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At least 1,423 records · Page 79Linked to original sources
PubMed1992

[Facial, lingual and pharyngeal electromyography in children: a method to study sucking and swallowing disorders and their pathophysiology].

The authors describe an electromyogaphic protocol developed with the aim of evaluating the sucking-swallowing function and of studying the pathophysiology of its disturbances in the newborn and in infants. This protocol consists of associating several techniques. Some of them are traditional: EMG of the facial muscles and nerves and blink reflex, while others are original: EMG of the tongue and hypoglossal nerve, EMG of the velum palatinum, and a dynamic study using a baby bottle, of the sucking and swallowing reflex for a liquid meal. For each technique, practical procedures are described together with normal results observed between birth and 3 years of age. The authors report on abnormalities observed in pathological conditions and discuss their significance in major nosological contexts. They emphasize the value of this EMG protocol in assessing the sucking-swallowing reflex, in revealing anatomo-functional disturbances in the brainstem and in tackling the pathophysiological aspects of aspiration pneumopathies, feeding difficulties and bucco-facial malformations.

Child, Preschool↗
PubMed1997

[Importance of electromyography in the diagnosis of botulism].

Botulism is a cause of neuromuscular transmission impairment. We report here an electrophysiological study of the neuromuscular junction in a patient presenting with botulism. Repetitive stimulation of a motor nerve showed a characteristic triad, indicating presynaptic block of neuromuscular transmission: the muscle action potential amplitude was low; repetitive high frequency stimulation (20 Hz) induced a more than 100% increment in the amplitude; low frequency repetitive stimulation (3 Hz) induced a more than 10% decrement in the amplitude. Progressive clinical improvement spontaneously occurred and the electrophysiological control recording that was done 1 month later was normal. Botulism toxin reduces acetylcholine quanta released in the autonomic and neuromuscular junction, causing presynaptic block. Electrophysiological recordings associated with clinical data contributed more to the diagnosis of botulism than serological analysis, which remained negative in this patients.

Adolescent↗
PubMed2003

Single-fiber electromyography.

Single-fiber EMG is a technique introduced in 1963 by Stålberg and Ekstedt for recording single muscle fiber action potentials by means of a specially constructed needle with a 25-microm recording surface. The needle is positioned in the muscle to record from two or more time-locked potentials belonging to the same motor unit. Jitter is the variability in the arrival time of action potentials to the recording electrode between consecutive discharges. This variability reflects end-plate conduction and is measured along with fiber density, which is the average number of fibers belonging to the same motor unit that is in the recording area. An abnormal test is one in which more than 10%, or the mean, of 20 fiber pairs has increased jitter when compared with normal reference values. Increased fiber density is seen with reinnervation. Single-fiber EMG is more sensitive than conventional EMG and is the most sensitive, but not specific, test for myasthenia gravis. Lambert-Eaton myasthenic syndrome, and other neuromusculasr junction pathology. It has been useful in the evaluation of some neuropathies and myopathies and has provided valuable information on the motor unit spatial arrangement, territory, microphysiology, and pathophysiology.

Action Potentials↗
PubMed2003

Quantitative electromyography.

Quantitative EMG is an MUAP analysis technique providing objective information on the NEE. The concept and techniques are not new; however, with the advancement of computer technology, quantitative EMG is now more easily performed. The study requires solid knowledge of basic neurophysiology and access to the appropriate instrument to provide smooth technique and accurate interpretation. Despite recent technical advances, the original MUAP parameters defined by Buchthal are still widely used today as reference values. It is increasingly recognized that many factors can influence the obtained parameters. The ability to measure something does not mean that it is fully understood. The future of quantitative EMG will depend on increased understanding of the physiologic and pathophysiologic significance of the detailed numeric parameters that are generated.

Action Potentials↗
PubMed2003

Electromyographic approach to neuromuscular junction disorders repetitive nerve stimulation and single-fiber electromyography.

Understanding the physiology of the NMJ aids the electromyographer in understanding how NMJ testing was developed. Practicing the RNS protocol on healthy subjects helps the electromyographer gain greater comfort with the implementation of a test that is not performed daily. The practice parameter proposed by the AAEM has established guidelines for testing and for diagnosing NMJ disorders using RNS and single-fiber EMG.

Electric Stimulation↗
PubMed2002

Electromyography of trunk muscles in isometric graded axial rotation.

This study was conducted to determine the pattern, magnitude, and phasic inter-relationship of the trunk muscles in maximal isometric and graded isometric axial rotational contractions and compare them with those previously observed from the same subjects in the same experimental session in dynamic conditions. In 50 normal young healthy subjects (27 male and 23 female), after a suitable skin preparation, bipolar silver-silver chloride recessed pregelled surface electrodes were placed on external oblique, internal oblique, rectus abdominis, pectoralis major, latissimus dorsi, erector spinae at T(10) and L(3) levels bilaterally with 2 cm interelectrode distance. EMG signals from grounded subjects were suitably preamplified and amplified by a fully isolated system. These subjects were stabilized in an upright-seated posture in the Axial Rotation Tester (AROT), which was placed in isometric mode for force and rotation output from the AROT. The 14 channels of EMG, the force and the rotation were sampled at 1 kHz. The subjects initially registered their isometric maximal voluntary contraction (MVC) on both sides which was used for reference and then performed their 25%, 50% and 75% of MVC bilaterally in an isometric mode in a random order. The EMG magnitude, the slope of the rise of the EMG, and the phasic interrelationship of muscles were analyzed. The results showed that female sample generated only 65% of torque of their male counterparts. There were no significant differences between the male and the female samples in the EMG variables. Exertions to the left and to the right were not significantly different from each other for the measured variables. However, the magnitude contribution of the muscles and the slope of rise of EMG were significantly different in two directions (p<0.001). The phasic interrelationship of the external obliques, the latissimus dorsi and the erector spinae were different from other muscles (p<0.01). With the increasing grades of contraction the latissimus dorsi and the external obliques increased their magnitude significantly whereas that of the erectores spinae underwent a decrease in proportionate terms (but not in absolute magnitude) suggesting their role as stabilizers but not as rotators.

Adult↗
PubMed2002

Sampling, noise-reduction and amplitude estimation issues in surface electromyography.

This paper reviews data acquisition and signal processing issues relative to producing an amplitude estimate of surface EMG. The paper covers two principle areas. First, methods for reducing noise, artefact and interference in recorded EMG are described. Wherever possible noise should be reduced at the source via appropriate skin preparation, and the use of well designed active electrodes and signal recording instrumentation. Despite these efforts, some noise will always accompany the desired signal, thus signal processing techniques for noise reduction (e.g. band-pass filtering, adaptive noise cancellation filters and filters based on the wavelet transform) are discussed. Second, methods for estimating the amplitude of the EMG are reviewed. Most advanced, high-fidelity methods consist of six sequential stages: noise rejection/filtering, whitening, multiple-channel combination, amplitude demodulation, smoothing and relinearization. Theoretical and experimental research related to each of the above topics is reviewed and the current recommended practices are described.

Artifacts↗
PubMed2002

Agonist-antagonist common drive during fatiguing knee extension efforts using surface electromyography.

AIM: This study examined the electromyographic (EMG) activity of knee extensor agonists and a knee extensor antagonist muscle during fatiguing isometric extensions across a range of force levels. METHODS: Five female subjects performed isometric knee extensions at 25%, 50%, 75% and 100% of their maximal voluntary contraction (MVC) with the knee flexed to 75 degrees. Surface EMG (SEMG) was recorded with bipolar electrodes from the vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF) and biceps femoris (BF) and the root-mean-squared (RMS) amplitude and the percentage frequency compression of these recordings were calculated. Commonality and cross talk between recordings were also examined. RESULTS: Cross talk between recordings was deemed negligible despite significant levels of commonality between the agonist and antagonist SEMG, which was attributed to common drive. SEMG RMS amplitude increased significantly for all muscles during the 25%, 50%, 75% MVC knee extensions until task failure, and decreased significantly for 100% MVC. The frequency spectrum of the SEMG compressed significantly for all muscles and % MVC levels. The VM, VL and BF SEMG recordings responded similarly to fatigue. The RF's frequency spectrum compressed to a significantly higher degree. CONCLUSIONS: The VM, VL, RF, and BF fatigue in parallel, with high similarity between VM, VL and BF, giving support to the concept of a shared agonist-antagonist motoneuron pool.

Adult↗
PubMed2003

Crosstalk in surface electromyography of the proximal forearm during gripping tasks.

Electromyographic (EMG) crosstalk was systematically analyzed to evaluate the magnitude of common signal present between electrode pairs around the forearm. Surface EMG was recorded and analyzed from seven electrode pairs placed circumferentially around the proximal forearm in six healthy individuals. The cross-correlation function was used to determine the amount of common signal, which was found to decrease as the distance between electrode pairs increased, but was not significantly altered by forearm posture (pronation, neutral, supination). Overall, approximately 40% common signal was detected between adjacent electrode pairs (3 cm apart), dropping to about 10% at 6 cm spacing and 2.5% at 9 cm. The magnitude of common signal approached 50% between adjacent electrode pairs over the extensor muscles, while over 60% was observed between neighbouring sites on the flexor aspect of the forearm. Although flexor and extensor EMG amplitude was similar, less than 2% common signal was present between flexor and extensor electrode pairs during both pinch and grasp tasks. Maximum grip force production was not affected by forearm rotation for pinch, but reduced 18% from neutral (mid-prone) to pronation during grasp (p=0.01). In spite of differences in grip force, mean muscle activity did not vary between the three forearm postures during maximum pinch or grasp trials. While this study improved our knowledge of crosstalk and electrode spacing issues, further examination of forearm EMG is required to improve understanding of muscle loading, EMG properties and motor control during gripping tasks.

Adult↗
PubMed2003

Surface electromyography assessment of back muscle intrinsic properties.

The purpose of this study was to assess (1) the reliability and (2) the sensitivity to low back pain status and gender of different EMG indices developed for the assessment of back muscle weakness, muscle fiber composition and fatigability. Healthy subjects (men and women) and chronic low back pain patients (men only) performed, in a static dynamometer, maximal and submaximal static trunk extension tasks (short and long duration) to assess weakness, fiber composition and fatigue. Surface EMG signals were recorded from four (bilateral) pairs of back muscles and three pairs of abdominal muscles. To assess reliability of the different EMG parameters, 40 male volunteers (20 controls and 20 chronic low back pain patients) were assessed on three occasions. Reliable EMG indices were achieved for both healthy and chronic low back pain subjects when specific measurement strategies were applied. The EMG parameters used to quantify weakness and fiber composition were insensitive to low back status and gender. The EMG fatigue parameters did not detect differences between genders but unexpectedly, healthy men showed higher fatigability than back pain patients. This result was attributed to the smaller absolute load that was attributed to the patients, a load that was defined relative to their maximal strength, a problematic measure with this population. An attempt was made to predict maximal back strength from anthropometric measurements but this prediction was prone to errors. The main difficulties and some potential solutions related to the assessment of back muscle intrinsic properties were discussed.

Abdominal Wall↗
PubMed1998

1998 ISEK Congress Keynote Lecture: The use of electromyography in applied physiology. International Society of Electrophysiology and Kinesiology.

Electromyogram (EMG) analyses (surface, intramuscular and evoked potentials) in studies of muscle function have attracted increasing attention during recent years and have been applied to assess muscle endurance capacity, anaerobic and lactate thresholds, muscle biomechanics, motor learning, neuromuscular relaxation, optimal walking and pedalling speeds, muscle soreness, neuromuscular diseases, motor unit (MU) activities (MU recruitment and rate coding), and skeletal muscle fatigue. This paper deals with the use of EMG analyses employed in the area of applied physiology and is divided into three sections: surface EMG analyses; intramuscular EMG analyses; and evoked potential analyses.

Adaptation, Physiological↗