Study on Neural Co-activation during Human Upper Limb Muscle Fatigue Based on Surface Electromyography / 中国运动医学杂志

Objectives To observe the co-activation phenomenon during exercise fatigue induced by the proximal muscles on the upper limbs.Methods Sixteen undergraduates not majoring in sports participated in this study,and their left arms were chosen as the observed arms and right arms were selected as the weighted arms.The weighted arm was alternatively in the state of relaxation without any load and fatigue after bending and extending elbow joints to uphold a 5 kg dumbbell.However,the observed arm kept weighing a 4 kg dumbbell with 90 degrees elbow flexion until the muscles were exhausted.The surface electromyography of biceps brachii and triceps brachii of the observed arms was measured using the ME6000.And the integrated surface electromyography (IEMG),root of mean square (RMS),mean power frequency (MPF)and median frequency (MF)were further analyzed.Results The IEMG and RMS of biceps brachii and triceps brachii of the observed arms increased gradually after the exercise began (P＜0.05)regardless of in the relaxed state or in the in the state of weighing a 5 kg dumbbell for the weighted arm,but in the state of weighting a 5 kg dumbbell the IEMG and RMS increased more significantly (P＜0.01),Meanwhile the electrical activities of the triceps brachii as an antagonistic muscle were intensively inhibited.The changes of MPF and MF of biceps brachii in the observed arms were more significant in the state of exercise fatigue than in the relaxed state (P＜0.01),but without such an impact on the triceps brachii.Conclusions The fatigue in one arm can trigger contingent changes in sEMG time domain and frequency domain indexes of its contralateral parallel muscles,suggesting that sEMG changes of upper limb proximal muscles have the co-activation effect.

<b>New Evaluation Method of Muscle Anti-Fatigue Effect</b> / 日本補完代替医療学会誌

Although a number of studies have reported the anti-fatigue effect of anserine, its evidence seems to be still insufficient except the subjective evaluations by questionnaires. The aim of the present study was to propose a method to evaluate the anti-fatigue effect of anserine by a simple protocol and to verify the effectiveness of the method. Subjects were 17 healthy male volunteers (35.5 ± 5 yr., 75.5 ± 5.0 kg). They performed the isometric exercise tolerance test (ETT) on the rectus femoris muscle twice. Median frequencies (MDFs) of electromyogram and their regression curves were calculated for two ETTs. The angles between these curves were defined as a muscle fatigue index and were compared between anserine and water (control) intakes. The results indicate that anserine can alleviate muscle fatigue in humans. To the best of our knowledge, this is the first direct demonstration of the anti-fatigue effect of anserine on muscle in humans.

Movement pattern and sEMG characteristics of upper limb muscles during one-finger pushing manipulation operation with different forces / 医用生物力学

Objective To observe the surface electromyography (sEMG) characteristics of upper limbs during one-finger pushing manipulation under different operating forces, so as to find out the muscle coordination movement pattern for key operating technology. Methods sEMG data of performing one-finger pushing manipulation by the expert, skilled and novice groups were collected. The manipulation force was divided into three different types, namely mild, moderate and severe. The continuous, stable data were adopted for analysis on Myo-Research software. Results Significant differences were found in the upper limb muscle integrated electromyography (iEMG) values (P0.05), with the flexor carpi ulnaris, deltoid, wrist flexors and extensors ranking the top three of iEMG ratio. The expert and skilled groups had the same core muscles in the same movement pattern during their manipulation operation, while the novice group had different core muscles under different forces. There were significant differences in co-contraction ratio among the expert, skilled and novice groups (P<0.01). The novice and expert groups had the highest and lowest co-contraction ratio, respectively, and the co-contraction ratio was gradually decreased with force increasing. During 6-minute manipulation operation, deltoid median frequency(MF) slope of the expert group was declined more slowly than that in the other two groups (P<0.05), which indicated that the expert group were better at resisting to fatigue. Conclusions The expert and skilled groups have the same sEMG characteristics during one-finger pushing manipulation operation with the same core muscles. The movement pattern of upper limb muscles is of regularity. The iEMG ratio, MF slope and co-contraction ratio can be used as reference standard for evaluating the durability, and homogeneity of the manipulation operation and normalization of force application.

Análise da reprodutibilidade de parâmetros no domínio da frequência do sinal EMG utilizados na caracterização da fadiga muscular localizada / Analysis of reliability of EMG signal frequency domain parameters used in the characterization of localized muscle fatigue

O objetivo deste estudo foi analisar a reprodutibilidade de parâmetros no domínio da frequência do sinal eletromiográfico (EMG) utilizados na caracterização da fadiga muscular localizada. Quinze sujeitos do sexo masculino foram submetidos a um teste de fadiga baseado na extensão isométrica de joelho, sendo realizados em três momentos distintos com intervalos de sete dias. Para avaliar a reprodutibilidade dos dados entres os testes calculou-se o coeficiente de correlação intraclasse (CCI) para a frequência mediana (Fmed) no tempo total de exercício (FmedT), para a Fmed obtida a cada 10% do tempo de exercício (Fmed10%) e para as potências das bandas de frequência, obtidas da divisão do espectro de potência a cada 20 Hz. Os resultados demonstraram: (1) boa reprodutibilidade para a FmedT; (2) boa reprodutibilidade para a Fmed10%; e (3) maior variação no sinal EMG nas bandas de 20 a 120 Hz, no qual se destacam as bandas de 20-40 Hz e de 40-60 Hz, demonstrando maior sensibilidade ao processo de fadiga muscular. Conclui-se que a Fmed é uma variável que apresenta boa reprodutibilidade e que a análise fragmentada do espectro de potência, por meio das bandas de frequência, demonstrou-se sensível as variações que ocorrem no sinal EMG durante a instalação do processo de fadiga, tendo potencial para se tornar um novo método para a caracterização da fadiga muscular localizada.

The aim of this study was to analyze the reproducibility of the electromyography signal's parameters (EMG) in the frequency domain used in the characterization of localized muscle fatigue. Fifteen male subjects underwent a fatigue test based on isometric knee extension, being held at three different times at intervals of seven days. To assess the reproducibility of data between the tests we calculated the correlation coefficient (ICC) for the median frequency (MF) in total exercise time (MF T), MF obtained for every 10% of exercise time (MF10%) and the powers of the frequency bands obtained by dividing the power spectrum at windows of 20 Hz. The results showed: (1) excellent reproducibility for MF T, (2) good reproducibility for MF10%, and (3) greater variation in the signal EMG bands from 20 to 120 Hz, especially at the bands of 20-40 Hz and 40-60 Hz, which showed greater sensitivity to the process of muscle fatigue. We conclude that the MF is a variable that shows good reproducibility and that the fragmented analysis of the power spectrum, by means of frequency bands, showed that significant variations occur in the EMG signal during the installation of the fatigue process, having potential to become a new method for the characterization of localized muscle fatigue.

Exercícios em curto prazo de resistência no quadríceps em indivíduos hipertensos refratários / Quadriceps short-term resistance exercise in subjects with resistant hypertension

INTRODUCTION: Resistant arterial hypertension may lead to muscle disuse and reduced functional capacity due to arterial and target-organs lesions. The main objective of this work is to evaluate the quadriceps strength and fatigue tolerance after a program of resistance exercise in subjects with resistant primary hypertension. METHODS: Six patients under pharmacological treatment were submitted to a four-week resistance exercise training program for the quadriceps (8-14 repetitions, 3 sets, 3 days per week). Strength was evaluated by isometric dynamometry, as the percentage change in maximum voluntary contraction over the four week program. Fatigue was analyzed by surface electromyography, as the change in both root mean square value and intercept of median frequency slope of vastus medialis and vastus lateralis. RESULTS: Significant increase in the maximum voluntary contraction was observed (p = 0.04). Fatigue tolerance was not improved as seen by root mean square as well as in the intercept of median frequency (p > 0.05). Additionally, no significant changes were observed in resting arterial blood pressure and heart rate throughout the training period. CONCLUSION: The prescribed protocol seemed to successfully increase localized muscle strength without negatively affecting the monitored cardiovascular variables in patients with resistant hypertension under pharmacological treatment.

INTRODUÇÃO: A hipertensão arterial resistente pode levar ao desuso muscular e redução da capacidade funcional devido a lesões arteriais e de órgãos-alvo. O objetivo deste trabalho é avaliar a força muscular e resistência à fadiga do quadríceps em indivíduos com hipertensão primária resistente após um programa de exercícios de resistência. MÉTODOS: Seis pacientes sob tratamento farmacológico foram submetidos a um programa de treinamento muscular do quadríceps por 4 semanas (8-14 repetições, 3 séries, 3 dias por semana). Força foi avaliada por meio de dinamometria isométrica e apresentada como o percentual de alteração na contração voluntária máxima ao longo do programa de treinamento. Fadiga foi analisada por meio da eletromiografia de superfície como a alteração tanto na raiz quadrática média e no ponto de interceptação da inclinação da frequência mediana dos músculos vasto lateral e medial. RESULTADOS: Foi observado aumento significante na força isométrica máxima (p = 0,04). A tolerância à fadiga não foi alterada, como evidenciado pela raiz quadrática média ou interceptação da frequência mediana (p > 0,05). Adicionalmente, não foram observadas alterações significativas na pressão arterial de repouso e frequência cardíaca ao longo do programa. CONCLUSÃO: O protocolo prescrito aumentou a força muscular localizada sem alterar negativamente as variáveis cardiovasculares monitoradas nos pacientes com hipertensão resistente sob tratamento farmacológico.

Application of Surface Electromyography in Functional Assessment of Patients with Lumbar Disc Herniation / 中国康复理论与实践

@# ObjectiveTo investigate the application of surface electromyography (sEMG) in patients with lumbar disc herniation. Methods44 patients with chronic lumbar disc herniation were divided into mild pain group (group A) and moderate to severe pain group (group B) according to their scores of Visual Analogue Scale (VAS). Their sEMG at erector spinae and gastrocnemius were collected, and the average EMG (AEMG), slope of median frequency (MFs) were analyzed. ResultsCompared with those in the healthy side, AEMG of erector spinae and gastrocnemius reduced significantly (P<0.05) in affected side in both groups, while the MFs (absolute value) increased (P<0.05). Compared with those in group A, the MFs (absolute value) in affected side significantly increased in group B (P<0.05). The ratio of healthy/affected side of AEMG increased in group B (P<0.05), but the ratio of MFs was no significantly difference between 2 groups (P>0.05). ConclusionSurface EMG, of both the erector spinae and gastrocnemius, can be used as a non-invasive tool in detecting neuromuscular function of lumbar and lower limb in patients with lumbar disc herniation. The sEMG imbalance may respond with the severity of pain.

Estimation procedures affect the center of pressure frequency analysis

Even though frequency analysis of body sway is widely applied in clinical studies, the lack of standardized procedures concerning power spectrum estimation may provide unreliable descriptors. Stabilometric tests were applied to 35 subjects (20-51 years, 54-95 kg, 1.6-1.9 m) and the power spectral density function was estimated for the anterior-posterior center of pressure time series. The median frequency was compared between power spectra estimated according to signal partitioning, sampling rate, test duration, and detrending methods. The median frequency reliability for different test durations was assessed using the intraclass correlation coefficient. When increasing number of segments, shortening test duration or applying linear detrending, the median frequency values increased significantly up to 137%. Even the shortest test duration provided reliable estimates as observed with the intraclass coefficient (0.74-0.89 confidence interval for a single 20-s test). Clinical assessment of balance may benefit from a standardized protocol for center of pressure spectral analysis that provides an adequate relationship between resolution and variance. An algorithm to estimate center of pressure power density spectrum is also proposed.

Patterns of Frequency Domain Indexes of Surface Electronic Signals of Adolescent Idiopathic Scoliosis Patients' Paraspinal Muscles / 中国康复理论与实践

@#Objective To investigate the patterns of frequency domain indexes of surface electronic signals of adolescent idiopathic scoliosis (AIS) patients' paraspinal muscles by using surface electromyographic (sEMG) techniques .Methods 25 AIS patients enrolled, 7 males, 18 females, ages range from 11 to 21 years old. All of the enrolled patients undertook the Biering Sorensen test(BST) and the object-lifting test, a Finland made type ME3000P sEMG instrument was applied to record the electronic activities of paraspinal muscles(convex /concave) of all subjects, and the frequency domain indexes: median frequency(MF）,mean power frequency(MPF）, zero crossing rate(ZCR）were analyzed.Results The wave amplitudes and scales of paraspinal muscles electronic frequency domain indexes(MF, MPF, ZCR) were lower than the other tested positions when recorded at the zone of apex vertebrae, and MFslope, MPFslope and ZCRslope all showed a linear degressive tendency as the exercise time was extended.Conclusion Paraspinal muscles at the zone of apex vertebrae have low fatigue durabilities and more likely to be exhausted. sEMG ought to be one of the objective examinations used to evaluate the differences of electronic activities of paraspinal muscles(convex /concave) of AIS patients, and may have a promising value in clinical practice.

Temporomandibular joint dysfunction and trapezius muscle fatigability

INTRODUCTION: It has been suggested that pain increases trapezius muscle activation in patients with temporomandibular joint dysfunction (TMD). Changes in muscle activation might change muscle resistance to fatigue. The purpose of this study was to evaluate the fatigability of the trapezius muscle in patients with TMD. METHOD: Fourteen patients with TMD (clinically diagnosed and referred by a dentist) and eleven healthy subjects performed a fatigue test consisting of shoulder elevation performed at 70 percent of the maximal voluntary isometric contraction, which was maintained for 30 seconds. Electromyographic signals were obtained from the upper portion of the trapezius muscle (sampling frequency: 2000 Hz/channel). Consecutive segments of three seconds in duration each were extracted from the electromyographic signal and analyzed in the frequency domain using a Fast Fourier Transform algorithm. Linear regression analysis was applied to the consecutive median frequencies for each subject. The slope of the regression line was used to describe muscle fatigability. RESULTS: No changes were observed in fatigability between the right and left trapezius of either group or between the left trapezius of the healthy and TMD groups. The linear regression for median frequencies in the right trapezius of the TMD group showed a slope of -0.15 ± 0.33 (mean ± SD), which was smaller than the slope for the healthy group (-0.44 ± 0.46; p= 0.049). These results suggested that the fatigability of the right trapezius was lower in the TMD group than in the healthy group.

INTRODUÇÃO: Tem sido sugerido que a dor aumenta a ativação do músculo trapézio em pacientes com disfunção temporomandibular (TMD). Mudanças na ativação do músculo podem alterar a resistência à fadiga. O objetivo do estudo foi investigar a fatigabilidade do músculo trapézio em pacientes com TMJ. MÉTODOS: Quatorze indivíduos com TMD (diagnosticados clinicamente e encaminhados pelo especialista odontólogo) e onze indivíduos saudáveis realizaram um protocolo de fadiga que consistiu em uma contração isométrica submáxima de elevação do ombro, em um nível de 70 por cento da contração voluntária máxima, mantida por um período de 30 segundos. O sinal eletromiográfico (EMG) foi obtido da porção superior do músculo trapézio, (taxa de amostragem de 2000Hz/canal). Três segundos consecutivos do sinal EMG foram analisados no domínio da freqüência usando a Transformada Rápida de Fourier (FFT). Uma análise de regressão linear foi aplicada para valores consecutivos da freqüência mediana (MF) de cada sujeito, e a inclinação da regressão linear foi utilizada para descrever a fatigabilidade muscular. RESULTADOS: Nenhuma diferença foi observada na fatigabilidade do músculo trapézio direito e esquerdo para ambos os grupos e entre o trapézio esquerdo do grupo saudável e com TMD. A MF do músculo trapézio direito do grupo com disfunção apresentou valores de inclinação da reta de regressão linear de -0,15 ± 0,33 (média ± SD), os quais foram menores que os valores do grupo saudável (-0,44 ± 0,46; média ± SD; p= 0,049). Esses resultados sugerem que a fatigabilidade do trapézio direito é menor no grupo com TMD do que no grupo saudável.

Quantitative EMG Changes During 12-Week DeLorme's Axiom Strength Training

Strength training is one of the most common exercises practiced in the field of physical therapy or sports training. However, limited methodology is available to evaluate its effect on the target muscle. This study aimed to test the hypothesis that surface electromyographic (EMG) data from both isometric and isotonic exercise can express changes within the muscle during a 12-week strength training program. Ten healthy male volunteer students (5 for training, 5 for controls) from Yonsei University were recruited for evaluation in this study. DeLorme's axiom was practiced for 12 weeks in the dominant elbow flexors and knee extensors of the training group. Tension for 1 repetition maximum and maximal voluntary isometric contraction, and surface EMG information such as the integrated EMG and three variables from the regression line of median frequency (MDF) data were measured at weeks 0, 3, 6, 9, and 12. The limb circumference was measured at weeks 0 and 12. During the strength training, which was enough for the increment of muscle strength and limb circumference, the rectified-integrated EMG and initial MDF increased with a significant linear pattern in both types of contraction. The two surface EMG variables were able to monitor the physiologic muscle changes during the training. Based on these results, we propose that these two surface EMG variables can be used for monitoring electrophysiological changes in the specific muscle that is undergoing the training program, under conditions where the contraction mode for EMG data collection is either static or dynamic.

Mechanism for Slowing Surface Electromyography During Fatiguing Contraction Revealed by Superimposed M-Wave Analysis / 体力科学

We studied the mechanism for slowing surface electromyography (EMG) during fatiguing contraction using superimposed M-wave analysis. Seven healthy male subjects exerted 60% maximum voluntary contraction of isometric abductions in the left first dorsal interosseous muscle (FDI) until exhaustion. Simultaneously with voluntary contractions, the ulnar nerve was electrically stimulated at supramaximal intensity, and volitional EMG and superimposed M-waves were obtained. We examined the behavior of muscle fiber conduction velocity (MFCV) and median frequency (MDF) for both EMG, with the following results:<BR>1) MFCV calculated from volitional EMG of FDI was about 6 m/s during 60% MVC.<BR>2) The waveform of voluntary EMG detected from FDI slowed in all subjects during fatiguing contraction at 60% MVC, indicating fatigue had developed in the muscle.<BR>3) As fatigue progressed, the waveform of the superimposed M-wave tended to decrease in amplitude and increase in duration.<BR>4) As fatigue progressed, MDF and MFCV in volitional EMG decreased significantly (p<0.04) . The rate of change was larger in MDF than in MFCV (p<0.01) .<BR>5) As fatigue progressed, MDF and MFCV in the superimposed M-wave decreased significantly (p<0.01) . The rate of change was larger in NIDF than in MFCV (p<0.05) .<BR>These results suggested that MFCV and other peripheral factors affected the slowing of volitional EMG. Elongation of the depolarization zone in muscle fiber is proposed as a peripheral factor.

Usefulness of Power Spectral Analysis for Measurement of Local Muscle Fatigue during Keyboard Task / 대한산업의학회지

OBJECTIVES: Work-related upper extremity disorders of the tendons, nerves, and musdes associated with. repetitive motion represent an increasing proportion of occupational illnesses, medical services, and workers' compensation costs. Severe local muscle fatigue may be a precursor of repetition strain injuries. The demand for objective and quantitative assessment of local muscle fatigue is now increasing. The purpose of this study is to determine the usefulness of power spectral analysis of individual muscle as one of the objective spectral parameters in quantification of local muscle fatigue. METHODS: From 10 normal male without neuromuscular dysfuction, motor unit action potentials (MUAPs) of three muscles (upper trapezius, infraspinatus, and anterior deltoid) of left shoulder girdle were obtained. The surface electrodes were used and the changes of power spectrum according to frequency components were calculated per minute during the keyboard task for 30-minute period by power spectral analysis of MUAPs signal. RESULTS: There was a linear relationship between median frequency (MF) and time flow in the upper trapezius muscle, however the same was not observed in other muscles. The MF slope of the upper trapezius muscle showed a decline of the MF over time and reflected the fatigue rate. Other spectral parameters, such as mean frequency and total power were not significantly correlated to time flow during the keyboard task in all three muscles. And no significant correlation was observed between keying rate and slope of median frequency of upper trapezius muscle. CONCLUSIONS: Above results suggested that the power spectral analysis on median frequency in upper trapezius muscle would be useful in quantification of local muscle fatigue during the keyboard task and local muscle fatigue of shoulder was affected by static posture, not by keying rate.