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Introduction: Neuromuscular electrostimulation (NMES) represents a therapeutic approach for addressing chronic low back pain (CLBP); however, the influence of NMES dose on muscle activity remains subject to debate.

Objective: To compare the impact of two distinct NMES protocols employing Aussie current, characterized by varying dosages emphasizing time cycle alterations, on electromyographic activity within the multifidus muscles in individuals afflicted with CLBP.

Methods: A randomized clinical trial encompassed 18 volunteers diagnosed with mechanical CLBP. These volunteers were randomly assigned to two NMES intervention groups with dissimilar dosages: 15 repetitions ($E$${}_{15}$) and 30 repetitions ($E$${}_{30}$ ). In both interventions, the current amplitude was tailored to individual perception and documented at the culmination of each session. Over the course of four weeks, two sessions took place per week. Electromyographic activity of the multifidus muscles was evaluated using surface electromyography before and after the intervention. The assessment focuses on both time-domain analysis using Root Mean Square (RMS) and frequency-domain analysis involving mean activation frequency (FREQ).

Results: There are no interactions between the time and intervention, but there is the time effect on RMS, indicating that post-intervention muscle activity exceeded pre-intervention values in both groups. FREQ values did not exhibit statistically significant discrepancies.

Conclusions: This study showed that NMES using the Aussie current is effective in increasing muscle activity in individuals with CLBP, and the results were not influenced by the different cycle times with equal volumes.

Vagus nerve stimulation (VNS) is a treatment for refractory epilepsy and depression. Previous studies using invasive recording electrodes showed that VNS induces laryngeal motor-evoked potentials (LMEPs) through the co-activation of the recurrent laryngeal nerve and subsequent contractions of the laryngeal muscles. The present study investigates the feasibility of recording LMEPs in chronically VNS-implanted rats, using a minimally-invasive technique, to assess effective current delivery to the nerve and to determine optimal VNS output currents for vagal fiber activation. Three weeks after VNS electrode implantation, signals were recorded using an electromyography (EMG) electrode in the proximity of the laryngeal muscles and a reference electrode on the skull. The VNS output current was gradually ramped up from 0.1 to 1.0 mA in 0.1 mA steps. In 13/27 rats, typical LMEPs were recorded at low VNS output currents (median 0.3 mA, IQR 0.2–0.3 mA). In 11/27 rats, significantly higher output currents were required to evoke electrophysiological responses (median 0.7 mA, IQR 0.5–0.7 mA, $p<0.001$). The latencies of these responses deviated significantly from LMEPs ($p<0.05$). In 3/27 rats, no electrophysiological responses to simulation were recorded. Minimally invasive LMEP recordings are feasible to assess effective current delivery to the vagus nerve. Furthermore, our results suggest that low output currents are sufficient to activate vagal fibers.

The neural command from motor neurons to muscles — sometimes referred to as the neural drive to muscle — can be identified by decomposition of electromyographic (EMG) signals. This approach can be used for inferring the voluntary commands in neural interfaces in patients with limb amputations. This paper proposes for the first time an innovative method for fully automatic and real-time intramuscular EMG (iEMG) decomposition. The method is based on online single-pass density-based clustering and adaptive classification of bivariate features, using the concept of potential measure. No attempt was made to resolve superimposed motor unit action potentials. The proposed algorithm was validated on sets of simulated and experimental iEMG signals. Signals were recorded from the biceps femoris long-head, vastus medialis and lateralis and tibialis anterior muscles during low-to-moderate isometric constant-force and linearly-varying force contractions. The average number of missed, duplicated and erroneous clusters for the examined signals was $0.5\pm 0.8$, $1.2\pm 1.0$, and $1.0\pm 0.8$, respectively. The average decomposition accuracy (defined similar to signal detection theory but without using True Negatives in the denominator) and coefficient of determination (variance accounted for) for the cumulative discharge rate estimation were $70\pm 9\%$, and $94\pm 5\%$, respectively. The time cost for processing each 200ms iEMG interval was $43\pm 16$ (21–97)ms. However, computational time generally increases over time as a function of frames/signal epochs. Meanwhile, the incremental accuracy defined as the accuracy of real-time analysis of each signal epoch, was $74\pm 18$% for epochs recorded after initial one second. The proposed algorithm is thus a promising new tool for neural decoding in the next-generation of prosthetic control.

When surface electromyography (EMG) signal is used in a real-time functional electrical stimulation (FES) system for feedback control, the artifact from electrical stimulation is a key challenge for EMG signal processing. To address this challenge, this study proposes a novel method to suppress stimulation artifacts in the EMG-driven closed-loop FES system. The proposed method is inspired by an experimental study that compares artifacts generated by electrical stimulations with different current intensities. It is found that (1) spikes of stimulation artifacts are susceptible to the current intensity and (2) tailing components are similar under different current intensities. Based on these observations, the proposed method combines the blanking and template subtracting strategies for suppressing stimulation artifact. The length of blanking window for suppressing the stimulation spike is adaptively determined by a spike detection algorithm and the first-order derivative analysis of signal. An autoregressive model is used to estimate the tailing part of stimulation artifact, which is an adaptive template for subtracting the artifact. The proposed method is evaluated on both semi-synthetic and experimental datasets. Verified on the semi-synthetic dataset, the proposed method achieves better performance than the classic blanking method. Validated on the experimental dataset, the proposed method substantially decreases the power of stimulation artifact in the EMG. These results indicate that the proposed method can effectively suppress the stimulation artifact while retains the useful EMG signal for an EMG-driven FES system.

Hybrid Brain–Computer Interfaces (BCIs) for upper limb rehabilitation after stroke should enable the reinforcement of “more normal” brain and muscular activity. Here, we propose the combination of corticomuscular coherence (CMC) and intermuscular coherence (IMC) as control features for a novel hybrid BCI for rehabilitation purposes. Multiple electroencephalographic (EEG) signals and surface electromyography (EMG) from 5 muscles per side were collected in 20 healthy participants performing finger extension (Ext) and grasping (Grasp) with both dominant and non-dominant hand. Grand average of CMC and IMC patterns showed a bilateral sensorimotor area as well as multiple muscles involvement. CMC and IMC values were used as features to classify each task versus rest and Ext versus Grasp. We demonstrated that a combination of CMC and IMC features allows for classification of both movements versus rest with better performance (Area Under the receiver operating characteristic Curve, AUC) for the Ext movement (0.97) with respect to Grasp (0.88). Classification of Ext versus Grasp also showed high performances (0.99). All in all, these preliminary findings indicate that the combination of CMC and IMC could provide for a comprehensive framework for simple hand movements to eventually be employed in a hybrid BCI system for post-stroke rehabilitation.

The purpose of this paper is to develop an effective method to identify upper limb motions based on EMG signal for community rehabilitation. The method will be applicable to the control system in the rehabilitation equipment and provide objective data for quantitative assessment. The recognition goal sets of upper limb motion are constructed by decomposing assessment activities of activity of daily living scale (ADL). The recognition feature vector space is established by Variance (VAR), Mean Absolute Value (MAV), the fourth-order Autoregressive (the 4thAR), Zero Crossings (ZC’s), integral EMG (IEMG), and Root Mean Square (RMS), and various feature sets are extracted to get the best classification. Locally linear embedding (LLE) algorithm is used to reduce the computational complexity, and upper limb motions about shoulder, elbow and wrist are quickly classified through extreme leaving machine (ELM), which obtained the average accuracy of 98.14%, 98.61% and 94.77%, respectively. Furthermore, when ELM is compared with Back-propagation (BP) and Support vector machine (SVM), it has performed relatively better than BP and SVM. The results show that the validity of the mixed model for recognition is verified. In addition, the method can also provide a basis for recognition and assessment of the angle of upper limb joint in the next study.

The aim of this investigation was to determine how the CNS controlled seven segments of the human deltoid muscle during a change in the direction of shoulder joint motion. Specifically, we wished to determine how the prime mover, synergist and antagonist muscle segments of this muscle were manipulated to assume new functional roles as the direction of shoulder motion was rapidly changed from shoulder abduction to shoulder adduction. Seven bipolar surface electrodes (7 mm inter-electrode distance) were placed over the seven segments (D1–D7) of the right deltoid, in seven young (19–24yrs) male subjects, to detect changes in muscle segment activation as the subjects transitioned from a rapid shoulder-abduction to a rapid-adduction force impulse (MT = 1000 ms). For each subject, fifteen trials were recorded at an inter-trial interval of 30 seconds. Comparisons of muscle segment timing and intensity of activation were made across 6 equal time intervals between just before the peak of the abduction force impulse and the subsequent peak of the adduction force impulse. The results of this study have shown that segments of the deltoid were activated during both the shoulder abduction and shoulder adduction motor task. In addition, the pattern of muscle segment activation (timing and intensity), during the transition from shoulder abduction to shoulder adduction, was dependent upon the muscle's moment arm and line of pull in relation to the axis of shoulder joint rotation. Three distinct patterns of neuromotor activation were noted within the segments of the deltoid muscle. During abduction the agonist prime mover and synergist segments (D1–D5) were totally deactivated (< 10% MVC) as they became antagonist segments during adduction. The antagonist segment (D7), during abduction, was deactivated and then reactivated as it became a synergist segment during adduction. Finally segment D6 was shown to have a nearly continuous period of activation. The study has shown that during a transition to a new movement direction, a muscle segment's line of pull and future function in the next phase of the movement appears to determine its period and intensity of activation.

Background: The influence of water immersion on neuromuscular function is of importance to a number of disciplines; however, the reliability of surface electromyography (SEMG) following water immersion is not known. This study examined the reliability of SEMG amplitude during maximal voluntary isometric contractions (MVICs) of the vastus lateralis following water immersion. Methods: Using a Biodex isokinetic dynamometer and in a randomized order, 12 healthy male subjects performed four MVICs at 60° knee flexion on both the dominant and nondominant kicking legs, and the SEMG was recorded. Each subject's dominant and nondominant kicking leg was then randomly assigned to have SEMG electrodes removed or covered during 15 min of water immersion (20°C–25°C). Following water immersion, subjects performed a further four MVICs. Results: Intraclass correlation coefficient (ICC) and the relative standard error of measurement (%SEM) of SEMG amplitude showed moderate to high trial-to-trial reliability when electrodes were covered (0.93% and 2.79%) and removed (0.95% and 2.10%, respectively). Conclusions: The results of the this study indicate that SEMG amplitude of the vastus lateralis may be accurately determined during maximal voluntary contractions following water immersion if electrodes are either removed or covered with water-resistive tape during the immersion.

The purposes of this study were to investigate the activation of neck muscles during movement of the head from the neutral position to the maximum points and back to the neutral position. The experiment was designed to compare between groups. There were in total 26 subjects: 11 in the young group (mean age 24.3 years old) and 15 in the middle-age group (mean age 55.9 years old) were recruited. The active ROM, velocity, and surface EMG activities of the left and right sternocleidomastoid (SCM) muscles were recorded during repetitive cervical movements in the six directions of flexion/extension, right/left rotation and side-bending. The data were evaluated with repeated-measures analysis of variance (ANOVA). The active ROM and maximum force in both flexion and extension were significantly lower for the middle-age group than for the young group. However, the integrated EMG values for the left and right SCM muscles during movement of the head to and from the maximum points of the ROM in three cardinal planes were significantly greater in the middle-age group than in the young group. Whether these over-activation of SCM is related to degeneration of the cervical spines requires further investigation.

Purpose: Differences in muscle activity have been observed between men and women in numerous lower extremity muscles in a variety of activities. These differences may be related to observed differences in the incidence of injuries between men and women. The purpose of this work is to determine if gender had an effect on the activity of the medial and lateral gastrocnemius muscles during the early part of the stance phase of gait. Method: An observational cohort study was set up using sixteen volunteers (9 men and 7 women, mean age = 27 years) with less than 5° of passive ankle-dorsiflexion range of motion. Maximum dorsiflexion, maximum knee flexion, stance time and EMG magnitude were measured for both men and women during early stance (heel strike to heel off). Results: EMG amplitude of the LG muscle in women was significantly higher than that of men. No significant differences were observed between men and women for maximum dorsiflexion, maximum knee flexion or stance time. Conclusions: A gender difference in gastrocnemius muscle EMG magnitude exists that is independent of knee and ankle kinematics and walking speed.

Purpose: The study analyzed the muscle activity during knee flexion while performing a squat with and without a load based on soft tissue deformation parameters (STDP) at four different angular positions of the vastus lateralis (VL) and vastus medialis (VM) muscles. Methods: An integrated knee-flexion analysis system is a novel tool used to analyze muscle activity during knee flexion and comprises hardware and software modules. A motion capture system and video cameras are interfaced with wireless electromyography (EMG) sensors, and the system software records the motion of the subjects during the squat and extracts relevant features. The STDP from the video of each knee flexion angle and data fusion of EMG, contain the root mean square value, mean absolute value, and integrated EMG of the EMG signals. Twelve healthy soldiers were used as test subjects using uniform criteria in a controlled environment. Results: A strong positive correlation was shown between features extracted using EMG and the STDP for the VL and VM muscles of all subjects. The Wilcoxon test (nonparametric) and paired-samples t-test results were significantly greater in the loaded than unloaded trials during activity of VL and VM muscles at greater knee flexion angles ($p<0.05$). Conclusion: The outcomes of this study signify the prominence of knee flexion and the associated contiguous balance and co-activation of the VL and VM at 10${}^{\circ }$, 20${}^{\circ }$, 30${}^{\circ }$, and 40${}^{\circ }$ of knee flexion during squatting with and without an external load. Thus, greater knee flexion during the squat is an important factor for greater muscle activation.

Purpose: To determine if there is a difference in trunk muscle activation in children with spastic diplegic cerebral palsy (CP) compared to typically developing (TD) children while being held in different positions on a hippotherapy simulator. Methods: Five children with spastic diplegic CP and five TD children of similar age were recruited through the Children’s Hospital of Wisconsin. The participants were held in static positions sitting on a hippotherapy simulator at 10${}^{\circ }$, 15${}^{\circ }$, and 20${}^{\circ }$ from the midline to front, back, and side positions. Surface electromyography (sEMG) data were collected from the left and right latissimus dorsi, hip adductor, middle trapezius, and rectus abdominis muscles. The pooled mean sEMG amplitude, at each position, served as the main outcome measurement. Results: The forward position at 20${}^{\circ }$ for the left and right lower rectus abdominis and right middle trapezius muscles had an effect size of $>1.5$. This was also evident in the right middle trapezius at 10${}^{\circ }$ in the forward and left tilted positions, and in the right latissimus dorsi at the 10${}^{\circ }$ left tilted position. Conclusion: Different sEMG in the abdominal, middle trapezius, and latissimus dorsi muscles in children with spastic diplegic CP suggests that utilizing a trunk position of different angles may improve the current therapeutic methods in the recruitment of trunk muscles.

Muscle Fiber Conduction Velocity (MFCV) can be calculated from the time delay between the surface electromyographic (sEMG) signals recorded by electrodes aligned with the fiber direction. In order to take into account the non-stationarity during the dynamic contraction (the most daily life situation) of the data, the developed methods have to consider that the MFCV changes over time, which induces time-varying delays and the data is non-stationary (change of Power Spectral Density (PSD)). In this paper, the problem of TVD estimation is considered using a parametric method. First, the polynomial model of TVD has been proposed. Then, the TVD model parameters are estimated by using a maximum likelihood estimation (MLE) strategy solved by a deterministic optimization technique (Newton) and stochastic optimization technique, called simulated annealing (SA). The performance of the two techniques is also compared. We also derive two appropriate Cramer–Rao Lower Bounds (CRLB) for the estimated TVD model parameters and for the TVD waveforms. Monte-Carlo simulation results show that the estimation of both the model parameters and the TVD function is unbiased and that the variance obtained is close to the derived CRBs. A comparison with non-parametric approaches of the TVD estimation is also presented and shows the superiority of the method proposed.

This study reports a new technique for the analysis of electromyographic signals from the low back muscles. More specifically, the effect of unexpected load on a normal subject and a subject with chronic low back pain was determined and quantified using wavelet based analysis (Morlet wavelet). The analysis was performed using a Wavelet software system, subsequently referred to as PSCW. The system identified automatically, accurately, and in a uniquely reproducible manner the time response of the erector spinae muscle. The exact number of responses as well as their corresponding time and amplitude were determined and tabulated. It was observed that the initial reaction time for the normal subject was faster than the reaction time for the subject chronic low back pain. The importance of this observation may help in the understanding of the physiology of the neuromuscular system associated with low back spine disorders. It is believed that an occupational and clinical test based on this observation that could give an accurate assessment of the status of low back disorder could be designed. Based on this assessment a rehabilitation program could be developed with the objective of improving the condition of a spine disorder (decrease the initial response time) by muscle strengthening.

Surface electromyography (EMG) has been used to estimate deep trunk muscle activity. However, it remains unknown whether surface EMG provides an accurate estimation of this activity. The purposes of this study were to compare surface and intramuscular EMG activity measurements and investigate the efficacy of surface EMG measurement for the transversus abdominis (TrA) and the multifidus (MF) muscles. Eight healthy men participated in the study. TrA and MF activities were simultaneously measured by both intramuscular and surface EMG during isometric trunk exercises. Spearman correlation coefficients for the relationship between the two activity measurements for the right TrA, left TrA, right MF, and left MF were 0.55, 0.36, 0.67, and 0.79, respectively. For the TrA, Bland–Altman plots revealed that mean differences between measurements obtained by intramuscular EMG and surface EMG were not close to zero, with a systematic bias toward higher surface EMG values. In conclusion, surface and intramuscular EMG activity measurements were strongly correlated for MF muscles, but poorly correlated for TrA muscles.

Tremor is the most common movement disorder and it is affecting more and more people as the world is aging. The cost involved is big considering the financial and social impact. This paper explores an assistive technology solution for upper limb pathological tremor compensation. Using both surface electromyography (SEMG) and accelerometer (ACC), a real-time pathological tremor compensation with functional electrical stimulation (FES) is proposed. One advantage of using SEMG is the electromechanical delay (SEMG data precedes the ACC data by 20–100 ms). Hence by detecting the tremor in advance, there is enough time window to do the necessary computation and to actuate the antagonist muscle by FES. This is also possible because the time taken for FES to actuate the muscle is significantly less than that of the neural signal, as detected by SEMG. For estimation of tremor parameters and separation between voluntary motion and tremor, an algorithm based on extended Kalman filter (EKF) is proposed. Experimental result from one essential tremor patient has shown 57% reduction in tremor power as measured by the ACC.

The purpose of this study was twofold: (i) to review the existing literature on electromyographic (EMG) analysis of the upper limb muscles of present overhead-throwing (OT) athletes during throwing and of cricket bowlers (CBs) during cricket bowling (CB) and, (ii) to discuss the importance of and generate recommendations for the EMG assessment of the muscle activity of CBs with respect to previous studies of OT athletes. A literature search of the PubMed, Scopus and Google Scholar electronic databases was performed to identify relevant articles published up to December 2012. This search was performed to evaluate the following areas, (i) what are the upper limb muscles that should be evaluated during OT sports and cricket bowling? (ii) what types of EMG methodologies have been used? (iii) what are the anthropometric, performance and physical functional variables that are usually selected? and (iv) what recommendations can be made for the assessment of the muscle activity of CBs? The search identifies 32 publications on OT athletes and 4 on CBs. The results note the following conclusions: (i) there are relatively few CB-related papers that utilize EMG, particularly for the assessment of muscle activity and coordination, (ii) a total of 22 upper limb muscles were investigated using EMG (from both criteria), (iii) surface electrodes are used more frequently than needle electrodes, (iv) most of the article normalized and analyzed the EMG amplitudes than the frequency, and the data was more often analyzed through a descriptive statistical analysis and (v) the majority of the studies analyzed the right limb of physically normal (uninjured) male's both the amateur and professional athletes that were 20 to 29 years of age. Finally, the published evidence on CBs is inadequate to validate a sound recommendation for the assessment of the muscles of CBs using EMG. However, the studies on OT athletes do provide guidelines that can be used to analyze CBs. The overall conclusion of this review show that, further studies are needed to evaluate the efficacy of EMG for the assessment of the upper limb muscle of CBs to ultimately identify and prevent injury which is still a matter of discussion in the sports medicine community.

Gait is one of the most common and important factor of human movements in daily life. Pelvis is closely connected with the gait due to it allows maintain stable posture by supporting the spine and lower extremities against the gravity. Therefore, pelvic asymmetry, which is caused by biomechanical stress and muscle imbalance, has been associated with postural imbalance and abnormal walking pattern. The purpose of this study was to manufacture customized foot orthotics for improving gait balance and evaluate the effectiveness of customized foot orthotics during walking by measuring lower extremity muscle activity and plantar pressure distribution. All subjects with pelvic asymmetry were asked to walk on a treadmill under three conditions: walking without foot orthotics, walking with customized foot orthotics and walking with non-customized foot orthotics. Root mean square (RMS) value of the electromyography signals, force and peak pressure of the plantar pressure distribution was analyzed based on the gait cycle. The results showed that excessive tension of the muscles and high pressure of the foot that was induced by pelvic asymmetry were more reduced when walking with custom-made foot orthotics than walking without foot orthotics and walking with non-customized foot orthotics. This paper suggest that custom-made orthotics for patients with pelvic asymmetry could be helpful to relieve the excessive loading of the foot and maintain balanced gait pattern.

In this study, lift chair was developed to reduce safety accidents in the daily lives of elderly people with reduced muscle strength as the importance of health and well-being of the elderly was emphasized by the increase in the elderly population. In addition, muscle strength characteristics of the elderly and those in their 20s were compared and analyzed when using lift chair. The lift chair used are chairs that can be raised and lowered and designed to reach the floor in full descent. The EMG was measured to compare the near-term use of lift chair to those in their 20s. As a result, the elderly had higher use of lower limb muscles compared to young participants. It was judged that the upper and lower extremities were difficult to move due to the characteristics of the elderly with reduced muscle strength, and that the upper and lower limbs were used simultaneously to complete the movement. The results showed the characteristics of everyday motion of the elderly for the development of lift chair and can help improve design, function, etc. in later development of lift chair.

Transcranial magnetic stimulation (TMS) is an electrophysiological technique that uses alternating magnetic fields to deliver electric current and stimulate the cerebral cortex. When TMS is used for the evaluation of brain diseases, it is necessary to detect the contraction of the corresponding muscles in the cerebral cortex stimulated by TMS, and the muscle activity referred to as motor evoked potential (MEP). This study simultaneously recorded the mechanomyography (MMG) and electromyography (EMG) from the right abductor pollicis brevis muscle during TMS with different intensities in order to observe whether the MEP parameters from MMG signals showed similar trait of EMG recordings. Moreover, the subspace method (N4SID) and transfer function were used to identify the TMS–MMG system. In this system, the input was a pulse signal of TMS, and the output was the MMG signal detected from the target muscle. The TMS–MMG system was identified as a fourth-order model. This study also analyzed the internal features of the system and demonstrated that the poles of healthy subjects were distributed in a range, and the gain increased with the increase of the TMS intensity. It was found that MMG signals can be used as diagnostic indicators of TMS, and the TMS–MMG model can be used to further explore the details of how TMS generates responses measured with MMG.