Muscle Electrical Activity Research Articles

Clinical Data-Driven Finite Element Analysis of the Kinetics of Chewing Cycles in Order to Optimize Occlusal Reconstructions

The occlusal design plays a decisive role in the fabrication of dental restorations. Dentists and dental technicians depend on mechanical simulations of mandibular movement that are as accurate as possible, in particular, to produce interference-free yet chewing-efficient dental restorations. For this, kinetic data must be available, i.e., movements and deformations under the influence of forces and stresses. In the present study, so-called functional data were collected from healthy volunteers to provide consistent information for proper kinetics. For the latter purpose, biting and chewing forces, electrical muscle activity and jaw movements were registered synchronously, and individual magnetic resonance tomograms (MRI) were prepared. The acquired data were then added to a large complex finite element model of the complete masticatory system using the functional information obtained and individual anatomical geometries so that the kinetics of the chewing process and teeth grinding could be realistically simulated. This allows developing algorithms that optimize computer-aided manufacturing of dental prostheses close to occlusion. In this way, a failure-free function of the dental prosthesis can be guaranteed and its damage during usage can be reduced or prevented even including endosseous implants.

Masticatory efficiency, bite force and electrical activity of the masseter and temporalis muscles in bodybuilders.

BackgroundThis study aimed to compare the masticatory efficiency, the maximum voluntary occlusal bite force (MVOBF) and the electrical activity (EMG) of masticatory muscles of practitioners of upper limb bodybuilding before and after physical activity. Material and MethodsTwenty healthy individuals (10 men and 10 women, age from 18 to 30 (mean of 24.7 years old) without masticatory system disorders, that regularly practice hypertrophic physical activity were submitted to the analyses of masticatory efficiency, MVOBF, and surface EMG of the temporalis and masseter muscles. The masticatory efficiency was analyzed by comminution of the artificial material (Optocal®) and a sieving method. The MVOBF was measured by a dynamometer, and EMG was evaluated during resting mandibular position, maximum voluntary clenching (MVC), and MVC with a Parafilm M tape between teeth, and free mastication of chewing gum. The analyses were made before (T0) and immediately after the performance of upper limb bodybuilding exercises (T1). The data of masticatory efficiency and MVOBF were submitted to the Student T-test, and their correlations were analyzed by the Pearson correlation test, and the EMG data were submitted to the 2-way repeated measures ANOVA, all tests with a 5% significance. ResultsThere was a significant decrease of masticatory efficiency after the training. No statistical difference in the MVOBF and EMG was found, and there was a positive correlation between masticatory efficiency and MVOBF. ConclusionsTherefore, changes were found for masticatory efficiency only, which decreased after hypertrophic exercise. There was a positive correlation between masticatory efficiency and MVOBF. Key words:Masticatory efficiency, bite force, physical activity, electromyography.

Состояние нейромоторного аппарата нижних конечностей у детей с болезнью Легга — Кальве — Пертеса

With the methods of global and stimulation electromyography, we examined 10 healthy boys aged 7 to 9 y. o. and 10 boys of the same age with a unilateral damage of a hip joint at the III–IV stages of Legg — Calve — Perthes disease. Compared to healthy subjects, all the examined patients had reduced amplitude of the evoked electrical activity of a quadriceps muscle of thigh and a soleus muscle, as well as increased thresholds and reduced maximal amplitude of М— and Н-responses of the soleus muscle. Prolonged epidural analgesia led to the increase of the amplitude of the evoked electrical activity in the soleus muscle only. At the same time, the thresholds of Н-responses of the soleus muscle were reduced and the share of reflexively stimulated motoneurons innervating it increased. Thus, the carried out treatment generally improved the condition of the central link of the neuromotor apparatus.

Analysis of Dynamics of EMG Signal Variations in Fatiguing Contractions of Muscles Using Transition Network Approach

The measurement and analysis of the electrical activity of muscle provide information that aids in the control of assistive devices. The investigation of these signals under varied physiological conditions, such as fatigue, enables reliable control. Muscle fatigue is a muscular condition associated with loss of muscle function. The early detection of muscle fatigue using surface Electromyography (sEMG)-based electrical measurements is challenging due to the nonlinear variations of the signal. In this work, an attempt has been made to understand the effect of dynamic nonlinear variations in the characteristics of the signal to develop a reliable fatigue index. The methodology involves the acquisition of myoelectric signals from the biceps brachii muscle of 52 healthy participants during dynamic contractions. The acquired signals are preprocessed and are analyzed with symbolic transition networks. Features such as symbolic entropy, network entropy, uniformity, and, minimum and maximum effective degrees (EDs) are extracted for further analysis. Appropriate decision boundaries are established for each feature using receiver operator characteristics (ROCs) and machine learning algorithms. The results indicate a decrease in signal complexity with fatigue. All the extracted features show a statistically significant difference (p < 0.05) between both conditions. Symbolic entropy achieves an accuracy of 89%, and the maximum ED yields an accuracy of 90% based on thresholds estimated with ROC. Furthermore, only a marginal improvement is observed with the combination of these features and the Naive Bayes classifier. It appears that the proposed maximum ED could be used as a reliable fatigue index in real-time applications for the improvement of rehabilitation efficacy.

Electromyographic evidence of reduced emotion mimicry in individuals with a history of non-suicidal self-injury.

Engaging in facial emotion mimicry during social interactions encourages empathy and functions as a catalyst for interpersonal bonding. Decreased reflexive mirroring of facial expressions has been observed in individuals with different non-psychotic disorders, relative to healthy controls. Given reports of interpersonal relationship difficulties experienced by those who engage in non-suicidal self-injury (NSSI), it is of interest to explore facial emotion mimicry in individuals with a history of this behaviour (HNSSI). Among other things, this will enable us to better understand their emotion regulation and social interaction challenges. Surface facial electromyography (fEMG) was used to record the reflexive facial mimicry of 30 HNSSI and 30 controls while they passively observed a series of dynamic facial stimuli showing various facial expressions of emotion. Beginning with a neutral expression, the stimuli quickly morphed to one of 6 prototypic emotional expressions (anger, fear, surprise, disgust, happiness, or sadness). Mimicry was assessed by affixing surface electrodes to facial muscles known to exhibit a high degree of electrical activity in response to positive and negative emotions: the corrugator supercilii and the zygomaticus major. HNSSI participants, relative to controls, exhibited significantly less electrical activity in the corrugator muscle in response to viewing angry stimuli, and significantly less of an expected relaxation in muscle activity in response to viewing happy stimuli. Mirroring these results, greater endorsement of social influence as a motivator for engaging in NSSI was associated with less mimicry, and greater endorsement of emotion regulation as a motivator was associated with greater incongruent muscle response when viewing happy faces. These findings lend support to the theory that social interaction difficulties in HNSSI might be related to implicit violations of expected social rules exhibited through facial mimicry nonconformity.

The condition of the respiratory muscles in obstructive sleep disordered breathing according to electromyographic data

Aim . To study functional state of respiratory muscles in patients with obstructive sleep-disordered breathing (oSDB) of varying severity based on changes in electrical activity when using a stepwise-increasing respiratory load. Materials and methods . According to results of cardiorespiratory monitoring, the examined patients were divided into 4 groups. Group 1 included 16 patients without oSDB, group 2 – 16 patients with mild oSDB, group 3 – 8 patients with moderate oSDB, group 4 – 8 patients with severe oSDB. The assessment of electrical activity of inspiratory muscles and expiratory muscles was carried out using electromyography (EMG) when performing tests with a stepwise-increasing inspiratory and expiratory load. Results . During inspiratory test, a decrease in EMG frequency was observed, indicating respiratory muscles fatigue development, with a simultaneous increase in EMG amplitude due to the involvement of additional motoneurons in muscle contraction. In all cases, degree of increase in EMG amplitude prevailed over degree of decrease in EMG frequency. In patients of groups 3 and 4, there were no signs of diaphragm fatigue. Results of expiratory test in group 1, degree of increase in EMG amplitude prevailed over degree of decrease in EMG frequency. In the groups of patients with oSDB, prevalence of decrease in the EMG frequency over increase in EMG amplitude was observed, which indicates development of neuromuscular fatigue of expiratory muscles. Conclusion . Changes in functional state of respiratory muscles are associated with severity of oSDB and are characterized by different dynamics of the electrical activity of inspiratory and expiratory muscles in response to a functional test.

Masticatory muscles electrical activity, stress and posture in preadolescents and adolescents with and without temporomandibular dysfunction

ObjectiveTo verify the difference between the masticatory muscles’ electrical activity, stress signals and the posture of preadolescents and adolescents with and without temporomandibular dysfunction (TMD). Methods24 preadolescents and adolescents aged between 11 and 18 years old were divided into two groups, TMD group (TMDG) and control group (CG). All subjects were submitted to anthropometric measurements, psychological stress analysis, temporomandibular joint clinical evaluation and TMD verification; postural evaluation and masseter and temporal muscles electrical activity analysis during chewing. For statistical analysis, the Student's t-test or Mann-Whitney U test were used according to data distribution. ResultsThere was a significant difference between the groups for the electrical activity of the right temporal muscles (7.43% ± 2.92 vs. 11.71% ± 5.37) and left (7.70% ± 4.04 vs.11.44% ± 4.03) in the inactive period of chewing between CG and TMDG, respectively. There was no difference in stress or posture variables between groups. ConclusionsDuring the inactive period of chewing, there was greater activation of the temporal muscles in the TMDG. Female gender was prevalent in TMDG. The study participants showed signs of stress, regardless of the group. The posture and TMD relationship still need to be studied.

Function test of the activity and interrelations of lower extremity muscles of football players with the use of surface electromyography method

Efficient performance of physical activity is becoming a vital trend in modern football, which requires maximum objectification of the functional state of muscles. Aim: studying the electrical activity and functional relationships of sartorius and crurae muscles involved in phase movements of walking (running) by the method of multichannel registration of surface electromyogram (SEMG). Materials and methods: the study engaged the students of KSMU attending the football section and participating in football matches (n = 12). The electrical activity (EA) of the muscles involved in the implementation of walking (running): biceps femoris, musculus semimembranosus of the thigh and tibilais anterior muscle was registered. EA research was conducted with maximum volitional muscle tension. The recording was conducted using an 8-channel electroneuromyograph Neuro-MVP-8 prior to the football training and 30-60 minutes after. The data obtained were checked using Shapiro - Wilk tests. Ansari-Bradley test was used for small groups. Lastly, Kendall correlation coefficient was calculated to evaluate the functional relationships between the parameters of muscle EA. Results : The most significant changes in EA parameters after training consisted in their correlation. The presence of medium negative correlations between musculus semimembranosus of the thigh on right and left (r = -0.349) and the absence of correlation between the latter in the amplitude of EA were registered. Concurrently, positive correlations were noted between the EA parameters of the biceps femoris and semimembranosus (values ram.= 0,204, rfreq.= 0,226), as well as biceps femoris and tibilais (values ram.= 0,486, rfreq.= 0,452) of the left feet of football players. Conclusion: SEMG allows you to quantify the changes in electrical activity and functional connection of the muscles of the thigh and crurae involved in stepping and running. A realignment of the functional muscle complexes appears, which contributes to motor actions and implementation of dribbling after a training.

Acute effects of functional dry needling on skeletal muscle function

IntroductionFunctional dry needling (FDN) is commonly used to treat soft tissue pain-related conditions. Previous research has demonstrated benefits to chronic resistance training; however, objective physiological measures sensitive to acute exercise have not been found. The purpose of this study was to evaluate the acute effects of FDN on muscle strength and endurance. MethodsTen subjects (height 168 ± 9 cm, mass 68.2 ± 11.3 kg) were tested bilaterally (pre and post) for vastus lateralis (VL) isometric strength, isokinetic fatigue index, muscle electrical activity, and muscle oxygenation. FDN was administered to one leg, while the other served as a control. ResultsLimited acute effects of functional dry needling were observed (p < 0.05). DiscussionFDN does not appear to acutely improve muscle function in healthy young adults. Although there were no improvements in muscle function, there were no adverse effects either, contributing to the safety of FDN healthy populations. ConclusionAcute FDN does not appear to enhance muscle performance in a healthy, non-clinical population. Thus, clinicians should consider the population and desired outcome when applying FDN.

Evaluation of Synergy Extrapolation for Predicting Unmeasured Muscle Excitations from Measured Muscle Synergies.

Electromyography (EMG)-driven musculoskeletal modeling relies on high-quality measurements of muscle electrical activity to estimate muscle forces. However, a critical challenge for practical deployment of this approach is missing EMG data from muscles that contribute substantially to joint moments. This situation may arise due to either the inability to measure deep muscles with surface electrodes or the lack of a sufficient number of EMG channels. Muscle synergy analysis (MSA) is a dimensionality reduction approach that decomposes a large number of muscle excitations into a small number of time-varying synergy excitations along with time-invariant synergy weights that define the contribution of each synergy excitation to all muscle excitations. This study evaluates how well missing muscle excitations can be predicted using synergy excitations extracted from muscles with available EMG data (henceforth called “synergy extrapolation” or SynX). The method was evaluated using a gait data set collected from a stroke survivor walking on an instrumented treadmill at self-selected and fastest-comfortable speeds. The evaluation process started with full calibration of a lower-body EMG-driven model using 16 measured EMG channels (collected using surface and fine wire electrodes) per leg. One fine wire EMG channel (either iliopsoas or adductor longus) was then treated as unmeasured. The synergy weights associated with the unmeasured muscle excitation were predicted by solving a nonlinear optimization problem where the errors between inverse dynamics and EMG-driven joint moments were minimized. The prediction process was performed for different synergy analysis algorithms (principal component analysis and non-negative matrix factorization), EMG normalization methods, and numbers of synergies. SynX performance was most influenced by the choice of synergy analysis algorithm and number of synergies. Principal component analysis with five or six synergies consistently predicted unmeasured muscle excitations the most accurately and with the greatest robustness to EMG normalization method. Furthermore, the associated joint moment matching accuracy was comparable to that produced by initial EMG-driven model calibration using all 16 EMG channels per leg. SynX may facilitate the assessment of human neuromuscular control and biomechanics when important EMG signals are missing.

Characterization of alternating neurogenic motor patterns in mouse colon.

Colonic motor complexes (CMCs) have been widely recorded in the large intestine of vertebrates. We have investigated whether in the smooth muscle, a single unified pattern of electrical activity, or different patterns of electrical activity give rise to the different neurogenic patterns of motility underlying CMCs in vitro. To study differences of the CMCs between proximal and distal colon, we used a novel combination of techniques to simultaneously record muscle diameter and force at multiple sites along the whole mouse colon ex vivo. In addition, electrical activity of smooth muscle was recorded by suction electrodes. Two distinct types of CMCs were distinguished; CMCs that propagated along the entire colon (complete CMC) and CMCs which were restricted to the proximal colon (incomplete CMC). The two types of CMC often occurred in the same preparations. Incomplete CMCs had longer bursts of smooth muscle action potentials than complete CMCs and propagated more slowly. Interestingly, both types of CMC were associated with similar frequency bursts of smooth muscle action potentials at ~2.4Hz. In the most proximal colon, an additional firing frequency was detected close to ~7Hz generating multiple peaks within each CMC. We report distinct characteristics underlying complete and incomplete CMCs in isolated mouse colon. Recognizing these distinct patterns of motility will be important for future interpretation of analysis of murine colonic motility recordings. The identification of alternating patterns of motor activity in proximal colon, but not distal colon may reflect specific neural mechanisms for fecal pellet formation.

Review on Muscle Movement Recording System Using EMG

Electromyography is a neurophysiological technique for examining the electrical activity of skeletal muscles. It occurred from the muscle membrane potential. In a healthy muscle at rest, the spontaneous physiological activity can be a record by End plate potential, insertion activity. EMG recording of the activity of selective cranial nerve muscles is currently included in the intraoperative set during surgical manipulation of the brainstem. When during the process, weak muscles can be detected and treat those muscles to regain their function. EMG is also used to diagnose neuromuscular performance. Its gain is less and frequency response may be broader. Using the EMG technique to record the potential of muscle is an easy way to generate the resting potential of muscle.

От «пустой» липосомы до сложной наноструктуры

В работе подводятся некоторые итоги почти 40-летней работы авторов в области липосомологии, начатые в 80-х годах прошлого века под руководством академика НАМН Украины Александра Викторовича Стефанова.Создание нужной концентрации лекарственных веществ в органе-мишени, не затрагивая при этом не вовлеченные в патологический процесс органы и ткани, – задача непростая. За последние несколько лет предпринято множество попыток решить эту проблему, и оказалось, что лучшимипереносчиками лекарств являются именно липосомы.Преимущества липосом перед другими носителями обусловлены такими их свойствами:– сродство с природными мембранами клеток по химическому составу;– универсальность. Липосомы способны переносить разнообразные фармакологически активныевещества, а также дополнительные источники энергии для клетки и генетический материал; &#x0D; - липосомы сравнительно легко биодеградируют, высвобождая доставленные вещества. В пути следования липосомы надежно укрывают свое содержимое от контакта с иммунной системой и не вызывают защитных и аллергических реакций организма;– способ взаимодействия липосом с клетками, который происходит в разных формах. При этом могут изменяться свойства клеточных мембран, например: вязкость и проницаемость; величина электрического заряда; фосфолипидное окружение ферментов и ионных каналов и, соответственно, их активность (вот почему даже так называемая пустая липосома может быть биологически активным агентом).Благодаря липосомам появляется новый способ направленного воздействия на клетку, который можно назвать «мембранной инженерией», то есть, появляется возможность модифицировать клеточную мембрану в заданном направлении.Оказалось, что липосомы могут быть не только переносчиками лекарств, но и обладают самостоятельной биологической активностью. Продемонстрирована способность так называемых пустых фосфатидилхолиновых липосом (ФХЛ) оказывать влияние на электрическую и сократительную активность сосудистых гладких мышц. При гипоксии ФХЛ восстанавливают измененную для ионов проницаемость плазматических мембран гладких мышц сосудов, а у крыс со спонтанной артериальной гипертензией улучшают эндотелий-зависимые дилататорные реакции сосудов.Кроме того, было показано, что «пустые» ФХЛ эффективно восстанавливают вызванное ацетилхолином эндотелий-зависимое расслабление изолированных колец грудной аорты, нарушенное воздействием гамма-облучения. Липосомы также восстанавливают пониженную после облучения чувствительность сосудистой ткани к ацетилхолину и оксиду азота.С целью усиления антигипоксического и антиоксидантного действия липосом в их структуру был внедрен антиоксидант кверцетин. Использование липосомальной формы кверцетина приводит к полноценному восстановлению коронарного кровотока в послеокклюзионном периоде приострой субтотальной ишемии миокарда, в значительной степени уменьшает проявления характерного для репеперфузионного периода окислительного стресса и предупреждает повышение содержания лейкотриенов С4 и Е4. Синтез простациклина при этом не уменьшается. Применение липосомальной формы кверцетина приводит к уменьшению зоны некроза миокарда в два раза.Липосомальная форма кверцетина практически полностью предотвращает или в значительной степени корригирует нарушения ритма сердечных сокращений и восстанавливает сократительную активность миокарда.Липосомальная форма кверцетина эффективно восстанавливает функцию калиевых каналов большой проводимости у облученных крыс.Перспективным может оказаться включение в состав липосом цитохрома С. Липосомальная форма цитохрома С приводит к коррекции нарушений гемостаза и предотвращает развитие синдрома ДВС при острой массивной кровопотере.Многочисленные патологические процессы, такие как гипертония, атеросклероз, нарушение кровотока в центральной нервной системе, вызваны недостаточностью эндогенного синтеза/высвобождения NO. В таких случаях дополнительное введение NO может быть очень эффективнойстратегией в лечении заболеваний, связанных с указанными патологическими процессами.Разработка современных доноров оксида азота, обладающих способностью контролируемого и дозированного высвобождения действующего вещества, представляет собой чрезвычайно сложную задачу. Создание липидной системы доставки NO, способной обеспечить естественную скорость высвобождения, и разработка ее стабильной лекарственной формы стало следующей целью наших исследований.Проведенные исследования специфического действия сконструированной липосомальной формы оксида азота (ЛФ NO) свидетельствуют о его ее чрезвычайно высокой дилататорной, антиишемической активности. Это подтверждается выраженным дозозависимым расслаблением сегментов интактной аорты крыс и продолжительной гипотензивной реакцией системного кровообращения. ЛФ NO предотвращает развитие критических нарушений насосной функции сердца и способствует сохранению его сократительной активности при субтотальной ишемии. Действие ЛФ NOпроявляется значительным также дозозависимым расслаблением полосок пещеристых тел полового члена и миометрия.Новый NO-содержащий липосомальный конструкт эффективно открывает одиночные кальцийзависимые калиевые каналы большой проводимости в сосудистых гладких мышцах и значительно увеличивает вероятность их нахождения в открытом состоянии.Таким образом, ЛФ NO обещает быть эффективной при лечении ангиопатий различного генеза (включая диабетическую), эректильной дисфункции, гиперактивного мочевого пузыря, артериальной гипертензии, геморрагического и ишемического инсульта. Учитывая возможность применения в ингаляционной форме, она может быть использована для лечения легочной гипертензии.Высказывается мнение, что потенциальные возможности липосом существенно выше пока известных нам. Мы только начали понимать, как липосомы работают с клеткой.

Characterization of protein-enriched yogurt and its effects on the lean body weight gain and electrical activity in skeletal muscle of physically active individuals

Protein-enriched yogurts have experienced a growth in marketability in recent years, being demanded especially by consumers interested in increasing their daily apportion of proteins. In this study, the objective was to develop a protein-enriched yogurt and to compare it with a non-enriched yogurt in terms of their physicochemical characteristics, texture, and sensory acceptance after different storage periods and their effects on the lean body weight gain and electrical activity in skeletal muscle of physically active individuals. The supplemented whey protein had a buffering effect on the product, leading to its lower syneresis. Both formulations had similar hardness, indicating that the textural parameters had been retained in the protein-enriched yogurt. Panelists indicated no differences in sensorial attributes between the non-enriched and protein-enriched yogurts, with the sensory characteristics of each product being mainly described by the presence of whey protein and the curdled texture. Consumption of the protein-enriched yogurt did not influence the lean body weight gain by physically active individuals.

Immediate effect of foot reflexology in patients with diabetic neuropathy -Randomized Clinical Trial

Introduction. Diabetic neuropathy (DN) is one of the most frequent chronic complications of type 2 diabetes mellitus (DM2). One technique capable of influencing the central and peripheral nervous system is foot reflexology (FR). Therefore, the objective of this study was to analyze the immediate effect of FR in DN type 2 patients. Method. This was a randomized controlled clinical trial, with 12 participants selected from a list of diabetic patients from the Basic Health Units of the city of Alfenas-MG. The sample consisted of two groups: Control Group (n=5) and Intervention Group (n=7). The instruments used were: surface electromyography for analysis of the lateral and medial gastrocnemius muscles, baropodometry to evaluate the balance from the variables of mean pressure and mass division, and the cardiofrequency meter to analyze the relationship between the sympathetic and parasympathetic nervous system and cardiovascular stress. Statistical analysis was used the Shapiro-Wilk test and later the independent t test and Mann Whitney for intergroup comparison. Results. There was only a difference in the EMG of the right lateral gastrocnemius muscle (p=0.04). Conclusion. It was concluded that FR was able to generate response in muscle electrical activity, besides influencing the balance of DN2 patients.

Activity Evaluation of Facial Muscles by Surface Electromyography.

Background:Surface electromyography (sEMG) is an easy, noninvasive, and reproducible way to assess spontaneous electrical activity of muscles in real time. In this study, we report data on the correlation between sEMG and mimetic muscle activity during specific tasks so as to create a case–control reference for future studies on acute, chronic, and congenital facial palsy.Methods:Twelve healthy participants were enrolled (6 women and 6 men) with a mean age of 42.75 (range, 26–58 years) years. sEMG signals were recorded at rest and while performing voluntary and specific tasks that elicited selective contraction of frontalis, orbicularis oculi, zygomaticus major, orbicularis oris, and platysma muscles simultaneously and bilaterally for each muscle group. Statistical analysis was performed to evaluate if there was a statistically significant difference of the average contraction values between left- and right-side data sets and between male and female participants.Results:No statistically significant difference was found between male and female participants or between the right and left sides at rest and while performing the requested tasks, even though they were not identical. No participant complained about the procedure.Conclusions:Interindividual and intraindividual variability of the sEMG signal as well as crosstalk between muscles groups were reported downsides that we did not encounter. The absolute noninvasiveness of our procedure makes it feasible to be applied even to young children. This dataset obtained in healthy participants might also be useful in the observation of patients undergoing regeneration/reinnervation procedure following recently acquired facial palsy or mimetic muscle reconstruction for congenital/inveterate one.

Studies of Interactions between Limbs in Humans Subjected to Noninvasive Electrical Stimulation of the Spinal Cord

The effects of activation of spinal locomotor centers at the cervical and lumbar levels on interlimb synergies were studied in humans. Subjects were placed on a biomechanical trainer in the supine position and carried out voluntary rhythmic leg movements, moving the carriage of the walking device of the trainer, or performing voluntary arm movements moving the levers of the trainer, or making simultaneous leg and arm movements. In the resting state, sequential transcutaneous stimulation of the spinal cord at three levels (cathode positioned between vertebrae C4/C5, T12/L1, or L1/L2) did not induce leg movements in most subjects, though performance of arm movements in combination with stimulation initiated low-amplitude (less than 10°) movements in all the leg joints. Stimulation of the spinal cord and simultaneous arm movements induced facilitation of the performance of voluntary leg movements, which was apparent as an increase in the integral characteristic of muscle electrical activity and an increase in movement amplitude at the hip joint. The results obtained here may be useful for developing a neurorehabilitation method for patients with impaired motor function.

Effect of viscoelastic properties on passive torque variations at different velocities of the knee joint extension and flexion movements.

This study aimed to investigate the rate of passive torque variations of human knee joint in the different velocities of knee flexion and extension movements. Ten healthy men were invited to participate in the tests. All passive torque tests were performed for the knee joint extension and flexion on the sagittal plane in three different angular velocities of 15, 45, and 120°/s; in 5 consecutive cycles; and within 0° to 100° range of motion. The electrical activity of knee joint extensor and flexor muscles was recorded until there was no muscle activity signal. A Three-element Solid Model (SLS) was used to obtain the viscose and elastic coefficients. As the velocity increases, the stretch rate in velocity-independent tissues increases, and the stretch rate in velocity-dependent tissues decreases. By increasing the velocity, the resistance of velocity-dependent parts increases, and the velocity-independent parts are not affected by velocity. Since the first torque that resists the joint movement is passive torque, the elastic and viscous torques should be simultaneously used. It is better to perform the movement at a low velocity so that less energy is lost. The viscoelastic resistance of tissues diminishes. Graphical abstract.

Online Grasp Force Estimation From the Transient EMG.

Myoelectric upper limb prostheses are controlled using information from the electrical activity of residual muscles (i.e. the electromyogram, EMG). EMG patterns at the onset of a contraction (transient phase) have shown predictive information about upcoming grasps. However, decoding this information for the estimation of the grasp force was so far overlooked. In a previous offline study, we proved that the transient phase of the EMG indeed contains information about the grasp force and determined the best algorithm to extract this information. Here we translated those findings into an online platform to be tested with both non-amputees and amputees. The platform was tested during a pick and lift task (tri-digital grasp) with light objects (200 g - 1 kg), for which fine control of the grasp force is more important. Results show that, during this task, it is possible to estimate the target grasp force with an absolute error of 2.06 (1.32) % and 2.04 (0.49) % the maximum voluntary force for non-amputee and amputees, respectively, using information from the transient phase of the EMG. This approach would allow for a biomimetic regulation of the grasp force of a prosthetic hand. Indeed, the users could contract their muscles only once before the grasp begins with no need to modulate the grasp force for the whole duration of the grasp, as required with continuous classifiers. These results pave the way to fast, intuitive and robust myoelectric controllers of limb prostheses.

Surface Electromyography Applied to Gait Analysis: How to Improve Its Impact in Clinics?

Surface electromyography (sEMG) is the main non-invasive tool used to record the electrical activity of muscles during dynamic tasks. In clinical gait analysis, a number of techniques have been developed to obtain and interpret the muscle activation patterns of patients showing altered locomotion. However, the body of knowledge described in these studies is very seldom translated into routine clinical practice. The aim of this work is to analyze critically the key factors limiting the extensive use of these powerful techniques among clinicians. A thorough understanding of these limiting factors will provide an important opportunity to overcome limitations through specific actions, and advance toward an evidence-based approach to rehabilitation based on objective findings and measurements.