Level Of Electromyographic Activity Research Articles

Effects of non-invasive cervical spinal cord neuromodulation by trans-spinal electrical stimulation on cortico-muscular descending patterns in upper extremity of chronic stroke.

Background: Trans-spinal electrical stimulation (tsES) to the intact spinal cord poststroke may modulate the cortico-muscular control in stroke survivors with diverse lesions in the brain. This work aimed to investigate the immediate effects of tsES on the cortico-muscular descending patterns during voluntary upper extremity (UE) muscle contractions by analyzing cortico-muscular coherence (CMCoh) and electromyography (EMG) in people with chronic stroke. Methods: Twelve chronic stroke participants were recruited to perform wrist-hand extension and flexion tasks at submaximal levels of voluntary contraction for the corresponding agonist flexors and extensors. During the tasks, the tsES was delivered to the cervical spinal cord with rectangular biphasic pulses. Electroencephalography (EEG) data were collected from the sensorimotor cortex, and the EMG data were recorded from both distal and proximal UE muscles. The CMCoh, laterality index (LI) of the peak CMCoh, and EMG activation level parameters under both non-tsES and tsES conditions were compared to evaluate the immediate effects of tsES on the cortico-muscular descending pathway. Results: The CMCoh and LI of peak CMCoh in the agonist distal muscles showed significant increases (p < 0.05) during the wrist-hand extension and flexion tasks with the application of tsES. The EMG activation levels of the antagonist distal muscle during wrist-hand extension were significantly decreased (p < 0.05) with tsES. Additionally, the proximal UE muscles exhibited significant decreases (p < 0.05) in peak CMCoh and EMG activation levels by applying tsES. There was a significant increase (p < 0.05) in LI of peak CMCoh of proximal UE muscles during tsES. Conclusion: The cervical spinal cord neuromodulation via tsES enhanced the residual descending excitatory control, activated the local inhibitory circuits within the spinal cord, and reduced the cortical and proximal muscular compensatory effects. These results suggested the potential of tsES as a supplementary input for improving UE motor functions in stroke rehabilitation.

Assessment and modelling of the activation-dependent shift in optimal length of the human soleus muscle in vivo.

Previous in vitro and in situ studies have reported a shift in optimal muscle fibre length for force generation (L0) towards longer length at decreasing activation levels (also referred to as length-dependent activation), yet the relevance for in vivo human muscle contractions with a variable activation pattern remains largely unclear. By a combination of dynamometry, ultrasound and electromyography (EMG), we experimentally obtained muscle force-fascicle length curves of the human soleus at 100%, 60% and 30% EMGmax levels from 15 participants aiming to investigate activation-dependent shifts in L0 in vivo. The results showed a significant increase in L0 of 6.5±6.0% from 100% to 60% EMGmax and of 9.1±7.2% from 100% to 30% EMGmax (both P<0.001), respectively, providing evidence of a moderate in vivo activation dependence of the soleus force-length relationship. Based on the experimental results, an approximation model of an activation-dependent force-length relationship was defined for each individual separately and for the collective data of all participants, both with sufficiently high accuracy (R2 of 0.899±0.056 and R2=0.858). This individual approximation approach and the general approximation model outcome are freely accessible and may be used to integrate activation-dependent shifts in L0 in experimental and musculoskeletal modelling studies to improve muscle force predictions. KEY POINTS: The phenomenon of the activation-dependent shift in optimal muscle fibre length for force generation (length-dependent activation) is poorly understood for human muscle in vivo dynamic contractions. We experimentally observed a moderate shift in optimal fascicle length towards longer length at decreasing electromyographic activity levels for the human soleus muscle in vivo. Based on the experimental results, we developed a freely accessible approximation model that allows the consideration of activation-dependent shifts in optimal length in future experimental and musculoskeletal modelling studies to improve muscle force predictions.

Multivariable closed-loop control of deep brain stimulation for Parkinson’s disease

Objective. Closed-loop deep brain stimulation (DBS) methods for Parkinson’s disease (PD) to-date modulate either stimulation amplitude or frequency to control a single biomarker. While good performance has been demonstrated for symptoms that are correlated with the chosen biomarker, suboptimal regulation can occur for uncorrelated symptoms or when the relationship between biomarker and symptom varies. Control of stimulation-induced side-effects is typically not considered. Approach. A multivariable control architecture is presented to selectively target suppression of either tremor or subthalamic nucleus beta band oscillations. DBS pulse amplitude and duration are modulated to maintain amplitude below a threshold and avoid stimulation of distal large diameter axons associated with stimulation-induced side effects. A supervisor selects between a bank of controllers which modulate DBS pulse amplitude to control rest tremor or beta activity depending on the level of muscle electromyographic (EMG) activity detected. A secondary controller limits pulse amplitude and modulates pulse duration to target smaller diameter axons lying close to the electrode. The control architecture was investigated in a computational model of the PD motor network which simulated the cortico-basal ganglia network, motoneuron pool, EMG and muscle force signals. Main results. Good control of both rest tremor and beta activity was observed with reduced power delivered when compared with conventional open loop stimulation, The supervisor avoided over- or under-stimulation which occurred when using a single controller tuned to one biomarker. When DBS amplitude was constrained, the secondary controller maintained the efficacy of stimulation by increasing pulse duration to compensate for reduced amplitude. Dual parameter control delivered effective control of the target biomarkers, with additional savings in the power delivered. Significance. Non-linear multivariable control can enable targeted suppression of motor symptoms for PD patients. Moreover, dual parameter control facilitates automatic regulation of the stimulation therapeutic dosage to prevent overstimulation, whilst providing additional power savings.

Electromyographic activation levels of gluteus maximus, hamstrings and quadriceps in squat and hip thrust exercises: a systematic review

This systematic review aimed to compare the activation levels of hip and knee extensors between the squat exercises and their variations and the hip thrust exercise (HT). To this end, articles published with a time window starting in November 2022 were collected from the electronic databases PubMed, Scopus and Web of Science. The following selection criteria were adopted: cross-sectional or longitudinal study (experimental or cohort); studies that evaluated the neuromuscular activation during the squat and HT exercises or their variations; studies that included healthy, injury-free participants; studies that analyzed the amplitude of electromyographic signals. In total, 4 articles met the study criteria. The following results were found: a) The HT provided greater activation of the hip extensors; b) The squat and its variations increased muscle activation in the vastus lateralis; c) The results are inconclusive for activation of the biceps femoris. The study presented some limitations, such as the low number of articles found, small sample size, lack of studies with a more complete analysis by EMG between the muscle groups of the lower limbs, and lack of chronic records related to muscle hypertrophy and neuromuscular activity.

Occurrence, presence and severity of bruxism and its association with altered state of consciousness in individuals with severe acquired brain injury.

Excessive jaw muscle activity is a frequent complication after acquired brain injury (ABI). The study aimed to identify the occurrence and severity of jaw muscle activity and its association with altered state of consciousness in patients with ABI. A total of 14 severe ABI patients with varied altered state of consciousness were recruited. A single-channel electromyographic (EMG) device was used to assess the jaw muscle activity for three consecutive nights during Week 1 and Week 4 following admission. Differences in number of EMG episodes/h between Week 1 and 4 were analysed using non-parametric tests and association between the EMG activity and altered state of consciousness were analysed using Spearman's correlation test. Nine of fourteen (64%) patients showed indications of bruxism (cutoff: >15 EMG episodes/h). The average EMG episodes/h at admission were 44.5 ± 13.6 with no significant changes after Week 4 of admission (43 ± 12.9; p = .917). The EMG episodes/h ranged from 2 to 184 during Week 1 and 4-154 during Week 4. There were no significant correlations between the number of EMG episodes/h during the three nights and the individuals altered state of consciousness during Week 1 and Week 4. Patients with ABI had a conspicuously high but variable level of jaw muscle activity at admission and it tend to remain high after 4 week of hospitalisation which could potentially lead to adverse effects such as excessive tooth wear, headaches and pain in jaw muscles. The lack of associations between individuals altered level of consciousness and EMG activity could be due to low sample size and further studies are clearly warranted in this patient group with special needs. Single-channel EMG devices can record jaw muscle activity early in the hospitalisation period and might be a helpful tools for early detection of bruxism in ABI patients.

The performance of an electromyography‐based deep neural network classifier for external and internal focus instructions

SummaryExternal focusing (directs focus to apparatus, environment or the effect of the action) enhances motor skill learning and reduces muscular activity compared to internal focusing (leads focus to the movement or the action itself). Nevertheless, in case of electromyography (EMG) based systems such as prosthetic arms, robotic controllers, and robot‐assisted musculoskeletal rehabilitation, low EMG activity is not preferred. This present study was based on classifying attentional focus‐based EMG signals using deep neural networks. Here DB4 and HAAR wavelet coefficients of the participants' signals were extracted to be used as inputs to the proposed DNNs. The accuracy rate results found to be for DB4 and HAAR 99.07% and 99.54%, respectively. Although in previous studies, attentional focusing types could be classified at EMG activity level using artificial neural networks, our DNN results would be more reliable to be used as alternate inputs to EMG‐based control mechanisms. Besides, this study also provides the potential advantages of internal focusing especially in musculoskeletal rehabilitation sessions. Verbal instructions via internal focus might lead physicians to plan effective muscular rehabilitation treatment for patients who has suffered a stroke or a disorder of lower or upper limb extremities.

Study on diagnosis and treatment of lumbar disc herniation and related factors based on dynamic electromyography

To analyze dynamic electromyography characteristics and related factors of lumbar back muscle activity in patients with lumbar disc herniation, and to clarify the clinical significance of dynamic electromyography in the diagnosis and treatment of patients with lumbar disc herniation(LDH). From September 2014 to March 2021, 40 patients with lumbar disc herniation(LDH group) were detected by surface electromyography telemeter. There were 14 males and 26 females, aged from 20 to 61 years old, with an average of(40.68±10.56) years old, the course of illness was from 1 to 120 months, with an average of (17.75±27.56) months. In addition, 12 normal people were recruited as the control group. There were 2 males and 10 females. The age ranged from 24 to 53 years old, with an average of(36.50±10.30) years old. All subjects were subjected to dynamic electromyographic tests of the subthoracic erector spinae, lumbar erector spinae, and multifidus muscles during static standing and trunk flexion and extension. Compare the EMG activity data (average EMG amplitude, median frequency, original EMG graph) of the tested muscles between patients with lumbar disc herniation and normal people, and analyze the correlation between the general data of patients with lumbar disc herniation and the tested muscle EMG data. When standing still, the average electromyographic amplitude of the erector spinal muscle of the right and left thoracic segments of the subjects in the LDH group increased compared with the control group, and the difference was significant(P<0.05). In the trunk flexion and extension, the average electromyographic amplitude of the right and left proximal thoracic erector spinae, the right left lumbar erector spinae, and the right left multifidus muscle of the subjects in the LDH group are all larger than the control group, and the difference was significant(P<0.05). In the trunk flexion and extension, the median frequencies of the right left proximal thoracic erector spinae、the right left lumbar erector spinae, and the right left multifidus muscle of the subjects in the LDH group were all larger than the normal control group, and the difference was significant (P<0.05). During trunk flexion and extension, the original electromyographic patterns of subjects in the LDH group were significantly different from those in the control group. During the maintenance of the maximum trunk flexion of the subjects in the LDH group, there was a high level of electromyographic activity of the lower back muscles, and the electromyographic static signals that should appear regularly in the original signal could not be distinguished. When the trunk was flexed and extended, had gender, age, weight and height of subjects in the LDH group were not significantly correlated with the average EMG amplitude and median frequency of bilateral proximal thoracic, lumbar erector spinae and bilateral multifidus muscles respectively(P>0.05). Patients with lumbar disc herniation have characteristic surface EMG changes in the back muscles that are different from those of normal people. These features can more objectively reflect the patient's muscle condition and can be an effective indicator for the diagnosis and treatment effect evaluation of patients with lumbar disc herniation. It can be seen that surface electromyography is not only a detection method, it can be considered in the routine diagnosis and treatment plan of LDH to guide clinical work.

EVOLUTION TREND AND HOT ISSUES OF GROUNDWATER ENVIRONMENT RESEARCH IN RECENT 40 YEARS BASED ON EMOTIONAL BEHAVIOR CHANGES: A SUMMARY OF SCIENTIFIC ECONOMETRIC ANALYSIS FROM 1981 TO 2021

BackgroundGroundwater pollution has become an important factor restricting regional economic development and environmental protection. The prevention and control of groundwater pollution has always been the focus of water resources management scholars. The purpose of this study is to systematically evaluate the knowledge system of groundwater pollution prevention and control from 1981 to 2021, and to explore the research trend and hot spots of groundwater pollution prevention and control knowledge system. And the emotional and behavioral changes of water conservancy workers.Topics and MethodsIn the field of groundwater environment from 1981 to 2021, taking “science network” (WOS) as the literature source database, the literature system and bibliometric characteristics were studied by means of bibliometrics, knowledge atlas and collaborative research. Occurrence analysis. This paper attempts to evaluate and sort out the similarities and differences between frontier hotspots and evolution trends in the field of groundwater environment. At the same time, the emotional behavior of water conservancy workers in various places was investigated. In order to investigate the regulation of psychological expectation on the emotional arousal effect of negative stimulation and its corresponding neural mechanism when excluding any cognitive strategy involvement in the emotional expectation stage. It is intended to mainly manipulate the predictability (predictable / unpredictable) and potency (negative / neutral) of the target stimulus. The experimental task is the expected stage from the emergence of the negative cue to the presentation of the negative target. The subjects are required to only pay attention to the fixation point in the center of the screen after watching the negative cue and do not take any coping strategies for the subsequent negative stimulus. In order to eliminate the fatigue effect, the experiment is divided into four sections. At the end of each section, the subjects took a proper rest, and then tested the success degree of the subjects following the experimental guidance requirement of “only pay attention to the fixation point from the presentation of the cord stimulus to the appearance of the target stimulus”, and scored with a 5-point scale (1 = very unsuccessful, 5 = very successful) to evaluate the success degree of non cognitive manipulation. 36 healthy subjects, 18 men and 18 women, were recruited to rule out possible gender differences in the process of emotional expectation (Galli et al., 2011). All subjects filled in the state trait anxiety questionnaire and Beck depression questionnaire before participating in the experiment to eliminate the possibility of anxiety disorder or depressive tendency. The experiment intends to simultaneously record the activity level of peripheral physiological indexes such as event-related brain potential (ERP), skin electricity, heart rate and skin temperature and frowning electromyography (electromyography index directly related to the negative expression of subjects under negative stimulation), so as to comprehensively reveal how the EEG, peripheral physiological activity level and electromyography activity level related to negative emotion change with expected factors.ResultsGroundwater pollution prevention and control is a general theory in the field of environmental risk of groundwater at home and abroad. There are many core trends in groundwater pollution prevention and control. This paper gives the evolution track, development stage and dynamic change of the research topic.ConclusionIn recent 40 years, the research on the change law of hot spot migration can be divided into three stages. 2009 is a watershed, and the problem has undergone earth shaking changes. Through the visual analysis of knowledge base system, 12 research hotspots are summarized. Explore the change law of topics in the form of dynamic knowledge map, observe the migration of research hotspots, and provide evidence and discussion for research trends and recent hotspots.AcknowledgementsSupported by a project grant from Key R&D Program of Shaanxi Province (Grant No. D5140200023) and Xi 'an Geological Survey, China Geological Survey (Grant No.211527180141).

Corticomuscular integrated representation of voluntary motor effort in robotic control for wrist-hand rehabilitation after stroke

Objective. The central-to-peripheral voluntary motor effort (VME) in the affected limb is a dominant force for driving the functional neuroplasticity on motor restoration post-stroke. However, current rehabilitation robots isolated the central and peripheral involvements in the control design, resulting in limited rehabilitation effectiveness. This study was to design a corticomuscular coherence (CMC) and electromyography (EMG)-driven control to integrate the central and peripheral VMEs in neuromuscular systems in stroke survivors. Approach. The CMC-EMG-driven control was developed in a neuromuscular electrical stimulation (NMES)-robot system, i.e. CMC-EMG-driven NMES-robot system, to instruct and assist the wrist-hand extension and flexion in persons after stroke. A pilot single-group trial of 20 training sessions was conducted with the developed system to assess the feasibility for wrist-hand practice on the chronic strokes (16 subjects). The rehabilitation effectiveness was evaluated through clinical assessments, CMC, and EMG activation levels. Main results. The trigger success rate and laterality index of CMC were significantly increased in wrist-hand extension across training sessions (p < 0.05). After the training, significant improvements in the target wrist-hand joints and suppressed compensation from the proximal shoulder-elbow joints were observed through the clinical scores and EMG activation levels (p < 0.05). The central-to-peripheral VME distribution across upper extremity (UE) muscles was also significantly improved, as revealed by the CMC values (p < 0.05). Significance. Precise wrist-hand rehabilitation was achieved by the developed system, presenting suppressed cortical and muscular compensation from the contralesional hemisphere and the proximal UE, and improved distribution of the central-and-peripheral VME on UE muscles. ClinicalTrials.gov Register Number NCT02117089

The Influence of Motoric Maneuvers on Cervical Vestibular Evoked Myogenic Potentials (cVEMPs).

The cervical vestibular evoked myogenic potential (cVEMP) is a vestibular response that is produced by the saccule in response to intense, often low-frequency, short-duration auditory stimuli, and is typically recorded from a contracted sternocleidomastoid (SCM) muscle. Previous research has shown that the amplitude of the cVEMP is related to the amount of SCM electromyographic (EMG) activity. The aim of this study was to determine the influence of various remote motoric maneuvers on the amplitude of the cVEMP, as well as whether they influence the level of SCM EMG activity. The cVEMP was recorded from the left SCM muscle to left ear stimulation, in response to the SCM condition, as well as three different motoric maneuvers (jaw clench, eye closure, and the Jendrassik maneuver). EMG activity was also varied between 50, 75, and 100% of maximal EMG activity. Data from 14 healthy subjects, with a mean age of 25.57 years (standard deviation = 5.93 years), was included in the present study. Mean latency and amplitude of the cVEMP were compared across the four conditions and varying magnitudes of EMG contraction. SPSS 26 was used to statistically analyze the results. cVEMP latency did not vary across condition. cVEMP amplitude decreased with decreasing EMG magnitude. SCM contraction with jaw clench produced the largest increase in cVEMP amplitude; however, this condition was not significantly different from the SCM condition alone. SCM contraction with the Jendrassik maneuver produced a cVEMP amplitude that was similar and not statistically different from SCM contraction alone, and the addition of the eye closure maneuver to SCM contraction resulted in the lowest cVEMP amplitude, which was found to be statistically different from the standard SCM condition at 100 and 75% EMG activity. The amplitude relationship across the conditions was not found to vary with changes in EMG activity; however, a significant increase in EMG amplitude was found during the 50% muscle contraction condition when subjects performed the Jendrassik maneuver in addition to the standard SCM contraction. The addition of the eye closure maneuver to SCM contraction resulted in a significant decrease in cVEMP amplitude, while the addition of the Jendrassik maneuver resulted in a significant increase in EMG activity at the lowest level of SCM activation (i.e., 50%). Additional research is necessary to determine how motoric maneuvers influence the cVEMP amplitude, and whether the results are also dependent on how SCM contraction is being produced (e.g., while supine vs. sitting).

Tremor Associated with Muscle Fatigue Is Temporary and Beneficial: A Case Report

Enhanced physiological tremor (EPT) associated with fatiguing static muscle contractions is generally thought to limit continuous muscle work. However, the EPT dies away, allowing the continuous muscle contraction to be maintained at low-level workload. Here, we report a case study of a 22-year-old male volunteer who performed static plantar flexion at 30% maximal voluntary contraction (MVC) for 66 min with repeated EPT events. Comparative analysis of 1 min pre- and post-EPT phases revealed lower electromyographic (EMG) activity, heart rate, and blood pressure levels during the post-EPT phases, while the popliteal artery blood-flow volume and vascular conductance were raised. EPT may therefore be a mechanism for removing factors that inhibit continuous muscle contraction. This unique case report provides new insight into the functional significance of EPT during prolonged static muscle contractions.

Home-based self-help telerehabilitation of the upper limb assisted by an electromyography-driven wrist/hand exoneuromusculoskeleton after stroke

BackgroundMost stroke survivors have sustained upper limb impairment in their distal joints. An electromyography (EMG)-driven wrist/hand exoneuromusculoskeleton (WH-ENMS) was developed previously. The present study investigated the feasibility of a home-based self-help telerehabilitation program assisted by the aforementioned EMG-driven WH-ENMS and its rehabilitation effects after stroke.MethodsPersons with chronic stroke (n = 11) were recruited in a single-group trial. The training progress, including the training frequency and duration, was telemonitored. The clinical outcomes were evaluated using the Fugl–Meyer Assessment (FMA), Action Research Arm Test (ARAT), Wolf Motor Function Test (WMFT), Motor Functional Independence Measure (FIM), and Modified Ashworth Scale (MAS). Improvement in muscle coordination was investigated in terms of the EMG activation level and the Co-contraction Index (CI) of the target muscles, including the abductor pollicis brevis (APB), flexor carpi radialis-flexor digitorum (FCR-FD), extensor carpi ulnaris-extensor digitorum (ECU-ED), biceps brachii (BIC), and triceps brachii (TRI). The movement smoothness and compensatory trunk movement were evaluated in terms of the following two kinematic parameters: number of movement units (NMUs) and maximal trunk displacement (MTD). The above evaluations were conducted before and after the training.ResultsAll of the participants completed the home-based program with an intensity of 63.0 ± 1.90 (mean ± SD) min/session and 3.73 ± 0.75 (mean ± SD) sessions/week. After the training, motor improvements in the entire upper limb were found, as indicated by the significant improvements (P < 0.05) in the FMA, ARAT, WMFT, and MAS; significant decreases (P < 0.05) in the EMG activation levels of the APB and FCR-FD; significant decreases (P < 0.05) in the CI of the ECU–ED/FCR–FD, ECU–ED/BIC, FCR–FD/APB, FCR–FD/BIC, FCR–FD/TRI, APB/BIC and BIC/TRI muscle pairs; and significant reductions (P < 0.05) in the NMUs and MTD.ConclusionsThe results suggested that the home-based self-help telerehabilitation program assisted by EMG-driven WH-ENMS is feasible and effective for improving the motor function of the paretic upper limb after stroke.Trial registration ClinicalTrials.gov. NCT03752775; Date of registration: November 20, 2018.

Surface wave elastography is a reliable method to correlate muscle elasticity, torque, and electromyography activity level.

The shear elastic modulus is one of the most important parameters to characterize the mechanical behavior of soft tissues. In biomechanics, ultrasound elastography is the gold standard for measuring and mapping it locally in skeletal muscle in vivo. However, their applications are limited to the laboratory or clinic. Thus, low‐frequency elastography methods have recently emerged as a novel alternative to ultrasound elastography. Avoiding the use of high frequencies, these methods allow obtaining a mean value of bulk shear elasticity. However, they are frequently susceptible to diffraction, guided waves, and near field effects, which introduces biases in the estimates. The goal of this work is to test the performance of the non‐ultrasound surface wave elastography (NU‐SWE), which is portable and is based on new algorithms designed to correct the incidence of such effects. Thus, we show its first application to muscle biomechanics. We performed two experiments to assess the relationships of muscle shear elasticity versus joint torque (experiment 1) and the electromyographic activity level (experiment 2). Our results were comparable regarding previous works using the reference ultrasonic methods. Thus, the NU‐SWE showed its potentiality to get wide the biomechanical applications of elastography in many areas of health and sports sciences.

Tibialis posterior muscle activity alteration with foot orthosis insertion measured by fine-wire electromyography

Orthoses are often used for the treatment or prevention of injuries. The effect of orthoses on the activity of calf muscles such as the tibialis posterior (TP), flexor digitorum longus (FDL), and peroneus longus (PL) during running is unclear. The purpose of this study was to measure the muscle activity alteration of the TP, FDL, and PL when running with orthoses. Sixteen healthy men participated in this study. Fine-wire and surface electromyography (EMG) were used to measure the TP, FDL, and PL. Participants ran in three conditions: barefoot, footwear only, and footwear with orthoses. The EMG data of the muscles were measured in three successful running trials in each condition. Then, the EMG data from the stance phase of each running trial were used for analysis. The stance phase was further divided into the contact and propulsion phases based on the force plate data. Data from eight participants were used for final analysis because the EMG measurements were unsuccessful for the other eight. The results showed that the TP EMG activity significantly decreased in the orthosis condition in comparison to that in the barefoot condition in all phases. There were no significant differences between barefoot and footwear and footwear and orthosis conditions. No significant changes in the FDL and PL EMG activities were detected in any phase for any of the three conditions. Orthotic use reduces the TP EMG activity level while running, and this result may be beneficial for patients with injuries related to TP overactivity.

Effect of Expertise on Shoulder and Upper Limb Kinematics, Electromyography, and Estimated Muscle Forces During a Lifting Task.

To highlight the working strategies used by expert manual handlers compared with novice manual handlers, based on recordings of shoulder and upper limb kinematics, electromyography (EMG), and estimated muscle forces during a lifting task. Novice workers involved in assembly, manual handling, and personal assistance tasks are at a higher risk of upper limb musculoskeletal disorders (MSDs). However, few studies have investigated the effect of expertise on upper limb exposure during workplace tasks. Sixteen experts in manual handling and sixteen novices were equipped with 10 electromyographic electrodes to record shoulder muscle activity during a manual handling task consisting of lifting a box (8 or 12 kg), instrumented with three six-axis force sensors, from hip to eye level. Three-dimensional trunk and upper limb kinematics, hand-to-box contact forces, and EMG were recorded. Then, joint contributions, activation levels, and muscle forces were calculated and compared between groups. Sternoclavicular-acromioclavicular joint contributions were higher in experts at the beginning of the movement, and in novices at the end, whereas the opposite was observed for the glenohumeral joint. EMG activation levels were 37% higher for novices but predicted muscle forces were higher in experts. This study highlights significant differences between experts and novices in shoulder kinematics, EMG, and muscle forces; hence, providing effective work guidelines to ensure the development of a safe handling strategy is important. Shoulder kinematics, EMG, and muscle forces could be used as ergonomic tools to identify inappropriate techniques that could increase the prevalence of shoulder injuries.

ELECTROMYOGRAPHIC ANALYSIS OF HIP MUSCLE ACTIVATION DURING A SINGLE LIMB SQUAT LATERAL SLIDE EXERCISE.

Slider exercises, which may use a gliding disc or "slider", are dynamic exercises used for strengthening. They are proposed to increase challenge as the friction between the body and ground is decreased which increases the demands on muscles of the weight bearing limb. The purposes of this study were (1) to compare the electromyographic (EMG) activity level of hip muscles of the weight bearing limb while performing a single limb slide squat to that of a standard isometric squat and (2) to investigate the influence of trunk position on hip EMG activity. It was hypothesized that the single limb slide squat would elicit greater hip EMG activity than an isometric squat and trunk position would influence EMG activity. Analytic, observational cross-sectional study design.Methods: Twenty healthy male participants (age = 23.7 ± 1.3) volunteered. EMG hip muscle activation of the stance leg was measured during a single limb slide squat and as a comparison, the same leg during a standard double limb isometric squat. Both exercises where performed with a knee flexion angle of 60˚ and the trunk positioned 40˚ (flexed trunk) and 60˚ (upright trunk) relative to the floor. Surface electrodes were used to collect EMG data. EMG activity of the gluteus maximus, gluteus medius, biceps femoris and rectus femoris was significantly greater with both single limb slide exercises as compared to both squat exercises. EMG activity was greater with the flexed trunk as compared to the upright trunk for the biceps femoris. Slider exercises produced a moderate or high level of activation for all muscles whereas all squat exercises produced a low-level activation. Level 3 Mechanism-based reasoning intervention study trial.

Effect of Five Bench Inclinations on the Electromyographic Activity of the Pectoralis Major, Anterior Deltoid, and Triceps Brachii during the Bench Press Exercise.

The bench press exercise is one of the most used for training and for evaluating upper-body strength. The aim of the current study was to evaluate the electromyographic (EMG) activity levels of the pectoralis major (PM) in its three portions (upper portion, PMUP, middle portion, PMMP, and lower portion, PMLP), the anterior deltoid (AD), and the triceps brachii (TB) medial head during the bench press exercise at five bench angles (0°, 15°, 30°, 45°, and 60°). Thirty trained adults participated in the study. The EMG activity of the muscles was recorded at the aforementioned inclinations at 60% of one-repetition maximum (1RM). The results showed that the maximal EMG activity for PMUP occurred at a bench inclination of 30°. PMMP and PMLP showed higher EMG activity at a 0° bench inclination. AD had the highest EMG activity at 60°. TB showed similar EMG activities at all bench inclinations. In conclusion, the horizontal bench press produces similar electromyographic activities for the pectoralis major and the anterior deltoid. An inclination of 30° produces greater activation of the upper portion of the pectoralis major. Inclinations greater than 45° produce significantly higher activation of the anterior deltoid and decrease the muscular performance of the pectoralis major.

Mind-Muscle Connection: Verbal Instructions Alter Electromyographic Activity for Elbow Flexors and Extensors During Co-Contraction Training.

Co-contraction training has demonstrated similar electromyographic (EMG) activity levels compared to conventional strength training. Since verbal instructions can increase EMG activity on target muscles during conventional exercises, the same should occur during co-contraction. In this study we analyzed whether different verbal instructions would alter the EMG activity of target muscles - biceps brachii (BB) and triceps brachii lateral head (TB) - during co-contraction training for the elbow joint. Seventeen males with experience in strength training performed a co-contraction set in two verbal instruction conditions to emphasize either elbow flexion or elbow extension. Surface electrodes were fixed over biceps brachii and triceps brachii lateral head muscles. We measured EMG mean amplitude and analyzed data with 2-way ANOVA. We found a significant interaction between muscle and verbal instruction (p = 0.002). Post hoc tests indicated that verbal instructions (p = 0.001) influenced the BB EMG activity (elbow flexion: M = 68.74, SD = 17.96%; elbow extension: M = 53.47, SD = 16.13%); and also showed difference (p = 0.006) in the EMG activity between BB and TB with verbal instruction emphasizing the elbow extension (BB: M = 53.47, SD = 16.13%; TB: M = 69.18, SD = 21.79%). There was a difference in the EMG ratio of BB/TB (p = 0.001) when focusing on elbow flexion (M = 1.09, SD = 0.30) versus elbow extension (M = 0.81, SD = 0.25). As verbal instruction modified the magnitude of muscle recruitment during co-contractions for elbow joint muscles, there is a clear mind-muscle connection of importance to this method of training. Also, of importance to trainers, verbal instructions seemed to affect individuals differentially.

Altered Corticomuscular Coherence (CMCoh) Pattern in the Upper Limb During Finger Movements After Stroke.

Background: Proximal compensation to the distal movements is commonly observed in the affected upper extremity (UE) of patients with chronic stroke. However, the cortical origin of this compensation has not been well-understood. In this study, corticomuscular coherence (CMCoh) and electromyography (EMG) analysis were adopted to investigate the corticomuscular coordinating pattern of proximal UE compensatory activities when conducting distal UE movements in chronic stroke.Method: Fourteen chronic stroke subjects and 10 age-matched unimpaired controls conducted isometric finger extensions and flexions at 20 and 40% of maximal voluntary contractions. Electroencephalogram (EEG) data were recorded from the sensorimotor area and EMG signals were captured from extensor digitorum (ED), flexor digitorum (FD), triceps brachii (TRI), and biceps brachii (BIC) to investigate the CMCoh peak values in the Beta band. EMG parameters, i.e., the EMG activation level and co-contraction index (CI), were analyzed to evaluate the compensatory muscular patterns in the upper limb.Result: The peak CMCoh with statistical significance (P < 0.05) was found shifted from the ipsilesional side to the contralesional side in the proximal UE muscles, while to the central regions in the distal UE muscle in chronic strokes. Significant differences (P < 0.05) were observed in both peak ED and FD CMCohs during finger extensions between the two groups. The unimpaired controls exhibited significant intragroup differences between 20 and 40% levels in extensions for peak ED and FD CMCohs (P < 0.05). The stroke subjects showed significant differences in peak TRI and BIC CMCohs (P < 0.01). No significant inter- or intra-group difference was observed in peak CMCoh during finger flexions. EMG parameters showed higher EMG activation levels in TRI and BIC muscles (P < 0.05), and higher CI values in the muscle pairs involving TRI and BIC during all the extension and flexion tasks in the stroke group than those in the control group (P < 0.05).Conclusion: The post-stroke proximal muscular compensations from the elbow to the finger movements were cortically originated, with the center mainly located in the contralesional hemisphere.

Rehabilitation Exercises for the Gluteus Medius Muscle Segments: An Electromyography Study.

Many different rehabilitation exercises have been recommended in the literature to target the gluteus medius (GMed) muscle based mainly on single-electrode, surface electromyography (EMG) measures. With the GMed consisting of 3 structurally and functionally independent segments, there is uncertainty on whether these exercises will target the individual segments effectively. To measure individual GMed segmental activity during 6 common, lower-limb rehabilitation exercises in healthy young adults, and determine if there are significant differences between the exercises for each segment. With fine-wire EMG electrodes inserted into the anterior, middle, and posterior segments of the GMed muscle, 10 healthy young adults performed 6 common, lower-limb rehabilitation exercises. Recorded EMG activity was normalized, then reported and compared with median activity for each of the GMed segments across the 6 exercises. For the anterior GMed segment, high activity was recorded for the single-leg squat (48% maximum voluntary isometric contraction [MVIC]), the single-leg bridge (44% MVIC), and the resisted hip abduction-extension exercise (41% MVIC). No exercises recorded high activity for the middle GMed segment, but for the posterior GMed segment very high activity was recorded by the resisted hip abduction-extension exercise (69% MVIC), and high activity was generated by the single-leg squat (48% MVIC) and side-lie hip abduction (43% MVIC). For each of the GMed segments, there were significant differences (P < .05) in the median EMG activity levels between some of the exercises and the side-lie clam with large effect sizes favoring these exercises over the side-lie clam. Open-chain hip abduction and single-limb support exercises appear to be effective options for recruiting the individual GMed segments with selection dependent on individual requirements. However, the side-lie clam does not appear to be effective at recruiting the GMed segments, particularly the anterior and middle segments.