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At least 1,279 records · Page 71Linked to original sources
PubMed2004

Evaluation of normal deglutition with the help of rectified surface electromyography records.

Surface electromyographic (sEMG) studies were performed on 300 normal adults to estimate normal values of sEMG records of muscle activity in the detection and evaluation of stages of normal swallowing. Our study was a prospective observational study of healthy volunteers. The parameters evaluated during swallowing include the timing, amplitude (voltage), and graphic patterns of activity of the orbicularis oris, masseter, submental, and laryngeal strap muscles covered by the platysma. Three tests were examined: voluntary single swallows of saliva ("dry" swallow), voluntary single water swallows ("normal"), and voluntary single swallows of excessive amounts of water (20 ml, "stress test"). Duration and amplitude of muscle activity in oral, pharyngeal, and initial esophageal stages of swallowing (mean + standard deviation, range + standard deviation) were measured for groups of adults of different ages (18-40, 41-70, 70+ years). Shapes of graphic records were evaluated relative to timing and voltage. The overall normal mean values for stage-by-stage duration of muscle activity during single swallowing were established for healthy adults. The duration of muscle activity in all tests showed insignificant increases with age except for the elderly group (70+) in which it was statistically significant (SPSS, chi2 criterion, 95% confidence interval, p < 0.05). There were no statistically significant gender-related differences in duration or amplitude of muscle activity during single swallowing for any age group (p > or = 0.05). We conclude that the rectified and filtered sEMG provides a noninvasive means to assess certain aspects of complex muscle activity in deglutition. Surface EMG of swallowing is a simple and reliable noninvasive screening method for evaluating swallowing with low levels of discomfort. Stage-by-stage evaluation of duration can be very important for diagnosing the etiology of dysphagia. The combined normative timing of events, amplitude, and graphic data can be used for evaluating complaints and symptoms, as well as for comparison purposes in pre- and postoperative stages and in EMG monitoring during otolaryngological or neurological treatment. These parameters represent stages required for normal deglutition and provide a basis for the comparison of swallowing performance both within and between patients.

Action Potentials↗
PubMed2004

Simultaneous measurement of intramuscular pressure and surface electromyography of the multifidus muscle.

The anatomic proof of a spinal compartment and the clinical symptoms of compartment syndrome in patients with chronic back pain are inconsistent with the rarely met measuring criteria of intramuscular pressure (IMP). Previous studies assume a dependence of the IMP on spinal alignment (degree of lumbar spine flexion) and the degree of muscle activation. The significance of these disturbance variables in the interpretation of IMP could explain the above discrepancy. This study therefore investigates the influence of both a 30% increase in trunk flexion and alterations in muscle contraction from 100% to 60%. Sixteen healthy subjects participated in the study. The IMP and mean rectified amplitude of the multifidus surface EMG signal were determined at rest and 0 degrees and approximately 30 degrees of lumbar spine flexion, and they were compared. Subsequently, both parameters were measured during both 100% and 60% maximal voluntary contraction (MVC) of the muscle and then correlated. During rest and 0 degrees flexion, the median IMP was 9.3 mmHg (range 0.0-22.5) while the median mean rectified amplitude (MRA) of the EMG signal was 1.98 microV (range 1.32-7.38). In 30 degrees flexion, the median IMP went up to 24.3 mmHg (range 1.4-97.3) with hardly any increase in the median MRA of 2.32 microV (range 1.20-9.72). Under 60% MVC, the median IMP rose to 186.6 mmHg (range 15.4-375.4) and the median MRA to 21.02 microV (range 4.63-43.63). During 100% MVC, the median MRA increased to 34.38 microV (range 12.99-102.54) while the median IMP rose to 273.4 mmHg (range 90.4-395.1). Spearman's rank correlation coefficient for the IMP and MRA quotients of the 100/60% MVC values was r= -0.21. To sum up, it can be said that IMP was subject to great interindividual variation in all the experiments. This parameter is highly dependent on spinal alignment and muscular activity. Further studies are needed so that the IMP can be interpreted properly when diagnosing a chronic compartment of the erector spinae muscles.

Adult↗
PubMed2004

The value of electromyography of the lumbar paraspinal muscles in discriminating between chronic-low-back-pain sufferers and normal subjects.

The authors studied the surface electromyographic (EMG) spectrum of the paraspinal muscles of 350 subjects. They were classified by their history as normal (n=175), chronic low back pain (n=145), or past history (n=30). They pulled upwards on a floor-mounted load cell at two-thirds of their maximum voluntary contraction for 30 s, while the EMG was measured from the paraspinal muscles at the L4/L5 level. From the EMG signal the root-mean-square (RMS) was calculated. Power spectrum analysis allowed calculation of the median frequency slope, the initial median frequency (IMF), modal frequency, peak amplitude and spectral width at half peak amplitude (half-width). All of the variables of the chronic group were significantly different from the normal group, except the median frequency slope, RMS slope and mode. Half-width, age and maximum voluntary contraction were shown to be independent predictors of back pain classification. Half-width classified the subjects with a sensitivity of 0.65 and a specificity of 0.75.

Chronic Disease↗
PubMed2002

Electromyography of superficial cervical muscles with exertion in the sagittal, coronal and oblique planes.

The purpose of the current study was twofold: (1) to determine the isometric force and electromyographic (EMG) relationship of the sternocleidomastoid, splenii and trapezii muscles bilaterally in graded and maximal exertions in the sagittal, coronal and oblique planes. and (2) to develop regression equations to predict force based on the EMG scores. A newly designed and validated cervical isometric strength testing device was used to measure the cervical muscle isometric strength and force/EMG relationship in cervical flexion, extension, bilateral lateral flexion, bilateral anterolateral flexion, and bilateral posterolateral extension, all beginning with an upright seated neutral posture. A group of 40 healthy subjects were asked to exert their cervical motions in the directions of interest, while the force output and EMG from the sternocleidomastoids, splenii, and trapezii were sampled bilaterally at 1 kHz. ANOVA, correlation, and regression analyses were carried out. The force and EMG scores were significantly different between the directions of effort (P<0.01). All regressions were significant (P<0.01). All subjects registered the highest forces in pure extension and the lowest in pure flexion, showing a gradual decrease from the posterior to anterior direction. There was a modest correlation between EMG of the investigated muscles and force (r=0.15-0.76, P<0.01). EMG output was, for example, approximately 66% higher in flexion than in extension (while force output was roughly 30% less in flexion than extension) - thus relatively more muscle activity was required in flexion than extension to generate a given force. The intermediate positions (i.e. anterolateral flexion) revealed force/EMG ratio scores that were intermediate in relation to the force/EMG ratios for pure flexion and pure extension. The cervical muscle strength and cervical muscle EMG are therefore dependent on the direction of effort.

Acceleration↗
PubMed1992

Detection of skeletal muscle fatigue in patients with heart failure using electromyography.

Patients with heart failure frequently report that leg fatigue limits maximal exercise capacity. However, objective documentation of muscle fatigue has not been obtained in such patients. In normal subjects, muscle fatigue during constant work load exercise is associated with an increase in electrical activity generated per contraction due to use of additional muscle fibers to compensate for fiber fatigue. The present study was performed to determine if this approach can be used to document muscle fatigue in patients with heart failure. Vastus lateralis surface electromyograms were monitored in 8 ambulatory patients with nonedematous heart failure and 6 normal subjects during maximal bicycle exercise (20 W increments every 2 minutes). The electromyogram was stored on tape and subsequently analyzed for integrated root-mean-square voltage/contraction (iRMSV). At each work load, the iRMSV of the first and last 30 seconds of the work load were compared. The maximal work load achieved by patients with heart failure was significantly lower (73 +/- 22 W) than that by normal subjects (150 +/- 15 W; p less than 0.01). Both groups had no significant difference between the initial and final iRMSV at submaximal work loads. However, during the 2 highest work loads, both groups reported leg fatigue and had significant increases in iRMSV, consistent with muscle fiber fatigue (maximal work load: 259 +/- 59 to 279 +/- 58 mv.ms [normals] vs 258 +/- 94 to 283 +/- 93 mv.ms [heart failure]; p less than 0.03). The data indicate that the surface electromyogram can be used to detect skeletal muscle fatigue in patients with heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Uterine electromyography: a critical review.

On the basis of a literature review, this work summarizes uterine animal and human electromyographic information obtained at cellular, myometrial, and abdominal levels during gestation and parturition. We show that both internal and external electromyograms occur in phase with intrauterine pressure increase and exhibit similar spectra, including a slow wave (0.01 < frequency < 0.03 Hz) probably because of mechanical artifacts and a fast wave whose frequency content can be subdivided into a low-frequency band always present in every contraction and a high-frequency band related to efficient parturition contractions. Application of classic spectral techniques to electromyogram envelopes has identified group propagation but not pacemaker areas. However, no time delay or classic propagation has been demonstrated by applying the same spectral techniques to the electromyogram itself, probably because of the nonlinearity and three-dimensional nature of the propagating process.

Animals↗
PubMed1987

A comparison of electromyography recorded parallel and transverse to the fibres of the anterior and posterior temporalis muscle in man.

Electrical activity recorded during voluntary clenching by platinum hook intra-cutaneous electrodes was significantly higher (p less than 0.01) when the electrodes were placed parallel to the muscle fibres than across the fibres. The correlation between the parallel and transverse EMG recordings was highly significant (p less than 0.001).

Action Potentials↗
PubMed1989

A comparison of the masseteric silent period in temporomandibular joint dysfunction and normal human subjects by surface electromyography and single motor-unit recordings.

Single electric stimuli were delivered to the lower lip and the reflex effects were monitored in the ipsilateral masseter. Two strengths of stimulus were delivered at two levels of background excitation (defined in terms of the firing frequency of a single motor unit). Although the threshold stimulus intensity required to produce a silent period in the single motor units was the same for the patients with temporomandibular joint dysfunction and normal subjects, there were qualitative differences in the pattern of reflex responses between the two groups. Of the two phases of inhibition elicited by the stimulus, the short-latency inhibitory period was the more prominent and more resistant to changes in the background excitation levels in the dysfunction group. In normal subjects, however this was true of the long-latency inhibition. This difference may be due to the changes in the inputs to one or more of the interneurones linking the afferent limb of the reflex to the masseteric motoneurones.

Adult↗
PubMed1989

Surface electromyography, force and single motor-unit data for inhibitory reflex responses in human masseter at two levels of excitatory drive.

The inhibitory reflex response evoked by mildly noxious lip stimulation was tested in up to 100 trials at two different levels of pre-stimulus excitation. To regulate that excitation, the subject voluntarily controlled the firing rate of one motor neurone at 10 Hz, and then at 15 Hz while the reflex was tested. When the frequency of the motor-unit action potential (MUAP) in the controlled unit increased or decreased, the frequency of other active units' MUAPs also changed in parallel: that is, the frequency of one MUAP was an index of whole muscle excitation. The inhibitory response in the surface electromyogram (EMG) was quantitated by rectifying and averaging the signal, and by measuring its depth and area. The best correlation between the responses evoked in single units and the response in the whole muscle EMG at the two levels of excitation was obtained when the area of inhibition in the surface record was normalized to the pre-stimulus EMG level. The inhibitory response to lip stimulation in the masseter EMG decreased when the level of pre-stimulus excitation in the muscle was increased. This was confirmed using the reflex response in the averaged force data. The findings suggest that controlling one motor unit's firing rate is a useful method for controlling the whole-muscle excitation in quantitative reflex studies.

Bite Force↗