orienting behaviour and passive avoidance in rabbits. Flight-fight behaviour was characterized by markedly increased heart rate and diminished overall heart rate variability. The effect was mediated by vagal inhibition and beta-adrenergic activation in a type-specific relation. Orienting behaviour was accompanied by a smaller heart rate increase and the exaggeration of slow heart rate fluctuations. The latter effect was absent during beta-adrenergic blockade suggesting a behaviourally provoked beta-adrenergic activation. Single beta-adrenergic blockade did not change the characteristics of the heart rate fluctuations at rest. During passive avoidance a vagally mediated heart rate deceleration was followed by a slow heart rate return toward the initial heart rate level. This level was not reached during beta-adrenergic blockade. The enhanced overall heart rate variability during passive avoidance was mainly caused by strengthened respiratory-induced heart rate fluctuations and, furthermore, by exaggerated slow rhythmical heart rate fluctuations. The latter effect was not observed during beta-adrenergic blockade and is referred to as an orienting component within passive avoidance. Three individual behavioural types may be differentiated in rabbits 'Weisses Gross-Silber' by stable behavioural characteristics i.e. spontaneous motor activities, preferred postures at rest and coping behaviour. The results of the present study suggest that different neurovegetative reaction types, i.e. dominating beta-adrenergic or vagal activation are correlated with stable behavioural characteristics, especially in terms of preferring active or passive coping behaviour, respectively.

Animals↗
PubMed1990

Heart rate fluctuations in rabbits during different behavioural states.

Heart rate fluctuations (HRF) were investigated in 18 adult female rabbits (Weisses Grosssilber) in chronical experiments at rest, during motor activity, passive and active avoidance. Pharmacological blockades of the neurovegetative transmission were used to determine the characteristics of neurovegetative mediation during the behavioural states examined. Mean heart rate was always increased during vagal blockade and decreased during beta-adrenergic blockade. At rest the HRF in rabbits are mainly vagally mediated. Vagal blockade reduced the overall heart rate variability by more than 50%. Vagal blockade did not abolish respiratory heart rate fluctuations. If the mean respiratory frequency is greater than half of the mean heart rate frequently occurring in rabbits, the respiratory HRF are generated not synchronously with respiration but in a slower frequency range according to the physiologic effect of "cardiac aliasing". The movement related heart rate increase was absent if the movements were performed during combined beta adrenergic and vagal blockade. The heart rate reaction during passive avoidance was characterized by a heart rate deceleration abolished by vagal blockade. Respiratory HR were increased. Furthermore, the heart rate was returned to the previous mean level and the slow HRF not induced by respiration increased, mediated by beta adrenergic activation. Vagal blockade and beta adrenergic blockade diminished the heart rate acceleration and reduced the overall heart rate variability by more than 50% during active avoidance. Combined vagal and beta-adrenergic blockade fully abolished the heart rate acceleration effect during active avoidance. The ratio of the vagal to sympathetic reaction components differed in behavioural types.

Adrenergic alpha-Antagonists↗
PubMed1988

Personality and quantified neuromuscular activity of the masticatory system in patients with temporomandibular joint dysfunction.

Patients suffering from temporomandibular joint dysfunction syndrome (TMJS) and healthy volunteers were examined by means of MMPI questionnaire and electromyography (masseter, anterior temporal and anterior digastric muscles) at rest and during natural chewing. In response to mental load (arithmetic chain task) TMJS patients showed an increase in postural activity and partly rhythmical short augmentations above the mean level of this activity. Chewing potentials were considerably diminished in patients compared with controls. There was evidence for neurotic disorders in the patients MMPI (neurotic triad: higher scores on hypochondria, depression, hysteria). Significant differences (multivariate variance and discriminant analysis: P less than 0.001) between patients and controls were found both in the group with psychic signs (MMPI scales) and in the group of quantitative electromyographic parameters. However, a sufficient discrimination was only obtained by a combination of both parameter groups. The results show that probably psychic dynamics, as well as the structure of neuromuscular activity within the masticatory system, are important in the aetiopathogenesis of TMJS.

Adolescent↗