Interference Electromyography Research Articles

Neuromuscular Adaptations in Response to Disuse and Weight-Training Rehabilitation are Enhanced in Resistance Trained Individuals

INTRODUCTION: Lower-limb disuse from immobilization results in a decrease in muscle strength, volume, and function. However, muscle atrophy from disuse does not entirely account for the observed strength and functional declines. Additionally, prior engagement in resistance training (RT) has been linked to the preservation of muscular strength and neuromuscular function. Therefore, the purpose of this study was to assess the influence of a single-leg immobilization protocol, followed by structured RT rehabilitation protocol, on muscle strength, volume, and neural activation in healthy young adults with and without previous strength training experience. Methods: Participants (10 Trained (T): 8 men, 2 women; 11 Untrained (UT): 8 men, 3 women) underwent 2-weeks of left-knee immobilization at 90° knee-flexion with a hinged immobilizer knee-brace. Participants were given a pair of axillary crutches for ambulation during this time. Following immobilization, all participants underwent an 8-week structured RT rehabilitation protocol. Participants visited the laboratory for three testing sessions (baseline test on Day 0; post-immobilization at the end of week 2; and post-RT rehab at the end of week 10). Maximal knee extensor isometric strength at 45°was quantified using an isokinetic dynamometer (Biodex). Voluntary muscle activation was quantified as the root mean square (RMS) of the interference electromyography (EMG) signals derived from two indwelling fine-wire electrodes in the vastus-lateralis muscle. Additionally, a continuous wavelet transform (CWT) was performed on the EMG to determine amplitude versus frequency characteristics of the signals and how this amplitude varied with time in the 13-30 (beta) and 30-60 (piper) Hz bands. Mid-thigh muscle cross-sectional area (mCSA) and density were also quantified using peripheral quantitative computed tomography (pQCT) during all testing sessions. Results: The T group was significantly stronger (p=0.019), had greater muscle density (p=0.005) and mid-thigh mCSA (p<0.001) across all sessions when compared with the UT group. However, there were no significant time or interaction effects for strength or muscle density losses (p>0.05). While both groups demonstrated increased muscle activation across sessions (RMS: p=0.04; CWT: p=0.021), the T group demonstrated a greater increase in the neural drive from baseline to week 10 when compared with the UT group (RMS: p= 0.002; CWT: p=0.027). CONCLUSION: In younger adults with or without prior strength training experience, we find that losses in knee extensor isometric strength, muscle density, and mid-thigh mCSA are minimal following a 2-week immobilization protocol. However, certain neuromuscular adaptations during immobilization and following weight-training rehabilitation are enhanced to a greater degree in those with prior training, which is seemingly indicative of greater synchrony in descending cortical drive and motor unit recruitment. These latter findings warrant continued investigation using additional innovative methodologies (e.g., fMRI, TMS, etc.) for assessing the mechanisms underlying the effects of prehab protocols on neuromuscular adaptations. PGRF and Nix family foundation scholarship to Marina Meyer. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Functional testing of the lower extremity muscles

The purpose of the study was to increase the efficiency of diagnostics of the strength indicators of the lower extremity muscles by determining the optimal conditions for the mutual location of segments of kinematic links for the best implementation of contractile capabilities during functional testing. The main focus of the work was to determine the positions for the maximum overlaying of myofilaments in the sarcomeres of the investigated contractile areas of the movable segments of the lower extremities during power loads. 20 experienced football players, whose average age was 26.8±6.2 years, took part in the study. In order to fulfill the set goal, interference electromyography was performed on all athletes. The function of a separate group of muscles was considered in accordance with the endogenous ability to overcome external resistance in a given direction. Dependence of contractile manifestations was coordinated in accordance with the approach or distance of areas of attachment of muscles. The positions of the muscles were regulated by the ventral and sagittal planes, as well as by the average amplitude of rotation. On the basis of the ratio of maximum, average amplitudes and frequency, data regarding the maximum overlaying of myofilaments in sarcomeres (maximum bioelectric activity), in accordance with the position angle of the movable segment of the lower extremity were obtained. It was established that for conducting functional testing, the location of the trunk and lower extremities in the same plane of movement and axis were the optimal positions for the diarticular muscles of the thigh and lower leg; for monoarticular extensors of the lower leg - a position at a right angle between the lower leg and thigh; for rotators of the lower leg and foot - location of these segments in a plane parallel to the sagittal one. On the basis of the obtained data, the optimal conditions for the mutual location of the segments of the kinematic links for the realization of the contractile capabilities of the muscles of the lower extremities have been determined, a protocol for functional testing of the muscles of the lower extremities has been developed, it is presented in graphic form with the possibility of entering data from both limbs, while test points of rotator muscles of the thigh and lower leg have been added.

MYOGRAPHY TECHNIQUE IN INVESTIGATING OROFACIAL MUSCULES IN HEARING-IMPAIRED PATIENTS (LITERATURE REVIEW)

This article briefly reviews the literature describing the application of electoromyography technique to investigate the muscles of the orofacial region. Muscle characteristics are an indicator of complex functional relationships of the dentofacial system. Disorders of muscle function lead to morphological changes in the normal structure of the teeth and bones of the maxillofacial area, as well as exacerbate existing bite pathologies. Today, the electromyography is considered as the latest, objective, and informative method of functional diagnostics of the dentofacial system. This study is an evidence-based method for diagnosis and evaluation of the treatment outcomes in orthodontics, and guarantees an unbiased and objective analysis of the functional state of the patient's maxillofacial apparatus at different stages: from diagnosis to treatment and after its completion. Interference electromyography, a non-invasive technique, is known as the most commonly applied in various fields of dentistry. In orthodontics, interference electromyography is used to control the remodelling of the coordination relationships between the temporal and masticatory muscles in the treatment of malocclusion. In orthodontics, the mandibular levators are of great importance, especially the masticatory muscle, the temporal muscle, the medial pterygoid muscle, and the lateral pterygoid muscle. The sublingual muscle also plays an important role in determining facial morphology. This muscle is responsible for stretching the tongue. Facial muscles, such as the orbicularis oris muscle, are also very important in orthodontics. In patients with hearing deprivation not all the muscles work, only some facial muscles function during speech. The scientific literature presents quite a few studies on the function of the facial and masticatory muscles in orthodontic patients with hearing deprivation, both in children and adults, indicating a greater activity of the masticatory muscles in such patients. However, there is no single scientific conception about the work of the orbicular oris muscle.

Only the Fastest Corticospinal Fibers Contribute to β Corticomuscular Coherence.

Human corticospinal transmission is commonly studied using brain stimulation. However, this approach is biased to activity in the fastest conducting axons. It is unclear whether conclusions obtained in this context are representative of volitional activity in mild-to-moderate contractions. An alternative to overcome this limitation may be to study the corticospinal transmission of endogenously generated brain activity. Here, we investigate in humans (N = 19; of either sex), the transmission speeds of cortical β rhythms (∼20 Hz) traveling to arm (first dorsal interosseous) and leg (tibialis anterior; TA) muscles during tonic mild contractions. For this purpose, we propose two improvements for the estimation of corticomuscular β transmission delays. First, we show that the cumulant density (cross-covariance) is more accurate than the commonly-used directed coherence to estimate transmission delays in bidirectional systems transmitting band-limited signals. Second, we show that when spiking motor unit activity is used instead of interference electromyography, corticomuscular transmission delay estimates are unaffected by the shapes of the motor unit action potentials (MUAPs). Applying these improvements, we show that descending corticomuscular β transmission is only 1-2 ms slower than expected from the fastest corticospinal pathways. In the last part of our work, we show results from simulations using estimated distributions of the conduction velocities for descending axons projecting to lower motoneurons (from macaque histologic measurements) to suggest two scenarios that can explain fast corticomuscular transmission: either only the fastest corticospinal axons selectively transmit β activity, or else the entire pool does. The implications of these two scenarios for our understanding of corticomuscular interactions are discussed.SIGNIFICANCE STATEMENT We present and validate an improved methodology to measure the delay in the transmission of cortical β activity to tonically-active muscles. The estimated corticomuscular β transmission delays obtained with this approach are remarkably similar to those expected from transmission in the fastest corticospinal axons. A simulation of β transmission along a pool of corticospinal axons using an estimated distribution of fiber diameters suggests two possible mechanisms by which fast corticomuscular transmission is achieved: either a very small fraction of the fastest descending axons transmits β activity to the muscles or, alternatively, the entire population does and natural cancellation of slow channels occurs because of the distribution of axon diameters in the corticospinal tract.

Individual differences in the neural strategies to control the lateral and medial head of the quadriceps during a mechanically constrained task.

The interindividual variability in the neural drive sent from the spinal cord to muscles is largely unknown, even during highly constrained motor tasks. Here, we investigated individual differences in the strength of neural drive received by the vastus lateralis (VL) and vastus medialis (VM) during an isometric task. We also assessed the proportion of common neural drive within and between these muscles. Twenty-two participants performed a series of submaximal isometric knee extensions at 25% of their peak torque. High-density surface electromyography recordings were decomposed into motor unit action potentials. Coherence analyses were applied on the motor unit spike trains to assess the degree of neural drive that was shared between motor neurons. Six participants were retested ∼20 mo after the first session. The distribution of the strength of neural drive between VL and VM varied between participants and was correlated with the distribution of normalized interference electromyography (EMG) signals (r > 0.56). The level of within- and between-muscle coherence varied across individuals, with a significant positive correlation between these two outcomes (VL: r = 0.48; VM: r = 0.58). We also observed a large interindividual variability in the proportion of muscle-specific drive, that is, the drive unique to each muscle (VL range: 6%-83%, VM range: 6%-86%). All the outcome measures were robust across sessions, providing evidence that the individual differences did not depend solely on the variability of the measures. Together, these results demonstrate that the neural strategies to control the VL and VM muscles widely vary across individuals, even during a constrained task.NEW & NOTEWORTHY We observed that the distribution of the strength of neural drive between the vastus lateralis and vastus medialis during a single-joint isometric task varied across participants. Also, we observed that the proportion of neural drive that was shared within and between these muscles also varied across participants. These results provide evidence that the neural strategies to control the vastus lateralis and vastus medialis muscles widely vary across individuals, even during a mechanically constrained task.

ELECTROGMYOGRAPHIC FEATURES OF MUSCLES SOLEUS IN PEOPLE WITH THE INCREASED SENSITIVITY OF THE VESTIBULAR ANALYZER

The article deals with the features of electromyographic indicators of the soleus muscles while maintaining a upright position in people with increased vestibular sensitivity. From the literature, it is concluded that the study of electromyographic features of indicators in the conditions of irritation of the vestibular analyzer in people with different vestibular sensitivity is an important area in physiology. Vestibular sensitivity was determined by the questionnaire, Voyachek's sample and Fukuda's written test. To assess the electromyographic activity of the soleus muscles, a computer DX complex was used for registration of interference electromyography. Registration was carried out during performing Romberg test, before and after vestibular loading. According to the results of the vestibular irritation, there was a greater decrease in the amplitude of the flap muscles of the lower extremities in persons with the increased vestibular sensitivity than in people with the adequate sensitivity. Based on the results achieved, it can be assumed, that in people with the increased sensitivity of the vestibular analyzer, the irritation of the receptors of the semicircular canals alters the activity of extensor motoneurons of the human spinal cord more significantly than in persons with the adequate sensitivity.

Patient myofunctional adaptation to orthodontic treatment

Myofunctional condition of the temporomandibular joint (TMJ) in everyday orthodontic practice is an important diagnostic criterion for evaluating the quality of orthodontic treatment. Pre-orthodontic preparation is often a necessary stage of orthodontic treatment. To evaluate and compare the adaptation of the masticatory muscles of patients during pre-orthodontic preparation based on interference electromyography of the masticatory and temporal muscles with the data of patients after orthodontic treatment without preparation and with the indicators in the control group. Electromyography indicators of the masticatory and temporal muscles of 82 patients aged 18 to 35 were obtained. Patients were divided into 3groups: 1st - with signs of TMJ dysfunction at the stage of pre-orthodontic preparation and orthodontic treatment; 2nd - patients after orthodontic treatment, having dissatisfaction with the state of the dentition; 3rd - a control group was compared composed of patients without signs of myofunctional dysfunction. Patients who have complaints after orthodontic treatment have different electromyography of the masticatory and temporal muscles in comparison with the control group. In patients with signs of TMJ dysfunction at the stage of preorthodontic preparation, after using a device of their own design, the structures of the temporomandibular joint were adapted to a new functional position. After using the device of its own design, myofunctional adaptation to a new functional position was obtained, which is confirmed by electromyographic studies.

Shannon entropy in the research on stationary regimes and the evolution of complexity

The questions of the identification of complex biological systems (complexity) as special self-organizing systems or systems of the third type first defined by W. Weaver in 1948 continue to be of interest. No reports on the evaluation of entropy for systems of the third type were found among the publications currently available to the authors. The present study addresses the parameters of muscle biopotentials recorded using surface interference electromyography and presents the results of calculation of the Shannon entropy, autocorrelation functions, and statistical distribution functions for electromyograms of subjects in different physiological states (rest and tension of muscles). The results do not allow for statistically reliable discrimination between the functional states of muscles. However, the data obtained by calculating electromyogram quasiatttractor parameters and matrices of paired comparisons of electromyogram samples (calculation of the number k of “coinciding” pairs among the electromyogram samples) provide an integral characteristic that allows the identification of substantial differences between the state of rest and the different states of functional activity. Modifications and implementation of new methods in combination with the novel methods of the theory of chaos and self-organization are obviously essential. The stochastic approach paradigm is not applicable to systems of the third type due to continuous and chaotic changes of the parameters of the state vector x(t) of an organism or the contrasting constancy of these parameters (in the case of entropy).

Neuromuscular state of children of different gestational ages during transition from intrauterine immersion to earth’s gravity

This study describes the neuromuscular state of premature babies in the context of the ontogenetic gravity and zero gravity model using the results of superficial interference electromyography (IEMG). During six postnatal weeks, the IEMG of premature babies is similar to the EMG of a full-term baby during the first days of extrauterine life; it is characterized by a “simplified” temporal structure, as well as low amplitude and frequency. The IEMG dynamics of a premature baby is slow, in contrast to that one in a full-term baby. This is, probably, due to the fact that the locomotion system of the latter is better prepared and more mature after spending as much time as possible in an intrauterine state. On the other hand, complexity and high amplitude of the IEMG in a premature baby, compared to a full-term baby of the same postconceptual age, are associated with the inevitable sensory stimulation after birth. Abilitation procedures provided to a premature baby could be adapted to the purposes of post-flight rehabilitation of astronauts.

Electromyographic characteristics of women in different phases of the menstrual cycle, depending on season and type of autonomic regulation

Quantitative characteristics of the neuromuscular state in women (n = 23; age, 19.9 ± 1.4 years) were studied in four (early and late follicular, ovulatory, and luteal) phases of the menstrual cycle, in the spring and autumn/winter seasons, depending on the type of regulation of the autonomic nervous system, based on linear and novel nonlinear parameters of interference electromyography in m. biceps br. and the activity of the motor units of m. triceps br. Statistically significant differences in the neuromuscular state, such as a decrease in all nonlinear parameters, i.e., simplification of the temporal structure of the interference electromyography signal and an increase in the frequency of impulses of motor units, are due to the combined effect of the ovulatory phase and the spring season. In addition, the greatest influences on the neuromuscular state were recorded in subjects with the vagotonic type of regulation of the autonomic nervous system.

Влияние возраста после зачатия на характеристики интерференционной электромиограммы у новорожденных детей

The purpose of the study was to investigate neuromuscular status in the preterm infants using surface electromyography (EMG). 10 preterm (gestational age 31/32 weeks) and 10 term infants (gestational age 38/39 weeks) participated in the study on the 2nd, 4th and 6th postnatal week. Linear and novel non-linear parameters of were used to quantitize interference EMG (iEMG) in 4 muscles (mm. bic. br. dext., tric. br. dext, tib. ant. sin., gastr. sin. In the preterm infants aged 33-37 weeks both linear and non-linear sEMG parameters were significantly lower in comparison with the term infants. Thus, sEMG of the preterm infants was characterized by a more "primitive" time-domain structure, lower amplitude and spectrum frequency. Also, unlike to term newborns, in the preterm infants the lifetime dynamics ofsEMG parameters was retarded. Thus, the motor system of the preterm infant is likely less prepared to the postnatal life due to shorter existence in utero. Nonetheless, sEMG of the preterm infants may be characterized as a more "complex" in comparison with the term newborns of the same post-conceptual age. It may be attributed to new postnatal sensory stimuli.

Increased voluntary drive is associated with changes in common oscillations from 13 to 60 Hz of interference but not rectified electromyography

The purpose of this study was to compare the capability of interference and rectified electromyography (EMG) to detect changes in the beta (13-30-HZ) and Piper (30-60-HZ) bands when voluntary force is increased. Twenty adults exerted a constant force abduction of the index finger at 15% and 50% of maximum. The common oscillations at various frequency bands (0-500 HZ) were estimated from the first dorsal interosseous muscle using cross wavelets of interference and rectified EMG. For the interference EMG signals, normalized power significantly (P < 0.01) increased with force in the beta (9.0 +/- 0.9 vs. 15.5 +/- 2.1%) and Piper (13.6 +/- 0.9 vs. 21 +/- 1.7%) bands. For rectified EMG signals, however, the beta and Piper bands remained unchanged (P > 0.4). Although rectified EMG is used in many clinical studies to identify changes in the oscillatory drive to the muscle, our findings suggest that only interference EMG can accurately capture the increase in oscillatory drive from 13 to 60 HZ with voluntary force.

Muscle Fatigue during Dynamic Contractions Assessed by New Spectral Indices

The aim of the present study was to test the applicability and sensitivity of new electromyography (EMG) spectral indices in assessing peripheral muscle fatigue during dynamic knee-extension exercise. Seven subjects completed 10 sets of 15 repetitions of right knee-extension exercise lifting 50% of their one-repetition maximum. Torque (T), knee-joint angle, and the interference EMG of rectus femoris muscle were recorded simultaneously. Maximal voluntary isometric contraction (MVC) was tested before and after exercise. Median spectral frequency (Fmed) and new spectral indices of muscle fatigue (FInsmk) were calculated for each repetition. The rate and range of FInsmk- and Fmed-relative changes against the first repetition of the corresponding set increased gradually across successive repetitions within the set, reflecting accumulation of peripheral muscle fatigue. The maximal change of FInsmk observed in the present experiment was approximately eightfold, whereas that of Fmed was only 32%. Significant between-subject variability in the range of FInsmk changes (P < 0.0001) was found, so a hierarchical cluster analysis of muscle fatigue indices was conducted. Three distinct subgroups of subjects were identified: high (N = 1, FInsmk change > 400%), medium (N = 4, 200% < FInsmk change < 400%), and low (N = 2, FInsmk change < 200%) muscle fatigability. The changes in muscle performance during (last vs first repetition peak T, P = 0.03) and after (post- vs preexercise MVC, P = 0.012) exercise were significantly different between clusters (one-way ANOVA). The rate of fatigue development was also significantly different between clusters (linear regression analysis of Fmed and FInsmk changes). The new spectral indices are a valid and reliable tool for assessment of muscle fatigability irrespective of EMG signal variability caused by dynamic muscle contractions, and these indices are more sensitive than those traditionally used.