• 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.

• 대한의용생체공학회:의공학회지
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• 제24권3호
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• pp.175-181
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• 2003

근피로 연구는 주로 등척성(isometric)운동에서 수행되었고 등장성(isotonic)운동에서 얻은 근전도 신호는 통제하기 힘든 잡음이 많아 등척성운동에서 사용된 주파수분석기법을 동일하게 적용하였을 때 신뢰할만한 중앙주파수 자료와 근피로 판정용 변수를 구하는데 어려움이 있었다 이에 본 연구에서는 등장성운동에서 측정한 근전도신호의 중앙주파수 검출방법에 따른 근피로 판정 변수들의 차이를 비교해 보고자 하였다 이를 위해 동일한 근전도신호를 가지고 FFT 수행간격과 연속적인 FFT구간의 중첩비율을 다르게 하여 중앙주파수를 검출하고 이들의 선형회귀직선을 구하여 회귀직선상의 변수인 초기중앙주파수, 기울기. 근피로지수를 비교한 결과, 초기중앙주파수의 경우 FFT 수행간격이 넓을수록 조금씩 상승하는 것으로 나타났고, 기울기의 경우 FFT 수행간격이 넓을수록 중첩구간이 적을수록 기울기의 감소경향이 뚜렷하게 나타났다. 근피로지수의 경우는 특정 FFT 수행간격에서 가장 높은 수치를 나타냈다

• 한국전문물리치료학회지
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• 제8권2호
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• pp.41-54
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• 2001

Fatigue is the decline in force produced as a result of prolonged muscle activity. Localized muscle fatigue can be identified by a shift toward low in the frequency components of the EMG signal, typically represented by a fall in the median frequency. Previous studies show that a shortened muscle develops a higher fatigue than elongated muscles. The purpose of this study was to investigate the time-related change of median frequency and torque during maximal isometric back extension exercises at different exercise angles ($0^{\circ}$, $12^{\circ}$, $36^{\circ}$, $72^{\circ}$). Twenty healthy subjects (mean age = $24.35{\pm}2.70$) were evaluated in this study. Median frequency was extracted from the EMG signals by fast Fourier transform (FFT). Initial median frequency and the slope of median frequency change over time were computed from linear regression analysis. Pearson's product moment correlation was used to quantify the relationship between slope of median frequency and torque. The results were as follows: 1) Significant differences in y-intercepts of torque regression equation with respect to exercise angle were shown. However, there were no differences in the slopes of the median frequency and torque, and y intercept of the median frequency among exercise angles. 2) There was no significant correlation between slope of median frequency and torque. 3) But there was moderate correlation between median frequency and torque at each exercise angle. In conclusion, the exercise angle during maximal isometric back extension exercise is not a direct effect on slope of median frequency and torque. But results showed that median frequency and torque shift were highly correlated in all subjects.

• 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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• 제6권2호
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• pp.16-31
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• 1999

The purpose of this study was to assess the fatigue in lumbar and abdominal muscles in patients with chronic low back pain compared with normal subjects using spectral analysis with mean power frequency and median power frequency. The experimental group consisted of twenty subjects who had experienced chronic low back pain for over one year after the onset day. A control group consisted of twenty normal subjects with no history of low back pain. All subjects stood in an apparatus to perform sustained contraction in the lumbar and abdominal muscles for 30 seconds with 60% maximal voluntary isometric contraction (MVIC). The resulting electromyographic (EMG) recorded time serial data were transformed into frequency serial data by Fast Fourier Transformation (FFT). The results were as follows: 1) lumbar muscles measured, the frequency change ratio of both median power frequency and mean power frequency was significantly greater for experimental group compared with control group group (p<0.05). In measured two abdominal muscles (inferior rectus abdominis, obliquus externus abdominis) except superior rectus abdominis, the frequency change ratio of both median power frequency and mean power frequency was significantly greater for experimental group compared with control group (p<0.05). 2) In all three (longissimus thoracis, iliocostalis lumborum, multifidus) lumbar muscles measured, the initial frequency value of both median power frequency and mean power frequency was significantly lower for the experimental group compared with the control group (p<0.05). In the two (inferior rectus abdominis, obliquus externus abdominis) abdominal muscles measured (superior rectus abdominis not included), the initial frequency value of both median power frequency and mean power frequency was significantly lower for the experimental group compared with the control group (p<0.05). These results suggest that in patients with chronic low back pain there is a trend for more fatigue to occur in both lumbar and abdominal muscles than in the normal control group. This would seem to suggest that in treatment programs for patients with chronic low back pain, improvement of endurance in all trunk muscles should be considered.

• 대한의용생체공학회:의공학회지
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• 제23권1호
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• pp.9-16
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• 2002

국부적 근 피로는 근전도 신호의 저주파역으로의 천이, 특히 중앙주파수의 감소로 특징된다. 여러 운동각도(0$^{\circ}$, 12$^{\circ}$, 36$^{\circ}$, 72$^{\circ}$)에서 등척성 요추신전운동을 수행하는 동안 근 피로에 따른 근전도 신호의 중앙주파수와 토크의 특성을 살펴보고자 총 20명 (평균 연령 24.35$\pm$2.70세)의 건강i한 피검자를 대상으로 본 실험연구를 수행하였다. 근전도 신호로부터 FFT를 사용하여 중앙주파수를 추출하였으며 선형회귀분석을 통해서 시간에 따른 초기중앙주파수의 초기값과 기울기를 계산하였다. 중앙주파수의 기울기와 토크의 기울기에 대한 상관관계를 정량화하기 위해서 피어슨 상관계수를 적용하였다 중앙주파수의 기울기(p〈0.656)나 v-절편(p〈0.609), 피로지수(p〈0.555)에서는 요추의 각도 타이에 영향을 받지 않아 유의한 차이가 없었으며. 토크의 기울기. 피로지수 역시 유의한 차이가 없었으나, 토크의 ｙ-절편에서는 차이(p〈0.04)가 나타나서, 근육의 길이 증가와 자세변화가 토크에 영향을 미침을 알 수 있었다. 또한, 개인간의 중앙주파수와 토크의 기울기에는 상관관계가 낮았으나, 개인 내에서 중앙주파수와 토크의 시계열 변화에는 유의한 상관관계(0.682)가 있음을 알 수 있었다.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제26권2호
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• pp.127-133
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• 2023

Purpose: Dyssynergic defecation (DSD) is one of the important causes of chronic constipation in children. We aimed to analyze the clinical features, diagnostic test results, and treatments for DSD in children. Methods: Children diagnosed with DSD using fluoroscopic defecography were enrolled in this study. Clinical data, including the results of colon transit time (CTT) test and biofeedback (BF) therapy, were collected from medical records retrospectively. Results: Nineteen children were enrolled. The median age was 9 years (6-18 years), the median frequency of bowel movement was 1/7 days (1-10 days), the median duration of constipation was 7.0 years (2-18 years), the median age of onset of constipation was 2.5 years (1-11 years). In the CTT test, outlet obstruction type was noted in 10/18 (55.6%), slow transit type in 5/18 (27.8%), and normal transit in 1/18 (5.6%). The median CTT was 52 hours (40-142 hours). Initial medical therapy was performed with the polyethylene glycol 4000, and the response was good in 9/19 (47.4%), fair in 9/19 (47.4%), and poor in 1/19 (5.0%). BF was performed in 8/19, with good results in 6/8 (75.0%) children and failure in 2/8 (25.0%) children. After long-term medical therapy (11/19), 3/5 showed good response with medication alone, 6/8 showed good response with BF and medication combined. Conclusion: DSD should be considered as a cause of chronic constipation in children, especially in those with abnormal CTT test results. BF combined with medical therapy is effective even with age-limited cooperation.

• 한국전문물리치료학회지
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• 제11권2호
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• pp.17-25
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• 2004

The purpose of this study was to assess the effect of applied insole types to lower extremities muscle fatigue during treadmill exercise. The control group and each different insole type group consisted of ten healthy male subjects. In the control group and each different insole type (soft type; 10 shore, semi-rigid type; 33 shore, rigid type; 50 shore) treadmill exercise was performed in twenty-five minutes. The electromyography (EMG) signals of four muscle (tibialis anterior, gastrocnemius medialis, rectus femoris, biceps femoris) were recording at sampling rate of 1024 Hz during treadmill exercise. The localized muscle fatigue (LMF) can be investigated using power spectral analysis. When did data analysis that excepted initial five minutes. The raw EMG signals was processed using the fast Fourier Transformation (FFT) and the median power frequency value was determined in initial ten second period and in last ten second period. Fatigue index was calculated and collected data were statistically analyzed by SPSS version 10.0 two-way using analysis of variance (ANOVA) with repeated measures ($4{\times}4$) was used to determine the main effect and interaction. Post hoc was performed with least significant difference. A level of significance was .05. Muscles fatigue index were significantly decreased in insole types (p<.05) and not significantly different in muscle (p>.05). Post hoc analysis shows that fatigue index in soft insole type, semi-rigid insole type and rigid insole type were lower than that control group (p=.028, p=.146, p=.095). There were no interaction between insole type and muscles (p>.05). The finding of this study can be used as a fundamental data when insole is applied and insole can be used to decreased of a fatigue during the dynamic exercise.

• The Journal of Korean Physical Therapy
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• 제16권3호
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• pp.176-191
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• 2004

The purpose of this study was to find the effects of the eccentric exercise induced delayed muscle soreness on proprioception, muscle strength, muscle fatigue, and muscle pain of the elbow flexor muscles. Thirty one healthy male subjects were participated in this study. Before resisted eccentric exercise of the elbow flexors and immediately and at 1, 3, 5, and 7 days post-exercise, pain threshold, proprioception, tension tracking, initial median frequency, and fatigue index were measured. Pain pressure threshold and visual analog scale (VAS) was used to measure muscle pain. Proprioception of the elbow joint was measured by using 3 dimension motion analysis system. Maximum isometric contraction was measured by using digital tensiometer. Electromyography and power spectrum analysis was used to measure initial median frequency (IMF) and fatigue index (FI). Immediately post-exercise, a significant decrease pain threshold was observed that continued to 5 days post-exercise. VAS score was significantly increased at 1 and 3 days post-exercise compared to that of immediately post-exercise. Maximum isometric contraction, IMF, tension tracking ability of the exercised elbow joint were significantly decreased at 1, 3, and 5 days post-exercise compared to that of pre-exercise. FI was significantly increased at 1 and 3 days post-exercise compared that of pre-exercise. Proprioception sense of exercised elbow joint was significantly decreased immediately and at 1, 3, and 5 days post-exercise compared to that of pre-exercise. Proprioception sense of the contralateral elbow joint was significantly decreased immediately post-exercise compared to that of pre-exercise. However, proprioception sense that was measured in close chain kinematic position was not significantly difference between pre-exercise and post-exercise. These results could be useful to determine the resume time for exercising and participating sports activities.

• 한국입자에어로졸학회지
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• 제13권3호
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• pp.127-132
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• 2017

In this paper, the effect of the irradiation of the median-frequency of ultrasonic wave on the aqueous solution have been investigated. In addition, the decomposition ability of radical species was observed using phytoncide oil of 0.1 wt %. By observing the degree of decomposition while maintaining magnetic stirring, the unirradiated aqueous solution maintained turbid condition and the particle size of the oil was the same as the initial size. On the other hand, the irradiated aqueous solution presented that the transparency degree became good after 3 days and became to the same as the original purified water after one week. The particle size of the after 3 days was about 0.1 to $0.5{\mu}m$. From these results it could be demonstrated that when a medium frequency (about 400 kHz) is applied to the aqueous solution, decomposition ability of radical species are formed and the medium frequency irradiation system can be possible to purify the turbid aqueous solution.