Reliability of surface electromyography in estimating muscle fiber conduction velocity: A systematic review

Reliability and Convergent Validity of Endurance Indices Derived from Near-Infrared Spectroscopy and Electromyography during a Bilateral Hanging Task in Amateur Rock Climbers

Background: The ability to hang for a long time before forearm muscle fatigue is a crucial element of successful rock climbing. Electromyography (EMG) and near-infrared spectroscopy (NIRS) are also useful for measuring hemoglobin oxygenation for determining muscle endurance. In the present study, we aimed to evaluate the reliability and validity of muscle endurance indices derived using EMG and NIRS during a hanging task. Methods: A bilateral hanging task was designed to compare rock climbers and non-climbers in terms of the slopes of changes in the median frequency (MDF) and tissue oxygenation index (TOI) of forearm muscles. Results: A total of 17 participants were included in each of the two groups. The intraclass correlation coefficient (3,1) values derived for the MDF slope, TOI slope, ΔTOI, percentage change in oxygen concentration, and ΔHbt were 0.85, 0.73, 0.65, 0.75, and 0.65, respectively. The MDF slope, TOI slope, and ΔHbt differed significantly between the groups (p < 0.05). The MDF slope, TOI slopes, and ΔHbt were significantly correlated with V-scale levels for climbing (p < 0.05). Conclusions: The satisfactory reliability and observed distinctions between climbers and non-climbers imply that these indices are a valuable tool for assessing muscle endurance.

Tutorial: Analysis of central and peripheral motor unit properties from decomposed High-Density surface EMG signals with openhdemg

High-Density surface Electromyography (HD-sEMG) is the most established technique for the non-invasive analysis of single motor unit (MU) activity in humans. It provides the possibility to study the central properties (e.g., discharge rate) of large populations of MUs by analysis of their firing pattern. Additionally, by spike-triggered averaging, peripheral properties such as MUs conduction velocity can be estimated over adjacent regions of the muscles and single MUs can be tracked across different recording sessions. In this tutorial, we guide the reader through the investigation of MUs properties from decomposed HD-sEMG recordings by providing both the theoretical knowledge and practical tools necessary to perform the analyses. The practical application of this tutorial is based on openhdemg, a free and open-source community-based framework for the automated analysis of MUs properties built on Python 3 and composed of different modules for HD-sEMG data handling, visualisation, editing, and analysis. openhdemg is interfaceable with most of the available recording software, equipment or decomposition techniques, and all the built-in functions are easily adaptable to different experimental needs. The framework also includes a graphical user interface which enables users with limited coding skills to perform a robust and reliable analysis of MUs properties without coding.

Consensus for experimental design in electromyography (CEDE) project: Single motor unit matrix

The analysis of single motor unit (SMU) activity provides the foundation from which information about the neural strategies underlying the control of muscle force can be identified, due to the one-to-one association between the action potentials generated by an alpha motor neuron and those received by the innervated muscle fibers. Such a powerful assessment has been conventionally performed with invasive electrodes (i.e., intramuscular electromyography (EMG)), however, recent advances in signal processing techniques have enabled the identification of single motor unit (SMU) activity in high-density surface electromyography (HDsEMG) recordings. This matrix, developed by the Consensus for Experimental Design in Electromyography (CEDE) project, provides recommendations for the recording and analysis of SMU activity with both invasive (needle and fine-wire EMG) and non-invasive (HDsEMG) SMU identification methods, summarizing their advantages and disadvantages when used during different testing conditions. Recommendations for the analysis and reporting of discharge rate and peripheral (i.e., muscle fiber conduction velocity) SMU properties are also provided. The results of the Delphi process to reach consensus are contained in an appendix. This matrix is intended to help researchers to collect, report, and interpret SMU data in the context of both research and clinical applications.

Automatic Assessment of Abdominal Exercises for the Treatment of Diastasis Recti Abdominis Using Electromyography and Machine Learning

Diastasis Recti Abdominis (DRA) is a medical condition in which the two sides of the rectus abdominis muscle are separated by at least 2.7 cm. This happens when the collagen sheath that exists between the rectus muscles stretches beyond a certain limit. The recti muscles generally separate and move apart in pregnant women due to the development of fetus in the womb. In some cases, this intramuscular gap will not be closed on its own, leading to DRA. The primary treatment procedures of DRA involve different therapeutic exercises to reduce the inter-recti distance. However, it is tedious for the physiotherapists to constantly monitor the patients and ensure that the exercises are being done correctly. The objective of this research is to analyze the correctness of such performed exercises using electromyogram (EMG) signals and machine learning. To the best of our knowledge, this is the first work reporting the objective evaluation of rehabilitation exercises for DRA. Experimental studies indicate that the surface EMG signals were effective in classifying the correctly and incorrectly performed movements. An extensive analysis was carried out with different machine learning models for classification. It was inferred that the RUSBoosted Ensembled classifier was effective in differentiating these movements with an accuracy of 92.3%.

Effects of a Single Dose of a Creatine-Based Multi-Ingredient Pre-workout Supplement Compared to Creatine Alone on Performance Fatigability After Resistance Exercise: A Double-Blind Crossover Design Study

Background

This study aims to investigate the acute effects of a single oral administration of a creatine-based multi-ingredient pre-workout supplement (MIPS) on performance fatigability and maximal force production after a resistance exercise protocol (REP).

Methods

Eighteen adult males (age: 23 ± 1 years; body mass: 76.4 ± 1.5 kg; height: 1.77 ± 0.01 m) were enrolled in a randomized, double-blind, crossover design study. Subjects received a single dose of a MIPS (3 g of creatine, 2 g of arginine, 1 g of glutamine, 1 g of taurine, and 800 mg of β-alanine) or creatine citrate (CC) (3 g of creatine) or a placebo (PLA) in three successive trials 1 week apart. In a randomized order, participants consumed either MIPS, CC, or PLA and performed a REP 2 h later. Before ingestion and immediately after REP, subjects performed isometric contractions of the dominant biceps brachii: two maximal voluntary contractions (MVCs), followed by a 20% MVC for 90 s and a 60% MVC until exhaustion. Surface electromyographic indices of performance fatigability, conduction velocity (CV), and fractal dimension (FD) were obtained from the surface electromyographic signal (sEMG). Time to perform the task (TtT), basal blood lactate (BL), and BL after REP were also measured.

Results

Following REP, statistically significant (P < 0.05) pre–post mean for ΔTtT between MIPS (−7.06 s) and PLA (+0.222 s), ΔCV slopes (20% MVC) between MIPS (0.0082%) and PLA (−0.0519%) and for ΔCV slopes (60% MVC) between MIPS (0.199%) and PLA (−0.154%) were found. A pairwise comparison analysis showed no statistically significant differences in other variables between groups and condition vs. condition.

Conclusion

After REP, a creatine-enriched MIPS resulted in greater improvement of sEMG descriptors of performance fatigability and TtT compared with PLA. Conversely, no statistically significant differences in outcomes measured were observed between CC and PLA or MIPS and CC.

Direct Effect of Local Cryotherapy on Muscle Stimulation, Pain and Strength in Male Office Workers with Lateral Epicondylitis, Non-Randomized Clinical Trial Study

Background: Local cryotherapy (LC) is one of the physiotherapeutic methods used in the conservative treatment of lateral epicondylitis (LE). The aim of the study was to verify the direct effect of a single LC procedure on the clinical symptoms of lateral epicondylitis enthesopathy (pain, pain free grip, PFG) and its effect on the bioelectrical properties of the wrist extensor muscles at rest, on maximal contraction and isometric contraction during fatigue. Methods: The study group was 28 men (35.4 ± 6.13 years) with confirmed unilateral epicondylitis. The performed procedures included the assessment of pain (visual analogue scale, VAS), PFG and ARMS (root-mean-square amplitude) and mean frequencies (MNF) of the sEMG signal before (T0) and after (T1) LC on the side with enthesopathy (ECRE) and without enthesopathy (ECRN/E). Results: There was an increase in the ARMS values of the signals recorded during rest and MVC from the ECR muscles both with and without enthesopathy (p = 0.0001, p = 0.006), an increased PFG after LC only on the side with LE (p < 0.0001) and decreased pain (p < 0.0001). During isometric fatigue contraction, a higher ARMS on both the ECRE side (p < 0.0001) and the ECRN/E side (p < 0.0001) was observed after LC treatment, and a lower MNF was observed on both the ECRN/E side (p < 0.0001) and the ECRE side (p < 0.0001) after LC. Conclusions: LC reduces the pain and increases PFG and muscle excitation expressed by ARMS and seems to delay muscle fatigue.

Influence of electrode configuration on muscle-fiber-conduction-velocity estimation using surface electromyography

OBJECTIVE

Muscle fiber conduction velocity (MFCV) is an important myoelectric parameter and can be estimated by analyzing surface electromyography (EMG). Among many factors, electrode configuration plays a key role on MFCV estimation. Most studies adopt bipolar configuration (BC) for CV estimation. However, a thorough understanding of the underlying mechanism is lacking, confusing the design of the most appropriate EMG measurement setup for CV estimation. The aim of this study is therefore to systematically investigate the influence of electrode configuration on MFCV estimation.

METHODS

Four possible configurations are considered, including BC, monopolar configuration (MC), common average reference (CAR), and a special monopolar configuration (SMC) using a fix channel on the active muscle as reference. For each configuration, mathematic models computing the time delay between adjacent channels are derived and evaluated by dedicated simulation as well as real EMG measurements. MFCV was calculated using the maximum likelihood algorithm with and without channel normalization.

RESULTS

The simulation results are in line with the mathematical models. The CVs estimated from the real EMG with and without normalization are 4.30.7 and 7.23.7 m/s, 5.71.3 and 20.44.7 m/s, 9.03.4 and 20.69.8 m/s, and 5.52.5 and 5.52.4 m/s for BC, MC, SMC, and CAR, respectively.

CONCLUSION

Our results show normalized BC to produce the most accurate CV estimation, in line with the mathematical models and the simulation results.

SIGNIFICANCE

These findings enable a better understanding of the influence of electrode configuration on MFCV estimation, providing useful information for EMG measurement setup design aiming at MFCV studies.

Screening for Sarcopenia (Physical Frailty) in the COVID-19 Era

Although the numbers of aged populations have risen considerably in the last few decades, the current coronavirus disease 2019 (COVID-19) has revealed an extensive vulnerability among these populations. Sarcopenia is an age-related disorder that increases hospitalization, dependencies, and mortality in older adults. It starts to develop in midlife or even earlier as a result of unbalanced diet/poor nutrition and low levels of physical activity, in addition to chronic disorders such as obesity and diabetes mellitus. Given that social isolation is adopted as the most protective measure against COVID-19, the level of physical activity and the intake of adequate diet have considerably declined, especially among older adults-denoting an increased possibility for developing sarcopenia. Research also shows a higher vulnerability of sarcopenic people to COVID-19 as well as the development of wasting disorders such as sarcopenia and cachexia in a considerable proportion of symptomatic and recovering COVID-19 patients. Muscular wasting in COVID-19 is associated with poor prognosis. Accordingly, early detection and proper management of sarcopenia and wasting conditions in older adults and COVID-19 patients may minimize morbidity and mortality during the current COVID-19 crisis. This review explored different aspects of screening for sarcopenia, stressing their relevance to the detection of altered muscular structure and performance in patients with COVID-19. Current guidelines recommend prior evaluation of muscle strength by simple measures such as grip strength to identify individuals with proven weakness who then would be screened for muscle mass loss. The latter is best measured by MRI and CT. However, due to the high cost and radiation risk entailed by these techniques, other simpler and cheaper techniques such as DXA and ultrasound are given preference. Muscle loss in COVID-19 patients was measured during the acute phase by CT scanning of the pectoralis muscle simultaneously during a routine check for lung fibrosis, which seems to be an efficient evaluation of sarcopenia among those patients with no additional cost. In recovering patients, muscle strength and physical performance have been evaluated by electromyography and traditional tests such as the six-minute walk test. Effective preventive and therapeutic interventions are necessary in order to prevent muscle loss and associated physical decline in COVID-19 patients.

A Survey on the Use and Barriers of Surface Electromyography in Neurorehabilitation

Historical, educational, and technical barriers have been reported to limit the use of surface electromyography (sEMG) in clinical neurorehabilitation settings. In an attempt to identify, review, rank, and interpret potential factors that may play a role in this scenario, we gathered information on (1) current use of sEMG and its clinical potential; (2) professional figures primarily dealing with sEMG; (3) educational aspects, and (4) possible barriers and reasons for its apparently limited use in neurorehabilitation. To this aim, an online 30-question survey was sent to 52 experts on sEMG from diverse standpoints, backgrounds, and countries. Participants were asked to respond to each question on a 5-point Likert scale or by ranking items. A cut-off of 75% agreement was chosen as the consensus threshold. Thirty-five invitees (67%) completed the electronic survey. Consensus was reached for 77% of the proposed questions encompassing current trends in sEMG use in neurorehabilitation, educational, technical, and methodological features as well as its translational utility for clinicians and patients. Data evidenced the clinical utility of sEMG for patient assessment, to define the intervention plan, and to complement/optimize other methods used to quantify muscle and physical function. The aggregate opinion of the interviewed experts confirmed that sEMG is more frequently employed in technical/methodological than clinical research. Moreover, the slow dissemination of research findings and the lack of education on sEMG seem to prevent prompt transfer into practice. The findings of the present survey may contribute to the ongoing debate on the appropriateness and value of sEMG for neurorehabilitation professionals and its potential translation into clinical settings.

Motor control integrated into muscle strengthening exercises has more effects on scapular muscle activities and joint range of motion before initiation of radiotherapy in oral cancer survivors with neck dissection: A randomized controlled trial

Background

Accessory nerve shoulder dysfunction is common after neck dissection in oral cancer survivors. This study aimed to investigate the short-term effects of scapular muscle strengthening exercises with motor-control techniques on neck dissection-related shoulder dysfunction in oral cancer survivors before the initiation of radiotherapy.

Methods

Thirty-eight participants were randomly allocated into the motor-control and regular-exercise groups. Each group received conventional physical therapy and specific scapular muscle strengthening exercises for 1 month immediately after neck dissection. Motor control techniques were integrated with scapular strengthening exercises for the motor-control group. Shoulder pain, active range of motion (AROM) of shoulder abduction, and scapular muscle activities including upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) when performing maximal voluntary isometric contraction (MVIC) and scapular muscle exercises were evaluated at baseline and after 1 month of training.

Results

Both groups reduced shoulder pain and increased muscle activity of maximum voluntary isometric contraction (MVIC) of each muscle after the intervention. Increased AROM of shoulder abduction was only observed in the motor-control group (95% CI 3.80 to 20.51, p = 0.004). Relative to baseline evaluation, muscle activities of UT decreased in the motor-control group when performing shoulder shrug with 1-kg weight (95% CI -33.06 to -1.29, p = 0.034). Moreover, the SA activity decreased in the motor-control group (95% CI -29.73 to -27.68, p<0.001) but increased in the regular-exercise group (95% CI 28.16 to 30.05, p<0.001) when performing shoulder horizontal adduction and flexion.

Conclusion

Early strengthening exercise with motor control techniques has greater benefits for improving AROM of shoulder abduction, muscle economy, and reducing compensatory scapular muscle activities in patients with neck dissection-related shoulder dysfunction before the initiation of radiotherapy.

Reproducibility of muscle fibre conduction velocity during linearly increasing force contractions

Muscle fibre conduction velocity (MFCV) is a basic physiological parameter biophysically related to the diameter of muscle fibres and properties of the sarcolemma. The aim of this study was to assess the intersession reproducibility of the relation between voluntary force and estimates of average muscle fibre conduction velocity (MFCV) from multichannel high-density surface electromyographic recordings (HDsEMG). Ten healthy men performed six linearly increasing isometric ankle dorsiflexions on two separate experimental sessions, 4 weeks apart. Each session involved the recordings of voluntary force during maximal isometric (MViF) and submaximal ramp contractions at 35-50-70% of MViF. Concurrently, the HDsEMG activity was detected from the tibialis anterior muscle and MFCV estimates were derived in 250-ms epochs. Absolute and relative reproducibility of MFCV initial value (intercept) and rate of change (regression slope) as a function of force were assessed by within-subject coefficient of correlation (CV_w) and with intraclass correlation coefficient (ICC). MFCV was positively correlated with voluntary force (R² = 0.75 ± 0.12) in all individuals and test conditions (P < 0.001). Average CV_w for MFCV intercept and slope were of 2.6 ± 2.0% and 11.9 ± 3.2% and ICC values of 0.96 and 0.94, respectively. Overall, MFCV regression coefficients showed a high degree of intersession reproducibility in both absolute and relative terms. These results may have important practical implications in the tracking of training-induced neuromuscular changes and/or in the monitoring of the progress of neuromuscular disorders when a full sEMG signal decomposition is problematic or not possible.