A multidimensional facial surface EMG analysis for objective assessment of bulbar involvement in amyotrophic lateral sclerosis.

OBJECTIVE: To develop a multidimensional facial surface electromyographic (EMG) analysis for assessing bulbar involvement in amyotrophic lateral sclerosis (ALS). METHODS: Fifty-four linear and nonlinear features were extracted from the surface EMG recordings for masseter, temporalis, and anterior belly of digastric in 13 patients with ALS and 10 healthy controls, each performed a speech task three times. The features were factor analyzed and then evaluated in terms of internal consistency, relation to functional speech outcomes, and efficacy for patient-control classification. RESULTS: Five internally consistent, interpretable factors were derived, representing the functioning of masseter, temporalis, digastric, antagonists, and agonists, respectively. These factors explained 40-43% of the variance in the functional speech outcomes and were ≥90% accurate in patient-control classification. The jaw muscle performance of individuals with ALS was characterized by (1) reduced complexity and coherence of antagonist muscle activities, and (2) increased complexity and irregularity of temporalis activity. CONCLUSIONS: Two important bulbar muscular changes were identified in ALS, related to both upper and lower motor neuron pathologies. These changes reflected (1) decreased motor unit recruitment and synchronization for jaw antagonists, and (2) a potential neuromuscular adaptation for temporalis. SIGNIFICANCE: The surface EMG-based framework shows promise as an objective bulbar assessment tool.

Development and Preliminary Validation of an Electromyography-Scoring Protocol for the Assessment and Grading of Muscle Involvement in Patients With Juvenile Idiopathic Inflammatory Myopathies.

INTRODUCTION: We performed a pilot study in order to investigate the feasibility of an electromyography (EMG)-scoring protocol for the assessment of disease activity in juvenile idiopathic inflammatory myopathies (JIIM). METHODS: Children with JIIM followed up in a tertiary-level care center underwent standardized clinical, laboratory, and EMG assessment. An EMG-scoring protocol was devised by a consensus panel including a pediatric neurophysiologist and two pediatric rheumatologists, based on a combined score obtained as the sum of (1) the presence of denervation signs (fibrillation potentials) and (2) motor unit remodeling (mixed pattern of short- and long-duration motor unit action potentials). The EMG-scoring protocol was then validated following the Outcome Measures in Rheumatoid Arthritis Clinical Trials filter for outcome measures in rheumatology and the consensus-based standards for the selection of health measurement instruments methodology. RESULTS: Thirteen children (77% females) were included in the study, with a median age of 10 years (interquartile range: 7-17 years) and median disease duration of 11.8 months (interquartile range: 2.1-44.5). A total of 39 EMG examinations were evaluated. A strong positive association between a standardized tool for muscle strength assessment and the combined score was observed. No significant associations were found with both creatine kinase and erythrocyte sedimentation rate levels. DISCUSSION: Our EMG-scoring protocol is the first standardized and reproducible tool for the neurophysiologic evaluation and grading of muscle involvement in patients with JIIM and could provide relevant additional information in the assessment and follow-up of these rare conditions.

Evaluation of movement and brain activity.

Clinical neurophysiology studies can contribute important information about the physiology of human movement and the pathophysiology and diagnosis of different movement disorders. Some techniques can be accomplished in a routine clinical neurophysiology laboratory and others require some special equipment. This review, initiating a series of articles on this topic, focuses on the methods and techniques. The methods reviewed include EMG, EEG, MEG, evoked potentials, coherence, accelerometry, posturography (balance), gait, and sleep studies. Functional MRI (fMRI) is also reviewed as a physiological method that can be used independently or together with other methods. A few applications to patients with movement disorders are discussed as examples, but the detailed applications will be the subject of other articles.

Gold Coast diagnostic criteria increase sensitivity in amyotrophic lateral sclerosis.

OBJECTIVE: This study evaluates diagnostic accuracy of the proposed 'Gold Coast' (GC) diagnostic criteria for amyotrophic lateral sclerosis (ALS). METHODS: Five European centres retrospectively sampled consecutive patients referred for electromyography on suspicion of ALS. Patients were classified according to the GC criteria, the revised El Escorial (rEE) criteria and the Awaji (AW) criteria without and with the 'Possible' category (+ Poss). Reference standard was ALS confirmed by disease progression at follow-up. RESULTS: Of 404 eligible patients 272 were diagnosed as ALS, 94 had mimicking disorders, 35 were lost for follow-up, and three had insufficient data. Sensitivity for the GC criteria was 88.2% (95% CI: 83.8-91.8%), which was higher than for previous criteria, of which the AW + Poss criteria reached the highest sensitivity of 77.6% (95% CI: 72.2-82.4%) (p < 0.001). Specificity was high for all criteria. The increase in sensitivity for the GC criteria was mainly due to the inclusion of 28 patients with progressive muscular atrophy (PMA). CONCLUSIONS: The simpler GC criteria increase the sensitivity, primarily due to considering PMA as a form of ALS with high specificity preserved. SIGNIFICANCE: This validation study supports that GC criteria should be used in clinical practice and may be used for inclusion in trials.

The Gold Coast criteria increases the diagnostic sensitivity for amyotrophic lateral sclerosis in a Chinese population.

OBJECTIVES: The aim of this study was to assess and compare the diagnostic utility of a new diagnostic criteria for amyotrophic lateral sclerosis (ALS), abbreviated as the 'Gold Coast Criteria', with the revised El Escorial (rEEC) and Awaji criteria. METHODS: Clinical and electrophysiological data of 1185 patients from January 2014 to December 2019 in the Peking Union Medical College Hospital ALS database were reviewed. The sensitivity of the Gold Coast criteria was compared to that of the possible rEEC and Awaji criteria (defined by the proportion of patients categorized as definite, probable, or possible ALS). RESULTS: A final diagnosis of ALS was recorded in 1162 patients. The sensitivity of the Gold Coast criteria (96.6%, 95% confidence interval [CI] = 95.3%-97.5%) was greater than that of the rEEC (85.1%, 95%CI = 82.9%-87.1%) and Awaji (85.3%, 95%CI = 83.2%-87.3%). In addition, the sensitivity of the novel criteria maintained robust across subgroups, and the advantage was more prominent in limb-onset ALS patients and those who completed electromyographic tests. In those who did not achieve any of the rEEC diagnostic categories, the sensitivity of Gold Coast criteria was 84.4%. CONCLUSIONS: The current study demonstrated that the Gold Coast criteria exhibited greater diagnostic sensitivity than the rEEC and Awaji criteria in a Chinese ALS population. The application of the Gold Coast criteria should be considered in clinical practice and future therapeutic trials.

The reliability of cerebellar brain inhibition.

OBJECTIVE: Connectivity between the cerebellum and primary motor cortex (M1) can be assessed by using transcranial magnetic stimulation to measure cerebellar brain inhibition (CBI). The aim of the present study was to determine the intra- and inter-day measurment error and relative reliability of CBI. The former informs the degree to which repeated measurements vary, whereas the latter informs how well the measure can distinguish individuals from one another within a sample. METHODS: We obtained CBI data from 83 healthy young participants (n = 55 retrospective). Intra-day measurements were separated by ~ 30 min. Inter-day measurmenets were separated by a minimum of 24 h. RESULTS: We show that CBI has low measurement error (~15%) within and between sessions. Using the measurment error, we demonstrate that change estimates which exceed measurment noise are large at an individual level, but can be detected with modest sample sizes. Finally, we demonstrate that the CBI measurement has fair to good relative reliability in healthy individuals, which may be deflated by low sample heterogeneity. CONCLUSIONS: CBI has low measurement error supporting its use for tracking intra- and inter-day changes in cerebellar-M1 connectivity. SIGNIFICANCE: Our findings provide clear reliability guidelines for future studies assessing modulation of cerebellar-M1 connectivity with intervention or disease progression.

Intraoperative lateral rectus electromyographic recordings optimized by deep intraorbital needle electrodes.

OBJECTIVE: We demonstrate the advantages and safety of long, intraorbitally-placed needle electrodes, compared to standard-length subdermal electrodes, when recording lateral rectus electromyography (EMG) during intracranial surgeries. METHODS: Insulated 25 mm and uninsulated 13 mm needle electrodes, aimed at the lateral rectus muscle, were placed in parallel during 10 intracranial surgeries, examining spontaneous and stimulation-induced EMG activities. Postoperative complications in these patients were reviewed, alongside additional patients who underwent long electrode placement in the lateral rectus. RESULTS: In 40 stimulation-induced recordings from 10 patients, the 25 mm electrodes recorded 6- to 26-fold greater amplitude EMG waveforms than the 13 mm electrodes. The 13 mm electrodes detected greater unwanted volume conduction upon facial nerve stimulation, typically exceeding the amplitude of abducens nerve stimulation. Except for one case with lateral canthus ecchymosis, no clinical or radiographic complications occurred in 36 patients (41 lateral rectus muscles) following needle placement. CONCLUSIONS: Intramuscular recordings from long electrode in the lateral rectus offers more reliable EMG monitoring than 13 mm needles, with excellent discrimination between abducens and facial nerve stimulations, and without significant complications from needle placement. SIGNIFICANCE: Long intramuscular electrode within the orbit for lateral rectus EMG recording is practical and reliable for abducens nerve monitoring.

Ipsilateral and Simultaneous Comparison of Responses from Acceleromyography- and Electromyography-based Neuromuscular Monitors.

BACKGROUND: The paucity of easy-to-use, reliable objective neuromuscular monitors is an obstacle to universal adoption of routine neuromuscular monitoring. Electromyography (EMG) has been proposed as the optimal neuromuscular monitoring technology since it addresses several acceleromyography limitations. This clinical study compared simultaneous neuromuscular responses recorded from induction of neuromuscular block until recovery using the acceleromyography-based TOF-Watch SX and EMG-based TetraGraph. METHODS: Fifty consenting patients participated. The acceleromyography and EMG devices analyzed simultaneous contractions (acceleromyography) and muscle action potentials (EMG) from the adductor pollicis muscle by synchronization via fiber optic cable link. Bland-Altman analysis described the agreement between devices during distinct phases of neuromuscular block. The primary endpoint was agreement of acceleromyography- and EMG-derived normalized train-of-four ratios greater than or equal to 80%. Secondary endpoints were agreement in the recovery train-of-four ratio range less than 80% and agreement of baseline train-of-four ratios between the devices. RESULTS: Acceleromyography showed normalized train-of-four ratio greater than or equal to 80% earlier than EMG. When acceleromyography showed train-of-four ratio greater than or equal to 80% (n = 2,929), the bias was 1.3 toward acceleromyography (limits of agreement, -14.0 to 16.6). When EMG showed train-of-four ratio greater than or equal to 80% (n = 2,284), the bias was -0.5 toward EMG (-14.7 to 13.6). In the acceleromyography range train-of-four ratio less than 80% (n = 2,802), the bias was 2.1 (-16.1 to 20.2), and in the EMG range train-of-four ratio less than 80% (n = 3,447), it was 2.6 (-14.4 to 19.6). Baseline train-of-four ratios were higher and more variable with acceleromyography than with EMG. CONCLUSIONS: Bias was lower than in previous studies. Limits of agreement were wider than expected because acceleromyography readings varied more than EMG both at baseline and during recovery. The EMG-based monitor had higher precision and greater repeatability than acceleromyography. This difference between monitors was even greater when EMG data were compared to raw (nonnormalized) acceleromyography measurements. The EMG monitor is a better indicator of adequate recovery from neuromuscular block and readiness for safe tracheal extubation than the acceleromyography monitor.

Reliability and laterality of the soleus H-reflex following galvanic vestibular stimulation in healthy individuals.

The vestibulospinal tract (VST) plays an important role in the control of the ipsilateral antigravity muscles, and the balance of left and right VST excitability is important in human postural control. A method for measuring VST excitability is the application of galvanic vestibular stimulation (GVS) before tibial nerve stimulation that evokes the soleus H-reflex; the change rate of the H-reflex amplitude is then evaluated. Assessments of VST excitability and the left and right balance could be useful when determining the pathology for interventions in postural control impairments. However, the reliability and laterality of this assessment have not been clarified, nor has its relationship to postural control. We investigated the reliability, laterality and standing postural control in relation to the degree of facilitation of the H-reflex following GVS in 15 healthy adults. The assessments were performed in two sessions, one each for the left- and right-sides, in random order. The inter-session reliability of the short-interval assessments of an increase in the H-reflex following GVS on both sides were sufficient. The degree of H-reflex facilitation by GVS showed no significant difference between the left- and right-sides in any session. There was a moderate positive correlation between the mediolateral position of the center of pressure in the eyes-closed standing on foam condition and the left/right ratio of the degree of increased H-reflex in the first-session. We concluded that this method for evaluating the increase in the soleus H-reflex following GVS has high inter-session reliability in the short-interval that did not differ between sides.

Analysis of motor unit spike trains estimated from high-density surface electromyography is highly reliable across operators.

There is a growing interest in decomposing high-density surface electromyography (HDsEMG) into motor unit spike trains to improve knowledge on the neural control of muscle contraction. However, the reliability of decomposition approaches is sometimes questioned, especially because they require manual editing of the outputs. We aimed to assess the inter-operator reliability of the identification of motor unit spike trains. Eight operators with varying experience in HDsEMG decomposition were provided with the same data extracted using the convolutive kernel compensation method. They were asked to manually edit them following established procedures. Data included signals from three lower leg muscles and different submaximal intensities. After manual analysis, 126 ± 5 motor units were retained (range across operators: 119-134). A total of 3380 rate of agreement values were calculated (28 pairwise comparisons × 11 contractions/muscles × 4-28 motor units). The median rate of agreement value was 99.6%. Inter-operator reliability was excellent for both mean discharge rate and time at recruitment (intraclass correlation coefficient > 0.99). These results show that when provided with the same decomposed data and the same basic instructions, operators converge toward almost identical results. Our data have been made available so that they can be used for training new operators.

Near-fiber electromyography.

OBJECTIVE: Describe and evaluate the concepts of near fiber electromyography (NFEMG), the features used, including near fiber motor unit potential (NFMUP) duration and dispersion, which relate to motor unit distal axonal branch and muscle fiber conduction time dispersion, and NFMUP segment jitter, a new measure of the temporal variability of neuromuscular junction transmission (NMJ), and axonal branch and muscle fibre conduction for the near fibres (i.e. NF jitter), and the methods for obtaining their values. METHODS: Trains of high-pass filtered motor unit potentials (MUPs) (i.e. NFMUP trains) were extracted from needle-detected EMG signals to assess changes in motor unit (MU) morphology and electrophysiology caused by neuromuscular disorders or ageing. Evaluations using simulated needle-detected EMG data were completed and example human data are presented. RESULTS: NFEMG feature values can be used to detect axonal sprouting, conduction slowing and NMJ transmission delay as well as changes in MU fiber diameter variability, and NF jitter. These changes can be detected prior to alterations of MU size or numbers. CONCLUSIONS: The evaluations clearly demonstrate and the example data support that NFMUP duration and dispersion reflect MU distal axonal branching, conduction slowing and NMJ transmission delay and/or MU fiber diameter variability and that NFMUP jiggle and segment jitter reflect NF jitter. SIGNIFICANCE: NFEMG can detect early changes in MU morphology and/or electrophysiology and has the potential to augment clinical diagnosis and tracking of neuromuscular disorders.

Standardization of neurophysiology signal data into the DICOM® standard.

A standard format for neurophysiology data is urgently needed to improve clinical care and promote research data exchange. Previous neurophysiology format standardization projects have provided valuable insights into how to accomplish the project. In medical imaging, the Digital Imaging and Communication in Medicine (DICOM) standard is widely adopted. DICOM offers a unique environment to accomplish neurophysiology format standardization because neurophysiology data can be easily integrated with existing DICOM-supported elements such as video, ECG, and images and also because it provides easy integration into hospital Picture Archiving and Communication Systems (PACS) long-term storage systems. Through the support of the International Federation of Clinical Neurophysiology (IFCN) and partners in industry, DICOM Working Group 32 (WG-32) has created an initial set of standards for routine electroencephalography (EEG), polysomnography (PSG), electromyography (EMG), and electrooculography (EOG). Longer and more complex neurophysiology data types such as high-definition EEG, long-term monitoring EEG, intracranial EEG, magnetoencephalography, advanced EMG, and evoked potentials will be added later. In order to provide for efficient data compression, a DICOM neurophysiology codec design competition will be held by the IFCN and this is currently being planned. We look forward to a future when a common DICOM neurophysiology data format makes data sharing and storage much simpler and more efficient.

Reliability and sources of variability of 3D kinematics and electromyography measurements to assess newly-acquired gait in toddlers with typical development and unilateral cerebral palsy.

The aim was to 1) determine intersession and intertrial reliability and 2) assess three sources of variability (intersubject, intersession and intertrial) of lower limb kinematic and electromyographic (EMG) variables during gait in toddlers with typical development (TD) and unilateral cerebral palsy (UCP) (age <3 years, independent walking experience ≤6 months). Gait kinematics and surface EMG were recorded in 30 toddlers (19 TD and 11 UCP), during two, 3D-motion capture sessions. Standard error of measurement (SEM) between trials (gait cycles) of the same session and between sessions was calculated to assess reliability. Standard deviations (SD) between subjects, sessions and trials were calculated to estimate sources of variability. Sixty-four percent of kinematic SEM-values were acceptable (2°-5°). Frontal plane measurements were most reliable (SEM 2°-4.6°). In toddlers with UCP, EMG variables were most reliable for affected side, distal muscles. Intrinsic (intertrial and intersubject) variability was high, reflecting both motor immaturity and the high variability of toddler gait patterns. In toddlers with UCP, variability was amplified by motor impairment and delayed motor development. 3D gait analysis and surface EMG are partially reliable tools to study individual gait patterns in toddlers in clinical practice and research, although some variables must be interpreted with caution.

A novel passive neck orthosis for patients with degenerative muscle diseases: Development & evaluation.

The current study evaluated the effect of a passive neck orthosis, developed for patients suffering from progressive muscular diseases, on neck muscle activity in 10 adult healthy participants. The participants performed discrete head movements involving pure neck flexion (-10 to 30°), pure neck rotation (up to 30° left and right) and combined neck flexion-rotation (-10 to 30°) in steps of 10° by moving a cursor on a screen to reach predefined targets and staying on target for 10 s. Surface electromyography (EMG) was recorded from upper trapezius and sternocleidomastoid muscles and amplitudes were averaged over the static phases in trials with and without the orthosis. Moreover, the variability in head position and time required to perform the tasks were compared between conditions. Wearing the orthosis caused significant reductions (p = 0.027) in upper trapezius activity (a change of 0.2-1.5% EMGmax) while working against gravity. The activity level of the sternocleidomastoid muscle increased (p ≤ 0.025) by 0.3-1.0% EMGmax during pure and combined rotations without any pain reported. The orthosis showed potential to reduce the activity level of the upper trapezius muscle, the main load bearing muscle of the neck. Further study will be carried out to evaluate the effect in different patient groups.

How to improve the muscle synergy analysis methodology?

Muscle synergy analysis is increasingly used in domains such as neurosciences, robotics, rehabilitation or sport sciences to analyze and better understand motor coordination. The analysis uses dimensionality reduction techniques to identify regularities in spatial, temporal or spatio-temporal patterns of multiple muscle activation. Recent studies have pointed out variability in outcomes associated with the different methodological options available and there was a need to clarify several aspects of the analysis methodology. While synergy analysis appears to be a robust technique, it remain a statistical tool and is, therefore, sensitive to the amount and quality of input data (EMGs). In particular, attention should be paid to EMG amplitude normalization, baseline noise removal or EMG filtering which may diminish or increase the signal-to-noise ratio of the EMG signal and could have major effects on synergy estimates. In order to robustly identify synergies, experiments should be performed so that the groups of muscles that would potentially form a synergy are activated with a sufficient level of activity, ensuring that the synergy subspace is fully explored. The concurrent use of various synergy formulations-spatial, temporal and spatio-temporal synergies- should be encouraged. The number of synergies represents either the dimension of the spatial structure or the number of independent temporal patterns, and we observed that these two aspects are often mixed in the analysis. To select a number, criteria based on noise estimates, reliability of analysis results, or functional outcomes of the synergies provide interesting substitutes to criteria solely based on variance thresholds.

Electrical impedance myography: A critical review and outlook.

Electrical impedance myography (EIM) technology is finding application in neuromuscular disease research as a tool to assess muscle health. Correlations between EIM outcomes, functional, imaging and histological data have been established in a variety of neuromuscular disorders; however, an analytical discussion of EIM is lacking. This review presents an explanation for clinicians and others who are applying EIM and interpreting impedance outcomes. The background of EIM is presented, including the relation between EIM, volume conduction properties, tissue structure, electrode configuration and conductor volume. Also discussed are technical considerations to guide the reader to critically evaluate EIM and understand its limitations and strengths.

Reliability of transcallosal inhibition measurements for the lower limb motor cortex in stroke.

Transcallosal inhibition (TCI) is a measure of between-hemisphere inhibitory control that can be evaluated with the ipsilateral silent period (iSP) transcranial magnetic stimulation (TMS) paradigm. The study of iSP for the lower extremity has been limited possibly due to the close orientation of the lower extremity motor representations. Change in TCI can provide insights into pathophysiological mechanisms underlying the asymmetry in corticomotor excitability in stroke. Here, we describe a method for iSP quantification and report reliability of iSP parameters for the tibialis anterior (TA) muscle in stroke. 26 individuals with stroke attended three sessions where single pulse TMS was used to measure TCI from the lesioned to non-lesioned hemisphere. A double cone coil was used for stimulating the ipsilateral motor cortex while the participant maintained an isometric contraction of the non-paretic TA. Absolute and relative reliability were computed for iSP latency, duration and area. iSP latency showed the lowest measurement error (absolute reliability) and iSP latency, duration and area showed good relative reliability (intraclass correlation coefficients > 0.6). This study suggests that iSP parameters for the tibialis anterior are reliable and attempts to provide a guideline for evaluating TCI for the lower extremity in stroke and other clinical populations.

Limitations of surface EMG estimate of parasternal intercostal to infer neural respiratory drive.

BACKGROUND: Recently, surface EMG of parasternal intercostal muscle has been incorporated in the "ERS Statement of Respiratory Muscle Testing" as a clinical technique to monitor the neural respiratory drive (NRD). However, the anatomy of the parasternal muscle risks confounding EMG "crosstalk" activity from neighboring muscles. OBJECTIVES: To determine if surface "parasternal" EMG: 1) reliably estimates parasternal intercostal EMG activity, 2) is a valid surrogate expressing neural respiratory drive (NRD). METHODS: Fine wire electrodes were implanted into parasternal intercostal muscle in 20 severe COPD patients along with a pair of surface EMG electrodes at the same intercostal level. We recorded both direct fine wire parasternal EMG (EMGPARA) and surface estimated "parasternal" EMG (SurfEMGpara) simultaneously during resting breathing, volitional inspiratory maneuvers, apnoea with extraneous movement of upper extremity, and hypercapnic ventilation. RESULTS: Surface estimated "parasternal" EMG showed spurious "pseudobreathing" activity without any airflow while real parasternal EMG was silent, during apnoea with body extremity movement. Surface estimated "parasternal" EMG did not faithfully represent real measured parasternal EMG. Surface estimated "parasternal" EMG was significantly less active than directly measured parasternal EMG during all conditions including baseline, inspiratory capacity and hypercapnic ventilation. Bland-Altman analysis showed consistent bias between direct parasternal EMG recording and surface estimated EMG during stimulated breathing. CONCLUSION: Surface "parasternal" EMG does not consistently or reliably express EMG activity of parasternal intercostal as recorded directly by implanted fine wires. A chest wall surface estimate of parasternal intercostal EMG may not faithfully express NRD and is of limited utility as a biomarker in clinical applications.

Cardiorespiratory monitoring in the delivery room using transcutaneous electromyography.

OBJECTIVE: To assess feasibility of transcutaneous electromyography of the diaphragm (dEMG) as a monitoring tool for vital signs and diaphragm activity in the delivery room (DR). DESIGN: Prospective observational study. SETTING: Delivery room. PATIENTS: Newborn infants requiring respiratory stabilisation after birth. INTERVENTIONS: In addition to pulse oximetry (PO) and ECG, dEMG was measured with skin electrodes for 30 min after birth. OUTCOME MEASURES: We assessed signal quality of dEMG and ECG recording, agreement between heart rate (HR) measured by dEMG and ECG or PO, time between sensor application and first HR read-out and agreement between respiratory rate (RR) measured with dEMG and ECG, compared with airway flow. Furthermore, we analysed peak, tonic and amplitude diaphragmatic activity from the dEMG-based respiratory waveform. RESULTS: Thirty-three infants (gestational age: 31.7±2.8 weeks, birth weight: 1525±661 g) were included.18%±14% and 22%±21% of dEMG and ECG data showed poor quality, respectively. Monitoring HR with dEMG was fast (median 10 (IQR 10-11) s) and accurate (intraclass correlation coefficient (ICC) 0.92 and 0.82 compared with ECG and PO, respectively). RR monitoring with dEMG showed moderate (ICC 0.49) and ECG low (ICC 0.25) agreement with airway flow. Diaphragm activity started high with a decreasing trend in the first 15 min and subsequent stabilisation. CONCLUSION: Monitoring vital signs with dEMG in the DR is feasible and fast. Diaphragm activity can be detected and described with dEMG, making dEMG promising for future DR studies.

EMG gait data from indwelling electrodes is attenuated over time and changes independent of any experimental effect.

The effect of time on the validity of electromyography (EMG) signals from indwelling fine-wire electrodes has not been explored. This is important because experiments using intramuscular electrodes are often long and biochemical and mechanical factors, may impair measurement accuracy over time. Measures over extended periods might therefore be erroneous. Twelve healthy participants (age = 33 ± 8 years) walked for 50 min at a controlled speed. Fine-wire electrodes were inserted into tibialis anterior and a surface EMG sensor attached near the fine-wire insertion site. EMG signals progressively and significantly decreased with time with the fine-wire electrode, but not the surface electrode. For the fine-wire electrode, after 25 min mean amplitude had reduced by 11% (p < 0.001) and after 50 min by 16% (p < 0.001), and peak amplitude reduced 22% at 20 min (p = 0.006) and 37% at 50 min (p < 0.001). Reduced amplitude with indwelling EMG without concurrent changes in surface EMG signal suggests an important inconsistency in data from fine-wire EMG electrodes. Changes in EMG signal will occur over time independent of the experimental condition and this questions their use in experiments of more than 30 min. These results should impact on experimental study design. They also invite reinterpretation of prior literature and sensor innovation to improve measurement performance.