Myoelectric Potential Research Articles

Brainstem-evoked muscle potentials: their prognostic value in experimental spinal cord injury in the rat

Recording myoelectric motor-evoked potentials is frequently used as an in vivo evaluation technique in experimental studies of spinal cord injury (SCI). The aim of the present study was to determine whether specific neuronal pathways conduct these potentials. Stainless steel screws were permanently implanted into the cranium of 18 rats for stimulation of brainstemevoked muscle potentials (B-MPs). Twelve rats were subjected to spinal cord lesions that restricted the continuity of the spinal cord to different discrete sections of the lateral and/or ventral white matter (WM) of the left hemicord. Sham rats ( n = 6) were subjected to laminectomy only. Left hind limb B-MPs and motor function (open field walking test) were recorded before surgery and weekly thereafter for six consecutive weeks. Motor function was severely affected by SCI in all rats but recovered significantly during the first 14 postoperative days. The degree of functional recovery depended not only on the amount of spared WM but also on the particular section of WM that had been spared. In contrast, B-MP amplitudes also were severely reduced by SCI, but did not recover during the survival period. Moreover, B-MP amplitudes correlated only weakly with the amount of spared WM and were not influenced by which section of WM had been spared. While functional recovery correlated significantly with the amount of spared WM, no correlation was found between B-MP amplitudes and functional recovery. B-MP conduction velocities were not affected by SCI. It is therefore believed that B-MPs have little prognostic value for experimental studies of SCI in the rat.

Extraction of Features in EEG

We take various information from the outside world into our brain by moving our eyes in every direction and sounds EEG contain basic rhythms of the brain, such as alpha waves, and components, such as myoelectric potentials. The results of the simulation indicated that the use of multiple windows would raise the accuracy in the detection of time delays and demonstrated the effectiveness of the present technique. However, the features of the estimated waveforms of the adaptive correlation filter are affected by various elements, and the level of accuracy is not so high as to be useful in clinical medicine.

Intestinal myoelectric alterations in rats chronically infected with the tapeworm Hymenolepis diminuta

This study determined that intestinal myoelectric activity was profoundly altered during a strictly luminal, chronic, tapeworm infection. Chronically implanted bipolar electrodes were attached to five sites on the serosal surface of the rat small intestine. One was placed on the duodenum, three on the jejunum, and the fifth on the ileum. Electromyographic recording in nonfasted unanesthetized animals was begun at day 5 postsurgery. All electromyographic recordings were analyzed for slow wave (SW) frequency, phase III frequency, duration of phase III, and percentage of SW with spike potentials. Three initial control recordings prior to infection confirmed the presence of normal interdigestive motility characterized by the three phases (I, II, III) of the migrating myoelectric complex (MMC). Two nonpropulsive myoelectric alterations were observed in infected animals: the repetitive bursts of action potentials (RBAP) and periods of sustained spike potentials (SSP). Myoelectric activity from infected animals indicated decreased cycling of the interdigestive MMC. RBAP and SSP were more prevalent in the distal small intestine corresponding to tapeworm location. The percent of spike potential activity indicated that there was a reversal in the spike potential gradient on the small intestine. The number of spike potentials was maximal in caudal and minimal in oral intestine. We propose that overall localized increases in myoelectric spike potential activity represent increased contractility and decreased propulsion triggered by the presence of the tapeworm. These motility changes were surprising, since the tapeworm Hymenolepis diminuta does not penetrate the intestinal mucosa. This interaction between parasite and host may prevent expulsion of the tapeworm from the small intestine.

The influence of electrical stimulation on strength and swimming performance

s-International Society of Biomechanics XIV Congress 1993 683 THE INFLUENCE OF ELECIXICAL STIh4ULATION ON STRENGTH AND SWIMMING PERFORMANCE Florence Pichon and Gillea Cometti Laboratoire d’Etude et de Recherche sur la Performance Sportive UFR-STAPS, Universitt! de Bourgogne, B.P 138,210OO Dijon, France. This study aims to examine the influence of a three week’s cycle of electrical stimulation on latissimus dorsi on strength development and swimming performance. Eighteen regional and national standard sprint swimmers were divided into two groups : the control group (N=8) and the study group (N=8) underwent with electrostimulation sessions (three sessions a week during three weeks) in addition to swimming training. Sessions are carried out using a portable stimulator (stywel) and lasted 12 minutes, the contraction time was five seconds and the rest one was 15 seconds. A biodex type (Biodex Corporation, Shirley, NY, USA) isokinetic ergometer was used to measure the maximum torque values developed over the arm flexion-extension movement at different velocities (-120, -6O,O, 60, 120, 180,240,300, 360%). Therefore, special tests in the pool (50 meters arms only and full movement) were carried out. At the end of training, the results for electrostimulated swimmers show a significant difference in peak torque concentrically at velocity of 180/s and 36O”/s and in peak torque isometrically (with ~4~05). Moreover an improvement of 0,44 s (p&,05) is recorded for the 50 meters full movement. While the control group showed no significant difference for all tests. A electrostimulation training for three weeks could be the consequence of a preferential solicitation of muscular type IIb fibres. The important improvements find in swimming indicate that electrostimulation training must be used in planning of swimmers. AN ATHLETIC SHOE AGAINST HYPERINVERSION IN THE ANKLE DURING HIGH LOAD PERFORMANCE Mark R.Pitkin Iv2 1 Department of Rehabilitation Medicine Tufts University, Boston, MA 02111, USA. ’ Newman Laboratory for Biomechanics and Human Rehabilitation, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. This work relates to an athletic shoe design made to reduce the risk of injury of the subt,alar joint. Said injury occurs when the ankle moves in frontal plane from neutral to the inverted position and the bending torque of the external forces becomes more than the counterresistance of the joint,‘s ligaments. Biomechanical analysis of the incorporation of the borders, wrapping, torsion sole, flaring, various midsole hardness did not prove their effectiveness in protection of l igaments in t,he subtalar joint. A model of the subtalar joint r&istance has been developed, which enabled to propose a new design of the athletic shoe, protecting subtalar joint from hyperinversion. The shoe has two soles having the shape of the controversial wedges in the frontal cross section, which are elastically connected. A shift of the upper sole in the lateral direction provides the lifting of its lateral upper edge, while its medial upper edge goes down. MUSCULAR SYNERGY PATTERNS IN WEIGHTLImING. A FOLLOW-UP STUDY R.Pozzo, M.Jahn, Institute of Biomechanics, Cologne, Germany In order to identify individual and general strategies in the motor control, combined analysis of EMG and of the biomechanical structure (Ground Reaction Forces, barbell kinematics) of the movement ( competitive movements and assistant exercises) were carried out during the training (5 months) of 6 elite weightlifters. AAer recording of myoelectrical potentials (CMRR r 70 db, BP= 1OHz lKHz, Zin= 1,s MQ , gain= 1000) EMG signals were full wave rectified, root mean squared and low-pass filtered (70 Hz). The intermuscular activity patterns (IMAP) of VM, BF, TR and BB are representative of the main characteristics of the movement sequences. For the pull phase of snatch and clean two main patterns were identified. By comparing the kinematics and kinetics of the movements with the EMG patterns, indicators of the “technique” goodness are indentified. By means of regression analysis the individual adaptation processes with respect to the variation of the load and to the type of exercise were determined in terms of traning induced effects. Differences in the IMAP are not necessarily matching similar variations in the GRF and barbell kinematics. This is essential for the usefullness of GRF as interpretative and diagnostic indicator in training. The analysis of the interphasic relations between the peak values of GRF, barbell velocity and EMG amplitude and between the EMG onset of different muscles permits to compare the neuromuscular strategies of these multi-joint movements with theoretical models (equlibrium-point hypothesis, speed strategy).

Control of a Robot Arm by Myoelectric Potential

Control of a Robot Arm by Myoelectric Potential

Observation of proportionality of myoelectrical activity of anterior temporalis to masseter muscle during clenching at varied jaw positions.

Twelve healthy subjects with an intact permanent dentition and normal occlusion were selected for sampling of myoelectrical activity of their left and right anterior temporal and masseter muscles during habitual clenching level in varied positions. The proportionality of normalized myoelectrical potentials of anterior temporal muscle to masseter muscle at ICP and RCP was greater than one, while the proportionality at PP was less than one. In the lateral position, the proportionality on the working side was approximately equal to that at RCP, while the proportionality on the non-working side was similar to that at PP. These results suggest that temporal muscle contraction can bring the mandible upward and backward whilst the masseter muscle can elevate the mandible upward and forward.

Noise characteristics of stainless-steel surface electrodes

Bioelectric events measured with surface electrodes are subject to noise components which may be significant in comparison with low-level biological signals such as evoked neuroelectric potentials, and myoelectric potentials. In an effort to better understand noise arising from these electrodes, electrode and measurement system noise is modelled. The effect of electrode surface area on electrode impedance and noise is studied using circular stainless-steel electrodes of varying diameters. The main contributions of the work are the development of a model for stainless-steel electrode noise as a function of electrode area, and demonstrating that, for the band-width of interest to evoked neuroelectric and myoelectric signals (8-10,000 Hz), the primary noise components are thermal and amplifier current generated. The magnitudes of both of these depend on the electrode impedance magnitude. Electrode impedance is shown to be a power function of both electrode diameter and frequency, consistent with a capacitive electrode model.

A comparative study of mastication between complete denture wearers and dentate subjects

A computer system was used for simultaneously collecting and processing mandibular movements and the myoelectric activities of the masticatory muscles of 15 dentate subjects and 11 complete denture wearers. The displacement, velocity, cycle of mandibular movements, and the muscular mean potentials were indices in observing mastication. A good complete denture should perform with physiologic characteristics, and restore masticatory function and oral health. The kinetic energy from the velocities of lateral and vertical directions can serve for the chewing and comminution of food, but lateral comminution may affect denture retention. The mean myoelectrical potentials of the mandibular elevator muscles of complete denture wearers tend to increase at the opening phase; however, the potentials decrease at the closing phase.

こう筋筋疲労過程における筋電位伝導速度および周波数パラメータの観察 ＩＩ 周波数パラメータについて

During sustained isometric contraction of the jaw muscles, muscular fatigue causes a shift towards lower frequencies in the EMG frequency power spectrum. This shift is due to a reduction of myoelectric conduction velocity. The purpose of this study was to investigate the effect of surface electrode location on the estimates of frequency components, and to determine the appropriate frequency parameters of surface EMG which provided the best fit when comparing conduction velocity. Studies were performed in the masseter muscles of 8 healthy subjects. The myoelectric potentials were derived using 12 differential amplifiers from electrode arrays. The frequency parameters calculated were as follows: peak frequency, mean power frequency, cumulative power function (10, 25, 50 and 75%), median frequency ratio, low frequency ratio and measure H. As the results, following findings were obtained: 1. The high frequency content occurred at the region of end-plate zone and tendonous insertion of the muscle. 2. EMG spectra obtained during fatigue were shifted to lower frequencies for all regions except adjacent end-plate zone. 3. The relationships between conduction velocity and frequency parameters during fatiguing contractions were almost linear except peak frequency. 4. It was concluded that the location between distal end-plate and the tendon was "stable" zone for studying muscular fatigue.

こう筋筋疲労過程における筋電位伝導速度および周波数パラメータの観察 Ｉ 筋電位伝導速度について

The muscle fiber conduction velocity is used as an indication of a localized muscular fatigue or some muscular diseases. The purpose of this study was non-invasively to estimate the conduction velocity of the human masseter muscle using surface electrode arrays. Informed consent was obtained from a group of 8 healthy subjects (24-27 yr) without functional disturbances of the jaws and with natural dentitions. Each subject was asked to perform a brief isometric contraction at 10, 20, 30, 40 and 50% of the maximum EMG amplitude and an endurance of 30 and 50% MVC in the intercuspal position. The myoelectric potential was derived from an adjacent pair of electrode wires and the velocity was estimated by the electrode distance divided by the time delay between two myoelectric signals. The time delay was calculated by the cross-correlation technique. The results obtained were as follows: 1. The muscle fiber conduction velocity slightly increased with contraction force. 2. The exponential reduction in velocity was shown during fatiguing contraction of 50% MVC. 3. The muscle fiber conduction velocity decreased with the time after fatiguing contraction. 4. It was suggested that the conduction velocity of the muscle membrane discharge was an important index of muscular fatigue.

The distribution of myoneural junctions in the biceps brachii investigated by surface electromyography

The location of the myoneural junction was investigated by a surface electromyogram. During a voluntary muscular contraction, an electrode array was placed on the skin overlying the muscle to detect myoelectric potentials propagating in both proximal and distal directions along the muscle fibers. The source of the propagating waves was presumed to mark the location of the myoneural junctions. The recordings were repeated to cover the whole muscle surface and the distribution of myoneural junctions was determined. Myoneural junctions in the biceps brachii were located nearly at the middle length of the muscle and were distributed in a zone across the muscle. The distribution showed differences in 3 subjects examined. In 1 subject, myoneural junctions occupied a single zone, while the other 2 subjects had 2 parallel zones separated by 10–20 mm. This information about the location of myoneural junctions is important for determining the electrode position in an electromyogram study.

A method for long-term artifact-free recording of single unit activity in freely moving, eating and drinking animals

A method for long-term artifact-free recording of single unit activity in freely moving, eating and drinking animals is described. A dual channel field effect transistor (FET) which functions as dual source followers is mounted directly on the head socket of the animal and the pins are connected directly to chronically implanted microwire electrodes. Unit activity inputs to the FETs from two closely spaced electrode wires, one recording and one indifferent, were differentially amplified through a circuit with high common mode rejection ratio. Use of the FETs reduced the signal source impedance of long lead wires from the electrodes to the main amplifier and differential recording from two close electrodes cancelled mastication-related myoelectric potentials as common mode signals. Both movement and chewing artifacts were completely eliminated by these techniques.

The Measurement of Muscle Fiber Conduction Velocity Using a Gradient Threshold Zero-Crossing Method

The conduction velocity of myoelectric potential along muscle fiber is known to be an index of the degree of muscular fatigue or muscular disease. When detecting the myoelectric potential by means of surface electrodes, the conduction velocity must be extracted from an apparently random wave of a myoelectric signal. In this paper, a method for determining conduction velocity is proposed based upon a zero-crossing time delay measurement with reference to the derivative of a myoelectric signal. The slope value of the input signal provides an effective criterion for rejecting undesired zero crossing caused by noise. This method needs no spectral analysis nor correlation calculation. Compared to another previously reported zero-cossing approach using digital filter preprocessing, it shows a more accurate and rapid estimation of velocity.

Myofeedback: a new method of teaching breathing exercises in emphysematous patients.

The diaphragm of the emphysematous patient is low and limited in its excursions, producing an increased functional residual capacity and decreased pulmonary ventilation. This report describes our experiences with a new technique for 1) the training of abdominal-diaphragmatic (A-D) breathing and 2) the relaxation of accessory respiratory muscles in emphysematous patients. Abdominal muscle contraction during expiration has been shown to increase diaphragmatic excursions and, hence, pulmonary ventilation. Use of this technique has been limited, however, because of the difficulty in learning this breathing pattern. Through continuous audio and visual feedback of myoelectric potentials (myofeedback) from abdominal muscles, 12 patients learned A-D breathing. The lower rectus abdominis muscle was found to be the most suitable muscle for obtaining the myoelectric potentials. Similarly, by providing the patients with myofeedback from their accessory muscles, they decreased the use of these muscles, thus increasing their respiratory efficiency. With myofeedback, patients appear to learn new breathing patterns effectively and in fewer sessions than with conventional procedures.

Myoelectric-control system for arm-hand prosthesis

A control system which uses myoelectric potentials to address commands in a read-only memory is described. A discussion of a conceptual prosthetic unit is included.

Paper 23: Statistical Analysis of Myoelectric Potentials in Man

The paper describes an initial study of the problem of automatically distinguishing the action potentials of single motor units in skeletal muscle in man. The implications of the results are discussed in relation to the use of EMG activity for controlling externally powered devices and as a possible means for categorizing pathological states.