Nikolaus Peter Schumann

Multi-channel EMG of the M. triceps brachii in rats during treadmill locomotion

OBJECTIVES The study aims at a precise characterisation of intramuscularly varying recruitment patterns within the triceps brachii muscle (long and lateral head; proximal, medial, distal regions) in the time course of averaged step cycles during locomotion. METHODS The triceps brachii muscle of 15 Hannover rats was investigated with a supramuscular 16-electrodes grid during treadmill locomotion. Multi-channel electromyogram (EMG) was recorded simultaneously with high-speed videography. The rectified and smoothed EMG was time-normalised. EMG profiles and dynamic EMG-map series were calculated. Differences between EMG distribution patterns were tested by multivariate analysis of variance. RESULTS In the pre-stance phase EMG activity increased especially in the proximal long head. It most likely propagated from lower muscle layers of the long head. During stance phase the EMG activity of the lateral head rose steeply and exceeded those of the long head in short time. The fastest steps show the highest EMG amplitudes. CONCLUSIONS EMG registrations with grid electrodes help in the identification of intramuscular co-ordination processes during locomotion. While the EMG profiles characterise the time course, the topographical distribution is better represented in dynamic EMG interference maps. The dynamic changing activation patterns of triceps brachii depend on the phase of the step cycle. This clearly indicates the different functions of the muscle heads.

Facial muscle activation patterns in healthy male humans: a multi-channel surface EMG study.

In order to accurately characterize essential muscle activity during facial movements a new surface EMG (SEMG) technique was introduced and applied. Results represent reference data of healthy persons for future diagnostic purposes. In 30 healthy males monopolar electromyograms of the facial muscles were simultaneously recorded from 48 bilateral-symmetrically applied small surface electrodes while performing 29 facial movements of high clinical relevance. Mean SEMG amplitudes were quantified by power spectral analysis, normalized and presented as movement-related SEMG profiles. The mean SEMG amplitudes increased significantly in response to facial movements. Critical values of the movement-related SEMG amplitude increase were ascertained, valid for 90% of all examined subjects. The mean SEMG amplitudes differed between the performed facial movements, the examined muscles, and intramuscularly between lateral-medial and superior-inferior electrode positions, but not systematically between right and left side of face. The results show that the interplay between individual facial muscles and intramuscularly between their functional subunits is more differentiated than was previously estimated. With the presented facial SEMG technique the produced SEMG profiles are highly relevant for better planning of facial movement restoration. Based on the established reference data, this method can be used to objectively evaluate a facial paresis and to monitor changes during the course of disease and treatment. To easily apply the method, a reduction of electrode positions is intended after the clinical evaluation.

A surface EMG multi-electrode technique for characterizing muscle activation patterns in mice during treadmill locomotion

In mice a new method for 2x4-channel surface electromyography (EMG) recordings of the vastus lateralis and biceps femoris muscles during locomotion on a treadmill with varying speed is presented. The approach involves high-speed-videography (sampling interval 2.5 ms) in concert with the application of chronically implanted surface EMG multi-electrodes (EMG sampling rate 4000 Hz, frequency range 10-700 Hz). The recordings are started 2 days after surgery and finished 2 weeks after surgery. During the whole investigation period EMG recordings of both muscles have been possible. The monopolar EMG activities recorded by the electrode-arrays and the bipolar EMG signals derived from the monopolar activities permit an evaluation of the extent of myo-electrical activation in larger regions of both muscles and co-ordination between the flexor and extensor muscles. Bipolar EMG signals indicate propagation of activities along the muscle fibers and a slight effect of non-propagating signal components. Thus, the cross talk between these muscles is small and does not influence the evaluation of the EMG results. The resolution of the simultaneously recorded synchronized data allows a precise temporal correlation of kinematic and EMG parameters.

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.

Kinematic and Electromyographic Tools for Characterizing Movement Disorders in Mice

Increasing interest in rodent models for movement disorders has led to an increasing need for more accurate and precise methods for both delineating the nature of abnormal movements and measuring their severity. These studies describe application of simultaneous high‐speed video kinematics with multichannel electromyography (EMG) to characterize the movement disorder exhibited by tottering mutant mice. These mice provide a uniquely valuable model, because they exhibit paroxysmal dystonia superimposed on mild baseline ataxia, permitting the examination of these two different problems within the same animals. At baseline with mild ataxia, the mutants exhibited poorly coordinated movements with increased variation of stance and swing times, and slower spontaneous walking velocities. The corresponding EMG showed reduced mean amplitudes of biceps femoris and vastus lateralis, and poorly modulated EMG activities during the step cycle. Attacks of paroxysmal dystonia were preceded by trains of EMG bursts with doublets and triplets simultaneously in the biceps femoris and vastus lateralis followed by more sustained coactivation. These EMG characteristics are consistent with the clinical phenomenology of the motor phenotype of tottering mice as a baseline of mild ataxia with intermittent attacks of paroxysmal dystonia. The EMG characteristics of ataxia and dystonia in the tottering mice also are consistent with EMG studies of other ataxic or dystonic animals and humans. These studies provide insights into how these methods can be used for delineating movement disorders in mice and for how they may be compared with similar disorders of humans.

Development of a novel larynx pacemaker multichannel array electrode: In vivo animal analysis

Electrical stimulation of posterior cricoarytenoid muscle offers a physiological approach to retain the function of the paralyzed larynx muscle after paralysis. The aim of this study was to develop and evaluate a durable, biocompatible, and atraumatic array electrode for inclusion in a larynx pacemaker. In addition to developing the electrode array, an evaluation methodology using in vivo multichannel electromyography was assessed.

Methods of evaluating and developing pedal and brake characteristics

The qualities of a particular car that are experienced by the driver in direct interaction with the car have come to be significant distinguishing features. The brake system is particularly important in this respect because it belongs to the essence of driving and of keeping the vehicle under control. An overview is given in this paper of methodology developed at the Ilmenau University of Tech- nology for comprehensive, objective and definitive investigation of the interaction taking place between the driver and the vehicle during braking.

Method to test the long-term stability of functional electrical stimulation via multichannel electrodes (e.g., applicable for laryngeal pacing) and to define best points for stimulation: in vivo animal analysis

The study aim was to identify and analyze intramuscular electrically sensitive points. Electrically sensitive points are herein defined as positions, which allow muscles stimulation with a minimum possible fatigue for a maximum amount of time. A multichannel array electrode was used which could be interesting to retain the function of larynx muscle after paralysis. Eight array electrodes were implanted in the triceps brachii muscle of four rats. While being under anesthesia, the animals were intramuscularly stimulated at 16 different positions. Sihler’s staining technique was used to make visible the nerves routes and the intramuscular position of the individual electrode plate. The positions of the motor end plates were determined by means of multichannel-electromyography. The positions that allow longest stimulation periods are located close to the points where the nerves enter the muscle. Stimulation at the position of the motor end plates does not result in stimulation periods above average. Locations initially causing strong muscle contractions are not necessarily identical to the ones allowing long stimulation periods. The animal model identified the stimulation points for minimal possible muscle fatigue stimulation as being located close to the points of entrance of the nerve into the muscle. Stimulation causing an initially strong contraction response is no indication of optimal location of the stimulation electrode in terms of chronic stimulation. The array electrode of this study could be interesting as a stimulation electrode for a larynx pacemaker.

Die Kennzeichnung funktionsabhängiger komplexer Aktivitäts- und Koordinationsmuster mittels Multikanal-Oberflächenelektromyographie am Beispiel der mimischen Muskulatur

ZusammenfassungMittels 48-Kanal-Oberflächen-Elektromyographie (EMG) wurde die mimische Muskulatur von 30 gesunden männlichen Probanden während definierter Gesichtsbewegungen untersucht. Für jede Testbewegung wurden die EMG-Aktivitäten (Wurzel aus der spektralen EMG-Gesamtleistung) in einem EMG-Aktivitätsprofil (Boxplot) zusammengestellt. Die daraus abzuleitenden inter- und intramuskulären Koordinationsmuster erscheinen überraschend komplex. Während der einzelnen Bewegung waren, quantitativ fein abgestuft und hinsichtlich der räumlichen Orientierung deutlich von einander abweichend, mehr Muskeln aktiv als zunächst erwartet. Auch innerhalb einzelner Muskeln wurden mit der mimischen Bewegung wechselnde Aktivitätsunterschiede nachgewiesen. Insgesamt zeigte sich, dass EMG-Aktivität von möglichst vielen Muskeln und Muskelbereichen erfasst werden sollte, um das Funktionsprinzip einer Bewegung oder Haltung zu ergründen.AbstractUsing 48-channel surface electromyography (sEMG) the facial muscles of 30 healthy male volunteers were examined while performing defined facial movements. EMG activities (square root of the spectral EMG total power) were illustrated by EMG activity profiles (boxplots). The inter- and intramuscular coordination patterns deduced from these EMG profiles appeared surprisingly complex. Muscles of different spatial orientation join the particular facial movements and muscle activities were found finely balanced between each other. Movement dependent activation differences were also found within the particular muscles. Overall, the study revealed that EMG activity should be recorded from as many muscles and muscle regions as possible to characterize the functional principle of a movement or a posture.

Bewertungs- und Entwicklungs methoden zur Pedal- und Bremscharakteristik

Fahrzeugeigenschaften, die wahrend der unmittelbaren Interaktion zwischen Fahrzeugfuhrer und Fahrzeug erlebt werden, sind entscheidende Differenzie rungs merk male. Besondere Bedeutung kommt der Betriebsbremse zu, weil sie die Fahrdynamik und die aktive Fahrzeugsicher heit unmittelbar betrifft. Der Beitrag gibt einen Uberblick zu einer an der TU Ilmenau entwickelten umfassenden Methodik fur die objektive und aussagekraftige Untersuchung der Wechsel wirkun gen zwischen Fahrer und Fahr zeug beim Bremsen.