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Purpose: The aim of this study is to define the intramuscular nerve distribution of the sternocleidomastoid muscle (SCM) and the innervation zones (IZ) to describe the optimal botulinum toxin injection sites. Methods: The cricoid cartilage (CC), laryngeal prominence (LP) and hyoid bone (HB) and angle of mandible (AM) were determined as landmarks. The length of the muscles were measured between the sternoclavicular joint and tip of the mastoid process. SCM was evaluated in two parts as anterior and posterior divided by the line where the length of the muscle was measured. Measurements were made to define the relationships of the SCM with common carotid artery, internal and external jugular veins. IZ were described according to these vessels. Afterwards, Modified Sihler's staining technique was applied to expose the intramuscular nerve distribution. Results: The average length of SCM was 160,1 mm. Motor entry point of the accessory nerve fibers were between the AM-HB lines, in the range of 30–40% of the muscle length, and in the posterior part of the muscles. IZ were between the HB-CC lines in the anterior and posterior part. When this interval was examined according to the vessels, the optimal injection sites were between the LP-CC lines. Conclusions: This study shows the position of the intramuscular nerve fibers endings of the SCM according to the chosen landmarks and the relationship of the IZ with the vessels to prevent complications. These results can be used as a guide for safe and effective botulinum toxin injections with optimal quantities. [ABSTRACT FROM AUTHOR]

Localization of motor unit (MU) innervation zones (IZs) is an important step in several clinical and non-clinical applications, such as 1) acquisition of surface electromyogram (sEMG) signal for accurate estimation of its amplitude and other parameters by avoiding placing electrodes on IZs, 2) accurate estimation of the EMG-Force relationship, 3) effective injection of Botulinum Toxin in Post-stroke Spasticity near the IZs, and 4) guiding obstetricians to perform episiotomy during child delivery by avoiding cutting near the IZs of External Anal Sphincter (EAS) muscle. The most minimally invasive way to identify the location of motor unit innervation zones (IZs) in any muscle, including the External Anal Sphincter (EAS) muscle, is to use multi-channel surface electromyography (sEMG) signals. In this manuscript, we propose a novel approach for automatic muscle motor unit innervation zone localization using multi-channel electromyography (EMG) signals. Our method is based on a linearity measure derived from eigenvalues of the Hessian matrix. The motor unit action potential (MUAP) propagation pattern is first detected in the spatio-temporal sEMG images using a Linearity measure based on eigenvalues of the Hessian matrix. The corresponding MU IZs is then identified as the starting point of propagation of the MUAP. A software is also developed which can be used to record and visualize the signals acquired from EAS and other muscles, detect, and display the IZs and more importantly compute and display the histogram of the IZs and generate reports which will help the obstetrician while performing episiotomy during child delivery to avoid cutting vulnerable regions that may lead to fecal incontinence at later age. The evaluations,on both simulated and experimental EMG signals, demonstrate the effectiveness and robustness of our proposed approach. Compared to existing methods, our approach achieves higher accuracy in innervation zone localization on experimental and simulated signals with mean absolute error of 0.53 and 0.53 inter electrode distance (IED).

Motion predictions for limbs can be performed using commonly called Hill-based muscle models. For this type of models, a surface electromyogram (sEMG) of the muscle serves as an input signal for the activation of the muscle model. However, the Hill model needs additional information about the mechanical system state of the muscle (current length, velocity, etc.) for a reliable prediction of the muscle force generation and, hence, the prediction of the joint motion. One feature that contains potential information about the state of the muscle is the position of the center of the innervation zone. This feature can be further extracted from the sEMG. To find the center, a wavelet-based algorithm is proposed that localizes motor unit potentials in the individual channels of a single-column sEMG array and then identifies innervation point candidates. In the final step, these innervation point candidates are clustered in a density-basedmanner. The center of the largest cluster is the estimated center of the innervation zone. The algorithm has been tested in a simulation. For this purpose, an sEMG simulator was developed and implemented that can compute largemotor units (1,000's of muscle fibers) quickly (within seconds on a standard PC). [ABSTRACT FROM AUTHOR]

This study examined methods for estimating the innervation zone (IZ) of a muscle using recorded monopolar high density M waves. Two IZ estimation methods based on principal component analysis (PCA) and Radon transform (RT) were examined. Experimental M waves, acquired from the biceps brachii muscles of nine healthy subjects were used as testing data sets. The performance of the two methods was evaluated by comparing their IZ estimations with manual IZ detection by experienced human operators. Compared with manual detection, the agreement rate of the estimated IZs was 83% and 63% for PCA and RT based methods, respectively, both using monopolar high density M waves. In contrast, the agreement rate was 56% for cross correlation analysis using bipolar high density M waves. The mean difference in estimated IZ location between manual detection and the tested method was 0.12 ± 0.28 inter-electrode-distance (IED) for PCA, 0.33 ± 0.41 IED for RT and 0.39 ± 0.74 IED for cross correlation-based methods. The results indicate that the PCA based method was able to automatically detect muscle IZs from monopolar M waves. Thus, PCA provides an alternative approach to estimate IZ location of voluntary or electrically-evoked muscle contractions, and may have particular value for IZ detection in patients with impaired voluntary muscle activation. [ABSTRACT FROM AUTHOR]

Fiber conduction velocity (CV) is a parameter correlated to the physiological membrane properties of the skeletal muscle fibers. Changes in muscle fiber CV are correlated to the gradation of force and fatigue, and can be measured by means of surface electromyography EMG (sEMG). sEMG measurement of CV during muscle contractions requires the correct identification of the skeletal muscle innervation zone (IZ). In superficial muscles, IZ location can be detected using linear electrode arrays and visually identified as the point of inversion of the detected motor unit action potential (MUAP) propagation. In the present work, we present a method for the effective and fast detection of the IZ location, through the following procedures: (1) identification of the target superficial muscle considering the muscle fiber architecture; (2) electrode array selection based on interelectrode distance and number of electrodes; (3) subject training to perform submaximal isometric contractions of the target muscle/s; (4) electrode array positioning along the muscle surface to investigate the IZ position during the contractions by visual identification of MUAP patterns.

Roberto Procópio Pinheiro, Matheus Aquesta Gaubeur, Ana Maria Itezerote, Samir Omar Saleh, Flávio Hojaij, Mauro Andrade, Alfredo Luiz Jacomo, Flávia Emi Akamatsu Department of Surgery, Laboratory of Medical Research—Division of Human Structural Topography, Faculty of Medicine of the University of São Paulo (FMUSP), São Paulo, SP, 01246903, BrazilCorrespondence: Flávia Emi Akamatsu Tel +55 11 971515516Fax +55 11 30618277Email flaea@usp.brBackground and Purpose: Myofascial pain syndrome (MPS) is widely prevalent in the general population; some reports estimate its prevalence ranges from 9 to 85%. Among the different locations where MPS may arise, pain related to the masseter muscle is referred as masticatory myofascial pain. MPS is characterized by myofascial trigger points (MTPs), which represent tender anatomical areas of a muscle where painful symptoms are elicited whenever stimulated. Previous publications have found MTPs to coincide with neuromuscular junctions at the motor end plate, at the innervation zone (IZ). Our study aimed to describe the innervation of the masseter muscle and relate it to clinically described myofascial trigger points (MTPs).Materials and Methods: We mapped the nerve fiber distribution into the masseter muscles from 16 cadavers by anatomical dissection. We divided the muscle into six regions, three superior (I–III) and three inferior (IV–VI), and classified the nerve’s branches distribution according to these predetermined areas. Statistical analyses was made by Poisson distribution and logarithm link function followed by Bonferroni multiple comparisons (P< 0.05).Results: All six areas received branches from the masseteric nerve. Areas I and II (upper posterior and upper intermediate, respectively) had a significant higher number of nerve entries as compared to the remaining areas.Conclusion: The penetration areas of the masseteric nerve have been established and MTPs are found in the innervation zones, clinicians should focus initially on the regions of the penetration points, for diagnostics and therapeutic measures, such as injections, dry needling and soft tissue interventions. Anatomical study of nerve supply to the masseter muscle can provide useful additional knowledge to further understanding masticatory myofascial pain and to direct therapeutic interventions and diagnostic studies of temporomandibular junction dysfunction.Keywords: pain, masseteric nerve, innervation zone, anatomy

Fiber conduction velocity (CV) is a parameter correlated to the physiological membrane properties of the skeletal muscle fibers. Changes in muscle fiber CV are correlated to the gradation of force and fatigue, and can be measured by means of surface electromyography EMG (sEMG). sEMG measurement of CV during muscle contractions requires the correct identification of the skeletal muscle innervation zone (IZ). In superficial muscles, IZ location can be detected using linear electrode arrays and visually identified as the point of inversion of the detected motor unit action potential (MUAP) propagation. In the present work, we present a method for the effective and fast detection of the IZ location, through the following procedures: (1) identification of the target superficial muscle considering the muscle fiber architecture; (2) electrode array selection based on interelectrode distance and number of electrodes; (3) subject training to perform submaximal isometric contractions of the target muscle/s; (4) electrode array positioning along the muscle surface to investigate the IZ position during the contractions by visual identification of MUAP patterns. [ABSTRACT FROM AUTHOR]

Abstract Background High density surface electromyography (EMG) can be used to estimate muscle innervation zones (IZ). The objective of this study was to compare the differences in the distribution of the biceps brachii (BB) IZ derived from voluntary contractions (VC) and electrical stimulation (ES) of the musculocutaneous nerve. Methods Surface EMG signals were recorded from the medial and lateral BB with two 64-channel high density electrode matrices in eight healthy men. The surface EMG was recorded at different percentages of the maximal voluntary contraction (MVC) force (20–100% MVC) and at different percentages of the current needed to elicit a maximal M-wave (20–100% Imax). The IZs of the medial and lateral BB were identified from the EMG signals and expressed as a row number within a given medial-lateral column. Results ES current intensity had no significant effect on the group mean IZ location (p > 0.05). However, The IZ during VC was located more proximally with increasing force (p 0.05), but was more proximal in the latter than the former during 60–100% MVC (p

Introduction and hypothesis: To assess the feasibility of objectively assessing pelvic floor hypertonicity (PFH) in women with interstitial cystitis/bladder pain syndrome (IC/BPS) using an intra-vaginal high-density surface electromyography (HD-sEMG) probe. Methods: Seven female subjects (mean age 44 ± 13 years) with a prior diagnosis of IC/BPS were recruited. A full digital pelvic examination was administered to identify hypertonic muscles. Intra-vaginal HD-sEMG was acquired during rest. Root-mean-squared (RMS) amplitude during rest was calculated for each channel to define a hypertonicity index and hypertonic zone. Innervation zones (IZs) were identified from the bipolar mapping of decomposed HD-sEMG signals and summarized into an IZ distribution mapping. Results: Of the seven subjects recruited, five had normal pelvic floor muscle tone and two exhibited hypertonicity upon muscle palpation. Subjects with PFH demonstrated a higher hypertonicity index (12.6 ± 3.5 vs. 4.5 ± 1.2) in sessions 1 and 2. The hypertonic zone defined by the 64-channel RMS mapping coincided with the digital pelvic examination findings. The corresponding IZs were localized for each motor unit. The hypertonicity indices between two consecutive sessions were well correlated (CC = 0.95). Conclusions: This study represents the first effort to employ intra-vaginal HD-sEMG to assess PFH in women with IC/BPS. Our results demonstrate the feasibility of HD-sEMG to provide a quantitative diagnosis of PFH and the precise localization of hypertonic muscles and IZs. The proposed HD-sEMG-based techniques provide promising tools for clinical diagnosis and treatment of PFH, such as the personalized guidance of BoNT injections. [ABSTRACT FROM AUTHOR]

Spasticity is a common post-stroke syndrome that imposes significant adverse impacts on patients and caregivers. This study aims to improve the efficiency of botulinum toxin (BoNT) in managing spasticity, by utilizing a three-dimensional innervation zone imaging (3DIZI) technique based on high-density surface electromyography (HD-sEMG) recordings. Stroke subjects were randomly assigned to two groups: the control group (n = 6) which received standard ultrasound-guided injections, and the experimental group (n = 6) which received 3DIZI-guided injections. The amount of BoNT given was consistent for all subjects. The Modified Ashworth Scale (MAS), compound muscle action potential (CMAP) and muscle activation volume (MAV) from bilateral biceps brachii muscles were obtained at the baseline, 3 weeks, and 3 months after injection. Intra-group and inter-group comparisons of MAS, CMAP amplitude and MAV were performed. An overall improvement in MAS of spastic elbow flexors was observed during the 3-week visit (p < 0. 0 1), yet no statistically significant difference found with intra-group or inter-group analysis. Compared to the baseline, a significant reduction of CMAP amplitude and MAV were observed in the spastic biceps muscles of both groups at 3-week post-injection, and returned to approximate baseline value at 12-week post injection. A significantly higher reduction was found in CMAP amplitude (3 4. 7 1 ± 5. 4 2 % versus 2 0. 9 2 ± 6. 7 3 %, p < 0. 0 1) and MAV (7 1. 5 1 ± 8. 2 0 % versus 4 4. 3 3 ± 2 1. 8 1 %, p < 0. 0 5) in the experimental group compared to the control group. The study has demonstrated preliminary evidence that precisely directing BoNT to the innervation zones (IZs) localized by 3DIZI leads to a significantly higher treatment efficiency improvement in spasticity management. Results have also shown the feasibility of developing a personalized BoNT injection technique for the optimization of clinical treatment for post-stroke spasticity using proposed 3DIZI technique. [ABSTRACT FROM AUTHOR]

Motor Unit Number Index (MUNIX) is a technique that provides a susceptive biomarker for monitoring innervation conditions in patients with neurodegenerative diseases. A satisfactory repeatability is essential for the interpretation of MUNIX results. This study aims to examine the effect of channel number and location on the repeatability of MUNIX. In this study, 128 channels of high-density surface electromyography (EMG) signals were recorded from the biceps brachii muscles of eight healthy participants, at 10, 20, 30, 40, 50, 60, 70, 80, and 100% of maximal voluntary contraction. The repeatability was defined by the coefficient of variation (CV) of MUNIX estimated from three experiment trials. Single-channel MUNIX (sMUNIX) was calculated on a channel-specific basis and a multi-channel MUNIX (mMUNIX) approach as the weighted average of multiple sMUNIX results. Results have shown (1) significantly improved repeatability with the proposed mMUNIX approach; (2) a higher variability of sMUNIX when the recording channel is positioned away from the innervation zone. Our results have demonstrated that (1) increasing the number of EMG channels and (2) placing recording channels close to the innervation zone (IZ) are effective methods to improve the repeatability of MUNIX. This study investigated two potential causes of MUNIX variations and provided novel perspectives to improve the repeatability, using high-density surface EMG. The mMUNIX technique proposed can serve as a promising tool for reliable neurodegeneration evaluation.

Background and Purpose: Myofascial pain syndrome (MPS) is widely prevalent in the general population; some reports estimate its prevalence ranges from 9 to 85%. Among the different locations where MPS may arise, pain related to the masseter muscle is referred as masticatory myofascial pain. MPS is characterized by myofascial trigger points (MTPs), which represent tender anatomical areas of a muscle where painful symptoms are elicited whenever stimulated. Previous publications have found MTPs to coincide with neuromuscular junctions at the motor end plate, at the innervation zone (IZ). Our study aimed to describe the innervation of the masseter muscle and relate it to clinically described myofascial trigger points (MTPs). Materials and Methods: We mapped the nerve fiber distribution into the masseter muscles from 16 cadavers by anatomical dissection. We divided the muscle into six regions, three superior (I–III) and three inferior (IV–VI), and classified the nerve's branches distribution according to these predetermined areas. Statistical analyses was made by Poisson distribution and logarithm link function followed by Bonferroni multiple comparisons (P< 0.05). Results: All six areas received branches from the masseteric nerve. Areas I and II (upper posterior and upper intermediate, respectively) had a significant higher number of nerve entries as compared to the remaining areas. Conclusion: The penetration areas of the masseteric nerve have been established and MTPs are found in the innervation zones, clinicians should focus initially on the regions of the penetration points, for diagnostics and therapeutic measures, such as injections, dry needling and soft tissue interventions. Anatomical study of nerve supply to the masseter muscle can provide useful additional knowledge to further understanding masticatory myofascial pain and to direct therapeutic interventions and diagnostic studies of temporomandibular junction dysfunction. [ABSTRACT FROM AUTHOR]

Motor Unit Number Index (MUNIX) is a technique that provides a susceptive biomarker for monitoring innervation conditions in patients with neurodegenerative diseases. A satisfactory repeatability is essential for the interpretation of MUNIX results. This study aims to examine the effect of channel number and location on the repeatability of MUNIX. In this study, 128 channels of high-density surface electromyography (EMG) signals were recorded from the biceps brachii muscles of eight healthy participants, at 10, 20, 30, 40, 50, 60, 70, 80, and 100% of maximal voluntary contraction. The repeatability was defined by the coefficient of variation (CV) of MUNIX estimated from three experiment trials. Single-channel MUNIX (sMUNIX) was calculated on a channel-specific basis and a multi-channel MUNIX (mMUNIX) approach as the weighted average of multiple sMUNIX results. Results have shown (1) significantly improved repeatability with the proposed mMUNIX approach; (2) a higher variability of sMUNIX when the recording channel is positioned away from the innervation zone. Our results have demonstrated that (1) increasing the number of EMG channels and (2) placing recording channels close to the innervation zone (IZ) are effective methods to improve the repeatability of MUNIX. This study investigated two potential causes of MUNIX variations and provided novel perspectives to improve the repeatability, using high-density surface EMG. The mMUNIX technique proposed can serve as a promising tool for reliable neurodegeneration evaluation. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study is to compare the performance of three strategies in determining the global innervation zone (IZ) distribution. Methods: High-density surface electromyography was recorded from the biceps brachii muscle of seven healthy subjects under isometric voluntary contractions at 20%, 50%, and 100% of the maximal voluntary contraction and supramaximal musculocutaneous nerve stimulations. IZs were detected: first, by visual identification in a column-specific manner (IZ-1D); second, based on decomposed bipolar mapping of motor unit action potentials (IZ-2D); and third, by source imaging in the three-dimensional muscle space (IZ-3D). Results: All three IZ detection approaches have exhibited excellent trial-to-trial repeatability. Consistent IZ results were found in the axial direction of the arm across all three approaches, yet a difference was observed in the mediolateral direction. Conclusions: Among all three approaches, IZ-3D is capable of providing the most comprehensive information regarding the global IZ distribution, while maintaining high consistency with IZ-1D and IZ-2D results. Significance: IZ-3D approach can be a potential tool for global IZ imaging, which is critical to the clinical diagnosis and treatment of neuromuscular disorders. [ABSTRACT FROM AUTHOR]

Surface electromyography (EMG) recorded by a linear or 2-dimensional electrode array can be used to estimate the location of muscle innervation zones (IZ). There are various neurophysiological factors that may influence surface EMG and thus potentially compromise muscle IZ estimation. The objective of this study was to evaluate how surface-EMG-based IZ estimation might be affected by different factors, including varying degrees of motor unit (MU) synchronization in the case of single or double IZs. The study was performed by implementing a model simulating surface EMG activity. Three different MU synchronization conditions were simulated, namely no synchronization, medium level synchronization, and complete synchronization analog to M wave. Surface EMG signals recorded by a 2-dimensional electrode array were simulated from a muscle with single and double IZs, respectively. For each situation, the IZ was estimated from surface EMG and compared with the one used in the model for performance evaluation. For the muscle with only one IZ, the estimated IZ location from surface EMG was consistent with the one used in the model for all the three MU synchronization conditions. For the muscle with double IZs, at least one IZ was appropriately estimated from interference surface EMG when there was no MU synchronization. However, the estimated IZ was different from either of the two IZ locations used in the model for the other two MU synchronization conditions. For muscles with a single IZ, MU synchronization has little effect on IZ estimation from electrode array surface EMG. However, caution is required for multiple IZ muscles since MU synchronization might lead to false IZ estimation.

Abstract Objective The present study aimed to test the effect of the electrode position and inter-electrode distance on the evoked force by neuromuscular electrical stimulation (NMES) with a low current intensity and a single pair of electrodes. Knee extensor forces during NMES to quadriceps femoris muscles were compared among four different electrode configurations in seven healthy men. Electrodes were located at 10 cm proximal and 15 cm distal (P10-D15), 10 cm proximal and 10 cm distal (P10-D10), 5 cm proximal and 15 cm distal, and 5 cm proximal and 10 cm distal (P5-D10) to the center of the longitudinal axis of the quadriceps femoris muscles. Results The evoked force–time area for P5-D10 was significantly higher than those for P10-D15 and P10-D10 (p

Aims: The innervation zone asymmetry of the external anal sphincter (EAS) has been investigated as a risk factor for the development of fecal incontinence (FI). This study aims to utilize an intra‐rectal high‐density surface electromyogram (HD‐sEMG) recording and advanced HD‐sEMG decomposition technique to characterize the effects of aging on the asymmetry of EAS functional innervation. Methods: HD‐sEMG signals were recorded intra‐rectally from six healthy young and seven healthy elderly women during voluntary contractions of the EAS. EMG signals were decomposed into constituent motor unit action potentials (MUAPs) and the innervation zone of each decomposed motor unit was identified. Asymmetry index (AI) was defined and calculated for all subjects. The maximum squeezing pressures of the EAS were also measured for all subjects as a comparison. Results: The HD‐sEMG decomposition and AI calculation were successfully performed from EMG data acquired from all the subjects. The AI values were 28.7 ± 17.0% for the young group and 55.6 ± 18.8% for the elderly group. The AI and EAS contraction strength were found to be negatively correlated (P < 0.05). A two‐tailed student's t‐test demonstrated a significant increase in AI with age by comparison between two groups (P < 0.05). Conclusions: Our work demonstrates, for the first time, that EAS functional innervation tends to become increasingly asymmetrical with advancing age, and this increase is associated with a compromised anorectal function. Results suggest that the intra‐rectal HD‐sEMG will serve as an advanced tool for assessing and monitoring the anorectal neuromuscular function minimally invasively under different pathophysiological conditions. [ABSTRACT FROM AUTHOR]

Introduction and hypothesis: Mediolateral episiotomy is one of the most frequent surgical interventions performed in obstetrics. There is conflicting evidence as to whether mediolateral episiotomy reduces the risk of obstetric anal sphincter injuries (OASI). Recent studies suggest that functional asymmetry of pelvic floor innervation exists in healthy women and is strongly associated with postpartum incontinence when the trauma occurs on the dominant side of innervation. Mediolateral episiotomy is the most common cause of perineal trauma during delivery, and the surgical incision is usually performed on the mediolateral right side. Surface electromyography (EMG) has been recently applied in obstetrics for detecting electrical activity of the external anal sphincter (EAS).Methods: Two hundred and forty-five pregnant nulliparous women at their second and third trimester of pregnancy were recruited, and EMG signals were detected using a multichannel cylindric anal probe. Measurements were repeated and compared 6-8 weeks after delivery on a subgroup of 167 women who were divided in two groups according to EMG amplitude asymmetry before delivery and two subgroups according to type of delivery: (1A) asymmetric left, episiotomy right; (1B) asymmetric left, other types of deliveries; (2A) asymmetric right, episiotomy right; (2B) asymmetric right, other type of deliveries.Results: The reduction of EMG amplitude after right episiotomy was larger in women with right asymmetric sphincter compared with women with left asymmetry and women with other types of delivery.Conclusions: Prenatal EMG may be used to predict the impact of right-sided mediolateral episiotomy on EAS and perhaps also function following delivery. [ABSTRACT FROM AUTHOR]

In monopolar electrode configuration, the shape of the motor unit potential (MUP) undergoes essential morphologic changes with increasing distance from the innervation zone. In particular, the rising phase of the MUP slows down and becomes longer as the electrode is moved further from the innervation zone. Based on this, it is hypothesized that the maximum slope of the rising phase of a monopolar MUP (SlopeMAX) would reach its highest value at the innervation zone. Herein, we sought to determine whether the location of the innervation zone coincides with the position in the muscle of the monopolar MUP with highest SlopeMAX and whether new criteria for the localization of the innervation region can be proposed based on the SlopeMAX of monopolar potentials. Multichannel surface (13×5 electrode array) and intramuscular (wire electrodes inserted with needles of lengths 15 and 25mm) EMG signals were concurrently recorded in monopolar configuration from the biceps brachii muscle of 10 healthy subjects. The spatial distribution of monopolar and bipolar MUPs along the fibers' direction were obtained by spike-triggered averaging of the surface EMG. We found that the monopolar MUP with steepest rising phase (i.e., highest SlopeMAX) was located either just above or at half of the inter-electrode distance from the innervation zone. High levels of agreement (94-98%) were found between the position of the innervation zone assessed with the SlopeMAX criteria of monopolar potentials and the position identified using the phase reversal criteria of bipolar potentials. The present results legitimize the use of compound muscle action potentials (M waves) to localize the innervation zone: this location would correspond to the electrode position which yielded the monopolar M wave with highest SlopeMAX. [ABSTRACT FROM AUTHOR]

Recently, the importance of targeting structures during botulinum neurotoxin applications has been discussed in a variety of disorders, including spasticity and dystonia. In this respect, the advantages of ultrasound imaging to traditional techniques have been emphasized. We would like underscore the importance of ultrasound guidance, with targeting innervation zone(s) of the over-active muscles to achieve effective clinical outcomes. Additionally, we also clarify the difference between the terms—innervation zone (motor end plate) and motor point—which have been used by the authors as if they were the same. Further, we disagree with the authors about the intramuscular botulinum neurotoxin application techniques i.e., in-plane vs. out-of-plane whereby the former is, for sure, superior.

This study examines the innervation zone (IZ) in the biceps brachii muscle in normal subjects and those with amyotrophic lateral sclerosis (ALS) using a 20-channel linear electromyogram (EMG) electrode array. Raster plots of individual waveform potentials were studied to estimate the motor unit IZ. While this work mainly focused on fasciculation potentials (FPs), a limited number of motor unit potentials (MUPs) from voluntary activity of 12 healthy and 7 ALS subjects were also examined. Abnormal propagation of MUPs and scattered IZs were observed in fasciculating units, compared with voluntarily activated MUPs in healthy and ALS subjects. These findings can be related to muscle fiber reinnervation following motor neuron degeneration in ALS and the different origin sites of FPs compared with voluntary MUPs.

In this study, specific changes in electromyographic characteristics of individual motor units (MUs) associated with different muscle contraction forces are investigated using multi-channel surface electromyography (SEMG). The gradient convolution kernel compensation (GCKC) algorithm is employed to separate individual MUs from their surface interferential electromyography (EMG) signals and provide the discharge instants, which is later used in the spike-triggered averaging (STA) techniques to obtain the complete waveform. The method was tested on experimental SEMG signals acquired during constant force contractions of biceps brachii muscles in five subjects. Electromyographic characteristics including the recruitment number, waveform amplitude, discharge pattern and innervation zone (IZ) are studied. Results show that changes in the action potential of single MU with different contraction force levels are consistent with those for all MUs, and that the amplitude of MU action potentials (MUAPs) provides a useful estimate of the muscle contraction forces. [ABSTRACT FROM AUTHOR]

Widespread misconceptions still exist regarding the formation of extracellular potentials over the innervation zone: the assumption (1) that the first phase of these potentials mainly reflects the process of initiation of the intracellular action potential (IAP) at the neuromuscular junction and that (2) these potentials are not sensitive to changes in fibre membrane properties (such as changes in the IAP length). Here, we examined the peculiarities of the extracellular potentials detected over the innervation region with the aim to clarify whether the changes in membrane properties are reflected in the amplitude of these potentials. These goals were addressed using a biophysical model of the IAP as well as a convolutional model of EMG generation. Also, the theoretical predictions made by these models were verified experimentally. We showed that only the initial portion of the potentials detected over the innervation zone corresponded to the origination of the IAP at the junction: the remaining (final) portion resulted from the propagation of the IAP along the fibre. It was found that, as radial distance increases, the portion of the rising phase with "propagating character" increased its duration, whereas the duration of the portion with "standing character" remained unchanged. Moreover, a lengthening of the IAP profile resulted in a distinct increase in the amplitude of the first phase of these potentials. These findings were confirmed experimentally and demonstrate that changes in fibre membrane properties influence the amplitude of surface EMG potentials recorded over the innervation zone to the same extent as they do surface potentials recorded elsewhere along the length of the muscle fibres. [ABSTRACT FROM AUTHOR]

Introduction and hypothesis: Knowledge of the innervation of pelvic floor and sphincter muscles is of great importance to understanding the pathophysiology of female pelvic floor dysfunctions. This report presents our high-density intravaginal and intrarectal electromyography (EMG) probes and a comprehensive innervation zone (IZ) imaging technique based on high-density EMG readings to characterize the IZ distribution. Methods: Both intravaginal and intrarectal probes are covered with a high-density surface electromyography electrode grid (8 × 8). Surface EMG signals were acquired in ten healthy women performing maximum voluntary contractions of their pelvic floor. EMG decomposition was performed to separate motor-unit action potentials (MUAPs) and then localize their IZs. Results: High-density surface EMG signals were successfully acquired over the vaginal and rectal surfaces. The propagation patterns of muscle activity were clearly visualized for multiple muscle groups of the pelvic floor and anal sphincter. During each contraction, up to 218 and 456 repetitions of motor units were detected by the vaginal and rectal probes, respectively. MUAPs were separated with their IZs identified at various orientations and depths. Conclusions: The proposed probes are capable of providing a comprehensive mapping of IZs of the pelvic floor and sphincter muscles. They can be employed as diagnostic and preventative tools in clinical practices. [ABSTRACT FROM AUTHOR]

This study examined the electromyographic (EMG) responses from the vastus medialis (VM) for electrodes placed over and away from the innervation zone (IZ) during a maximal voluntary isometric contraction (MVIC) and sustained, submaximal isometric muscle action. A linear electrode array was placed on the VM to identify the IZ and muscle fiber pennation angle during an MVIC and sustained isometric muscle action at 50% MVIC. EMG amplitude and frequency parameters were determined from 7 bipolar channels of the electrode array, including over the IZ, as well as 10 mm, 20 mm and 30 mm proximal and distal to the IZ. There were no differences between the channels for the patterns of responses for EMG amplitude or mean power frequency during the sustained, submaximal isometric muscle action; however, there were differences between channels during the MVIC. The results of the present study supported the need to standardize the placement of electrodes on the VM for the assessment of EMG amplitude and mean power frequency. Based on the current findings, it is recommended that electrode placements be distal to the IZ and aligned with the muscle fiber pennation angle during MVICs, as well as sustained, submaximal isometric muscle actions. [ABSTRACT FROM AUTHOR]

Background: The innervation zone (IZ) corresponds to the location of the neuromuscular junctions. Its location can be determined by using arranged surface linear electrode arrays. Typically, voluntary muscle contractions (VC) are used in this method. However, it also may be necessary to locate the IZ under clinical conditions such as spasticity, in which this type of contraction is difficult to perform. Therefore, contractions imposed by electrostimulation (ES) can be an alternative. There is little background comparing the locations of IZ obtained by two different types of contractions.Objective: Evaluate the concordance between using voluntary and imposed contractions from electrostimulation in order to determine the location of the innervation zone of the tibialis anterior muscle in healthy volunteers.Methods: The tibialis anterior (TA) muscle of sixteen volunteers (men: 8; women: 8; age: 22.1±1.4years, weight: 61.6±7.5kg, height: 167.1±7.5cm) were evaluated using a linear electrode array. The IZ of the TA muscle was located using two types of muscle contractions, voluntary (10% MVC) and imposed contractions by ES. The concordance between both conditions was evaluated using the Bland-Altman method and the concordance correlation coefficient (CCC). The analyses were applied to the absolute and relative positions to the length of an anatomical landmark frame.Results: CCC for absolute position was 0.98 (p<0.0001, 95% CI [0.98-1.00], and CCC for relative positions also was 0.98 (p<0.0001, 95% CI [0.97-1.00]). The Bland-Altman analysis for absolute data showed an average difference of -0.63mm (SD: 4.1). Whereas, for adjusted data, the average difference was -0.20% (SD: 1.2). The power of the results, based on absolute data, was 98%, whereas for relative data, 82%.Conclusion: In healthy volunteers, there was a substantially concordance between the location of the IZ of the TA muscle derived from using contractions imposed by ES and the location derived from using VC. [ABSTRACT FROM AUTHOR]

Introduction: In this study we evaluated the reliability of bipolar electrode recordings, which allow for undistorted compound muscle action potentials (CMAPs) while minimizing cross-talk during voluntary contractions.Methods: Twenty-four men completed maximal voluntary wrist flexion contractions in 4 test sessions. Compound muscle action potentials were also evoked during each session. Surface electromyography was recorded from the flexor carpi radialis (FCR) with the recording electrode (G1) placed on the motor point and a second recording electrode (G2) adjacent to G1. Reliability was assessed using intraclass correlational analysis of variance and standard error of measurement.Results: Root-mean-square (RMS) amplitude and mean power frequency (MPF) were highly reliable (R = 0.89 and 0.84, respectively). The CMAPs also exhibited good reliability (R = 0.75). Normalization of RMS amplitude reduced the intraclass reliability coefficient (R = 0.85).Conclusion: The electrode placement resulted in reliable measures from voluntary contractions and CMAPs. Normalization can decrease reliability. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the influence of a bout of repeated and prolonged passive static stretching on the innervation zone (IZ) location of the human biceps brachii muscle. Eleven men performed 12 sets of 100-s passive stretches on their biceps brachii. Before (Pre) and immediately after (Post) the stretching intervention, isometric strength was tested during the maximal voluntary contractions (MVCs) of the forearm flexors. The subjects also performed several separate isometric forearm flexion muscle actions at 30%, 50%, and 70% of their predetermined MVCs for examining the locations of the IZ at different contraction intensities. The IZ was identified through multi-channel surface electromyographic (EMG) recordings from a linear electrode array. The stretching intervention induced an average of 10% isometric strength loss for the forearm flexors (mean ± SD: Pre-MVC vs. Post-MVC = 332.12 ± 59.40 N vs. 299.53 ± 70.51 N; p < 0.001). In addition, the average IZ shift was nearly 4.5 mm in average in the proximal direction. However, this shift was not specific to the contraction intensity. We believe that the IZ shift was caused by the elongation of the entire muscle-tendon unit in the proximal direction. Therefore, caution should be taken when using surface EMG technique to examine possible changes in the EMG variables after a stretching protocol, as these variables can be contaminated by the shift of the IZ. [ABSTRACT FROM AUTHOR]

Purpose: Developing a real time method to estimate generation, extinction and propagation of muscle fibre action potentials from bi-dimensional and high density surface electromyogram (EMG). Method: A multi-frame generalization of an optical flow technique including a source term is considered. A model describing generation, extinction and propagation of action potentials is fit to epochs of surface EMG. Results: The algorithm is tested on simulations of high density surface EMG (inter-electrode distance equal to 5 mm) from finite length fibres generated using a multi-layer volume conductor model. The flow and source term estimated from interference EMG reflect the anatomy of the muscle, i.e. the direction of the fibres (2° of average estimation error) and the positions of innervation zone and tendons under the electrode grid (mean errors of about 1 and 2 mm, respectively). The global conduction velocity of the action potentials from motor units under the detection system is also obtained from the estimated flow. The processing time is about 1 ms per channel for an epoch of EMG of duration 150 ms. Conclusions: A new real time image processing algorithm is proposed to investigate muscle anatomy and activity. Potential applications are proposed in prosthesis control, automatic detection of optimal channels for EMG index extraction and biofeedback. [ABSTRACT FROM AUTHOR]

A method to detect automatically the location of innervation zones (IZs) from 16-channel surface EMG (sEMG) recordings from the external anal sphincter (EAS) muscle is presented in order to guide episiotomy during child delivery. The new algorithm (2DCorr) is applied to individual motor unit action potential (MUAP) templates and is based on bidimensional cross correlation between the interpolated image of each MUAP template and two images obtained by flipping upside-down (around a horizontal axis) and left–right (around a vertical axis) the original one. The method was tested on 640 simulated MUAP templates of the sphincter muscle and compared with previously developed algorithms (Radon Transform, RT; Template Match, TM). Experimental signals were detected from the EAS of 150 subjects using an intra-anal probe with 16 equally spaced circumferential electrodes. The results of the three algorithms were compared with the actual IZ location (simulated signal) and with IZ location provided by visual analysis (VA) (experimental signals). For simulated signals, the inter quartile error range (IQR) between the estimated and the actual locations of the IZ was 0.20, 0.23, 0.42, and 2.32 interelectrode distances (IED) for the VA, 2DCorr, RT and TM methods respectively. [ABSTRACT FROM AUTHOR]

Background Botulinum toxin (BTX) acts on the neuromuscular junction which can be located by the innervation zone (IZ). Clinically, the motor point (MP) is homologous to the IZ and it is used as the injection site of BTX. Differences in the effectiveness of the application of BTX between MP and IZ locations have been determined. Objective Compare the location of the MP obtained using electrical stimulation and the location of the IZ using a linear surface electrodes array on the biceps brachii muscle. Methods The biceps brachii muscle of twenty men was assessed. The MP was located using the torque measurement generated by electrical stimulation. The IZ was detected using a linear surface electrodes array. Results A difference between the MP and the IZ positions (75.8 vs. 86.5 mm, delta 10.7 mm; p = 0.003, post-hoc power 0.89) was observed. Discussion The magnitude of the difference between the MP and the IZ may be clinically relevant. The IZ location using surface electromyography as a guide to optimize BTX injection is proposed. [ABSTRACT FROM AUTHOR]

Introduction and hypothesis: A correlation exists between external anal sphincter (EAS) damage during birth and the subsequent development of fecal incontinence. This study evaluated the effect of delivery-related trauma on EAS innervation by means of intra-anal EMG performed with a rectal probe with 16 silver electrodes equally spaced along the circumference, before and after delivery. Methods: Pre-partum EMG measurements were performed on 511 women, by nine clinical partners from five European countries at the 28th to 34th gestational weeks and the 6th to 8th post-delivery weeks; 331 women returned, after delivery, for the second test. The innervation zones (IZ) of EAS single motor units were identified by means of an EMG decomposition algorithm. Results: The subjects were divided into four groups according to the delivery mode (Caesarean, vaginal with no evident damage, spontaneous lacerations and episiotomies). The number of IZs before and after delivery was compared. In the 82 women who underwent right mediolateral episiotomy, a statistically significant reduction of IZs was observed, after delivery, in the right ventral quadrant of the EAS (side of the episiotomy). Women who had Caesarean section, spontaneous lacerations or lack of evident damage did not present any significant change in the innervation pattern. Conclusions: Right episiotomy reduces the number of IZs on the right-ventral side of the EAS. The fast and reliable test proposed indicates the sphincter innervation pattern before delivery and helps obstetricians to evaluate the risks and to choose the preferred side of the episiotomy, if deemed necessary at the time of delivery. [ABSTRACT FROM AUTHOR]

Introduction and hypothesis: Locating the innervation zones (IZs) of the external anal sphincter (EAS) is helpful to obstetricians to identify areas particularly vulnerable to episiotomy in pregnant women. The aim was to investigate the motor unit (MU) properties of the EAS during voluntary contractions. Methods: Electromyographic signals were detected, from 478 pregnant women, by means of an intra-anal cylindrical probe carrying a circumferential array of 16 electrodes. The signals were decomposed into the constituent MU action potential trains and 5,947 templates were extracted and analyzed in order to identify the IZ position. Results: MUs innervated at one end are concentrated in the dorsal portion of the sphincter, while MUs innervated in the middle are distributed symmetrically in the left and right portions of the EAS. The angular propagation velocity was estimated for each MU resulting in 260 ± 45 rad/s, corresponding to 1.8 m/s on the probe surface and to about 4 m/s at a radial depth of 10 mm from the probe surface. Conclusions: A novel method for identification and classification of MUs of the EAS is proposed and applied to a large-scale study. It is possible to distinguish MUs of the EAS in a minimally invasive way and identify their IZs. This information should be used to plan episiotomies and minimize risks of EAS denervation. [ABSTRACT FROM AUTHOR]

ABSTRACT Introduction: We describe the innervation zone (IZ) location in 43 muscles to provide information for appropriate positioning of bipolar electrodes for clinical and research applications. Methods: The IZ was studied in 40 subjects (20 men and 20 women) using multichannel surface electromyography (sEMG). Signal quality was checked visually to identify motor unit action potentials and estimate muscle fiber conduction velocity. Results: Results in 33 muscles were classified as excellent or good, because it was possible to identify an area which is favorable for appropriate positioning of an electrode pair without the need to previously determine the IZ location. Conclusions: Knowledge of IZ location will increase standardization and repeatability of sEMG measures. Muscle Nerve 49:413-421, 2014 [ABSTRACT FROM AUTHOR]

Objective: We aimed to describe the optimal places for intramuscular applications like botulinum toxin (BT) used in the treatment of common diseases such as cervical dystonia by determining the intramuscular nerve distribution of the splenius capitis muscle (SC). We targeted to describe the nerve innervation zones (IZ) of the muscles and the injection sites according to the bone landmarks that can be applied to the patient. Methods: In our study, 14 neck muscles of 7 cadavers fixed with 10% formalin were used. Posterior edge of the mastoid process superiorly and the tip of the spinous process of the first thoracic vertebra inferiorly were selected for the length of the muscle. Motor entry points (MEP) were measured on the muscles. The modified Sihler's staining technique (MST) was applied after the muscles were dissected. The distribution of stained nerve fibers between transparent muscle fibers was examined. IZ were determined at 10% intervals. Results: The lengths of SC were respectively 116.6±2.76 mm according to the selected landmarks. It was determined that SC had 3 MEP in 28.6% cases, 2 MEP in 35.7% cases and 1 MEP in 35.7% cases. IZ of the SC was intense at the level of 10--30% of the muscle length in the medial part and 50--70% and 80--100% in the lateral part of the muscle. Conclusion: The MST has been successfully applied to the SC and IZ were determined. In cervical dystonia, the BT injection may give more effective results if it's applied to these muscles' IZ. It is important to know the MEP of the muscles to prevent muscle paralysis in surgical interventions. [ABSTRACT FROM AUTHOR]

Abstract: The assessment of abdominal muscles has became popular in recent years because the study of “core muscles” is now considered a pivotal approach for a number of fields. The purpose of this study was to describe the innervation zone (IZ) locations and optimal electrode sites in two core muscles: the obliquus externus (OE) and the obliquus internus (OI) abdominis muscles. Twenty healthy male subjects were recruited and the IZ location was studied during a submaximal isometric contraction using multichannel surface EMG. The optimal electrode position for OI was found to be 2cm lower the most prominent point of the anterior superior iliac spine, just medial and superior to the inguinal ligament. The optimal electrode position for OE was found to be 14cm from the median line, lower the level of 1cm above umbilicus, parallel to the line extending from the most inferior point of the costal margin to the opposite pubic tubercle (almost 45° with respect to the median line). Findings showed that for OI and OE muscles it is possible to provide indications for a muscle belly area suited for proper positioning of at least an electrode pair. [Copyright &y& Elsevier]

Background: Myofascial trigger points (MTrPs) are hyperirritable spots located in taut bands of muscle fibres. Electrophysiological studies indicate that abnormal electrical activity is detectable near MTrPs. This phenomenon has been described as endplate noise and it has been purported to be associated MTrP pathophysiology. Thus, it is suggested that MTrPs will be overlap the innervation zone (IZ). The purpose of this work was to describe the location of MTrPs and the IZ in the right upper trapezius. Methods: We screened 71 individuals and eventually enrolled 24 subjects with neck pain and active MTrPs and 24 neck pain-free subjects with latent MTrPs. Surface electromyography (sEMG) signals were detected using an electrode matrix during isometric contraction of the upper trapezius. A physiotherapist subsequently examined the subject's trapezius to confirm the presence of MTrPs and establish their location. IZ locations were identified by visual analysis of sEMG signals. IZ and MTrPs locations were described using an anatomical coordinate system (ACS), with the skin area covered by the matrix divided into four quadrants. Results: No significant difference was observed between active and latent MTrPs locations (P = 0.6). Forty-five MTrPs were in the third quadrant of the ACS, and 3 were included in second quadrant. IZs were located approximately midway between the seventh cervical vertebrae and the acromial angle in a limited area in the second and third quadrants. The mean distance between MTrP and IZ was 10.4 ± 5.8 mm. Conclusions: According to the acquired results, we conclude that IZ and MTrPs are located in well-defined areas in upper trapezius muscle. Moreover, MTrPs in upper trapezius are proximally located to the IZ but not overlapped. [ABSTRACT FROM AUTHOR]

The flexor pollicis brevis (FPB) is a muscle of the thenar eminence that plays an important role in thumb function. There is data about its innervation zone (IZ) distribution and sex differences. Knowing the location of the ZI of FPB could be helpful in treating spastic hand, serving to define the site of injection of the botulinum toxin. The aim of this study was to describe the IZ location in the FPB using surface electromyography (sEMG), and also make a comparison between male and female subjects. Thirty young healthy volunteers participated in this study (15 males: 21.5 ± 2.6 years, 70.7 ± 7.2 kg y 175.0 ± 5.5cm. 15 Females: 19.9 ± 1.4 years, 57.9 ± 11.1 kg y 161.9 ± 6.6 cm). The IZ was identified by recording the action potentials of the FPB motor units, using a sixteen-electrode array. The action potentials were recorded during isometric contractions at 10% of maximum voluntary contraction. The location of the IZ was expressed as absolute and relative values in relation to a reference system constructed in the palm of the hand, based on anatomic references. There were not significant differences in the location of the IZ between male and female subjects. Of all the subjects, the IZ of the FPB was found at the 41.9% of the distance between the most distal and medial palpable extreme of the metacarpophalangeal joint line of the thumb and the line which rises at the palpable apex of the proximal side of the first phalanx of the third finger passing through the radial longitudinal fold. [ABSTRACT FROM AUTHOR]

The present study applied a log-transformation model to compare the electromyographic (EMG) amplitude versus torque relationships from monopolar EMG signals up to 35 mm proximal and distal from the innervation zone (IZ). Seven men (age = 23 ± 2 year; mass = 82 ± 10 kg) and two women (age = 21 ± 1 year; mass = 62 ± 8 kg) performed isometric ramp contractions of the right leg extensors with an eight-channel linear electrode array positioned over the vastus lateralis with the IZ located between channels 4 and 5. Linear regression models were fit to the log-transformed monopolar EMGRMS-torque relationships with the b terms (slope) and the a terms (Yintercept) calculated for each channel and subject. The b terms for channels 4, 5, and 6were higher (P 0.05) than themore distal channels 7 and 8 (P<0.05). In contrast, there were no differences (P > 0.05) among the a terms of the eight channels. Thus, the shapes of the monopolar EMGRMS-torque relationships were altered as a function of distance between the IZ and recording area, which may be helpful for clinicians and researcherswho infer changes in motor control strategies based on the shapes of the EMGRMS-torque relationships. [ABSTRACT FROM AUTHOR]

Abstract: Measuring muscle forces in vivo is invasive and consequently indirect methods e.g., electromyography (EMG) are used in estimating muscular force production. The aim of the present paper was to examine what kind of effect the disruption of the physiological signal caused by the innervation zone has in predicting the force/torque output from surface EMG. Twelve men (age 26 (SD ±3)years; height 179 (±6)cm; body mass 73 (±6)kg) volunteered as subjects. They were asked to perform maximal voluntary isometric contraction (MVC) in elbow flexion, and submaximal contractions at 10%, 20%, 30%, 40%, 50% and 75% of the recorded MVC. EMG was measured from biceps brachii muscle with an electrode grid of 5 columns×13 rows. Force–EMG relationships were determined from individual channels and as the global mean value. The relationship was deemed inconsistent if EMG value did not increase in successive force levels. Root mean squared errors were calculated for 3rd order polynomial fits. All subjects had at least one (4–52) inconsistent channel. Two subjects had inconsistent relationship calculated from the global mean. The mean root mean squared error calculated using leave one out method for the fits of the individual channels (0.33±0.17) was higher (P <0.001) than the error for the global mean fit (0.16±0.08). It seems that the disruption of the physiological signal caused by the innervation zone affects the consistency of the force–EMG relationship on single bipolar channel level. Multichannel EMG recordings used for predicting force overcame this disruption. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to compare the accuracy of the estimated innervation zone (IZ) locations obtained from cross-correlation, the minimum amplitude, and maximum center frequency criteria. Eight healthy men (mean±SD age=23.0±4.3 yrs) performed isometric muscle actions of the leg extensors, and 15 separate bipolar surface electromyographic (EMG) signals were detected from the vastus lateralis. A custom software program was used to estimate the location of the IZ based on: (1) the EMG channel that demonstrated the lowest amplitude, (2) the EMG channel that showed the highest mean frequency, and (3) the EMG channel that demonstrated the lowest peak cross-correlation between the signals from adjacent channels. The IZ location estimates from the lowest amplitude and highest mean frequency criteria were accurate in only 43.75% and 7.5% of the cases, respectively. The accuracy of the cross-correlation-based method was 90%. The cross-correlation-based method was much more accurate for estimating IZ location than were the lowest amplitude and highest mean frequency criteria. Cross-correlation could potentially be used for estimating the location of the IZ without the need for visual inspection of EMG signals. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to examine the effects of skinfold (SF) thicknesses at four locations on the vastus lateralis (VL) muscle and the placement of accelerometers relative to the innervation zone (IZ) on the mechanomyographic (MMG) amplitude and mean power frequency (MPF) responses during incremental cycle ergometry. Twenty adults (age±SD=23.8±3.0years) participated in the investigation. The MMG signals were detected during incremental cycle ergometry using four accelerometers placed on the right VL. Prior to the cycle ergometer test, SF thicknesses were measured. Simple linear regression analyses and one-way repeated measures analyses of variance (ANOVAs) were performed. The present study found that only 10% of the regression analyses and mean comparisons were significant (p <0.05). Furthermore, the accelerometer placed at the most proximal site (Prox 2) had significantly greater MMG amplitude and MMG MPF than accelerometers placed at more distal sites (Prox 1, Over IZ, and Dist). There were no significant differences, however, in SF thickness between accelerometer placement sites. In addition, the IZ had no effect on MMG amplitude and little effect on MMG MPF values. The results of the present study indicated that the SF thickness values and IZ did not affect the MMG signal. [Copyright &y& Elsevier]

Abstract: The identification of the motor unit (MU) innervation zone (IZ) using surface electromyographic (sEMG) signals detected on the skin with a linear array or a matrix of electrodes has been recently proposed in the literature. However, an analysis of the reliability of this procedure and, therefore, of the suitability of the sEMG signals for this purpose has not been reported. The purpose of this work is to describe the intra and inter-rater reliability and the suitability of surface EMG in locating the innervation zone of the upper trapezius muscle. Two operators were trained on electrode matrix positioning and sEMG signal analysis. Ten healthy subjects, instructed to perform a series of isometric contractions of the upper trapezius muscle participated in the study. The two operators collected sEMG signals and then independently estimated the IZ location through visual analysis. Results showed an almost perfect agreement for intra-rater and inter-rater reliability. The constancy of IZ location could be affected by the factors reflecting the population of active MUs and their IZs, including: the contraction intensity, the acquisition period analyzed, the contraction repetition. In almost all cases the IZ location shift due to these factors did not exceed 4mm. Results generalization to other muscles should be made with caution. [Copyright &y& Elsevier]