• 대한전기학회논문지:시스템및제어부문D
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• 제55권7호
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• pp.344-351
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• 2006

The fatigue of back muscle in the repetitive lifting motion was studied using multiple parameters(FFT_MDF, RMS, 2C, NT) in this study. Recent developments in the time-frequency analysis procedures to compute the IMDF(instantaneous median frequency) were utilized to overcome the nonstationarity of EMG signal using Cohen-Posch distribution. But the above method has a lot of computation time because of its complexity. So, in this study, FFT_MDF(median frequency estimation based on FFT) algorithm was used for median frequency estimation of back muscle EMG signal during muscle work in uniform velocity portion of lumbar movement. The analysis period of EMG signal was determined by using the run test and lumbar movement angle in dynamic task, such as lifting. Results showed that FFT_MDF algorithm is well suited for the estimation of back muscle fatigue from the view point of computation time. The negative slope of a regression line fitted to the median frequency values of back muscle EMG signal was taken as an indication of muscle fatigue. The slope of muscle fatigueness with FFT_MDF method shows the similarity of 77.8% comparing with CP_MDF(median frequency estimation based on Cohen Posch distribution) method.

• 한국전문물리치료학회지
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• 제10권3호
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• pp.141-149
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• 2003

Median frequency can be regarded as a valid indicator of local muscle fatigue. As local muscle fatigue develops, the muscle fiber conduction velocity decreases, the fast twitch fibers are recruited less, and consequently the median frequency shifts toward the lower frequency area. The aim of this study was to test the characteristics of the median frequency according to exercise load (30% and 60% of MVC on the biceps brachii, 40% and 80% of MVC on the vastus lateralis) during the fatiguing isometric exercise. Thirteen healthy male volunteer students of Yonsei University were recruited. After the testing maximal voluntary isometric contraction, three variables (initial median frequency, regression slope, fatigue index) from the regression line of MDF data were measured in each exercise load. The results showed that the regression slope and fatigue index were significantly different for the biceps brachii, but not for the vastus lateralis initial MDF was not significant difference according to the exercise load on both muscles. The regression slope and fatigue index could monitor physiologic muscle change during fatiguing isometric exercise. The results showed that two MDF variables reflect the local muscle fatigue according to the exercise load.

• 한국전문물리치료학회지
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• 제8권3호
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• pp.63-76
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• 2001

Many studies have shown that the initial median frequency (MDF) and slope correlate with the muscle fiber composition. This study tested the hypothesis that the initial MDF and slope are fixed, regardless of the interval at which data are collected. MDF data using moving fast Fourier transformation of EMG signals, following local fatigue induced by isotonic exercise, were obtained. An inverse FFT was used to eliminate noise, and characteristic decreasing regression lines were obtained. The regression analysis was done in three different periods, the first one third, first half, and full period, looking at variance in the initial MDF, slope, and fatigue index. Data from surface EMG signals during fatiguing isotonic exercise of the biceps brachii and vastus lateralis in 20 normal subjects were collected. The loads tested were 30% and 60% maximum voluntary contraction (MVC) in the biceps brachii and 40% and 80% MVC in the vastus lateralis. The rate was 25 flexions per minute. There were no significant differences in the initial MDF or slope during the early or full periods of the regression, but there was a significant difference in the fatigue index. Therefore, to observe the change in the initial MDF and slope of the MDF regression line during isotonic exercise, this study suggest that only the early interval need to be observed.

• 한국전문물리치료학회지
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• 제13권1호
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• pp.38-46
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• 2006

The purposes of this study were to investigate the median frequency (MDF) between initiation and termination of muscle contraction through surface electromyographic (sEMG) analysis and to propose the basis of clinical treatment for movement problems in early hemiparetic upper limbs. Thirteen patients who had stroke with onset less than 3 months prior to the study and seven control subjects participated in the study. The median frequency in initiation and termination of muscle contraction was recorded from wrist flexor and extensor muscles using the sEMG, with 3 second beeper signals, during maximal isometric wrist flexion and extension. Flexion and extension must be done as quickly and forcefully as possible. The results of the study were as follows: 1. The MDF of the onset and offset sections were significantly lower on the paretic than the nonparetic and control sides. 2. The MDF of the offset section significantly decreased on the paretic and nonparetic sides. Consequently, this study showed that the lowering of the MDF was due to the hemiparetic wrist motor impairment and muscle weakness. These results are also related to Fugl-Meyer motor assessment (FMA) scores in hemiparetic upper limbs. This study also suggests that since muscle weakness of early stroke patients affects the functional decrease of upper limbs, further studies must focus on the treatment to improve muscle agility and muscle fiber recruitment efficiency that can induce the functional recovery correlated to motor control.

• 한국전문물리치료학회지
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• 제8권3호
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• pp.11-26
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• 2001

In rehabilitation programs involving muscle re-education and endurance exercise, it is necessary to confirm when fatigue occurs. It is also necessary to quantify fatigue, to confirm whether the muscle has been exercised sufficiently. In general, as fatigue occurs, the force-generating ability of the muscle is reduced. If the median frequency (MDF) obtained from electromyogram (EMG) power spectrum is correlated highly with work, then the timing and degree of fatigue may be confirmed. This study examined the relationship between work and MDF obtained from the EMG power spectrum during repetitive isokinetic exercise. Surface EMG signals were collected from biceps brachii and vastus lateralis of 52 normal subjects (26 males, 26 females) at $120^{\circ}/sec$ and $60^{\circ}/sec$ while performing an isokinetic exercise. The exercise was finished at 25% of peak work. MDF data was obtained using a moving fast Fourier transformation (FFT), and random noise was removed using the inverse FFT, then a new MDF data was obtained from the main signal. There was a high correlation between work and MDF during repetitiv isokinetic exercise in the biceps brachii and vastus lateralis of males and the biceps brachii of females (r=.50~.77). However, there was a low correlation between work and MDF in the vastus lateralis of females (r=.06~.19).

• 한국정보전자통신기술학회논문지
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• 제3권1호
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• pp.8-12
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• 2010

본 연구에서는 t-test와 ANOVA를 이용하여 근전도의 중앙주파수 추출을 위한 AR모델 차수결정 및 중앙주파수 비교에 관한 연구이다. 근전도의 근피로와 관계된 특징인자인 영교차율 및 저대역에너지, 중앙주파수를 추출하여 근피로에 이를 때까지의 변화를 평가해 봄으로써 근피로 정도나 시점까지의 변화 정도를 비교 및 고찰하였다.

• 한국정보전자통신기술학회논문지
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• 제5권1호
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• pp.20-25
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• 2012

표면근전도의 중앙주파수 특징을 이용하여 근지구력시간에 대한 남녀 성별차별을 구분할 수가 있다. 중앙주파수는 근육의 피로속도를 측정하는데 주로 사용하는 인자이다. 본 연구에서는 상완이두근의 등장성 운동을 통한 근전도의 성별차이를 알아보았다. 등장성운동은 피실험자가 근육피로가 피곤해 질 때까지를 측정하였다. 남녀 성별차이는 근지구력시간에 대한 중앙주파수의 선형회귀선의 기울기로 구분되어지는 특성을 보였다.

• 대한임상전기생리학회지
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• 제4권1호
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• pp.27-38
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• 2006

This study analyzed changes in action potential of supraspinal neuron and motor unit depending on maximum tolerance isometric contraction(MTIC) by electrical stimulation and examined influence of functional electrical stimulation (FES) on spinal neuron adaptation. It selected 40 university students in their twenties and divided into experimental groups of 25% MTIC(I), 50% MTIC I (II), 75% MTIC(III) and 100% MTIC(IV) depending on MTIC by electrical stimulation, and performed isometric contraction of plantar flexor muscle to each experimental group with given contraction for 20 times. It measured V/Mmax and MDF pre and post exercise, compared volume of contraction. 1. V/Mmax ratio showed no significant difference in comparison among experimental groups. 2. There was significant difference in median frequency of gastrocnemius and soleus in action potential motor unit according to comparison among experimental groups(p<.001). When contraction by electrical stimulation was maximum, change was greatest. This results suggest that muscle contraction by electrical stimulation was influence to action potential of spinal motor neuron system which appear optimal level though aspect and difference degree were not in accordance. Consequently, optimal stimulation level of MTIC(50%) by FES would be lead to central nerve adaptation. muscle contraction by electrical stimulation was influence highly to MDF which should be consider to fatigue of motor unit for muscle contraction by electrical stimulation.

• 대한의용생체공학회:의공학회지
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• 제25권5호
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• pp.377-382
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• 2004

본 연구에서는 건강한 남성 13명을 대상으로 최대자발 근수축의44%, 55%, 66%에 해당하는 40, 50, 60kg의 부하를 주었으며 초당 48$^{\circ}$의 속도로 요추신전 운동을 반복함으로써 근피로를 유발 시켰으며, 피검자의 왼쪽 척추기립근에 표면전극을 부착하여 근전도 신호를 측정하였다. 웨이브렛을 이용하여 '시-주파수'영역에서 근전도 신호를 주파수대역별로 분리하여 근피로도를 측정하고 중앙주파수를 이용하여 얻은 결과를 비교하였다. 본 연구에서는 중앙주파수가 시간에 따라 더 맞은 주파수 영역으로 천이되며 단지 대표 주파수의 경향만 나타냄을 확인할 수 없었다. 그러나 웨이브렛을 이용한 근피로도 분석 방법은 중앙주파수와는 달리 근육의 피로함에 따라 고주파수 대역의 신호(375～438Hz)는 일정하거나 감소하고 저주파영역의 신호(0∼125Ha)는 증가하는 경향이 확인되어 웨이브렛 분석을 통해서 근피로를 정량화할 수 있음을 알 수 있었다. 본 연구를 통해 동 적운동 시 웨이브렛을 이용한 분석방법이 중앙주파수 보다 근피로도를 분석하는데 있어 더욱 유용함을 확인할 수 있었다.확인할 수 있었다.

• 대한의용생체공학회:의공학회지
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• 제44권3호
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• pp.218-224
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• 2023

This study aimed to analyze the coordination of muscle and muscle fatigue between biceps, lateral deltoid, and anterior deltoid during dumbbell side lateral raise using bio-signal. One male subject performed dumbbell side lateral raise with 3% of 1RM dumbbell at the rate of 30bpm until failure (8 minutes). While performing, ECG were recorded to observe the participant's performance. EMG were recorded from biceps, lateral deltoid, and anterior deltoid for observing coordination and fatigue. ECG were analyzed in time and frequency domain to observe Heart rate, normLF, normHF. Changes in heart rate, normLF, and normHF indicate that the sympathetic nervous system is activated, while changes in median frequency (MDF) indicate the occurrence of muscle fatigue. Moreover, the coordination relationship of muscle changed. The correlation of MDF between each muscles indicated that lateral deltoid is associated with biceps and anterior deltoid. These results showed that our study can contribute to improving understanding of muscle fatigue and muscle coordination relationships.