Roland Grassme

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.

Simultaneous surface electromyography (SEMG) and 31P-MR spectroscopy measurements of the lumbar back muscle during isometric exercise

The aim of this study was to demonstrate the feasibility of simultaneous surface electromyography (SEMG) and 31P-MR spectroscopy (31P-MRS) measurements on the back muscle of volunteers during the performance of an isometric exercise. Six volunteers (three male, three female) performed a modified Biering-Sörensen test inside a 1.5 T MR scanner while simultaneously recording SEMG signals. A surface coil was used for 31P-MRS with a CSI sequence. Spectra were collected with a voxel resolution of 40 mm x 40 mm x 100 mm and a temporal resolution of 30 s during periods of rest, sustained muscle contraction and recovery. The duration of muscle contraction was 150 s. SEMG analysis yielded a decrease of the mean SEMG frequency of approximately 20%. The SEMG amplitudes were constant or increased up to approximately 150% during exercise. 31P-MRS showed a maximum decrease of the phosphocreatine (PCr) amplitude down to approximately 32% of its initial value. Simultaneously, a doubling of the inorganic phosphate (Pi) signal was observed. The present study demonstrates that simultaneous SEMG and 31P-MRS measurements of the back muscle are feasible during isometric exercises.

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.

Fersendämpfungselemente in Sicherheitsschuhen bewirken eine Ökonomisierung der Muskelaktivität

ZusammenfassungWährend des Tragens von Sicherheitsschuhen lässt sich mit zunehmender Tragedauer ein deutlicher Optimierungseffekt im muskulären Aufwand bei Verwendung einer gewichtsangepassten Fersendämpfung nachweisen, der ohne Verwendung dieser Dämpfung nicht nur nicht, sondern sogar in umgekehrter Richtung sichtbar wird: ohne Dämpfung erhöht sich der muskuläre Aufwand mit längerer Tragedauer. Eine gewichtsangepasste Fersendämpfung kann den Arbeitnehmer somit vor unnötiger Mehrbelastung der Muskulatur und daraus resultierenden gesundheitlichen Folgen bewahren.AbstractFor subjects wearing safety shoes, an optimizing effect on the muscular effort can be achieved by applying weight-adjusted cushioning elements if they are worn for longer periods of time. Without optimal damping this effect is reversed: the muscular effort increases throughout continuing activity. Thus weight-adjusted cushioning elements can help to prevent employees from unnecessary increased muscle activity and therefore from health consequences.