Electromyographic Amplitude Research Articles

Inhibiting Matrix Metalloproteinases Protects Evoked Electromyography Amplitudes and Muscle Tension in the Orbicularis Oris Muscle in a Rat Model of Facial Nerve Injury.

Facial nerve injury results in degradation of the neuromuscular junction (NMJ) and blocks neurotransmission between the pre- and postsynaptic structures, which are separated by a synaptic cleft. Matrix metalloproteinases (MMPs), enzymes that degrade and modify the extracellular matrix, play critical roles in regulating NMJ remodeling. We previously demonstrated that MMP1, MMP2, MMP3, MMP7, and MMP9 are overexpressed in facial nerve-innervated orbicularis oris muscle after facial nerve injury in a rat model. In the present study, the MMP inhibitor prinomastat was administered to rats after facial nerve injury. The MMP levels, agrin expression, and muscle-specific kinase (MuSK) phosphorylation were evaluated. Variations in evoked electromyography (EEMG) amplitude were also recorded. Compared with the control group, MMP expression in the orbicularis oris after facial nerve injury was significantly reduced in the prinomastat group. Inhibition of MMP expression maintained agrin expression and MuSK phosphorylation; the NMJ morphology was also protected after the injury. Moreover, prinomastat treatment sustained EEMG amplitude and muscle tension after the injury. These findings indicate that inhibiting MMPs can protect the function and morphology of the NMJ and demonstrate the need for protection of the NMJ at early stages after facial nerve injury.

Analysis of pain relief and functional recovery in patients with rotator cuff tendinopathy through therapeutic ultrasound and photobiomodulation therapy: a comparative study

This study aimed to compare shoulder tendinopathy treatment with therapeutic ultrasound combined with LED photobiomodulation therapy using LED-infrared (850nm) or LED-red (640nm). The study assessed 75 patients, aged 45 to 70years, distributed into five experimental groups (15 patients each): therapeutic ultrasound (US), infrared light irradiation (IR), visible red light irradiation (VR), infrared light and ultrasound combined (IR-US), and red light in conjunction with ultrasound (VR-US). The ultrasound parameters are 1MHz, 0.5W/cm2 (SATA), and 100Hz repetition rate, applied for 4min each session. LED irradiation protocols were as follows: 3 points, 7.5J per point, IR-LED 750 mW, 10s, VR-LED 250 mW, 30s. LED irradiation is followed by ultrasound in the combined therapies. The efficiency of the five therapies was evaluated assessing 12 parameters: quality of life (Health Assessment Questionnaire, HAQ), pain intensity (Visual Analog Scale, VAS), articular amplitude of shoulder movement (flexion, extension, abduction, adduction, medial rotation, lateral rotation), muscle strength (abduction, lateral rotation), and electromyography (lateral rotation, abduction). Treatments comprised 12 sessions for 4weeks. Intra-group analysis showed that the five therapies significantly improved the recovery of all parameters after treatment. Regarding the comparison of irradiated therapies and ultrasound, statistical analysis showed that IR-US was a better treatment than US for all 12 parameters. IR treatment exceeded US on 9 items, whereas that VR and VR-US therapies exceeded US in 7 and 10 parameters, respectively (p < 0.05). Because of that, IR-US shows to be the best treatment for rotator cuff tendinopathy. In conclusion, improvements in quality of life, pain intensity relief, shoulder amplitude motion, and muscle strength force obtained with ultrasound therapy are enhanced by adding infrared LED irradiation to ultrasound for patients suffering from rotator cuff tendinopathy. This study was registered with the Brazilian Registry of Clinical Trials (ReBEC) under Universal Trial Number (UTN) U1111-1219-3594 (2018/22/08).

만성 요통환자의 굽힘과 폄편향이 허리근육의 횡단면적과 근활성도에 미치는 영향

The purpose of study was to explore the influence of flexion and extension bias on the electromyographic (EMG) activities and cross-sectional area of lumbar muscles in chronic low back pain. twenty-two patients with chronic low back pain were divided into either flexion bias or extension bias groups by symptom provoking posture. The multifidus, iliopsoas, and erector spinae muscles were measured by magnetic reasoning imaging (MRI) and calculated with ratio by body of the 4th lumbar vertebra. EMG activities of multifidus and erector spinae was measured, and all the EMG amplitude were normalized into %maximum voluntary isometric contraction (%MVIC). Flexion bias group has significantly lower ratio of iliopsoas cross-sectional area than that of extension bias group (p<.05). As a result, flexion bias group has higher ratio of cross-sectional area of multifidus at the more involved side (p<.05). Flexion bias group has significantly higher %MVIC in erector spinae than extension bias group during trunk flexion and extension (p<.05). Consequently, the results of this study suggest that necessity of exercise for preventing multifidus muscle atrophy for flexion bias group.

Can a Short-term Daily Oral Administration of Propolis Improve Muscle Fatigue and Recovery?

This study investigated the effect of 1-week oral administration of propolis on muscle fatigue and recovery after performing a fatigue task (total 100 maximal voluntary concentric knee extension repetitions). In this placebo-controlled, double-blind study, 18 young men consumed a formulation with high Brazilian green propolis dose (H-BGP), a formulation with low Brazilian green propolis dose, or a placebo, for 1 week before performing the fatigue task (an interval between each intervention: 1-2 weeks). Maximal voluntary contraction torque, central fatigue (voluntary activation and root mean square values of the surface electromyography amplitude), and peripheral fatigue (potentiated triplet torque) were assessed before, immediately after, and 2 minutes after the fatigue task. Maximal voluntary contraction torque decreased immediately after the fatigue task in all conditions (P<0.001); however, it recovered from immediately after to 2 minutes after the fatigue task only in the H-BGP condition (P<0.001). Furthermore, there was a significant decrease in voluntary activation (P<0.001) and root mean square values of the surface electromyography amplitude (P≤0.035) only in the placebo condition. No significant difference was observed in the time-course change in potentiated triplet torque between the conditions. These results suggest that oral administration of propolis promotes muscle fatigue recovery by reducing central fatigue.

Quadriceps electromyography during flywheel-based inertial training (FIT) and dynamic constant external resistance (DCER) squats at similar tempo

ABSTRACT Flywheel-based iso-inertial training (FIT) has been purported to provide enhanced adaptations to muscle overload compared to dynamic constant external resistance (DCER), but previous studies have not controlled for exercise intensity. We compared quadriceps electromyography (EMG) amplitude between FIT- and DCER-squats with similar tempo. Eleven (5 M and 6F) resistance-trained participants completed sets of five maximal velocity FIT (0.025 kg∙m2) and DCER (55 ± 15 %1RM) squats. Sagittal plane knee joint angles and surface EMG activity of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) were measured. Repetition time and peak knee angles were similar between FIT and DCER squats. Mean knee angular velocity during the concentric (122.2 ± 23.6 vs. 108.9 ± 22.9, p = 0.022, Cohen’s D: 0.820), but not eccentric, phase was significantly greater during FIT. Peak VM (210.4 ± 49.3 vs. 177.5 ± 56.3 %MVIC, p = 0.001; Cohen’s D: 1.416), but not VL or RF, EMG amplitude was significantly greater in FIT compared to DCER. Mean EMG amplitude was significantly (p < 0.001) greater during the concentric than the eccentric phase for the VL and VM but not RF. Mean EMG amplitude was not significantly different between modes during either the concentric or eccentric phase. Quadriceps EMG amplitude is largely similar between FIT and DCER squats when matched for movement velocity.

Effects of different modalities of afferent stimuli of the lumbo-sacral area on control of lumbar paravertebral muscles.

Somatosensory feedback to the central nervous system is essential to plan, perform and refine spine motor control. However, the influence of somatosensory afferent input from the trunk on the motor output to trunk muscles has received little attention. The objective was to compare the effects of distinct modalities of afferent stimulation on the net motoneuron and corticomotor excitability of paravertebral muscles. Fourteen individuals were recruited. Modulation of corticospinal excitability (motor-evoked potential [MEP]) of paravertebral muscles was measured when afferent stimuli (cutaneous noxious and non-noxious, muscle contraction) were delivered to the trunk at 10 intervals prior to transcranial magnetic stimulation. Each peripheral stimulation was applied alone, and subsequent electromyography (EMG) modulation was measured to control for net motoneuron excitability. MEP modulation and MEP/EMG ratio were used as measures of corticospinal excitability with and without control of net motoneuron excitability, respectively. MEP and EMG modulation were smaller after evoked muscle contraction than after cutaneous noxious and non-noxious stimuli. MEP/EMG ratio was not different between stimulation types. Both MEP and EMG amplitudes were reduced after evoked muscle contraction, but not when expressed as MEP/EMG ratio. Noxious and non-noxious stimulation had limited impact on all variables. Distinct modalities of peripheral afferent stimulation of the lumbo-sacral area differently modulated responses of paravertebral muscles, but without an influence on corticospinal excitability with control of net motoneuron excitability. Muscle stimulation reduced paravertebral activity and was best explained by spinal mechanisms. The impact of afferent stimulation on back muscles differs from the effects reported for limb muscles.

A Comparison of Double Poling Physiology and Kinematics Between Long-Distance and All-Round Cross-Country Skiers.

PurposeThe objective of this study was to compare physiological and kinematic responses to double poling (DP) between long-distance (LDS) and all-round (ARS) cross-country skiers.MethodsA number of five world-class LDS (28.8 ± 5.1 years, maximal oxygen uptake (VO2max): 70.4 ± 2.9 ml·kg−1·min−1) and seven ARS (22.3 ± 2.8 years, VO2max: 69.1 ± 4.2 ml·kg−1·min−1) athletes having similar training volumes and VO2max performed three identical tests; (1) submaximal and incremental tests to exhaustion while treadmill DP to determine gross efficiency (GE), peak oxygen uptake (DP-VO2peak), and peak speed; (2) submaximal and incremental running tests to exhaustion to determine GE, VO2max (RUN-VO2max), and peak speed; and (3) an upper-body pull-down exercise to determine one repetition maximum (1RM) and peak power. Physiological responses were determined during both DP and running, together with the assessments of kinematic responses and electromyography (EMG) of selected muscles during DP.ResultsCompared to ARS, LDS reached higher peak speed (22.1 ± 1.0 vs. 20.7 ± 0.9 km·h−1, p = 0.030), DP-VO2peak (68.3 ± 2.1 vs. 65.1 ± 2.7 ml·kg−1·min−1, p = 0.050), and DP-VO2peak/RUN-VO2max ratio (97 vs. 94%, p = 0.075) during incremental DP to exhaustion, as well as higher GE (17.2 vs. 15.9%, p = 0.029) during submaximal DP. There were no significant differences in cycle length or cycle rate between the groups during submaximal DP, although LDS displayed longer relative poling times (~2.4% points) at most speeds compared to ARS (p = 0.015). However, group × speed interaction effects (p < 0.05) were found for pole angle and vertical fluctuation of body center of mass, with LDS maintaining a more upright body position and more vertical pole angles at touchdown and lift-off at faster speeds. ARS displayed slightly higher normalized EMG amplitude than LDS in the muscles rectus abdominis (p = 0.074) and biceps femoris (p = 0.027). LDS performed slightly better on 1RM upper-body strength (122 vs. 114 kg, p = 0.198), with no group differences in power in the pull-down exercise.ConclusionsThe combination of better DP-specific aerobic energy delivery capacity, efficiency, and technical solutions seems to contribute to the superior DP performance found among specialized LDS in comparison with ARS.

The effect of low back pain on neuromuscular control in cyclists

ABSTRACT This study was designed to identify neuromuscular adaptations of low back pain (LBP) cyclists , and the impact of a cycling effort on spinal shrinkage. Forty-eight trained cyclists rode their road bike on a smart trainer for 1-hour. Surface electromyography (EMG) recorded muscle activity of the lumbar erector spinae (LES), 3D motion analysis system recorded kinematic of the trunk, and stadiometry measured spinal height. Statistical comparisons were made using repeated measure ANOVAs. The LBP group presented increase in pain levels throughout the effort (p < 0.001). A significant group difference was only observed for the thoracic angle (p = 0.03), which was less flexed for LBP. The one-hour cycling effort (time effect) significantly increased the trunk flexion (p < 0.001) and thoracic flexion (p < 0.001) for both groups. Significant lower LES activation (35% less) was observed at the end of the effort as well as a decrease in spinal height (p = 0.01) for both groups. Neuromuscular adaptations to cycling effort is identified by a decrease in LES EMG amplitude and an increase flexion of the trunk. Adaptation to pain is seen by an increase in thoracic flexion. Despite these adaptations, LBP cyclists could not ride their bike pain-free.

Diaphragmatic Activity and Respiratory Function Following C3 or C6 Unilateral Spinal Cord Contusion in Mice.

Simple SummaryTetraplegia is one of the most devastating conditions that an individual can sustain and affects more than 2.5 million people worldwide. Tetraplegia not only affects mobility but also impacts spontaneous breathing such that survivors can be rendered ventilator dependent and have increased mortality. Although no treatment can restore respiratory function after tetraplegia, there is a need for more exploratory studies defining therapeutic approaches to ameliorate respiratory decline in tetraplegia. Here, we studied two models of tetraplegia mimicking human forms of injury, using spinal cord contusion in mice, either above the third cervical metameric segment (C3 model) or below the sixth cervical metameric segment (C6 model) innervation of the phrenic nerves. These nerves are responsible for contraction of the diaphragm, the main inspiratory muscle. Using measurements of spontaneous breathing and muscle activity of the diaphragm, we found reduced diaphragmatic activity in both models, but only the C3 model led to reduced spontaneous breathing similar to what is seen in humans with tetraplegia. Moreover, we found a decline in basal contractility of the diaphragm in the C3 model only. We conclude that the C3 model is an appropriate model to explore interventions aimed at restoring breathing following tetraplegia.The majority of spinal cord injuries (SCIs) are cervical (cSCI), leading to a marked reduction in respiratory capacity. We aimed to investigate the effect of hemicontusion models of cSCI on both diaphragm activity and respiratory function to serve as preclinical models of cervical SCI. Since phrenic motoneuron pools are located at the C3–C5 spinal level, we investigated two models of preclinical cSCI mimicking human forms of injury, namely, one above (C3 hemicontusion—C3HC) and one below phrenic motoneuron pools (C6HC) in wild-type swiss OF-1 mice, and we compared their effects on respiratory function using whole-body plethysmography and on diaphragm activity using electromyography (EMG). At 7 days post-surgery, both C3HC and C6HC damaged spinal cord integrity above the lesion level, suggesting that C6HC potentially alters C5 motoneurons. Although both models led to decreased diaphragmatic EMG activity in the injured hemidiaphragm compared to the intact one (−46% and −26% in C3HC and C6HC, respectively, both p = 0.02), only C3HC led to a significant reduction in tidal volume and minute ventilation compared to sham surgery (−25% and −20% vs. baseline). Moreover, changes in EMG amplitude between respiratory bursts were observed post-C3HC, reflecting a change in phrenic motoneuronal excitability. Hence, C3HC and C6HC models induced alteration in respiratory function proportionally to injury level, and the C3HC model is a more appropriate model for interventional studies aiming to restore respiratory function in cSCI.

Corticomuscular coherence is reduced in relation to dorsiflexion fatigability to the same extent in adults with cerebral palsy as in neurologically intact adults.

Fatigue is frequent in adults with cerebral palsy (CP) and it is unclear whether this is due to altered corticospinal drive. We aimed to compare changes in corticospinal drive following sustained muscle contractions in adults with CP and neurologically intact (NI) adults. Fourteen adults with CP [age 37.6 (10.1), seven females, GMFCS levels I-II] and ten NI adults [age 35.4 (10.3), 6 females] performed 1-min static dorsiflexion at 30% of maximal voluntary contraction (MVC) before and after a submaximal contraction at 60% MVC. Electroencephalography (EEG) and electromyography (EMG) from the anterior tibial muscle were analyzed to quantify the coupling, expressed by corticomuscular coherence (CMC). Adults with CP had lower MVCs but similar time to exhaustion during the relative load of the fatigability trial. Both groups exhibited fatigability-related changes in EMG median frequency and EMG amplitude. The CP group showed lower beta band (16-35Hz) CMC before fatigability, but both groups decreased beta band CMC following fatigability. There was a linear correlation between decrease of beta band CMC and fatigability-related increase in EMG. Fatigability following static contraction until failure was related to decreased beta band CMC in both NI adults and adults with CP. Our findings indicate that compensatory mechanisms to fatigability are present in both groups, and that fatigability affects the corticospinal drive in the same way. We suggest that the perceived physical fatigue in CP is related to the high relative load of activities of daily living rather than any particular physiological mechanism.

Feedforward and Feedback Function of Selected Lower Limb Muscles Following Plyometric Exercises and Cryotherapy

Purpose: Despite the widespread use of cryotherapy in sports, there is no specific evidence of its impact on muscle activation, especially following fatigue-induced exercises. This study aimed to assess the impact of cryotherapy alone and after plyometric exercises on knee muscle activation during the drop jump task. Methods: A total of 35 active female subjects (mean±SD age of 22.74±2.10 years, mean body mass index [BMI] of 20.02±2.55 kg/m2) participated in this quasi-experimental study with a pretest-Post-test design. There were three experimental groups (20-minute cryotherapy, plyometric, and plyometric-cryotherapy) and a control group. Electromyography (EMG) amplitudes of knee muscle activation (rectus femoris [RF], biceps femoris [BF], tibialis anterior [TA], medial gastrocnemius [MG]) were measured and compared in three phases of the drop-jump task (one feedforward preactivation and two feedback eccentric and concentric phases). Skin temperature was recorded before and after cooling intervention as well. For comparisons, repeated measure analysis of variance (ANOVA) was used at a significant level of 0.05. Results: The results showed that the skin temperature decreased significantly after cryotherapy and was maintained for 20 minutes. No significant changes were observed in the EMG of knee muscles in the feedforward and concentric phase of the drop jump task in any groups (P&gt;0.05). However, RF activation decreased following cryotherapy immediately and after 20 minutes as an eccentric phase (P=0.01) and had a significant difference from the control group (P=0.01); besides, EMG activation decreased in cryotherapy, plyometric, and plyometric-cryotherapy groups immediately (P=0.01). However, no significant differences were seen between them and the control group (P&gt;0.05). Conclusion: According to the present results, cryotherapy alone and after fatigue-induced plyometric training had a minor effect on the knee muscle activation during a functional jumping movement, but the impact of these changes on knee biomechanics is insignificant; hence, further studies are essential for a better conclusion.

Electromyography analysis: Comparison of maximum voluntary contraction exercises for the latissimus dorsi.

A prerequisite for interpreting electromyography (EMG) data is to normalize them to a maximum voluntary contraction (MVC), expressing them as percentage of the MVC. The objective of this study was to compare different recommended MVC exercises for the latissimus dorsi and identify the exercise that elicits the highest EMG amplitude. Fifteen male participants were recruited. Five recommended MVC exercises were investigated, including chest-supported shoulder extension, prone shoulder extension, lat-pull down, abducted shoulder flexion, and internal shoulder rotation. Chest-supported shoulder extension reported the highest mean EMG, which was not significantly different from the mean EMG of prone shoulder extension. Both of these exercises led to significantly greater EMG means than the other exercises. Sixty percent of the participants achieved their highest EMG amplitude with chest-supported shoulder extension and 40% with prone shoulder extension. None of the other exercises elicited the highest EMG amplitude in any of the participants. Both chest-supported shoulder extension and prone shoulder extension proved to be effective MVC exercises, with the former showing more consistency in eliciting the highest EMG amplitude. If the true MVC is desired, the authors recommend performing both exercises and then using the overall highest EMG amplitude for normalization purposes.

Blood flow restriction exercise of the tibialis anterior in people with stroke: a preliminary study

Blood flow restriction exercise (BFR-E) could be a useful training adjunct for patients with weakness after stroke to augment the effects of exercise on muscle activity. We aimed to examine neurophysiological changes (primary aim) and assess patient perceptions (secondary aim) following BFR-E. Fourteen participants with stroke performed BFR-E (1 session) and exercise without blood flow restrictsion (Exercise only) (1 session), on two days, ≈7 days apart. In each session, two sets of tibialis anterior (TA) contractions were performed and electromyography (EMG) was recorded. Eight participants underwent transcranial magnetic stimulation (single-pulse stimulation, short interval intracortical inhibition (SICI), intracortical facilitation (ICF)) and peripheral electrical stimulation (maximal peak-to-peak M-wave (M-max)) of the TA before, immediately-after, 10-min-after and 20-min-after BFR-E and Exercise only. Numerical rating scores (NRS) for pain, discomfort, fatigue, safety, focus and difficulty were collected for all subjects (n = 14). Paired comparisons and linear mixed models assessed the effects of BFR-E and Exercise only. No adverse events due to exercise were reported. There was no contraction-number × condition interaction for EMG amplitude during exercise (p = 0.15), or time × condition interaction for single-pulse stmulation, SICI, ICF or M-max amplitude (p = 0.34 to p = 0.97). There was no difference between BFR-E and Exercise only in NRS scores (p = 0.10 to p = 0.50). Using our training paradigm, neurophysiological parameters, feasibility, tolerability and perceptions of safety were not different between BFR-E and Exercise only. As participants were generally well-functioning, our results are not generalizable to lower functioning people with stroke, different (more intense) exercise protocols or longer term training over weeks or months.

Functional Condition Of Inspiratory Muscles In Obstructive Sleep Apnea Patients

Background — Recurrent upper airway obstruction during the sleep is a key feature of obstructive sleep apnea (OSA). In patients with OSA, an intermittent upper airway obstruction yields an increase in inspiratory effort and, consequently, an augmented impact on inspiratory muscles (IM). However, the issue of IM fatigue development in OSA patients is still controversial. Objective — to investigate the functional condition of IM in patients with OSA of various degrees of severity. Material and Methods — Were examined 82 men (30-65 years old), who were distributed among four groups depending on the OSA severity. Cardiorespiratory monitoring was performed to detect OSA. IM electrical activity was detected via surface electromyography (EMG) while holding the breath (during the inhalation). Results — In the course of our study, we detected a reduction in the frequency of EMG of accessory IM, specifically sternocleidomastoid muscle (SCMM) and external intercostal muscles (EIM), accompanied by a simultaneous increase in the amplitude of EMG of SCMM, EIM, and diaphragm (D), while holding the breath (during the inhalation), in the group of patients without OSA. In patients with mild OSA, when holding the breath during the inhalation, the frequency of EMG of SCMM and EIM decreased, while the amplitude of SCMM and EIM increased. In patients with moderate OSA, when holding the breath during the inhalation, a decrease in the frequency of SCMM EMG with a simultaneous increase in the amplitude of the EIM EMG were revealed. Same maneuver in the group of patients with severe OSA yielded no significant changes in the frequency and amplitude of EMG of respiratory muscles. Conclusion — Periodic obstruction of the upper airways with OSA leads to the development of fatigue resistance in accessory IM.

A Preliminary Study on the Use of HD-sEMG for the Functional Imaging of Equine Superficial Muscle Activation during Dynamic Mobilization Exercises.

Simple SummaryAn evidence-based approaches to assess the effect of rehabilitation protocols is currently under investigation in animal physiotherapy. Research aimed to identify objective outcome measurements are of major importance in this field. Functional muscle assessment remains challenging during the application of specific exercises to activate core muscles in horses. This study introduces for the first time the use of bi-dimensional High-Density Surface Electromyography (HD-sEMG) in horse as a non-invasive tool that provides a functional imaging of superficial skeletal muscle activation, and contraction. Using a 32 and/or 64 surface EMG electrode grids positioned on two superficial core muscles, a colour scale image obtained from recorded signals allowed visual assessment of muscle activation. The exercises used to test this technology were the destabilization exercise, the “chin-to-lateral” bending and the “chin-to-knees” flexion exercise. Our results support the use of HD-sEMG in equine physiotherapy to obtain an immediate biofeedback of muscle activation and objectively tracking the physiotherapy treatments.Superficial skeletal muscle activation is associated with an electric activity. Bidimensional High-Density Surface Electromyography (HD-sEMG) is a non-invasive technique that uses a grid of equally spaced electrodes applied on the skin surface to detect and portray superficial skeletal muscle activation. The goal of the study was to evaluate the feasibility of HD-sEMG to detect electrical activation of skeletal muscle and its application during rehabilitation exercises in horses. To fulfil this aim, activation of the superficial descending pectoral and external abdominal oblique core muscles were measured using HD-sEMG technology during dynamic mobilization exercises to induce lateral bending and flexion/extension tasks of the trunk. Masseter muscle was instrumented during mastication as a control condition. A 64 surface EMG channel wireless system was used with a single 64 electrode grid or a pair of 32 electrode grids. HD-sEMG provided unique information on the muscular activation onset, duration, and offset, along each motor task, and permitting inferences about the motor control strategy actuated by the central nervous system. Signals were further processed to obtain firing frequencies of few motor-neurons. Estimation of electromyographic amplitude and spectral parameters allowed detecting the onset of muscular fatigue during the motor tasks performed. HD-sEMG allows the assessment of muscular activation in horses performing specific motor tasks, supporting its future application in clinical and research settings.

Corticospinal Excitability Is Lower During Eccentric Than Concentric Cycling in Men.

How corticospinal excitability changes during eccentric locomotor exercise is unknown. In the present study, 13 volunteers performed 30-min strenuous concentric and eccentric cycling bouts at the same power output (60% concentric peak power output). Transcranial magnetic and electrical femoral nerve stimulations were applied at exercise onset (3rd min) and end (25th min). Motor-evoked potentials (MEPs) amplitude was measured for the rectus femoris (RF) and vastus lateralis (VL) muscles with surface electromyography (EMG) and expressed as a percentage of maximal M-wave amplitude (MMAX). EMG amplitude 100 ms prior to MEPs and the silent period duration were calculated. There was no change in any neural parameter during the exercises (all P > 0.24). VL and RF MMAX were unaffected by exercise modality (all P > 0.38). VL MEP amplitude was greater (26 ± 11.4 vs. 15.2 ± 7.7% MMAX; P = 0.008) during concentric than eccentric cycling whereas RF MEP amplitude was not different (24.4 ± 10.8 vs. 17.2 ± 9.8% MMAX; P = 0.051). While VL EMG was higher during concentric than eccentric cycling (P = 0.03), RF EMG showed no significant difference (P = 0.07). Similar silent period durations were found (RF: 120 ± 30 ms; VL: 114 ± 27 ms; all P > 0.61), but the silent period/MEP ratio was higher during eccentric than concentric cycling for both muscles (all P < 0.02). In conclusion, corticospinal excitability to the knee extensors is lower and relative silent period longer during eccentric than concentric cycling, yet both remained unaltered with time.

Clarify Sit-to-Stand Muscle Synergy and Tension Changes in Subacute Stroke Rehabilitation by Musculoskeletal Modeling.

Post-stroke patients exhibit distinct muscle activation electromyography (EMG) features in sit-to-stand (STS) due to motor deficiency. Muscle activation amplitude, related to muscle tension and muscle synergy activation levels, is one of the defining EMG features that reflects post-stroke motor functioning and motor impairment. Although some qualitative findings are available, it is not clear if and how muscle activation amplitude-related biomechanical attributes may quantitatively reflect during subacute stroke rehabilitation. To better enable a longitudinal investigation into a patient's muscle activation changes during rehabilitation or an inter-subject comparison, EMG normalization is usually applied. However, current normalization methods using maximum voluntary contraction (MVC) or within-task peak/mean EMG may not be feasible when MVC cannot be obtained from stroke survivors due to motor paralysis and the subject of comparison is EMG amplitude. Here, focusing on the paretic side, we first propose a novel, joint torque-based normalization method that incorporates musculoskeletal modeling, forward dynamics simulation, and mathematical optimization. Next, upon method validation, we apply it to quantify changes in muscle tension and muscle synergy activation levels in STS motor control units for patients in subacute stroke rehabilitation. The novel method was validated against MVC-normalized EMG data from eight healthy participants, and it retained muscle activation amplitude differences for inter- and intra-subject comparisons. The proposed joint torque-based method was also compared with the common static optimization based on squared muscle activation and showed higher simulation accuracy overall. Serial STS measurements were conducted with four post-stroke patients during their subacute rehabilitation stay (137 ± 22 days) in the hospital. Quantitative results of patients suggest that maximum muscle tension and activation level of muscle synergy temporal patterns may reflect the effectiveness of subacute stroke rehabilitation. A quality comparison between muscle synergies computed with the conventional within-task peak/mean EMG normalization and our proposed method showed that the conventional was prone to activation amplitude overestimation and underestimation. The contributed method and findings help recapitulate and understand the post-stroke motor recovery process, which may facilitate developing more effective rehabilitation strategies for future stroke survivors.

Design and Evaluation of a Custom-Made Electromyographic Biofeedback System for Facial Rehabilitation.

BackgroundIn the rehabilitation of postoperative facial palsy, physical therapy is of paramount importance. However, in the early rehabilitation phase, voluntary movements are often limited, and thus, the motivation of patients is impacted. In these situations, biofeedback of facial electromyographic (EMG) signals enables the visual representation of the rehabilitation progress, even without apparent facial movements. In the present study, we designed and evaluated a custom-made EMG biofeedback system enabling cost-effective facial rehabilitation.MethodsThis prospective study describes a custom-made EMG system, consisting of a microcontroller board and muscle sensors, which was used to record the EMG of frontal and zygomatic facial muscles during frowning and smiling. First, the mean EMG amplitudes and movement onset detection rates (ACC) achieved with the custom-made EMG system were compared with a commercial EMG device in 12 healthy subjects. Subsequently, the custom-made device was applied to 12 patients with and without postoperative facial paresis after neurosurgical intervention. Here, the ratio [laterality index (LI)] between the mean EMG amplitude of the healthy and affected side was calculated and related to the facial function as measured by the House and Brackmann scale (H&B) ranging from 1 (normal) to 6 (total paralysis).ResultsIn healthy subjects, a good correlation was measured between the mean EMG amplitudes of the custom-made and commercial EMG device for both frontal (r = 0.84, p = 0.001) and zygomatic muscles (r = 0.8, p = 0.002). In patients, the LI of the frontal and zygomatic muscles correlated significantly with the H&B (r = −0.83, p = 0.001 and r = −0.65, p = 0.023). The ACC of the custom-made EMG system varied between 65 and 79% depending on the recorded muscle and cohort.ConclusionThe present study demonstrates a good application potential of our custom-made EMG biofeedback device to detect facial EMG activity in healthy subjects as well as patients with facial palsies. There is a correlation between the electrophysiological measurements and the clinical outcome. Such a device might enable cost-efficient home-based facial EMG biofeedback. However, movement detection accuracy should be improved in future studies to reach ranges of commercial devices.

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).

Aerobic Capacity Determines Habitual Walking Acceleration, Not Electromyography-Indicated Relative Effort

Objective: Habitual walking is important for health and can be measured with accelerometry, but accelerometry does not measure physiological effort relative to capacity. We compared accelerometer-measured absolute intensity and electromyography (EMG)-measured relative muscle activity between people with low versus excellent aerobic fitness levels during their habitual walking. Methods: Forty volunteers (19 women; age 49.3 ± 17.1 years, body mass index 24.0 ± 2.6 kg/m2; peak oxygen uptake 40.3 ± 12.5 ml/kg/min) wore EMG-shorts and a hip-worn accelerometer simultaneously for 11.6 ± 2.2 hr on 1.7 ± 1.1 days. Continuous gait bouts of at least 5-min duration were identified based on acceleration mean amplitude deviation (MAD, in milli gravitational acceleration, mg) and mean EMG amplitude, with EMG normalized to maximal isometric knee extension and flexion (EMG, in percentage of maximal voluntary contraction EMG). Peak oxygen uptake was measured on a treadmill and maximal strength in isometric leg press (leg press max). MAD and EMG were compared between age- and sex-specific fitness groups (low-average, good, and excellent) and in linear models. Results: During habitual walking bouts (4.1 ± 4.1 bouts/day, 0.9 ± 1.0 min/bout), the low-average fit participants had an approximately 28% lower MAD (245 ± 64.3 mg) compared with both good fit and excellent fit participants (313 ± 68.1 mg, p &lt; .05), but EMG was the same (13.1% ± 8.42% maximal voluntary contraction EMG, p = .10). Absolute, relative to body mass, and relative to skeletal muscle mass peak oxygen uptake (but not leg press max) was positively associated with MAD independent of age and sex (p &lt; .01), but there were no associations with EMG. Conclusions: People with low-average aerobic capacity habitually walk with a lower accelerometer-measured absolute intensity, but the physiological stimulus for lower-extremity muscles is similar to those with excellent aerobic capacity. This should be considered when measuring and prescribing walking for health.