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At least 1,531 records · Page 85Linked to original sources
PubMed2002

Multiple motor unit recordings of laryngeal muscles: the technique of vector laryngeal electromyography.

OBJECTIVES: To display time-series firing rate and recruitment data for multiple, simultaneously active motoneurons activating human laryngeal muscles. These data provide specific information about how laryngeal muscle force is being controlled by the central nervous system at the level of the lower motoneuron. METHODS: A quadrifilar needle electrode was used to record multi-channel myoelectric signals from thyroarytenoid muscle of normal subjects during tasks ranging from quiet breathing to a short sentence. Motor unit action potentials of the signal space were identified and tracked throughout task productions using pattern recognition and Precision Decomposition software. RESULTS: We present the first recordings and analyses of multiple motor unit activations in the larynx. The firing times and mean firing rates are plotted for each identified motor unit, which reveal recruitment and decruitment information and the database from which common firing statistics across motor units may be derived. CONCLUSIONS: This study provides new information about neuromuscular physiology of the larynx. Specifically, the results reveal the ordered recruitment and firing patterns of multiple motor units and the existence of common drive from the central nervous system. The technique may prove fundamental to understanding various neuromuscular pathologies such as laryngeal spasm and to assist clinical prognosis of laryngeal paresis and the diagnosis of certain neurogenic disorders.

Adult↗
PubMed2001

Leg electromyography and the VO2-power relationship during bicycle ergometry.

PURPOSE: The relationship between oxygen consumption and power is not linear. The purpose of this investigation was to examine the nature of the relationship and the cause of the nonlinearity. METHODS: Eight male cyclists (60.5 +/- 3.8 mL O2.min-1.kg(-1) VO2 peak) completed an incremental exercise test (1 W.5 s(-1)) to exhaustion. VO2 was measured every breath, and rmsEMG was recorded continuously over the belly of vastus lateralis, biceps femoris, and lateral gastrocnemius. RESULTS: VO2 is a linear function of power in moderate exercise; the slope of the linear portion was approximately 9.7 mL O2.min(-1).W(-1), which is consistent with the steady state gain for moderate exercise. Beyond this initial break from linearity, the VO2.W(-1) plot demonstrates a second break that is not different from the point of respiratory compensation (break in VE.VCO2(-1)). These breaks were coincident with increased neuromuscular activity (1st break: 194 +/- 27 W for VO2, 191 +/- 25 W for vastus lateralis; 2nd break: 262 +/- 34 W for VO2, 258 +/- 27 W for vastus lateralis) and corresponded to approximately 58% VO2 peak for the first and 75% VO2 peak for the second break. CONCLUSIONS: VO2 is not a linear function of power. During an incremental test, neuromuscular activity and VO2 increase more rapidly in heavy exercise. Both VO2 and neuromuscular activity exhibit a second break at very high power output, which may mark an upper limit for sustainable exercise.

Adult↗
PubMed2000

Quantitative parameters of intraoperative electromyography predict facial nerve outcomes for vestibular schwannoma surgery.

OBJECTIVE: Facial nerve monitoring is an established method that is routinely used during cerebellopontine angle tumor surgery. The aim of this study was to determine quantitative electromyographic (EMG) parameters that were predictive of facial nerve outcomes. METHODS: In 137 patients with intra-/extrameatal vestibular schwannomas, the most proximal (the exit from the brainstem) and distal (the fundus of the internal auditory canal) parts of the facial nerve were stimulated after total tumor removal. A quantitative analysis of absolute values and ratios (proximal/distal) of evoked EMG parameters (amplitude, latency, and duration) was performed, and parameters were correlated with postoperative (1 and 6 wk and 6 mo) facial nerve function (FNF). RESULTS: Absolute values of EMG amplitudes were statistically correlated with FNF (P < 0.05). Amplitude ratios (proximal/distal) demonstrated an even greater predictive power. The risk of exhibiting facial palsy 6 months after surgery increased from 1.6% (amplitude ratio of >0.8) to 75% (ratio of <0.1). For EMG latencies, only the ratios revealed a significant correlation with FNF. The latency ratio-dependent risk of facial palsy after 6 months increased from 2.9% (ratio of <1.05) to 33% (ratio of >1.35). The durations of the muscle responses were not significantly correlated with clinical outcomes. CONCLUSION: The predictive power of the amplitudes and latencies of electrically evoked muscle responses could be improved by calculating proximal/distal ratios. The proximal/distal amplitude ratio proved to be the most powerful parameter for intraoperative assessment of postoperative FNF.

Adult↗
PubMed1978

A study of the evoked electromyography of the superior orbicularis oris muscle in man.

A study was made of the impulse conduction speed by moving recording electrodes at 5 mm intervals, successively, after stimulating facial nerves on one side in normal subjects. The findings showed that the speed of the potentials was fast and the amplitude was large, up to a distance of 0.5 cm across the midline. This makes us believe that there is an intermingling, of approximately one cm, of the left and right superior orbicularis oris muscles. Evoked potentials were recorded up to 1.5 to 2.5 cm across the midline--but as the speed reduced abruptly and the amplitude became small, we believe these potentials were conveyed by volume conductors. Six patients with facial palsy were studied, but in none were these findings indicating any reinnervation from the normal side. However, the conduction speed was delayed in them (as compared to normal subjects).

Adolescent↗
PubMed1979

Predicting by electromyography the results of nonsurgical treatment of temporomandibular joint syndrome.

This study of 308 patients demonstrated that reliance upon physical findings alone is not reliable for the diagnosis and the prediction of treatment success in TMJS. However, those patients who had a lengthened masseteric silent period on the EMG had a 93% success rate from treatment with occlusal splint and occlusal adjustment. In contrast, those patients who had a normal masseteric silent period on the EMG had only a 21 percent success rate from the same therapy.

Adolescent↗
PubMed1995

Fatigue of the erector spinae muscles. A quantitative assessment using "frequency banding" of the surface electromyography signal.

STUDY DESIGN: The authors investigated fatigue-induced changes in the frequency content of the surface electromyographic (EMG) signal from the erector spinae muscles. OBJECTIVES: The objective of the study was to understand the EMG changes in fatiguing muscle and to obtain a reliable index of fatigue. SUMMARY OF BACKGROUND DATA: Power spectral analysis has been used increasingly in recent years to monitor muscle fatigue, but parameters other than the mean or median frequency have received little attention. METHODS: Thirty-five healthy volunteers participated. They pulled upward with constant force on a handlebar attached to a floor-mounted load cell while the EMG signal from the erector spinae was recorded at the levels of T10 and L3 at 1024 Hz; 1.0-sec "windows" of the signal were analyzed using fast Fourier transforms, and the resulting power spectra were divided into 10 frequency bands between 5 Hz and 300 Hz. The median frequency, total power, and peak amplitude of the spectra were also calculated. Changes in the frequency content of the EMG signal were examined during submaximal contractions of different intensity and duration. RESULTS: Median frequency decreased steadily during the contractions, whereas total power and peak amplitude increased. The most repeatable and linear index of change was the increase in the EMG signal in the 5-30 Hz frequency band. The middle-to-high frequency component of the EMG signal increased during the early stages of the contractions, but decreased as the endurance limit was approached. CONCLUSIONS: Changes in the 5-30 Hz band of the EMG power spectrum provide a more reliable and linear index of fatigue in the erector spinae muscles than do changes in median frequency. In the erector spinae, the early effects of fatigue appear to be delayed by the recruitment of additional motor units.

Adult↗
PubMed1999

Wavelet analysis of electromyography for back muscle fatigue detection during isokinetic constant-torque exertions.

STUDY DESIGN: An investigation of the effects of human trunk extensor muscle fatigue on the temporal change in frequency content of the electromyogram as quantified using the Fourier and wavelet transforms during the performance of repetitive dynamic trunk extension. OBJECTIVE: To evaluate whether alterations in the Fourier and wavelet transform measures were consistent with a shift of the signal power to lower frequencies, and to determine which measures were more highly correlated with the decline in maximal trunk extension torque. SUMMARY OF BACKGROUND DATA: Objective assessment of trunk muscle fatigue is likely to play a more important role in the rehabilitation and prevention of low back injuries, given the association between lack of trunk muscle endurance and acquisition of low back pain. Validation of new methods designed to quantify the level of fatigue using the surface electromyogram is necessary before these techniques can be used in industrial rehabilitation settings. The wavelet transform is a recent development in the signal processing of electromyograms that shows promise as a method for assessment of fatigue. METHODS: Trunk muscle electromyograms obtained from study participants performing repetitive isokinetic trunk extension endurance tests were analyzed using the wavelet and the traditional Fourier methods. Trunk extension torque was controlled at 35% and 70% of the participants' maximal voluntary contraction while they exerted at 5 and 10 repetitions per minute. The decline in maximal trunk extension torque was measured once per minute. Linear regression quantified the rate of change in Fourier and wavelet measures caused by fatigue, whereas Pearson's correlation coefficient determined their association with the decline in maximum torque. RESULTS: Changes in the characteristics of the electromyogram were consistent with a shift to lower frequencies: The signal power at higher frequencies was reduced, whereas the power at lower frequencies was elevated. The amount of change was dependent on the task conditions (exertion level and repetition rate). The wavelet-based measures demonstrated as strong an association with the decline in maximal torque output as the Fourier-based measures. CONCLUSIONS: This study demonstrates that assessment of trunk muscle fatigue during isokinetic movementis possible using both Fourier and wavelet measurements. However, the methods were not as likely to change significantly during lower rates of exertion. These methods, when implemented in a controlled setting, may be used to document the rehabilitation process and guide preventive exercise training.

Adult↗
PubMed2001

Effects of electrical stimulation of the sciatic nerve on background electromyography and static stretch reflex activity of the trunk muscles in rats: possible implications of neuronal mechanisms in the development of sciatic scoliosis.

STUDY DESIGN: The effects of electrical stimulation of the sciatic nerve on background electromyographic and static stretch reflex activity of the trunk muscles were studied. OBJECTIVES: To verify the hypotheses that sciatic scoliosis is induced reflexively by radiculopathic pain, and that scoliosis might be maintained by prolonged asymmetric alteration of the trunk muscle tonus caused by central sensitization of the spinal neurons that constitute the postural reflex pathways. SUMMARY OF BACKGROUND DATA: Sciatic scoliosis usually occurs with convexity to the side of the herniated disc. The neuronal mechanism of sciatic scoliosis has not been well clarified. Recently, prolonged alteration of motor function in the hindlimbs of animals caused by central sensitization has been reported. METHODS: In spinalized rats (transection of the spinal cord), the sciatic nerve was stimulated electrically as a conditioning stimulus. Muscle stretch elicited by bending of the lumbar spine was applied as a test stimulus. Background and stretch reflex activities of the bilateral oblique abdominal, psoas, and quadratus lumborum muscles were recorded. Rats in which MK-801, an N-methyl-d-aspartate antagonist, was preadministered also were used. RESULTS: The conditioning stimulus enhanced background electromyographic activity in bilateral oblique abdominal, contralateral psoas, and quadratus lumborum muscles. Furthermore, the conditioning stimulus induced prolonged facilitation and depression of stretch reflex activity of the contralateral psoas and quadratus lumborum, and ipsilateral psoas and quadratus lumborum muscles, respectively. Preadministration of MK-801 reduced these excitatory and inhibitory effects. CONCLUSION: It was found that the pattern of electromyographic activity of the trunk muscles evoked by sciatic nerve stimulation coincided with the typical direction of sciatic scoliosis in patients with lumbar disc herniation. It was supposed that the prolonged asymmetric alteration of the trunk muscle tonus was caused by central sensitization, and that central sensitization of spinal neurons may underlie the neuronal mechanism of sciatic scoliosis.

Animals↗
PubMed2004

The relation between electromyography and growth velocity of the spine in the evaluation of curve progression in idiopathic scoliosis.

STUDY DESIGN: A prospective study in which patients with idiopathic scoliosis were examined longitudinally by radiographic and electromyographic measurements according to a protocol. OBJECTIVES: To measure the growth velocity of the spine and the electromyographic ratio of the paraspinal muscles to determine their relation to progression of the scoliotic curve. SUMMARY OF BACKGROUND DATA: Several factors have been reported to be involved in the progression of idiopathic scoliosis. Possible factors may be growth disturbances and muscular abnormality. METHODS: Thirty patients with idiopathic scoliosis were examined over periods of 4 to 5 months. The periods were scored for progression, defined as an increase in Cobb angle of >10 degrees. Spinal growth velocity was measured as the length difference of the scoliotic spine between two consecutive radiographs. The electromyographic activity on both sides of the spine expressed as an electromyographic ratio was measured during relaxed upright standing using bipolar surface electrodes. Predictability of progression was evaluated with regression analysis and receiver operating characteristic analysis. RESULTS.: There was an independent association between both spinal growth velocity and electromyographic ratio and progression of the scoliotic curve. An equal sensitivity and specificity of spinal growth velocity for progression of 79.1% was observed at a growth velocity cutoff point of 11 mm/year. Similarly, a cutoff point of 1.25 for the electromyographic ratio could be determined with a predictive value for progression of 68.9%. In the presented nomogram, a spinal growth velocity >15 mm/year combined with an electromyographic ratio >2 gave an 89% probability of progression of the scoliotic deformity. Growth velocities 38 mm/year never resulted in progression. CONCLUSIONS: The combined measurement of spinal growth velocity and electromyographic ratio has significant predictive potential and may be valuable in the evaluation and treatment of idiopathic scoliosis.

Adolescent↗
PubMed1985

Investigations of long-term treatment with perhexiline maleate using therapeutic monitoring and electromyography.

Experience is reported with 41 patients taking perhexiline maleate for angina pectoris for periods of up to 70 months, while serum concentrations of the drug were monitored, and liver function tests and electromyographic tests were made before and during treatment. Severe side effects did not occur unless serum perhexiline levels were greater than 1.5 mg/L. The drug seems effective for prolonged dosage, and the monitoring of weight, liver function test results, and serum concentrations should prevent or reduce toxicity. A starting dose of 100 mg daily is recommended. The drug is not recommended for routine use in angina pectoris.

Adult↗
PubMed2006

Comparison of shock transmission and forearm electromyography between experienced and recreational tennis players during backhand strokes.

OBJECTIVE: To test the hypothesis that recreational tennis players transmit more shock impact from the racket to the elbow joint than experienced tennis players during the backhand stroke. Also, to test whether recreational tennis players used higher electromyographic (EMG) activities in common wrist extensor and flexor around epicondylar region at follow-through phase. DESIGN: A repeated-measure, cross-sectional study. SETTING: National College of Physical Education and Sports at Taipei, Taiwan. PARTICIPANTS: Twenty-four male tennis players with no abnormal forearm musculoskeletal injury participated in the study. According to performance level, subjects were categorized into 2 groups: experienced and recreational. MAIN OUTCOME MEASUREMENTS: Impact transmission and wrist extensor-flexor EMG for backhand acceleration, impact, and follow-through phases were recorded for each player. An independent t test with a significance level of 0.05 was used to examine mean differences of shock impact and EMG between the 2 test groups. One-way ANOVA associated with Tukey multiple comparisons was used to identify differences among different impact locations and EMG phases. RESULTS: Experienced athletes reduced the racket impact to the elbow joint by 89.2%, but recreational players reduced it by only 61.8%. The largest EMG differences were found in the follow-through phase (P<0.05). Experienced athletes showed that their extensor and flexor EMGs were at submaximal level for follow-through phase, whereas recreational players maintained their flexor and extensor EMGs at either supramaximal or maximal level. CONCLUSIONS: Our results support the hypothesis that recreational players transmit more shock impact from the racket to the elbow joint and use larger wrist flexor and extensor EMG activities at follow-through phase of the backhand stroke. Follow-through control is proposed as a critical factor for reduction of shock transmission. Clinicians or trainers should instruct beginners to quickly release their grip tightness after ball-to-racket impact to reduce shock impact transmission to the wrist and elbow.

Adult↗
PubMed2005

Four-channel electromyography of the facial nerve in vestibular schwannoma surgery: sensitivity and prognostic value for short-term facial function outcome.

OBJECTIVE: To evaluate the short-term facial prognostic value of a four-channel facial electromyographic device in vestibular schwannoma surgery. STUDY DESIGN: Eighty-nine vestibular schwannomas operated on and intraoperatively monitored by a four-channel facial electromyographic device between October 2002 and September 2003 were included in this prospective study. Detection was performed in frontal, orbicularis oculi, orbicularis oris, and platysma muscles. MAIN OUTCOME MEASURE: Facial function grading at postoperative Days 1, 8, 30, and 180 (House-Brackmann classification). SETTING: Tertiary referral center. RESULTS: Postoperative facial function at Day 180 was assessed as Grade 1 or 2 in 80%, as Grade 3 or 4 in 16%, and as Grade 5 or 6 in 4% (n=80). The postoperative facial function was related to the intraoperative nerve stimuli thresholds (range, 0.01-3 mA for a response >100 microV) near the brainstem and the proximal-to-distal ratio of the stimulation threshold. A proximal threshold between 0.01 and 0.04 mA had a positive predictive value of 94% for good facial function (Grade 1 or 2). The proximal threshold was lower in patients with improving or stable facial function in comparison with those with a delayed deterioration between Days 8 and 30. The stimulation threshold at the adhesion zone was related to the immediate facial function outcome. The maximal electromyographic response was detected in the frontal muscle or the platysma in 27% of cases and in orbicularis oris and oculi in 73% of cases. CONCLUSION: A four-channel device may enhance electromyographic sensitivity. Determination of stimulation threshold below 0.05 mA yields facial prognostic information.

Adolescent↗
PubMed2003

Biomechanics and electromyography of a common idiopathic low back disorder.

STUDY DESIGN: In vivo feline preparation groups loaded into lumbar flexion at different magnitudes and an unloaded control group. OBJECTIVE: To demonstrate that a static, constant load flexion of the lumbar spine results in a complex neuromuscular disorder. SUMMARY OF BACKGROUND DATA: Epidemiology suggests that static lumbar flexion is a cause of low back disorders. There is little direct experimental evidence describing the physiologic and biomechanical processes that elicit the disorder. Recent evidence shows that static flexion of the spine under constant displacement results in muscular spasms and a prolonged recovery period. The response of the spine to flexion under constant load of various magnitudes (as opposed to constant displacement) is not known. It was hypothesized that static lumbar flexion under constant load may elicit creep in spinal ligaments, discs, etc., causing microdamage and development of a neuromuscular disorder. METHODS: The lumbar spine of the feline was subjected to 20 minutes of constant load static flexion at physiologic load intensities from light to heavy while creep of lumbar viscoelastic tissues and EMG from the multifidus muscles of L3-L4 to L5-L6 were recorded. Recordings were continued over a 7-hour rest period after the static flexion was terminated. RESULTS: Spasms and decreasing reflexive EMG were evident during the loading period, and a transient surge of EMG activity occurred at the beginning of the rest period. A second surge of EMG activity was seen 3-4 hours later. The four components of the neuromuscular disorder were present regardless of the load magnitude. A model was developed to quantify the disorder. CONCLUSION: A four-component neuromuscular disorder was elicited by a 20-minute constant load static flexion even when very light loads were applied. The disorder was elicited by creep of the viscoelastic tissues, which resulted in spasms and muscular hyperexcitability lasting for >24 hours. Although the disorder was transient, the physiologic and biomechanical principles associated with its development could also explain cumulative trauma disorders.

Animals↗
PubMed2004

Ability of a normal dysfunctional voiding symptom score to predict uroflowmetry and external urinary sphincter electromyography patterns in children.

PURPOSE: We correlated uroflowmetry/electromyography (EMG) patterns and post-void residual urine volume (PVR) in children with a normal dysfunctional voiding symptom score (DVSS) and determined whether a normal DVSS can predict uroflowmetry/EMG/PVR results. MATERIALS AND METHODS: We prospectively studied 51 children with a normal DVSS, and negative neurological and urological history who underwent uroflowmetry/EMG and PVR measurements. Statistical results were correlated with patient age and gender using Cohen's kappa and Fisher's exact test. RESULTS: All children had a normal DVSS for gender and 37 (73%) had bell-shaped uroflowmetry curves. Eight of the 14 children with nonbell-shaped uroflowmetry curves had plateaued and 6 had fractionated curves. Five boys and 13 girls (35%) had decreased EMG patterns, 7 boys and 8 girls (29%) had increased patterns and 5 boys and 13 girls (35%) had variable patterns (Cohen's kappa score 0.11). Of the 37 children (65%) with bell-shaped uroflowmetry curves 24 had normal PVR, while 13 of 37 (35%) had elevated PVR. Eight of the 14 children (57%) with nonbell-shaped uroflowmetry curves had normal PVR and 6 (43%) had elevated PVR (Cohen's kappa score 0.13). Seven of 37 children (19%) with bell-shaped uroflowmetry curves and 7 of 14 (50%) with nonbell-shaped uroflowmetry curves had a significantly distended bladder (p = 0.04). Nine of the 14 children (64%) with a significantly distended bladder had abnormal PVR. Ten of the 37 children (27%) without a significantly distended bladder had abnormal PVR (p = 0.02). CONCLUSIONS: Normal DVSS for gender is able to predict a bell-shaped uroflowmetry curve in most children, while EMG patterns and PVR do not correlate with uroflowmetry curves in these children. Children with a significantly distended bladder frequently have nonbell-shaped uroflowmetry curves as well as elevated PVR.

Adolescent↗