Electromyographic Bursts Research Articles

Endurance measurement of hyoid muscle activity and hyoid-laryngeal position during tongue lift movement.

Tongue lift movement (TLM) is used as a therapy to improve tongue pressure against the hard palate for dysphagic patients. The present study aimed to characterize the time-dependent endurance changes in hyoid muscle activity and hyoid-laryngeal displacement during TLM in different ways. Sixteen young healthy volunteers were instructed to perform TLM at maximum effort (100%) against the anterior and posterior parts of the hard palate using a balloon-type tongue pressure instrument, followed by a 10-second recording during anterior 80% TLM, anterior 100% TLM, posterior 80% TLM and posterior 100% TLM with visual feedback. Electromyography (EMG) of suprahyoid (S-Hyo) and infrahyoid (I-Hyo) muscles and videofluorography were simultaneously recorded. To evaluate temporal changes, the recording period was divided into three substages: early, middle and late. Tongue pressure, integrated EMG (iEMG), power frequency of EMG burst and hyoid-laryngeal position were compared among the conditions (80% vs 100%, anterior vs posterior and early vs middle vs late). Tongue pressure was stably maintained for 10seconds in all conditions. S-Hyo iEMG and I-Hyo iEMG were significantly greater at 100% than at 80%, while no significant difference was observed between positions. S-Hyo iEMG and I-Hyo iEMG significantly increased at the late stage, while power frequency of EMG burst gradually decreased. Significant temporal changes in laryngeal elevation were observed only in posterior 100% TLM. The current results suggested that isometric posterior TLM may be more useful compared with anterior TLM in clinical situations for dysphagic patients to elevate the hyolaryngeal complex.

Uterine electromyography (EMG) measurements to predict preterm caesarean section in patients with complete placenta previa

The objective of the study was to evaluate uterine electrical activity (EA) with EMG methods in pregnant women with complete placenta previa with preterm caesarean section (CS). This prospective study included 78 patients with complete placenta previa who were recorded for uterine EA activity from 32 to 34 weeks of gestation. The clinical and the uterine EMG burst characteristics, that are responsible for contractions, were compared between a preterm CS group (case group, n = 33) and an elective control group (control group, n = 45). The uterine EA burst duration was longer in the case group compared with the control group (28.79 ± 3.75 vs 19.35 ± 2.56 s; p < .001). Also, the number of burst per 30 min was also higher in the case group compared with the control group (3.28 ± 0.18 vs 1.72 ± 0.22; p < .001), Similarly, the RMS was higher in the case group compared with the control group (0.07 ± 0.01 vs 0.04 ± 0.01 mV; p = .041). In addition, the PDS was higher in the case group compared with the control group (0.47 ± 0.03 vs 0.39 ± 0.02 Hz; p = .023). This study demonstrates that women with complete placenta previa have higher uterine EA at 32–34 weeks of gestation and this is associated with a higher risk of preterm CS due to massive vaginal bleeding. IMPACT STATEMENT What is already known on this subject? Antepartum massive bleeding in complete placenta previa causes maternal and foetal mortality and morbidity, currently there is no effective method to predict it. What do the results of this study add? This study showed in patients with complete placenta previa who were delivered preterm via emergent caesarean section, the uterine electrical activity measured by uterine electromyography (EMG) at 32–34 weeks of gestation had an active pattern What are the implications of these findings for clinical practice and/or further research? Uterine EMG is a potential tool to measure uterine electrical activity and can guide clinical management of patients with complete placenta previa, further study are needed to confirm its effectiveness in a large sample size.

Muscle Function During Feeding Through Infancy

Infant mammalian feeding is a complex process that requires the integration of different behaviors and over twenty‐five muscles controlled by multiple cranial nerves. Despite extensive characterization of muscle activity during a feeding sequence, from suckling to swallowing, specific biomechanics of muscle function are unknown. The function of a muscle is determined by both when the muscle is active and the line of action of the muscle, as well as the change in length during activity. In mammals, there is potential for the line of action of the muscles involved in swallowing to change through ontogeny, as infants have a compressed oropharyngeal anatomy relative to adults. Additionally, while we understand when muscles are active during infant feeding, little has been done to understand whether those activity patterns correspond to concentric, eccentric, or isometric contractions. Here, we used contrast‐based microCT scanning coupled with electromyography (EMG) and fluoromicrometry to test the possibility that muscle function changes through infancy using our validated infant pig model. We collected anatomical data from pigs at infancy and just prior to weaning (21 days old), and isolated muscles of interest in Avizo. We collected EMG and fluoromicrometry data from five muscles involved in feeding (Geniohyoid, Digastric, Stylohyoid, Thyrohyoid, and Omohyoid) at the same ages. We found substantive changes in muscle anatomy through infancy and found extensive variation in muscle firing patterns and function within muscles. Some muscles (eg thyrohyoid) exhibited concentric contractions, whereas other muscles were eccentric (eg omohyoid). Still others exhibited multiple functions, and were eccentric during sucking EMG bursts, but isometric during swallowing EMG bursts (eg geniohyoid). Additionally, we found regional heterogeneity in muscle firing patterns in some muscles (eg stylohyoid), whereby electrodes placed in the middle of the muscle showed activity during swallows, but electrodes placed closer to the hyoid (more ventrally) recorded activity during sucking and swallowing. These results highlight the complexity of infant mammal feeding and demonstrate that muscle activity does not necessarily indicate muscle function. Instead, many muscles that are traditionally thought to function to pull the hyoid along their line of action may actually be functioning to stabilize the hyoid during swallowing. This suggests that control and coordination of the oropharyngeal structures is likely to be more important for successful feeding function than strength or the velocity of moving those structures.Support or Funding InformationAAA Postdoctoral Fellowship

Botulinum Toxin Therapy for Managing Sleep Bruxism: A Randomized and Placebo-Controlled Trial.

The purpose of this study is to evaluate the effects of botulinum toxin type A (BoNT-A) for managing sleep bruxism (SB) in a randomized, placebo-controlled trial. Thirty SB subjects were randomly assigned into two groups evenly. The placebo group received saline injections into each masseter muscle, and the treatment group received BoNT-A injections into each masseter muscle. Audio–video–polysomnographic recordings in the sleep laboratory were made before, at four weeks after, and at 12 weeks after injection. Sleep and SB parameters were scored according to the diagnostic and coding manual of American Academy of Sleep Medicine. The change of sleep and SB parameters were investigated using repeated measures analysis of variance (RM-ANOVA). Twenty-three subjects completed the study (placebo group 10, treatment group 13). None of the SB episode variables showed a significant time and group interaction (p > 0.05) except for electromyography (EMG) variables. The peak amplitude of EMG bursts during SB showed a significant time and group interaction (p = 0.001). The injection decreased the peak amplitude of EMG bursts during SB only in the treatment group for 12 weeks (p < 0.0001). A single BoNT-A injection cannot reduce the genesis of SB. However, it can be an effective management option for SB by reducing the intensity of the masseter muscle.

Effects of a low concentration of ropivacaine on maternal labor force during labor analgesia

Objective To investigate the effects of a low concentration of ropivacaine on the contraction of the uterine and abdominal muscles during labor analgesia. Methods One hundred and fifty primiparous women who expected to have a natural birth were selected. Then, 100 primiparous women were divided into two groups according to the random number table method: a 0.062 5% ropivacaine group (group ropivacaine, n=50) and a 0.062 5% levobupivacaine group (group levobupivacaine, n=50). Meanwhile, 50 primiparous women who did not take analgesic measures during vaginal delivery were set as a control group. Their age, body mass index(BMI), gestational age, cesarean section rate, forceps delivery rate, the duration of the first and second stages of labor, the rate of oxytocin use, and blood loss 2 h after delivery were recorded. The maternal pain was evaluated on the basis of Visual Analogue Scale (VAS) scores at the beginning of labor analgesia (T1), 15 min after labor analgesia (T2), 30 min after labor analgesia (T3) and 45 min after labor analgesia (T4). Then, the parameters of electromyography (EMG) burst wave energy were recorded, including the number and duration of burst waves, root mean square (RMS), and power and peak frequency, so as to comprehensively evaluate the contraction of the uterine and abdominal muscles. Results There was no significant difference in age, BMI, gestational age, cesarean section rate, forceps delivery rate, and blood loss 2 h after delivery among the three groups (P>0.05). Compared with groups control and ropivacaine, group levobupivacaine presented significantly extended duration of the first and second stages of labor, and marked increases in the rate of oxytocin use (P<0.05). Compared with group control, groups ropivacaine and levobupivacaine showed obviously decreased maternal VAS scores at T2, T3, and T4 (P<0.05). In the first stage of labor, compared with group control, the RMS of uterine muscle EMG in groups ropivacaine and levobupivacaine significantly reduced (P<0.05), compared with groups control and ropivacaine, the maternal power of group levobupivacaine significantly reduced (P<0.05). In the second stage of labor, compared with groups control and ropivacaine, group levobupivacaine presented significantly extended duration of EMG burst wave in the uterine muscle (P<0.05), compared with group control, groups ropivacaine and levobupivacaine showed significantly reduced RMS (P<0.05). Conclusions The use of 0.062 5% ropivacaine for epidural analgesia can achieve good effects, without significant impacts on maternal labor force, and does not prolong labor stage. Key words: Ropivacaine; Levobupivacaine; Labor analgesia; Electromyography; Labor stage

Real world use of a neurophysiology service for the differential diagnosis of hyperkinetic movement disorders

IntroductionClinical neurophysiology constitutes a potentially useful aid in differentiating hyperkinetic movement disorders (HMD). Parameters including presence of a Bereitschaftspotential on back-averaged electroencephalography (EEG) have been demonstrated to help distinguish between these disorders. In 2008, a Movement Disorder neurophysiology service was established in Greater Manchester to aid in the diagnostic process. MethodsWe retrospectively reviewed records of patients with HMD who underwent EEG back-averaging through this service from January 2009 until January 2018. The aim was (i) to characterise the clinical features of our patient cohort and (ii) to determine how frequently neurophysiological testing altered the final diagnosis. ResultsA total of 39 patients (23 females, 16 males), with a mean age at onset of 42.6 years and mean disease duration of 2.0 years underwent neurophysiological examination. The clinical diagnosis was changed in 16 cases (41%) and refined in a further seven. Distractibility (P = 0.001), variability (P = 0.002), the presence of a Bereitschaftspotential (P < 0.0001), and electromyography burst duration > 300 ms (P = 0.012) were more frequent in those with an eventual diagnosis of functional movement disorder (n = 24) compared to other HMDs (n = 15). ConclusionNeurophysiology is an invaluable adjunct in complex HMD, altering the diagnosis and treatment options for a significant proportion of patients. Our data also demonstrate, consistent with previous studies, that the majority of patients referred for jerky HMDs to a tertiary movement disorder service have a functional movement disorder.

GABA and glycine neurons from the ventral medullary region inhibit hypoglossal motoneurons.

Obstructive sleep apnea (OSA) is a common disorder characterized by repetitive sleep-related losses of upper airway patency that occur most frequently during rapid eye movement (REM) sleep. Hypoglossal motoneurons play a key role in regulating upper airway muscle tone and patency during sleep. REM sleep activates GABA and glycine neurons in the ventral medulla (VM) to induce cortical desynchronization and skeletal muscle atonia during REM sleep; however, the role of this brain region in modulating hypoglossal motor activity is unknown. We combined optogenetic and chemogenetic approaches with in-vitro and in-vivo electrophysiology, respectfully, in GAD2-Cre mice of both sexes to test the hypothesis that VM GABA/glycine neurons control the activity of hypoglossal motoneurons and tongue muscles. Here, we show that there is a pathway originating from GABA/glycine neurons in the VM that monosynaptically inhibits brainstem hypoglossal motoneurons innervating both tongue protruder genioglossus (GMNs) and retractor (RMNs) muscles. Optogenetic activation of ChR2-expressing fibers induced a greater postsynaptic inhibition in RMNs than in GMNs. In-vivo chemogenetic activation of VM GABA/glycine neurons produced an inhibitory effect on tongue electromyographic (EMG) activity, decreasing both the amplitude and duration of inspiratory-related EMG bursts without any change in respiratory rate. These results indicate that activation of GABA/glycine neurons from the VM inhibits tongue muscles via a direct pathway to both GMNs and RMNs. This inhibition may play a role in REM sleep associated upper airway obstructions that occur in patients with OSA.

Inhibiting errors while they are produced: Direct evidence for error monitoring and inhibitory control in children

The maturation of processes involved in performance monitoring, crucial for adaptive behavior, is a core aspect of developmental changes. Monitoring processes are often studied through the analysis of error processing. Previous developmental studies generally focused on post-error slowing and error-related EEG activities. Instead, the present study aims at collecting indicators of error monitoring processes occurring within trials that is, before the erroneous response is produced. Electromyographic (EMG) activity and force produced during responding were registered in 6 to 14-year-olds performing a choice-response task. As already reported in adults, force produced was weaker, EMG bursts were smaller, and motor times (interval between EMG onsets and responses) were longer during errors compared to correct responses. In contrast, the rising part of EMG burst, reflecting the initial motor command, was the same for both response outcomes. This suggests that error inhibition was applied online after the response was triggered but before the actual key was pressed. This error correction was already present in children as young as 6 years old. The effects of reduced EMG and force amplitudes remained stable across childhood. However, the prolonged motor times in young children suggests that they need more time to implement motor inhibition than their older peers.

Properties of hyoid muscle contraction during tongue lift measurement.

Tongue lift movement (TLM) task is considered a treatment strategy in dysphagic patients. However, there is no evidence of effect of sustained tongue movements on the related muscle contraction. The present study aimed to characterise the properties and time-dependent changes of the electromyographic (EMG) features of suprahyoid muscles during TLM. Twenty young healthy volunteers were instructed to perform TLM at maximum effort in either the anterior or the posterior position, during measurement of tongue pressure for 7s. Supra- (S-hyo) and infra-hyoid (I-hyo) EMGs were recorded. The area and power frequency of EMG burst and the area under the curve of tongue pressure were compared among the conditions: trials (1st, 2nd vs 3rd trials); anterior vs posterior TLM; and early vs late 3s of each trial. There was no difference in the tongue pressure among trials or between the early and late 3s. Anterior tongue pressure was significantly higher than posterior tongue pressure (P<.001). The area of I-hyo EMG burst was significantly larger (P=.044), and the power frequency of I-hyo EMG burst was significantly smaller (P=.042) during posterior TLM than anterior TLM. A significant difference in the power frequency of both EMG bursts was observed between early and late stages during both anterior (P<.05) and posterior (P<.01) TLM. Hyoid muscles may compensate for rapid fatigue of the tongue muscle to maintain tongue pressure by changing their activity pattern during tongue pressure generation.

Activity-Based Training Alters Penile Reflex Responses in a Rat Model of Spinal Cord Injury

IntroductionMultisystem functional gains have been reported in males with spinal cord injury (SCI) after undergoing activity-based training (ABT), including increases in scoring of sexual function and reports of improved erectile function. AimThis study aims to examine the effect of daily 60-minute locomotor training and exercise in general on sexual function in a rat SCI contusion model. MethodsMale Wistar rats received a T9 contusion SCI. Animals were randomized into 4 groups: a quadrupedal stepping group (SCI + QT), a forelimb-only exercise group (SCI + FT), a non-trained harnessed group (SCI + NT), and a home cage non-trained group (SCI + HC). The 2 non-trained groups were combined (SCI) post hoc. Daily training sessions were 60 minutes in duration for 8 weeks. Urine samples were collected during bi-weekly 24-hour metabolic cage behavioral testing. Latency, numbers of penile dorsiflexion, and glans cupping were recorded during bi-weekly penile dorsiflexion reflex (PDFR) testing. Terminal electromyography (EMG) recordings of the bulbospongiosus muscle (BSM) were recorded in response to stimulation of the dorsal nerve of the penis (DNP). OutcomesABT after SCI had a significant effect on PDFR, as well as BSM EMG latency and burst duration. ResultsSCI causes a significant decrease in the latency to onset of PDFR. After 8 weeks of ABT, SCI + QT animals had a significantly increased latency relative to the post-SCI baseline. BSM EMG response to DNP stimulation had a significantly decreased latency and increase in average and maximum amplitude in SCI + QT animals. SCI animals had a significantly longer burst duration than trained animals. Time between PDFR events, penile dorsiflexion, glans cupping, and urine testosterone were not affected by ABT. Clinical ImplicationsABT has a positive influence on sexual function and provides a potential therapy to enhance the efficacy of current sexual dysfunction therapies in the male SCI population. Strengths and LimitationsSeveral significant small improvements in sexual function were found in a clinically relevant rat model of SCI using a readily available rehabilitative therapy. The limited findings could reflect insensitivity of the PDFR as a measure of erectile function. ConclusionsThese results indicate that task-specific stepping and/or loading provide sensory input to the spinal cord impacting the neural circuitry responsible for sexual function.Steadman CJ, Hoey RF, Montgomery LR, et al. Activity-Based Training Alters Penile Reflex Responses in a Rat Model of Spinal Cord Injury. J Sex Med 2019; 16:1143–1154.

Measurement of Uterine and Abdominal Muscle Electromyography in Pregnant Women for Estimation of Expulsive Activities during the 2nd Stage of Labor

Background: The progression of labor and delivery of the fetus is dependent upon uterine contractions and the voluntary effort of abdominal muscle contractions. A good monitor of uterine contractions and pushing is necessary for obstetrical care. Electromyography (EMG) is the underlying basis for contractility of muscle including the myometrium. Objectives: The aim of this study was to determine the relationship between EMG activity of uterine and abdominal muscles and the duration of the 2nd stage of labor in pregnant women. Methods: EMG of both uterine and abdominal muscles was simultaneously recorded from electrodes placed on the abdominal surface of 45 active 2nd stage-laboring nulliparous patients. EMG was recorded using filters to separate uterine and abdominal EMG signals, and various EMG signal parameters were analyzed. The duration of the 2nd stage of labor and other maternal and fetal characteristics were also recorded. Results: Uterine EMG bursts precede abdominal bursts and are accompanied by feelings of “urge to push” by the patients. Abdominal root mean square (RMS) and power, but not uterine EMG parameters, are reduced (p< 0.005) in patients with longer labors and linear regression analysis demonstrated a negative correlation to the duration of 2nd stage of labor (p < 0.001). Multivariate linear regression analysis of clinical characteristics (fetal weight, body mass index, placental location, etc.) and parameters of EMG showed that only abdominal RMS is negatively correlated with the duration of labor. Conclusions: (1) Uterine and abdominal EMG activities reflect the expulsive involuntary (uterine) and voluntary (abdominal) muscular activities during the 2nd stage of labor. (2) RMS and power of abdominal EMG diminish with longer labor when uterine EMG intensities are similar. (3) Recording of uterine and abdominal muscle activity provides objective evaluation of the muscle activity during the 2nd stage of labor and may aid in the evaluation of any interventions.

Voluntary control of forward leaning posture relates to low-frequency neural inputs to the medial gastrocnemius muscle

BackgroundVariability is an inherent feature of the motor output. Although low-frequency oscillations (<0.5 Hz) are the most important contributor to the variability of force during single-joint isolated force tasks, it remains unclear whether they contribute to the variability of a more complex task, such as a voluntary postural task. Research questionDo low-frequency oscillations contribute to postural sway (center of pressure (COP) variability) when participants attempt to voluntarily maintain posture in a forward leaning position? MethodsFourteen healthy young adults performed two tasks: 1) stand quietly (control condition); 2) leaned their body forward to 60% of their maximum lean distance by dorsiflexing the ankle joint. We recorded the COP and electromyographic (EMG) activity from the medial gastrocnemius (MG) and soleus (SL) muscles. We quantified the following: 1) COP variability as the standard deviation (SD) of anteroposterior COP displacements; 2) modulation of COP as the power in COP displacements from 0 to 2 Hz; 3) modulation of EMG bursting as the power in the rectified and smoothed EMG from 0 to 2 Hz; 4) modulation of the interference EMG as the power in the EMG from 10 to 35 and 35–60 Hz. ResultsThe SD of COP displacements related to the COP oscillations <0.5 Hz in both quiet standing and lean tasks. However, only for the lean task, the <0.5 Hz COP oscillations related to the EMG burst oscillations <0.5 Hz of the MG muscle. The EMG burst oscillations <0.5 Hz of the MG muscle further related to the interference EMG oscillations from 35 to 60 Hz for the lean task. SignificanceVoluntary control of forward leaning posture relates to low-frequency neural inputs to the MG muscle.

Involvement of hypoglossal and recurrent laryngeal nerves on swallowing pressure.

Swallowing pressure generation is important to ensure safe transport of an ingested bolus without aspiration or leaving residue in the pharynx. To clarify the mechanism, we measured swallowing pressure at the oropharynx (OP), upper esophageal sphincter (UES), and cervical esophagus (CE) using a specially designed manometric catheter in anesthetized rats. A swallow, evoked by punctate mechanical stimulation to the larynx, was identified by recording activation of the suprahyoid and thyrohyoid muscles using electromyography (EMG). Areas under the curve of the swallowing pressure at the OP, UES, and CE from two trials indicated high intrasubject reproducibility. Effects of transecting the hypoglossal nerve (12N) and recurrent laryngeal nerve (RLN) on swallowing were investigated. Following bilateral hypoglossal nerve transection (Bi-12Nx), OP pressure was significantly decreased, and time intervals between peaks of thyrohyoid EMG bursts and OP pressure were significantly shorter. Decreased OP pressure and shortened times between peaks of thyrohyoid EMG bursts and OP pressure following Bi-12Nx were significantly increased and longer, respectively, after covering the hard and soft palates with acrylic material. UES pressure was significantly decreased after bilateral RLN transection compared with that before transection. These results suggest that the 12N and RLN play crucial roles in OP and UES pressure during swallowing, respectively. We speculate that covering the palates with a palatal augmentation prosthesis may reverse the reduced swallowing pressure in patients with 12N or tongue damage by the changes of the sensory information and of the contact between the tongue and a palates. NEW & NOTEWORTHY Hypoglossal nerve transection reduced swallowing pressure at the oropharynx. Covering the hard and soft palates with acrylic material may reverse the reduced swallowing function caused by hypoglossal nerve damage. Recurrent laryngeal nerve transection reduced upper esophageal sphincter negative pressure during swallowing.

Effects of vaginal progesterone for maintenance tocolysis on uterine electrical activity.

The effectiveness of vaginal progesterone for maintenance tocolysis after arrested preterm labor remains controversial. Myometrial contractility can be assessed objectively and non-invasively after progesterone treatment by monitoring uterine electromyography (EMG). We examined the effects of vaginal progesterone on uterine EMG after successful acute tocolysis. This was a randomized, double-blind, single-center study performed between 2012 and 2015. Thirty women who experienced preterm labor between 24 0/7 and 33 6/7 weeks were randomly allocated to groups administered either 400 mg vaginal progesterone or a placebo 48 h after acute tocolysis. EMG measurements were taken prior to and 1 h and 2 h following treatment. Mann-Whitney U tests were used to compare EMG power density spectrum peak frequency and peak amplitude, propagation velocity of EMG signals, and duration and number of EMG bursts in 30 min recordings between the groups (P < 0.05). EMG propagation velocity was higher in patients receiving the placebo compared to those treated with progesterone at 1 h (27.83 ± 10.66 vs 15.60 ± 2.94 cm/s) and 2 h (26.97 ± 13.39 vs 15.12 ± 2.58 cm/s) following treatment (P = 0.001). PDS peak frequencies were higher in the placebo compared to the progesterone group at 2 h following treatment (0.54 ± 0.11 vs 0.44 ± 0.06 Hz; P = 0.003). Treatment of 400 mg of vaginal micronized progesterone as maintenance tocolysis significantly reduces the propagation velocity of electrical signals within the myometrium and is associated with a shift toward lower uterine electrical signal frequencies.

Palatal Tremor Revisited: Disorder with Nosological Diversity and Etiological Heterogeneity.

This case series aimed to describe clinicoradiological, electromyographic, and etiological spectra in palatal tremor (essential=1; symptomatic=26). Patients with symptomatic palatal tremor had 2 to 10 Hz arrhythmic electromyographic bursts, a spectrum of changes in inferior olivary nucleus, with/without lesions in Guillain Mollaret triangle, and varied etiologies (genetic=9, vascular=6, trauma=3, infections=3). Exome sequencing showed variations in POLG, WDR81, NDUFS8, TENM4, and EEF2. Clinical phenotypes of patients with POLG, WDR81, and NDUFS8 variations were consistent with that described in literature. We highlight salient magnetic resonance imaging features, electrophysiological observations, and diverse etiologies in a large cohort of palatal tremor.

Uterine and Abdominal Muscle Electromyographic Activities in Control and PCEA-Treated Nulliparous Women During the Second Stage of Labor.

Patient-controlled epidural analgesia (PCEA), used to relieve pain during delivery, delays labor but the mechanism is unknown. The aim was to investigate the effects of PCEA on uterine and abdominal muscles electromyographic (EMG) activity during the second stage of labor. This study included 45 nulliparous pregnant women without PCEA, 42 women with standard PCEA treatment given during the first stage of labor and stopped near the end of the first stage, and 22 women with standard PCEA treatment with continued use throughout the first and second stages of labor. The EMG signals were recorded from the abdominal surface using PowerLab hardware and LabChart software (ADInstruments, New South Wales, Australia) and filtered to separate uterine and abdominal EMG. Various EMG burst parameters were obtained. There are no differences ( P > .05) in the age, body mass index, fetal weight, and Apgar scores between the patients from the various groups. PCEA (both stopped and continued) inhibits ( P < .05) duration, number of bursts, and root mean square of uterine EMG. PCEA also produces statistically significant ( P < .001) reductions in abdominal EMG. The decrease in EMG activity is accompanied by a significant ( P < .001) prolongation of the second stage duration (PCEA continued = 95.08 ± 8.60 minutes, PCEA stopped = 79.39 ± 6.25 minutes, no PCEA = 61.00 ± 7.23 minutes). PCEA suppresses uterine and abdominal muscle EMG during the second stage of labor but inhibition depends upon the treatment schedule. PCEA prolongs the duration of labor by inhibition of uterine and abdominal muscle and neural activity.

Relationships between chewing rate, occlusion, cephalometric anatomy, muscle activity, and masticatory performance

ObjectiveMastication consists of rhythmic jaw openings and closings. Recent studies suggest that muscle mechanical properties determine the rhythmic rate; however, speed-accuracy tradeoffs may also play a role. This study evaluated how variation in chewing rate affected chewing performance, how masticatory muscle activity varied with chewing rate, and whether morphology and demographics contributed to performance. DesignChewing performance and muscle activity were sampled in 23 healthy, fully-dentate adults, who chewed a standardized test food to a metronome set at 0.5, 0.75, 1, 2 and 3 times their ‘natural’ chewing rates. Subjects produced ten chews per trial, and five trials for each of the five rates. Surface electromyographic (EMG) activity was sampled from masseter and temporalis muscles bilaterally. Demographic, occlusal, and cephalometric data were also obtained. ResultsChewing performance, defined by median particle size, was inversely related to chewing rate; however, performance was not remarkably improved at rates slower than the natural chewing rate. Above the natural chewing rate, variability in EMG bursts diminished, suggesting a reduction in muscle activity modulation at fast rates. Occlusal contacts and most morphological features appeared to play a limited or no role in performance. ConclusionsResults support the hypothesis that the ‘natural’ chewing rate is selected to be as fast as possible while providing sufficient time to allow EMG modulation for improved performance. The interplay between EMG modulation and individual variation in skeletal morphology is likely critical for optimal chewing performance.

Temporal and spatial characteristics of post-silent period electromyographic bursting in low back muscles: comparison between persons with and without low back pain

ABSTRACTPurpose/aim: Recently, a novel measure of cortical disinhibition was identified using transcranial magnetic stimulation (TMS). This measure, described as post-silent period electromyographic (EMG) bursting, may inform on the corticomotor control of movement in health and disease; however, it has not been investigated for muscles outside the hand or in musculoskeletal conditions. Thus, the aim of this study was to investigate the temporal and spatial characteristics of “EMG bursting” in individuals with and without low back pain (LBP).Materials and Methods: TMS was used to map the motor cortical representation of paraspinal muscles in 11 individuals with LBP and 11 pain-free controls. The latency, duration and magnitude of bursting, number of active burst sites, map volume and coordinates of the burst “hotspot” were compared between the groups.Results: In pain-free controls, the latency, duration and magnitude of bursts were similar to the hand; however, bursts occurred earlier and were of smaller magnitude in LBP. Bursting was widespread throughout the cortical representation in both groups; however, there was a trend towards smaller mean EMG burst and map volume in LBP.Conclusions: We confirm the presence of EMG bursting in back muscles and provide a description of the spatial profile of this mechanism. Our observations in LBP suggest that cortical disinhibition may be altered in this condition.

Children with chronic stress-induced recurrent muscle pain have enhanced startle reaction.

Children with recurrent pain of negative chronic stress origin from different locations have a characteristic pattern of tender points in the temporal, trapezoid, great pectoral and abdominal muscles. We tested the hypothesis that the startle reaction is activated in these children and that some of the startle-activated muscles are related to the tender point pattern and the recurrent pain. In children/adolescents, aged 10-17years, 19 with recurrent psychosomatic pain (PAIN) and 23 controls (CON) we measured and analysed resting activity and acoustic startle response with electromyography (EMG) for the muscles involved in the pattern of tender points and also the lumbar erector spinae. The PAIN group showed higher resting activity and higher acoustic startle response values than the CON group for all six muscles together regarding the mean amplitude in the initial 200ms, and during the burst of activity, and longer burst duration and shorter burst latency. For PAIN versus CON, all separate muscles showed generally higher values of EMG amplitudes and burst durations, and shorter latencies for the burst onset in all measures; with significance or strong trends for several parameters and muscles. For the first time in children with recurrent psychosomatic pain, increased resting activity and potentiated startle response were demonstrated in the muscles involved in the stress tender point pattern. This study demonstrates in adolescents how recurrent pain of negative stress origin from the head, stomach, back and chest is related to increased startle reaction and increased muscular tension in these regions. This study contributes to the understanding of the mechanisms underlying the global burden of recurrent pain.

The Difficulty Of EMG Burst Identification

Surface electromyography (EMG) is commonly used to add physiologic context to observed patterns of movement. The onset of the EMG is often used to determine when a person responds to stimuli or to identify maladaptive muscle coordination strategies. Our research group has previously shown that Bayesian Changepoint Analysis (BCP) is superior to the standard linear envelope methodologies when determining a single EMG onset in a data series. PURPOSE: Examine the effectiveness of visual inspection and the novel BCP algorithm to detect EMG bursts in multiple muscles during complex movements. METHODS: Muscle activity from 10 healthy subjects was collected from the gastrocnemius, biceps femoris, and vastus lateralis muscles using surface EMG electrodes (4kHz sampling rate). Subjects completed 4 minutes of exercise on three modalities: treadmill running, ergometer cycling and stair climbing. All exercises were performed at self-selected low-to-moderate intensities. Six to ten seconds of EMG was collected at 90 and 210 seconds into the exercise. Three researchers visually identified the number of bursts in a trial twice (randomized, double-blind methodology). The instances where all six identifications (three reviewers, twice) agreed on the number of bursts, were compared with the identification results from the BCP algorithm. RESULTS: While the within rater reliability (ICC: 0.85) and between rater reliability (ICC: 0.83) were good, the visual review only resulted in 111 trials (out of 180) where all raters agreed on the number of bursts (61.7% total agreement). The correlation between the number of bursts raters identified and the BCP algorithm was moderate (Pearson’s R: 0.52). Furthermore, across all trials, there was a difference of 711 EMG bursts between the two methods. CONCLUSIONS: While visual assessment of the EMG is the “gold standard” for burst detection, its reproducibility is generally poor in dynamic tasks. Despite initial success with the BCP algorithm in determining EMG onset, the current iteration of the algorithm is insufficient for EMG burst identification in complex waveforms. This work highlights the need for a standardized algorithm of EMG burst detection, but also indicates that further work is necessary to make algorithms of sufficient accuracy and reliability.