sEMG Measurements Research Articles

Pelvic floor electromyography in men with chronic pelvic pain syndrome: A case‐control study

The objectives of this study were (1) to identify differences between men with chronic pelvic pain syndrome (CPPS), compared with pain-free men, in surface electromyography/biofeedback (sEMG/BFB) readings of pelvic floor muscles and (2) to determine which pelvic floor muscle sEMG readings may have differential diagnostic and treatment selection value by accurately predicting group membership, CPPS versus normal. Twenty-one men with CPPS and 21 healthy men without pelvic pain underwent a standardized sEMG examination by a licensed physical therapist. On group difference measures men with CPPS showed significantly greater sEMG instability in preliminary resting baseline. Three sEMG measures reliably categorized CPPS versus normals with CPPS showing greater preliminary resting baseline hypertonicity and instability with lowered voluntary endurance contraction amplitude. CPPS patients manifest pelvic floor muscle instability compared to normals. Prebaseline resting hypertonicity and instability along with endurance contraction weakness reliably predicts subject membership in the CPPS vs. normal group. Pelvic floor muscle sEMG may be a valuable screening tool to identify patients with CPPS who may benefit from therapies aimed at correcting pelvic floor muscle dysfunction.

Are changes in pain induced by myofeedback training related to changes in muscle activation patterns in patients with work-related myalgia?

The objective of this explorative study was to investigate to what extent changes in perceived pain, induced by myofeedback training, are correlated to changes in muscle activation patterns. Thirty subjects with work-related myalgia received myofeedback training. Before (T(0)), directly after (T(1)) and 4 weeks or, in a subset of patients, 3 months after (T(2)) this training, surface electromyography (sEMG) measurements of the upper trapezius muscle were performed during standardized computer tasks; a typing and a stress task. Besides this, visual analogue scales (VAS) were filled in to assess the levels of pain in the neck and shoulders. From the sEMG, root mean square (RMS) and relative rest time (RRT, i.e. the percentage of time RMS is below a certain threshold) were used for data analysis. The relationships between RRT, RMS and VAS at T(0) as well as for the changes between T(1)-T(0) and T(2)-T(0) were investigated using Spearman correlation coefficients. The results revealed no significant correlations between VAS and RMS both at baseline (range R = -0.22 to 0.17) and for the observed changes (range R = -0.33 to 0.32). Also, for VAS and RRT, low correlations were found for baseline (range R = -0.27 to 0.21) and for changes between T(1)-T(0) (range R = -0.02 to 0.38). However, for the changes between T(2)-T(0), correlation coefficients for the VAS for the shoulder and the RRT of the right trapezius during both the typing and stress tasks were significant at the P = 0.05 level, whereas the correlation coefficients for the VAS for the neck and both the left and right trapezii during the stress task approached significance (P = 0.05 and P = 0.1, respectively). These results suggest that decreases in pain observed at long term follow up after myofeedback training might occur as a result of an increased ability to relax but not as a result of decreased muscle activation level. However, the largest correlation found was 0.6. This means that the maximal explained variance (R (2)) is low (36%), and that there are also other processes than the changes in muscle activation that contribute to changes in perceived pain.

Comparison of surface electromyography and myotonometric measurements during voluntary isometric contractions

Objectives: Muscle stiffness increases during muscle contraction. The purpose of this study was to determine the strength of the correlation between myotonometric measurements of muscle stiffness and surface electromyography (sEMG) measurements during various levels of voluntary isometric contractions of the biceps brachii muscle. Subjects: Eight subjects (four female; four male), with mean age of 30.6±8.23 years, volunteered to participate in this study. Methods: Myotonometer and sEMG measurements were taken simultaneously from the right biceps brachii muscle. Data were obtained: (1) at rest, (2) while the subject held a 15 lb (6.8 kg) weight isometrically and, (3) during a maximal voluntary isometric contraction. Myotonometer force–displacement curves (amount of tissue displacement to a given unit of force applied perpendicular to the muscle) were compared with sEMG measurements using Pearson’s product–moment correlation coefficients. Results: Myotonometer and sEMG measurement correlations ranged from −0.70 to −0.90. The strongest correlations to sEMG were from Myotonometer force measurements between 1.00 and 2.00 kg. Conclusions: Myotonometer and sEMG measurements were highly correlated. Tissue stiffness, as measured by the Myotonometer, appears capable of assessing changes in muscle activation levels.

Surface electromyography diagnostics in women with partial vaginismus with or without vulvar vestibulitis and in asymptomatic women

The aim of this study was to investigate to what extent women with superficial dyspareunia can be diagnosed for both partial vaginismus (PaV) and vulvar vestibulitis (VVS) and to discover to what extent surface electromyography (sEMG) of the pelvic floor muscles (PFM) can distinguish between women with PaV solely, PaV + VVS, and asymptomatic women. A total of 224 consecutive women with superficial dyspareunia were examined clinically for both PaV and VVS diagnoses. We examined 47 women with PaV ± VVS and 27 asymptomatic women with sEMG of the PFM. The results showed that 102/224 women with superficial dyspareunia and 33/47 women with PaV in the sEMG part of the study had both PaV and VVS. All women with VVS had vaginismus, while 42/224 had PaV but not VVS. sEMG measurements revealed no significant differences between the three groups of women (PaV solely, PaV + VVS, and asymptomatic). Almost half of the women with superficial dyspareunia referred to our clinic have both the diagnosis PaV and VVS. sEMG was not a method of any value to distinguish between women with PaV solely, PaV + VVS, or asymptomatic women. The increased tone found clinically in the PFM of women with PaV ± VVS may be of other origin than electrogenic contractions.

Multichannel surface EMG: Basic aspects and clinical utility

The generation of the surface electromyogram (sEMG) is described with regard to the properties of the single muscle fiber action potential as source, the physical aspects of volume conduction and recording configuration, and the properties and firing pattern of motor units (MUs). The spatial aspect of the motor unit action potential (MUP) is emphasized in relation to the results of high-density, multichannel sEMG measurements. The endplate zone, depth, size, and position of MUs can be estimated. The use of muscle fiber conduction velocity measurements in channelopathies and the changes in pathological fatigue are described. Using the unique patterns of spatial spread of MUPs over the skin (MU fingerprint), MU classification and the determination of firing moments is done noninvasively. Clinical applications of high-density sEMG measurements are reviewed. Emerging possibilities provided by MUP size and fingerprint measurements in neuromuscular disease and motor control are discussed. We conclude that multichannel sEMG adds unique, and sometimes indispensable, spatial information to our knowledge of the motor unit.

Application of Principal Components Analysis for Evaluation and Classification of Complex Emg Data

Many biomechanical models used to produce injury risk estimates for the lower trunk require lower trunk muscle forces as inputs. These forces are typically estimated through the use of surface electromyography (sEMG). The variability inherent in sEMG measurements can, and should, be analyzed to determine the possible presence and sources of excessive variation in the data. Principal components analysis (PCA) provides a robust and straightforward method for performing an analysis of the variability of complex sEMG datasets. This paper describes the results obtained from the application of PCA to a dataset consisting of activation levels for several lower trunk muscles. The results demonstrate the value of the technique in identifying clusters of observations in the data and in simplifying the multidimensional dataset. The use of PCA as a hypothesis generation tool is also explored.

Cervical flexion: A study of dynamic surface electromyography and range of motion

Background: In the comprehensive assessment of painful conditions, dynamic surface electromyography (sEMG) and range of motion (ROM) recordings can provide information regarding muscle spasm, antalgic postures, fear of pain (protective guarding), muscle injury, and disordered movement caused by pain. This study examines ROM and sEMG patterns observed during cervical flexion. Objective: To demonstrate 2 distinctive sEMG recruitment and dynamic ROM patterns observed during cervical flexion and return to mid-line. Design: Single-subject design with independent measurement of dynamic ROM and sEMG. Setting: Applied clinical setting. Participants: Two subjects with normal ROM and cervical muscles were studied. Main Outcome Measure: One subject was studied with sEMG, looking at the cervical paraspinals and sternocleidomastoid muscles; the other subject was studied with an active ROM device. Three cervical movements were studied: lower cervical flexion, atlantoaxial (upper) cervical flexion, and a combination upper/lower cervical flexion. Results: The active ROM device indicates larger movements (higher degress of flexion) for the lower cervical flexion compared with upper flexion. The combined movement indicates a differential movement from 2 spinal segments. The sEMG recordings indicated differential recruitment patterns. The sternoclei-domastoid recruits briskly during the flexion phase of the upper cervical flexion movement, whereas the cervical paraspinals recruit briskly during return to mid-line when the lower cervical flexion is used. The combined upper then lower cervical flexion movement recruits both sets of muscles. Conclusions: The results of the study indicate 2 distinct movement patterns associated with upper versus lower cervical flexion and 2 distinct sEMG recruitment patterns. The study suggests that these 2 distinct movements involve 2 distinct cervical segments and are associated with recruitment of different muscle groups. Applied clinical research on the cervical spine should use sEMG recordings to assess both the upper and lower flexion movements as the standard for the study of cervical flexion. (J Manipulative Physiol Ther 1999;22:570–5)

Simple test of pelvic muscle contraction during pelvic examination: Correlation to surface electromyography

The objective of this work was to evaluate the utility of a "Kegel" contraction test in a primary care setting. Fifty-seven adult women completed a questionnaire, underwent pelvic examination, "Kegel" assessment, and measurement of same by vaginal sensor electromyography. Thirty-seven underwent repeat evaluations within 4 weeks. Inter- and intra-rater reliability of digital scale, intra-rater reliability for sEMG measurement, correlation between raters and sEMG, and correlation between scale scores and sEMG with history and pelvic exam were determined. Fifty-six percent were pre-menopausal, 44% post-menopausal. Urinary (62%) and rectal (37%) dysfunction were reported. Inter-rater reliability, intra-observer reproducibility for both raters and sEMG measurements, and correlation between raters and sEMG were significant (P< 0.05). Comparison of continence status and digital scores showed scores </=4 were more frequently associated with reported urinary incontinence (P<0.05). sEMG data also correlated to hormonal status and parity (P < 0.05). This digital scale is a useful assessment of "Kegel" contraction, correlating well to sEMG vaginal sensor readings and self-reported overall urinary continence status. Neurourol. Urodynam. 18:603-612, 1999.