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At least 19 recordsLinked to original sources

PubMed1992

Acoustic myography of the human quadriceps muscle during intermittent fatiguing activity.

Integrated acoustic myography (IAMG) and electromyography (IEMG) were recorded over rectus femoris (RF) in six healthy subjects during a series of intermittent isometric contractions of quadriceps. Contractions were held for 10 sec with 10 sec rest between each, commencing at 75% maximum voluntary contraction (MVC) force and continuing to 40% MVC. The IAMG activity initially decreased (75%-60% MVC) in a linear relationship (r = 0.9) with fatigue (i.e. force loss) but then plateaued and increased once force fell below 52% MVC. The AMG/force relationship for the whole fatiguing protocol (i.e. 75%-40% MVC) was quadratic (r = 0.87). The IEMG also showed a quadratic relationship with force (r = 0.85) but activity initially increased before decreasing. The results of the present study quantify the relationship between AMG and force in quadriceps during fatigue from intermittent contractions commencing at 75% MVC. The findings confirm previous observations that AMG decreases with fatigue during strong contractions but the quadratic relationship found in the present study differs to that for other muscles during sustained contractions. The results also suggest that simultaneous recordings of AMG and EMG may help distinguish central and peripheral fatigue. Acoustic myography may therefore be a useful non-invasive monitor of force during early fatiguing activity using the present protocol but the need to study AMG during fatigue of different muscles and force levels is stressed.

Acoustics↗

PubMedDate not supplied

Acoustic myography: a noninvasive monitor of motor unit fatigue.

Acoustic myography is the recording of sounds produced by contracting muscle. These sounds become louder with increasing force of contraction. We have compared muscle sounds with surface EMG to monitor the dissociation of electrical from mechanical events (presumably, the loss of excitation-contraction coupling) which occur with motor unit fatigue. Acoustic signals were amplified using a standard phonocardiograph, recorded on FM magnetic tape, and digitally analyzed. Muscles were examined at rest, with intermittent contractions, and with sustained contractions. We found that with fatigue, the acoustic amplitude decayed, but the surface EMG amplitude did not. With decreased effort, however, the acoustic and the surface EMG amplitudes declined simultaneously. By simultaneously recording acoustic signals and needle EMG, individual motor units were resolved acoustically in two muscles with decreased numbers of motor units and increased motor unit size. Fasciculations also produced acoustic signals, although no acoustic signal has yet been found that correlates with fibrillations. Analysis of acoustic signals from muscle provides a noninvasive method for monitoring motor unit fatigue in vivo. It may also be useful in distinguishing muscle fatigue from decreased volition.

Acoustics↗

PubMed1992

Electro and acoustic myography for noninvasive assessment of lumbar paraspinal muscle function.

In 31 normal subjects (17 male), aged 19-48 years, and 8 patients with chronic low back pain (4 male), aged 37-55 years, the repeatability of surface recordings of acoustic myography (AMG) and electromyography (EMG) were examined in the lumbar paraspinal muscles. Five isometric test positions were examined. In 21 of the normal subjects, four positions tested were: quiet standing, half extension from prone lying, full extension from prone with and without resistance. In 10 of the normal subjects and the 8 back pain patients, a standardised, unsupported horizontal position with the upper body over the end of a couch was tested. The AMG and EMG signals were full-wave rectified and integrated (iAMG and iEMG). The variability of recordings during repeated 5-s isometric contractions was assessed by analysis of variance (ANOVA) and the coefficient of variation (CV) was calculated from the ANOVA. Both recording techniques produced the most repeatable results during the unsupported, horizontal hold position. In the normal subjects, CV were, iAMG 5.6%, iEMG 4.9%; and in the patients, iAMG 4.4%, iEMG 2.6%. The CV for the other four isometric test positions ranged from 15.3% to 29.4% for iAMG, and 8% to 15.7% for iEMG. These results demonstrated that a controlled test manoeuvre for examining AMG and EMG of the paraspinal muscles was vital for repeatable recordings. The CV for the standardised, horizontal position were lower than for previously published results.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Acoustic myography reflects force changes during dynamic concentric and eccentric contractions of the human biceps brachii muscle.

The relationship between acoustic myography (AMG), electromyography (EMG) and force during submaximal dynamic contractions was examined in the biceps brachii muscles of eight healthy males (aged 17-26 years). Different weights were lifted and lowered at a constant speed, using a wall pulley system, to perform concentric and eccentric contractions, respectively. Integrated AMG (iAMG) and integrated EMG (iEMG) activity both increased linearly with force during concentric (iAMG r = 0.94; iEMG r = 0.99) and eccentric (iAMG r = 0.90; iEMG r = 0.94) contractions. The slopes of the concentric regression lines were significantly different from the eccentric slopes (P less than 0.01) for both iAMG and iEMG with concentric contractions showing greater levels of activity. The results indicated that AMG can be used to detect changes in force during dynamic contractions which has important implications for the use of AMG in rehabilitation. The differences in iAMG activity between concentric and eccentric contractions are discussed in relationship to the origin of the AMG signal.

Adolescent↗

PubMed1993

Ultrasound myography: application in nerve conduction velocity assessment and muscle cooling.

A new application of ultrasound for studying muscle twitch induced by electrical stimulation is described and some preliminary results are presented. The method, called "ultrasound myography" (UMG), uses Doppler ultrasound to measure muscle movement velocity. The Doppler signals were measured simultaneously with the electromyography (EMG) signals from the thenar muscle of a healthy subject. Averaged EMG and full-wave rectified UMG responses to repeated electrical stimuli were measured after cooling of the hand and adaptation to room temperature. Latency times over the wrist of cold hands adapted to a surrounding temperature of 8 degrees C were 4.5 ms and 16.9 ms for the EMG and averaged rectified UMG responses, respectively. Both latency times decreased considerably after 1 h adaptation to a room temperature of 21 degrees C:20% for the EMG response and 35% for the UMG response. The conduction velocities of the median nerve in the forearm determined by both methods yield comparable results. The results of both methods are discussed. It is concluded that UMG possibly offers a new method in clinical practice for the assessment of nerve conduction velocities in the forearm, and basically is a new simple-to-use technique for noninvasive analysis of deep biomechanical processes.

Adult↗

PubMed2006

Electrical impedance myography: transitioning from human to animal studies.

OBJECTIVE: To determine the feasibility of performing electrical impedance myography (EIM) in rats. METHODS: EIM was performed on the hamstring muscles of 6 healthy adult rats with applied frequencies of 2-300 kHz. Studies were performed over a 6-week period, with 3 rats having recordings made from the skin (surface EIM) and 3 with recordings directly from the muscle (direct-muscle EIM). In addition, sciatic nerve crush was performed on one rat and comparisons made pre- and post-injury. Reactance and resistance were measured and the primary outcome variable, the phase angle (theta), calculated. RESULTS: EIM patterns in the rat hamstring muscles were qualitatively similar to those observed in human subjects. This held true for both surface and direct-muscle recordings, although direct-muscle data appeared less repeatable. Sciatic nerve crush data in the single rat showed a dramatic reduction in phase and a relative loss of frequency-dependence. CONCLUSIONS: EIM data similar to that obtained from human subjects can be acquired from rat muscles with surface recordings proving more consistent and easier to obtain than direct-muscle recordings. Changes seen with sciatic nerve crush mirror those seen in patients with neurogenic injury. SIGNIFICANCE: These results support the possibility of performing EIM on rat models of neuromuscular disease.

Animals↗

PubMed2003

[Opacification of a coronary vein during left ventriculography with inadvertent myography in a 78-year-old woman with aortic stenosis].

A 78 year-old woman had a NYHA II dyspnoea, which was related to a calcified aortic stenosis. Functional aortic valvular surface was calculated to 0.75 cm2 by echocardiography. In addition, there were important mitral calcifications without mitral stenosis. The left ventricular contractility was normal, but there was a significant left ventricular hypertrophy. At the time of the coronary angiography, the aortic valve was crossed with difficulty. A "pigtail" probe was positioned and during left ventricular angiography, an unexpected aspect of myography was observed with an unusual opacification of the interventricular posterior coronary vein, draining in the coronary sinus. The patient remained strictly asymptomatic during all the procedure. Two echographic controls carried out in the 24 following hours appeared normal, without pericardial effusion nor new parietal anomaly of the left ventricle. Five weeks later, the patient underwent an aortic valve replacement without complication.

Aged↗

PubMed1998

Acoustic myography, electromyography and bite force in the masseter muscle.

Acoustic myography (AMG) offers some advantages over electromyography (EMG) in certain circumstances, but the use of AMG on the jaw-closing muscles has not been fully tested. The purpose of this study was to examine the relationship between AMG, EMG and force in the masseter muscles of nine healthy male subjects. The AMG was recorded using a piezoelectric crystal microphone and the EMG was recorded simultaneously with surface electrodes. Force was recorded between the anterior teeth with a strain-gauge transducer. Analysis showed that Pearson's correlation coefficient was 0.913 for force/AMG and 0.973 for force/EMG in all subjects, indicating a linear relationship between force, AMG and EMG at the four different force levels tested (25-75% of maximum). It is apparent that AMG may be used as an accurate monitor of masseter muscle force production, although some care is required in the technique.

Acoustics↗

PubMed2006

Effects of age on muscle as measured by electrical impedance myography.

Electrical impedance myography (EIM) is a painless and non-invasive technique for the assessment of muscle which we apply here to the effects of normal aging. The paper presents a cross-sectional analysis of EIM data from the quadriceps and tibialis anterior of 100 healthy subjects (44 men, 56 women, ages 18-90 years). The principal EIM parameter, the spatially averaged phase theta(avg), shows a roughly quadratic reduction with increasing age, declining more steeply beyond 60 years. The correlation was stronger in men (quadriceps: r2 = 0.68 for men, 0.52 for women; tibialis anterior: r2 = 0.74 for men, 0.38 for women; p < 0.001 throughout). Additionally, four subjects (age greater than 75 years) were asked to return for repeat testing several years after their initial assessment. These longitudinal results qualitatively confirm the cross-sectional data, though with greater reductions in theta(avg) at high age. The findings of this study support the potential use of EIM as a simple and effort-independent test of muscle health in the elderly.

Adult↗

PubMed1993

Acoustic myography in the assessment of human masseter muscle.

The feasibility of examining electro-mechanical activity of the human masseter muscles using non-invasive recording techniques was examined in six healthy dentate adults (aged 34-57 years). Electrical activity of the muscle was examined by surface electromyography (EMG) and the mechanical activity, in the form of muscle sounds, was examined by acoustic myography (AMG). Bilateral recordings of EMG and AMG were made simultaneously using composite probes which were placed on the skin over the masseter muscles. A standardized pressure was applied to the probes via adjustable rods attached to a safety helmet. Pressures were monitored by strain gauges placed between the ends of the rods and the probes. With the subject seated, recordings of AMG and EMG were obtained during maximal jaw clenching for 4 s and the raw signals were stored on a computer. Of three maximal contractions performed, the last two were used in the analysis. The raw amplified signals underwent frequency analysis by fast Fourier Transform. Total activity was also assessed after amplification, full-wave rectification and integration, and repeatability of the results was assessed. The AMG frequency range was 6-15 Hz and was similar to values for other human skeletal muscles. The integrated values for EMG and AMG were repeatable on both sides of the face (IEMG, right r = 0.99, left r = 0.99; IAMG right r = 0.70, left r = 0.71). Simultaneous recordings of AMG and EMG from the masseter muscles may be useful for assessing electro-mechanical muscle function but further validation studies are required before the technique can be used clinically.

Acoustics↗

PubMed1991

Acoustic myography for investigating human skeletal muscle fatigue.

Sounds produced during voluntary isometric contractions of the quadriceps muscle were studied by acoustic myography (AMG) in five healthy adults. With the subject seated, isometric force, surface electromyography (EMG), and AMG were recorded over rectus femoris, and the EMG and AMG signals were integrated (IEMG and IAMG). Contractions lasting 5 s each were performed at 10, 25, 50, 60, 75, and 100% of maximum voluntary contraction (MVC) force. Fatigue was then induced by repeated voluntary contractions (10 s on, 10 s off) at 75% MVC until only 40% MVC could be sustained. After 15 min of rest, the different force levels were again tested in relation to the fresh MVC. Both before and after fatiguing activity the relationships between force and IEMG [r = 0.99 +/- 0.01 (SD), n = 10] and force and IAMG (r = 0.98 +/- 0.02) were linear. After activity, however, the slopes of the regression lines for force and IEMG increased (P less than 0.01) but those for force and IAMG remained the same (P greater than 0.05). The present results clarify the relationship between AMG and isometric force in fatigued muscle without the problem of fatigue-induced tremor, which hampered previous studies of prolonged activity. This study contributes to the validation of AMG and shows that it is a potentially useful method for noninvasive assessment of force production and fatigue. Further studies to establish the origin of AMG activity are required before AMG can be accepted for use in neuromuscular physiology or rehabilitation.

Acoustics↗

PubMed2005

Electrical impedance myography in the bedside assessment of inflammatory myopathy.

Electrical impedance myography (EIM) is a new technique with potential for the noninvasive bedside assessment of myopathy. EIM was performed on the quadriceps of 10 patients with inflammatory myopathy and 10 normal subjects. The major EIM parameter, the spatially averaged phase, was 35% lower in the myositis patients and correlated with whole-body (r = 0.765, p = 0.01) and quadriceps (r = 0.673, p = 0.03) strength.

Electric Impedance↗

PubMed2005

A guide to wire myography.

Wire myography is an in vitro technique that allows us to examine functional responses and vascular reactivity of isolated small resistance arteries. Vessels from various species, including transgenic models, and vascular beds can be examined in a variety of pathological disease states. Vessels are dissected, cleaned, and then mounted onto a four-channel myograph under isometric techniques. Each vessel is then normalized to determine maximum active tension development. This allows the standardization of initial experimental conditions, an important consideration when examining pharmacological differences between vessels.

Animals↗

PubMed1986

Acoustic myography as a control signal for an externally powered prosthesis.

Contracting skeletal muscle produces sounds that are easily recorded with a standard microphone. The recording of these sounds is known as acoustic myography, or AMG. As a control signal for an externally powered prosthesis, some advantages of AMG over surface EMG are: there is no need for direct skin contact; the AMG signal is unaffected by changes in skin impedence; AMG intensity is high enough to produce a 50 mV output from a standard microphone, requiring less amplification and electrical shielding; the AMG signal is qualitatively less sensitive to placement on the muscle than EMG. Disadvantages, such as the susceptibility of AMG to interference by extraneous environmental noise, are relatively easy to overcome. To demonstrate this, we have constructed a myoacoustically controlled prosthetic hand, whose tristate control via a single microphone (vs differential control) proves its feasibility in the more difficult case. The control circuitry for this device costs less than $50. The existing device utilizes a free-standing hand; a prosthetic shell which will allow comparison of AMG vs EMG control is currently being designed. The two patients who have tried it have learned to open and close the hand reliably after only three minutes of practice. Protocols are being established for functional assessment of AMG control.

Acoustics↗

PubMed2005

Electrical impedance myography in the detection of radiculopathy.

Electrical impedance myography (EIM) is a new bioimpedance-based technique for neuromuscular disease assessment. Past work has focused on EIM in the evaluation of diffuse diseases (such as myopathy). In this study, the method's most basic form, linear-EIM, was used for the assessment of restricted radiculopathic disease. Ten normal subjects and 10 patients with unilateral cervical or lumbosacral radiculopathy, diagnosed by electromyography and clinical criteria, were enrolled. Linear-EIM was performed bilaterally on all individuals, and comparisons with the major outcome variable, theta(avg), were made. In normal subjects, side-to-side differences in theta(avg) averaged 0.64% and were no greater than 15.9% in magnitude. In the 10 patients with radiculopathy, theta(avg)was consistently lower in the affected extremity, with a mean side-to-side difference of 15.3%, but ranging as low as 72.3%; there was a tendency for muscles with more prominent chronic neurogenic change to show greater relative reductions in theta(avg). These findings support the potential utility of EIM in assessment of localized neuromuscular disease.

Arm↗

PubMed2006

Assessing neuromuscular disease with multifrequency electrical impedance myography.

Electrical impedance myography (EIM) is a noninvasive technique for neuromuscular assessment in which low-intensity alternating current is applied to a muscle and the consequent surface voltage patterns are evaluated. Previous work using a single frequency of 50 kHZ has demonstrated quantitative correlation of EIM parameters with disease status. In this investigation we examined the use of multifrequency EIM, studying a prototypical neurogenic disease (amyotrophic lateral sclerosis, ALS) and myopathic disorder (inflammatory myopathy, IM). Eleven ALS patients, 7 IM patients, and 46 normal subjects participated in the study. Although disease-specific patterns were not identified such that IM could be differentiated from ALS, impedance vs. frequency patterns for diseased subjects differed substantially from those of the age-matched normal subjects, with the greatest alterations occurring in the most severe cases. Multifrequency EIM may be well-suited to serve as an easily applied technique to assess disease severity in a variety of neuromuscular conditions.

Action Potentials↗

PubMed2005

Electrode position and size in electrical impedance myography.

OBJECTIVE: Linear-electrical impedance myography (EIM) is a non-invasive technique for the evaluation of muscle, in which high-frequency alternating current is injected into the body via two surface electrodes, and the resulting voltage pattern over a selected muscle is measured using a second, larger set of electrodes. The precise location and size of the electrodes can be critical to the data obtained, and in this study the effects of variation in these factors were evaluated. METHODS: Linear-EIM was performed in 5 subjects while varying the location of the current injecting electrodes and in an additional 8 subjects while varying the position of the voltage electrodes. RESULTS: The major outcome variable, the 'spatially averaged phase' (theta(avg)), decreased as the ipsilateral current injecting electrode was moved farther from the voltage electrodes, reaching a plateau 15-20 cm distant. As for the voltage electrode array, distal-proximal shifts resulted in the greatest changes, with variation in theta(avg) being as high as 14% per cm; circumferential shifts around the limb had more modest effects. CONCLUSIONS: Linear-EIM results depend systematically on current and voltage electrode positions, but with reasonable care variation can be minimized. SIGNIFICANCE: With proper attention to electrode placement, linear-EIM has sufficient reproducibility to become an important clinical tool in neuromuscular disease evaluation.

Adult↗

PubMed2006

Test-retest reproducibility of 50 kHz linear-electrical impedance myography.

OBJECTIVE: Electrical impedance myography (EIM) is a method for evaluating muscle in which high-frequency, low-intensity alternating current is applied to a body region and the resulting surface voltage pattern over a muscle of interest is measured. In this study, the reproducibility for the simplest of these techniques, 50 kHz linear-EIM, was assessed for three muscles. METHODS: Fifty kilohertz linear-EIM was performed on the biceps, quadriceps, and tibialis anterior of 30 normal subjects ranging in age from 21 to 90 years, and the major outcome variable, the spatially averaged phase (thetaavg), measured. The measurements were repeated within 250 days and comparisons between the two data sets made. RESULTS: Reproducibility, as measured by the intraclass correlation coefficients for all three muscles, was very high at 0.970, 0.971, and 0.938 for biceps, quadriceps, and tibialis anterior, respectively. Variability between measurements was on average 4.2% for all muscle combined, with an upper limit of 16.8%. CONCLUSIONS: Fifty kilohertz linear-EIM demonstrates excellent test-retest reproducibility. SIGNIFICANCE: These results support the view that 50 kHz linear-EIM has the potential to be used as a simple, fast, and non-invasive measurement for the assessment of disease status, either as part of individual patient care or as a surrogate outcome measure in clinical trials work.

Adult↗