Real-time surface electromyography in Parkinson's disease patients during exercise-induced muscle fatigue

To explore the mechanisms underlying exercise-induced local muscle fatigue in patients with idiopathic Parkinson＇s disease （PD）,we used surface electromyography to record myoelectric signals from the tibialis anterior muscle during isometric contraction-induced fatigue until exhaustion.The results revealed no significant differences between patients with idiopathic PD and healthy controls in maximum voluntary contraction of the tibialis anterior muscle.The basic characteristics of surface electromyography were also similar between the two groups.The duration of isometric contraction at 50% maximum voluntary contraction was shortened in PD patients.In addition,PD patients exhibited a stronger increase in mean square amplitude,but a weaker decrease in median frequency and mean power frequency compared with healthy controls during isometric contraction.The skeletal muscles of PD patients revealed specificity of surface electromyography findings,indicating increased fatigability compared with healthy controls.

Role of a wireless surface electromyography in dystonic gait in functional movement disorders: A case report

BACKGROUND Dystonic gait(DG) is one of clinical symptoms associated with functional dystonia in the functional movement disorders(FMDs). Dystonia is often initiated or worsened by voluntary action and associated with overflow muscle activation. There is no report for DG in FMDs caused by an abnormal pattern in the ankle muscle recruitment strategy during gait.CASE SUMMARY A 52-year-old male patient presented with persistent limping gait. When we requested him to do dorsiflexion and plantar flexion of his ankle in the standing and seating positions, we didn’t see any abnormality. However, we could see the DG during the gait. There were no evidences of common peroneal neuropathy and L5 radiculopathy in the electrodiagnostic study. Magnetic resonance imaging of the lumbar spine, lower leg, and brain had no definite finding. No specific finding was seen in the neurologic examination. For further evaluation, a wireless surface electromyography(EMG) was performed. During the gait, EMG amplitude of left medial and lateral gastrocnemius(GCM) muscles was larger than right medial and lateral GCM muscles. When we analyzed EMG signals for each muscle, there were EMG bursts of double-contraction in the left medial and lateral GCM muscles, while EMG analysis of right medial and lateral GCM muscles noted regular bursts of single contraction. We could find a cause of DG in FMDs.CONCLUSION We report an importance of a wireless surface EMG, in which other examination didn’t reveal the cause of DG in FMDs.

Influence of different acupoint combinations on immediate effect of surface electromyography of patients with cervical spondylosis

Objective To observe the influence of different acupoint combinations on immediate effect of surface electromyography of patients with cervical spondylosis, and to explore the interactions and laws among different acupoint combinations. Methods Acupuncture in three kinds of different acupoint combinations was conducted on 90 patients with cervical spondylosis（three groups）： group A [distal point selection group： Kūnlún（昆仑 BL 60） and Hòuxī（后溪 SI 3）]; group B [local point selection group： Fēngchí（风池 GB 20） and Tiānzhù（天柱 BL 10）]; group C（distal and local point selection group： BL 60, SI 3, GB 20 and BL 10）. Self control before and after treatment was adopted to observe the mean value of surface electromyography（SEMG） amplitude, to measure the mean values of integrated electromyography（IEMG） and electromyography root mean square（RMS）, and to calculate the variation rate of electromyography amplitude of trapezius on the affected side of patients before and after acupuncture. The differences of influences of different acupoint combinations on immediate effect of surface electromyography were compared intra-group, and the differences among the three groups after acupuncture were also compared. Results According to the intragroup comparison before and after acupuncture, the differences of mean value of electromyography amplitude, variation rate of electromyography amplitude, IEMG and RMS were both statistically significant（all P〈0.05）. According to the inter-group comparison after acupuncture, the mean value of electromyography amplitude, variation rate of electromyography amplitude, IEMG and RMS varied in different degrees, however, the differences were not significant（all P〉0.05）; there was no significant difference in the total effective rate among the three groups（P〉0.05）. Conclusion Acupuncture treatment in different acupoint combinations can increase IEMG and RMS and reduce mean value of electromyography amplitude and variation rate of electromyography amplitude, enhance cervical vertebral stability and active contractility of muscle fiber, and improve the fatigue resistance of neck flexion; while, the therapeutic effect of acupuncture on cervical spondylosis has nothing to do with the distance or the number of selected acupoint.

Prosthetic Leg Locomotion-Mode Identification Based on High-Order Zero-Crossing Analysis Surface Electromyography

The research purpose was to improve the accuracy in identifying the prosthetic leg locomotion mode.Surface electromyography(sEMG)combined with high-order zero-crossing was used to identify the prosthetic leg locomotion modes.sEMG signals recorded from residual thigh muscles were chosen as inputs to pattern classifier for locomotion-mode identification.High-order zero-crossing were computed as the sEMG features regarding locomotion modes.Relevance vector machine(RVM)classifier was investigated.Bat algorithm(BA)was used to compute the RVM classifier kernel function parameters.The classification performance of the particle swarm optimization-relevance vector machine(PSO-RVM)and RVM classifiers was compared.The BA-RVM produced lower classification error in sEMG pattern recognition for the transtibial amputees over a variety of locomotion modes:upslope,downgrade,level-ground walking and stair ascent/descent.

Evaluation of neuromuscular activity in patients with obstructive sleep apnea using chin surface electromyography of polysomnography

Background It is believed that defects in upper airway neuromuscular control play a role in sleep apnea pathogenesis. Currently, there is no simple and non-invasive method for evaluating neuromuscular activity for the purpose of screening in patients with obstructive sleep apnea. This study was designed to assess the validity of chin surface electromyography of routine polysomnography in evaluating the neuromuscular activity of obstructive sleep apnea subjects and probe the neuromuscular contribution in the pathogenesis of the condition. Methods The chin surface electromyography of routine polysomnography during normal breathing and obstructive apnea were quantified in 36 male patients with obstructive sleep apnea. The change of chin surface electromyography from normal breathing to obstructive apnea was expressed as the percent compensated electromyography value, where the percent compensated electromyography value = （normal breath surface electromyography - apnea surface electromyography）/normal breath surface electromyography, and the percent compensated electromyography values among subjects were compared. The relationship between sleep apnea related parameters and the percent compensated electromyography value was examined. Results The percent compensated electromyography value of the subjects varied from 1% to 90% and had a significant positive correlation with apnea hypopnea index （R2=0.382, P 〈0.001）. Conclusions Recording and analyzing chin surface electromyography by routine polysomnography is a valid way of screening the neuromuscular activity in patients with obstructive sleep apnea. The neuromuscular contribution is different among subjects with obstructive sleep apnea.

A simulation study on the relation between muscle motor unit numbers and the non-Gaussianity/non-linearity levels of surface electromyography

Recent research has demonstrated that surface electromyography （sEMG） signals have non-Gaussianity and non-linearity properties. It is known that more muscle motor units are recruited and firing rates （FRs） increase as exertion increases. A hy- pothesis was proposed that the Gaussianity test （Sg） and linearity test （St） levels of sEMG signals are associated with the num- ber of active motor units （nMUs） and the FR. The hypothesis has only been preliminarily discussed in experimental studies. We used a simulation sEMG model involving spatial （active MUs） and temporal （three FRs） information to test the hypothesis. Higher-order statistics （HOS） from the bi-frequency domain were used to perform Sg and St. Multivariate covariance analysis and a correlation test were employed to determine the nMUs-Sg relationship and the nMUs-St relationship. Results showed that nMUs, the FR, and the interaction of nMUs and the FR all influenced the Sg and St values. The nMUs negatively correlated to both the Sg and St values. That is, at the three FRs, sEMG signals tended to a more Gaussian and linear distribution as exertion and nMUs increased. The study limited experiment factors to the sEMG non-Gaussianity and non-linearity levels. The study quantitatively described nMUs and the FR of muscle that are not directly available from experiments. Our finding has guiding significance for muscle capability assessment and prosthetic control.

A surface electromyography controlled steering assistance interface

Purpose–Two-handed automobile steering at low vehicle speeds may lead to reduced steering ability at large steering wheel angles and shoulder injury at high steering wheel rates(SWRs).As afirst step toward solving these problems,this study aims,firstly,to design a surface electromyography(sEMG)controlled steering assistance interface that enables hands-free steering wheel rotation and,secondly,to validate the effect of this rotation on path-following accuracy.Design/methodology/approach–A total of 24 drivers used biceps brachii sEMG signals to control the steering assistance interface at a maximized SWR in three driving simulator scenarios:U-turn,908 turn and 458 turn.For comparison,the scenarios were repeated with a slower SWR and a game steering wheel in place of the steering assistance interface.The path-following accuracy of the steering assistance interface would be validated if it was at least comparable to that of the game steering wheel.Findings–Overall,the steering assistance interface with a maximized SWR was comparable to a game steering wheel.For the U-turn,908 turn and 458 turn,the sEMG-based human–machine interface(HMI)had median lateral errors of 0.55,0.3 and 0.2 m,respectively,whereas the game steering wheel,respectively,had median lateral errors of 0.7,0.4 and 0.3 m.The higher accuracy of the sEMG-based HMI was statistically significant in the case of the U-turn.Originality/value–Although production automobiles do not use sEMG-based HMIs,and few studies have proposed sEMG controlled steering,the results of the current study warrant further development of a sEMG-based HMI for an actual automobile.

Passive activity enhances residual control ability in patients with complete spinal cord injury

Patients with complete spinal cord injury retain the potential for volitional muscle activity in muscles located below the spinal injury level.However,because of prolonged inactivity,initial attempts to activate these muscles may not effectively engage any of the remaining neurons in the descending pathway.A previous study unexpectedly found that a brief clinical round of passive activity significantly increased volitional muscle activation,as measured by surface electromyography.In this study,we further explored the effect of passive activity on surface electromyographic signals during volitional control tasks among individuals with complete spinal cord injury.Eleven patients with chronic complete thoracic spinal cord injury were recruited.Surface electromyography data from eight major leg muscles were acquired and compared before and after the passive activity protocol.The results indicated that the passive activity led to an increased number of activated volitional muscles and an increased frequency of activation.Although the cumulative root mean square of surface electromyography amplitude for volitional control of movement showed a slight increase after passive activity,the difference was not statistically significant.These findings suggest that brief passive activity may enhance the ability to initiate volitional muscle activity during surface electromyography tasks and underscore the potential of passive activity for improving residual motor control among patients with motor complete spinal cord injury.

Automatic Detection of Outliers in Multi-Channel EMG Signals Using MFCC and SVM

The automatic detection of noisy channels in surface Electromyogram(sEMG)signals,at the time of recording,is very critical in making a noise-free EMG dataset.If an EMG signal contaminated by high-level noise is recorded,then it will be useless and can’t be used for any healthcare application.In this research work,a new machine learning-based paradigm is proposed to automate the detection of low-level and high-level noises occurring in different channels of high density and multi-channel sEMG signals.A modified version of mel fre-quency cepstral coefficients(mMFCC)is proposed for the extraction of features from sEMG channels along with other statistical parameters i-e complexity coef-ficient,hurst exponent,and root mean square.Several state-of-the-art classifiers such as Support Vector Machine(SVM),Ensemble Bagged Trees,Ensemble Sub-space Discriminant,and Logistic Regression are used to automatically identify an EMG channel either bad or good based on these extracted features.Comparison-based analyses of these classifiers have also been considered based on total classi-fication accuracy,prediction speed(observations/sec),and processing time.The proposed method is tested on 320 simulated EMG channels as well as 640 experi-mental EMG channels.SVM is used as our main classifier for the detection of noisy channels which gives a total classification accuracy of 99.4%for simulated EMG channels whereas accuracy of 98.9%is achieved for experimental EMG channels.

Three-dimensional MXene/carbon nanotube composite electrodes in flexible 64-channel arrays for noninvasive electromyography signal acquisition

Non-invasive surface electromyography(sEMG)electrodes have vast potential in fields such as healthcare,human-computer interaction,and entertainment,providing diverse information related to electromyographic signals.Non-invasive sEMG electrodes reduce user risks but gather sEMG signals of lower quality compared to invasive ones.Currently,various advanced electrode materials have been developed for detecting physiological electrical signals,but the majority of them are single channel electrodes.Here,we report 64-channel three-dimensional(3D)Ti_(3)C_(2)MXene/CNT composite electrodes fabricated using bonding-driven self-assembly technologies.These electrodes are characterized by low skin-electrode contact impedance and a high signal-to-noise ratio(SNR)for collection of EMG signals.These electrode arrays exhibit remarkable flexibility,conforming seamlessly to the skin’s curvature.Specifically,the skin-electrode contact impedance of 3D Ti_(3)C_(2)MXene/CNT electrodes decreases by 10-fold compared to Ag/AgCl gel electrodes at a frequency of 100 Hz.Furthermore,when collecting sEMG signals from the arm,the prepared Ti_(3)C_(2)MXene/CNT electrodes exhibit lower baseline noise and higher SNR compared to Ag/AgCl gel electrodes.Furthermore,Ti_(3)C_(2)MXene/CNT electrodes can collect sEMG signals of different hand gestures,while maintaining a high SNR(∼25 dB).By combining machine learning,sEMG signals from different gestures can be identified with a recognition rate exceeding 90%.The exceptional performance and scalability of these 3D Ti_(3)C_(2)MXene/CNT electrodes indicate a promising future for shaping electronic skin and wearable device technologies.

Detection of an increase in EMG regularity during fatiguing contractions

The changes in the evolvement patterns of surface electromyography（EMG）signals during both static and dynamic fatiguing contractions are studied.The main finding is that the EMG signal tends to be more and more regular as muscle fatigues.An increase in the summation of all the regular evolvement patterns denoted by Dreg reflects such a tendency.Compared with traditional measurements,Dreg shows less variability among subjects when characterizing a fatigue process.In addition,the calculation of Dreg in the time domain is free from the restrictions disturbing those of spectral parameters.The detection of an increase in the EMG regularity not only proposes a new and easy way to inspect changes in EMG during the fatigue process,but also provides strong supports to estimate muscle fatigue by means of nonlinear analysis methods such as entropy and complexity measures.The detection method of signal regularity can also be applied to other physiological signals.

A novel functional electrical stimulation-control system for restoring motor function of post-stroke hemiplegic patients

Hemiparesis is one of the most common consequences of stroke. Advanced rehabilitation techniques are essential for restoring motor function in hemiplegic patients. Functional electrical stimulation applied to the affected limb based on myoelectric signal from the unaffected limb is a promising therapy for hemiplegia. In this study, we developed a prototype system for evaluating this novel functional electrical stimulation-control strategy. Based on surface electromyography and a vector machine model, a self-administered, muki-movement, force-modulation functional electrical stimulation-prototype system for hemiplegia was implemented. This paper discusses the hardware design, the algorithm of the system, and key points of the self-oscillation-prone system. The experimental results demonstrate the feasibility of the prototype system for further clinical trials, which is being conducted to evaluate the efficacy of the proposed rehabilitation technique.

Paraspinal strength and electromyographic fatigue in patients with sub-acute back pain and controls:Reliability,clinical applicability and between-group differences

BACKGROUND Paraspinal muscle strength and fatigue are considered important in low back pain(LBP)prevention and rehabilitation.High reliability of paraspinal strength and electromyographic(EMG)-fatigue parameters has not been universally reported.Moreover,the discriminative validity of these parameters requires further exploration,under the threat of potentially poor reliability of the methods examined.AIM To investigate the reliability and discriminative validity of paraspinal strength and EMG-related fatigue in subjects with recurrent LBP and healthy participants.METHODS Test-retest measurements were performed in 26 healthy and 66 LBP volunteers,for reliability.Paraspinal isometric maximal and mean strength were determined with a maximum voluntary isometric contraction(MVIC)protocol,performed in a custom-made device.For the fatigue test,participants performed a 60% MIVC level continuous isometric contraction of the paraspinals,in conjunction with EMG analysis from 4 muscle sites of the lumbar spine.Initial median frequency(IMF),the median frequency slope(MFslope),as well as the root mean square(RMS)slope EMG parameters were used as fatigue measures.Data were analysed with repeated measures ANOVA for test-retest differences.For reliability,the intraclass correlation coefficient(ICC3,1),standard error of the measurement(SEM)and the smallest detectable difference(SDD)were reported.Group-related differences for fatigue measures were analysed with a Multivariate Analysis of Covariance,with age,weight and strength as covariates.RESULTS Isometric strength presented statistically significant between-day differences(P<0.01),however these did not exceed 10%(healthy:7.2%/LBP-patients:9.7%)and ICC reliability values were excellent,yet test-retest error was increased for the patient group(healthy:ICC3,1:0.92-0.96,SEM:5.72-5.94 Hz,SDD:18.51%-18.57%/LBP-patients:ICC3,1:0.91-0.96,SEM:6.49-6.96,SDD:30.75%-31.61%).For the frequency data,IMF reliability was excellent(healthy:ICC3,1:0.91-0.94,SEM:3.45-7.27 Hz,SDD:9.56%-20.14%/patients:ICC3,1:0.90-0.94,SEM:6.41-7.59 Hz,SDD:17.75%-21.02%)and of MF raw and normalised slopes was good(healthy:ICC3,1:0.78-0.82,SEM:4.93-6.02 Hz,SDD:13.66-16.67%/LBP-patients:ICC3,1:0.83-0.85,SEM:6.75-7.47 Hz,SDD:18.69%-20.69%).However,the reliability for RMS data presented unacceptably high SDD values and were not considered further.For discriminative validity,less MVIC and less steep MFslopes were registered for the patient group(P<0.01).CONCLUSION Reliability and discriminative ability of paraspinal strength and EMG-related frequency parameters were demonstrated in healthy participants and patients with LBP.

The effect of shoe type on gait in forefoot strike runners during a 50-km run

Purpose:To observe the relative change in foot-strike pattern,pressure characteristics,surface electromyography(sEMG) recordings,and stride characteristics in forefoot strike runners wearing both minimalist and traditional shoes during a 50-km run.Methods:Four experienced minimalist runners were enrolled in this study.Each runner ran a 50-km simulated run in both minimalist shoes and traditional shoes.Pressure data,sEMG recordings,and limited 3D motion capture data were collected during the initial 0.8 km and final 0.8 km for each trial.Results:Three runners in the traditional shoe type condition and one runner in the minimalist shoe type condition demonstrated a more posterior initial contact area(midfoot strike(MFS) pattern) after the 50-km run.which was supported by increased activity of the tibialis anterior in the pre-contaet phase(as per root mean square(RMS) values).In addition,in both pre- and post-run conditions,there were increased peak pressures in the minimalist shoe type,specifically in the medial forefoot.Muscle fatigue as defined by a decreased median frequency observed in isometric,constant force contractions did not correspond with our hypothesis in relation to the observed foot strike change pattern.Finally,step rate increased and step length decreased after the 50-km run in both shoe type conditions.Conclusion:More runners adopted a more posterior initial contact area after the 50-km run in the traditional shoe type than in the minimalist shoe type.The runners who adopted a more posterior initial contact area were more closely associated with an increased median frequency of the medial gastrocnemius,which suggests there may be a change in motor unit recruitment pattern during long-distance,sustained velocity running.The increased peak pressures observed in the medial forefoot in the minimalist shoe type may predispose to metatarsal stress fractures in the setting of improper training.

Analysis of sEMG signal for KOA classification

The sEMG signals are collected from the vastus lateralis,vastus medialis,biceps femoris,and semitendinosus of lower extremity during level walking among control subjects and knee osteoarthritis (OA) patients,the latter including mild,moderate and severe degree.The 5-fold cross-validation is used to measure the accuracy of the proposed analysis algorithm on collected sEMG recordings.For comparison,the more classical feature vectors of form factor,degree of skewness,kurtosis,and wavelet entropy are also tested.In experiment,the normalized energy ratio and marginal spectrum ratio achieve larger accuracy than the other features for all the four muscular groups.Moreover the accuracy of vastus medialis and biceps femoris are larger than that of vastus lateralis and semitendinosus.These results suggest that the normalized energy ratio and marginal spectrum ratio via the analysis of knee sEMG signals by HHT can server as characteristic parameters to easily classify osteoarthritis with noninvasive method.The more important muscular groups for maintaining the knee joint function are medialis and biceps femoris;as a result of that they should be exercise especially for rehabilitation.

Design of a weak bioelectric signal acquisition circuit

A surface electromyography(sEMG)signal acquisition circuit based on high-order filtering is designed.We use a two-stage adjustable amplifier and a high-order Sallen-Key bandpass filter to solve the problems of non-adjustable amplification gain and low filtering order in traditional acquisition circuits.The experimental results show that the designed sEMG signal acquisition device can eliminate power frequency interference effectively,the stopband drop of the filtering part reaches approximately-100 dB/dec,which can effectively extract useful signals between 20-500 Hz,and the amplification gain reaches 60 dB.

Comparing the efficiency of artificial neural networks in sEMG-based simultaneous and continuous estimation of hand kinematics

Surface Electromyography(sEMG)plays a key role in many applications such as control of Human-Machine Interfaces(HMI)and neuromusculoskeletal modeling.It has strongly nonlinear relations to joint kinematics and reflects the subjects’intention in moving their limbs.Such relations have been traditionally examined by either integrated biomechanics and multi-body dynamics or gesture-based classification approaches.However,these methods have drawbacks that limit their usability.Different from them,joint kinematics can be continuously reconstructed from sEMG via estimation approaches,for instance,the Artificial Neural Networks(ANNs).The Comparison of different ANNs used in different studies is difficult,and in many cases,impossible.The current study focuses on fairly evaluating four types of ANN over the same dataset and conditions in proportional and simultaneous estimation of 15 hand joint angles from 10 sEMG signals.The presented ANNs are Feedforward,Cascade-Forward,Radial Basis Function(RBFNN),and Generalized Regression(GRNN).Each ANN is applied to its special parametric study.All the methods efficiently solved the regression problem of the complex multi-input multi-output bio-system.The RBFNN has the best performance over the others with a 79.80%mean correlation coefficient over all joints,and its accuracy reaches as high as 92.67%in some joints.Interestingly,the highest accuracy over individual joints is 93.46%,which is achieved via the GRNN.The good accuracy suggests that the proposed approaches can be used as alternatives to the previously adopted ones and can be employed effectively to synchronously control multi-degrees of freedom HMI and for general multi-joint kinematics estimation purposes.

Role of biomechanical assessment in rotator cuff tear repair: Arthroscopic vs mini-open approach

BACKGROUND Rotator cuff(RC)tears are one of the most frequent pathologies within the shoulder girdle.Hand dominance and older age are associated with RC tears.Two different surgical procedures,the mini-open(MO)and all-arthroscopic(AA)approach,represented the standard of treatment.AIM To compare the clinical and biomechanical outcomes of two surgical techniques(AA vs MO procedure)performed to address the painful shoulder syndrome with partial or total supraspinatus tendon tear.METHODS Eighty-eight participants,50 following RC repair with AA and 38 with MO approach,were recruited in the present cross-sectional case-control study(ORTHO-SHOULDER,Prot.0054602).All patients underwent postoperative clinical evaluation for pain(Visual analogic scale),impairment,and disability(disability of the arm,shoulder,and hand)and limitation in daily activity(Constant-Murley score).Patients’shoulder mobility was also assessed in our Laboratory of Functional Movement through a wearable inertial sensor and surface electromyography to monitor kinematics and muscle activity during the movement on the frontal(abduction/adduction)and sagittal(flexion-extension)planes.RESULTS No statistically significant differences between the two procedures were observed in either main clinical score or range of motion.A significant increase in velocity during the movement execution and a higher contribution of upper trapezius muscles were found in the AA group compared with MO patients.CONCLUSION In terms of clinical scores,our findings were in line with previous results.However,the use of technology-based assessment of shoulder mobility has revealed significant differences between the two techniques in terms of mean velocity and pattern of muscle activation.

Randomized Controlled Pilot Trial of Truncal Exercises after Stroke to Improve Gait and Muscle Activity

The purpose of the present study was to evaluate the effects of a trunk exercise program on the gait and muscle activity in stroke patients. The participants of this pilot study included six hemiplegic stroke patients. The outcomes were surface electromyography (sEMG) and spatiotemporal gait parameters. In analysis of sEMG, no statistically difference was found between pre- and post-training of Maximal Voluntary Isometric Contraction (MVIC) in rectus abdominis and external abdominal oblique muscle, but it tended to increase. However, the gait parameter significantly increased in walking speed, walking cycle, and affected stride length in stroke patients. These results suggest that the trunk exercise program may in part improve the gait of chronic stroke patients.

Systematic reduction of leg muscle activity throughout a standard assessment of running footwear

Purpose This study aimed to investigate whether there is a systematic change of leg muscle activity,as quantified by surface electromyography(EMG),throughout a standard running footwear assessment protocol at a predetermined running speed.Methods Thirty-one physically active adults(15 females and 16 males)completed 5 testing rounds consisting of overground running trials at a speed of 3.5 m/s.The level of muscle activity from 6 major leg muscles was recorded using surface EMG.The variables assessed were the EMG total intensity as a function of time and the cumulative EMG overall intensity.Systematic effects of the chronological testing round(independent variable)on the normalized EMG overall intensity(dependent variable)were examined using Friedman analysis of variates and post hoc pairwise Wilcoxon signed-rank tests(α=0.05).Results There was a systematic reduction in overall EMG intensity for all 6 muscles over the time course of the running protocol(p<0.001)until the fourth testing round when EMG intensities reached a steady state.The one exception was the biceps femoris muscle,which showed a significant reduction of EMG intensity during the stance phase(p<0.001)but not the swing phase(p=0.16).Conclusion While running at a predetermined speed,the neuromuscular system undergoes an adaptation process characterized by a progressive reduction in the activity level of major leg muscles.This process may represent an optimization strategy of the neuromuscular system towards a more energetically efficient running style.Future running protocols should include a familiarization period of at least 7 min or 600 strides of running at the predetermined speed.