• Physical Therapy Korea
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• v.8 no.2
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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.

• Journal of Biomedical Engineering Research
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• v.23 no.1
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• pp.9-16
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• 2002

Localized muscle fatigue can be identified by a downward shift of the EMG frequency typically represented by a fall in the median frequency The Present experimental study was Performed to investigate the time change of the median frequency and the muscle torque during maximal isometric back extension exercises at different exercise angles (0$^{\circ}$, 12$^{\circ}$, 36$^{\circ}$and 72$^{\circ}$) Twenty heath subjects (mean age : 24.35 $\pm$ 2.70) were Participated in this study Median frequency was extracted from EMG signals by employing the fast Fourier transform. Initial median frequency and the slope of median frequency was not significantly correlated with the muscle torque. Pearson's Product moment correlation was used to quantify the relationship between slopes of median frequency and torque. The results may suggest that the exorcise angle during maximal isometric back extension exercises does not affect the slopes of the median frequency and torque, and y-intercept of the median frequency among exercise angles There was no significant correlation between slopes of median frequency and torque. But there was a 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 slopes of median frequency and torque. But results showed that the shift of median frequency and torque shift were highly correlated in all subjects.

• Journal of Korean Institute of Industrial Engineers
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• v.19 no.4
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• pp.87-96
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• 1993

Spectrum analysis of surface electromyogram (FMG) signals is an effective approach to the study of localized muscular fatigue during isometric contraction. Many investigators have con firmed the frequency of the EMG signals being lowered during sustained contaction. In this study, the cyclic loading tasks were performed, and a comparison was made for the median power frequency shift pattern of the EMG signals with the sustained contraction of the same load. The median power frequency shift of the EMG signals for the cyclic loading task was found to be a part of that for the sustained contraction. Based on this result, a new muscle fatigue index was computed by normalizing the duration of the sustained contraction. A fatigue index was obtained as a function of exertion level and the work/rest schedule. With the proposed fatigue index, it is possible to evaluate or predict the degree of muscular fatigue for a physically demanding task.

• Journal of the Ergonomics Society of Korea
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• v.18 no.1
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• pp.55-69
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• 1999

It is very common to use the powered hand tools to enhance the productivity in various types of industry. But the use of the powered hand tools could cause health problems such as cumulative trauma disorders and vibration white fingers. In this study. the effects of hand-arm vibration and anatomical hand position on localized muscle fatigue were analyzed. Eight healthy male subjects volunteered for the study. Vibration frequencies of 0, 40, 80, 100, 150, and 200Hz and hand position of flexion and ulnar deviation were selected for the independent variables of the experiment. Median frequency shifting was used as a dependent variable. The results indicated that at the vibration frequency of 40Hz and accelation of 2g, the muscle fatigue was the greatest. For the hand position. there was significant difference between neutral and flexion. and neutral and ulnar deviation, but no difference between flexion and ulnar deviation. These results could be applied in designing powered hand tools to minimize the health problems.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.17 no.3
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• pp.141-145
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• 2024

Because of muscle fatigue, motor unit recruitment and firing rates decrease and EMG power spectrum shifts toward lower frequencies as spectral compression which represented by a falling shift in the median frequency. However, changes of this frequency shows relatively less than those of the magnitudes of the low frequency band. This paper aims to examine the moderate ranges of the frequency bands in the existed ones as spectral fatigue indices of biceps femoris muscle. Twelve subjects participate in this experiment, and EMG signals are measured from these muscles during treadmill walking on the speed of 4.5 km/h. ANOVA analysis is used to compare changes of the low and high frequency band with reference to those of median frequency. Experimental results demonstrate that the low frequency band 25-82 Hz and the high frequency band 142-300 Hz could be appropriate for spectral fatigue indices of biceps femoris muscles.

• Journal of the Ergonomics Society of Korea
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• v.27 no.3
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• pp.71-79
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• 2008

Walking shoes for walking and jogging have been used to enjoy lots of leisure time. Functional shoes such as walking shoes have special functions to improve body motility by changing of shoe shapes. The walking shoes could improve the motility by structural transformation of outsole as increase degrees of heel and toe. The study on insoles has not been conducted enough on the contrary of the study of outsole. The purpose of this study is to perform ergonomics analysis whether the Arch Supported insoles have an improving effect of muscle activities or not. Experiments were performed with 6 subjects who are health and haven't experienced any diseases past. EMG(Electromyography) and Foot Pressures were measured repeatedly for 5 seconds at 0 hour, after 1 hour and after 2 hours of walking. Insoles used for experiment are normal insole, insole inserted Arch Support and pad. The electrodes for EMG measurement were set on waist (erector spinae), and thigh (vastus lateralis), calf (gastrocnemius). Evaluations of EMG were analyzed by shift of MF (Median Frequency) and MPF (Mean Power Frequency). Foot Pressure was analyzed by mean pressure of feet and change of walking time. As results, Arch Support insole had larger frequency shift value than that of normal insole. Frequency shift between Arch Support insoles and normal insole showed significant difference on 95% confidence interval. And insole 1 has the highest value of frequency shift. For results of foot pressure, Arch Support insoles show continuous decreasing tendency when comparing with normal insoles by changing of times. Also, insole 1 has the highest decreasing value of foot pressure. Therefore, this study presented that the Arch Support insole can promote muscle activities and improves comfort for a prolonged walking.

• Journal of Korean Neurosurgical Society
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• v.30 no.sup2
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• pp.221-227
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• 2001

Objective : The therapeutic impact of tumor resection in glioblastomas is poorly defined and still questionable. Therefore, we conducted the current study to verify the role of tumor resection in the treatment of these highly malignant tumors. Methods : A retrospective study was performed(1990-1999) to compare the treatment results of surgical resection plus radiotherapy(130 patients) with those of stereotactic biopsy plus radiotherapy(19 patients) in glioblastomas. Only adult patients with supratentorial, de novo glioblastoma located in one lobe were included. Survival time/rate was analysed with Kaplan-Meier method, and prognostic variables were obtained from the univariate log-rank test and the multivariate Cox's proportional hazards model. Results : The resection group and the biopsy group did not differ in terms of age, gender, duration of symptoms, presenting symptoms, tumor location, tumor side, tumor size, and the frequency of midline shift. Patients in the biopsy group more often were found to have worse preoperative Karnofsky performance status(KPS)(p=0.001). On univariate analysis, age, KPS, and tumor side were associated with survival(p=0.0053, 0.0001, and 0.0331 respectively). Median survival time and 1-year survival rate were also statistically improved by tumor resection ; resection group - 13 months and 61.2%, and biopsy group - 8 months and 19.7%, respectively(p=0.0001). In patients with midline shift of the tumor, resection was highly effective comparing to biopsy(p=0.0001), but in patients without midline shift, external beam radiation alone was as effective as tumor resection(p=0.0605). Other prognostic variables did not affect survival. On multivariate analysis after variable selection, survival was independently associated with KPS(p=0.001), but not the surgical resection(p=0.2837). Even in biopsy group with midline shift of the tumor, survival rate was not different from that seen after tumor resection(p=0.3505). Conclusions : Radiotherapy alone was as effective as tumor resection plus radiotherapy in patients without midline shift of the tumor. Although there was not statistically significant, tumor resection looked like effective in patients with midline shift. For supratentorial, lobar glioblastoma patients without mass effect of the tumor, biopsy with radiotherapy is one of rational treatment strategies. We consider that tumor resection should be performed in patients with pretreatment midline shift.

• Journal of the Ergonomics Society of Korea
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• v.26 no.2
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• pp.157-165
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• 2007

The Work-Related Musculoskeletal Disorders (WMSDs) can be occurred by various factors such as repetition, forceful exertions and awkward postures. Especially, occurrences of the WMSDs on the waist and lower limb are reported in workplaces, demanded standing postures for a long time, in service and manufacturing industry. The static and standing postures without movement for a long time increase work loads to the lower limb and the waist. Accordingly, anti-fatigue mat or anti-fatigue insole is used as a preventing device of the WMSDs. However anti-fatigue mats are limited in space and movement. In this study, multi-elastic insoles are designed and shown the effects of the workload reduction for a long time under the standing work. The foot pressures and EMG (Electromyography) are measured at 0 hour and after 2 hours by 6 health students in their twenties. The 6 prototype insoles are designed with three elastic (Low, Medium and High). These insoles are compared with no insole (insole type 7) as control group. The EMG measurement was conducted to waist (erector spinae muscle), thigh (vastus lateralis muscle) and calf (gastrocnemius muscle). The foot pressure is analyzed by mean pressure value and the EMG analysis is investigated through MF (Median Frequency), MPF (Mean Power Frequency) and ZCR (Zero Crossing Rate). The results of the foot pressure show that the multi-elastic insoles had smaller foot pressure value than that of no-insole. Moreover, Insole 2 and Insole 3 have the smallest increasing rate in foot pressure. The EMG results show that the multi-elastic insoles had smaller EMG shift value than that of no-insole in 2 hour, and then shift value shows the smallest value in Insole 2. Therefore, this study presents that the multi-elastic insoles have reducing effects of the work load for a long time standing work in both side of foot pressure and EMG.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.20 no.3
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• pp.139-146
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• 2010

Recent studies suggest that prolonged standing at work is associated with varicose veins (VV). The objective of this study was to analyze the differences of VV risk in terms of work types in casino dealers and hotel service workers. Symptoms of VV were evaluated using a self-reported questionnaire from 2,092 participants, and muscle fatigue in the lower legs were evaluated using surface electromyography. The shift rate of median frequency in Gastrocnemius was -30.0% among the casino dealers working in prolonged static standing posture, and - 14.3% among the casino dealers sitting during working time. After adjusting age, gender, smoking, and family history of VV, the risk ratio of VV was 3.67(95% CI 2.03-6.59) in group I (prolonged standing and occasional walking at work), 6.29(95% CI 3.48-11.35) in group II (prolonged standing, occasional walking and heavy lifting at work), and 8.07(95% CI 4.51-14.43) in groupIII(prolonged static standing at work). In conclusion, prolonged standing at work may be a work related risk factor of VV.

• Korean Journal of Occupational Health Nursing
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• v.8 no.2
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• pp.156-161
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• 1999

The EMG(Electromyography) analysis was used to identify the fact the degree of inclined step was selected as dependent variable and feet muscle fatigue was selected as a independent variable. In a final result from EMG test. the shift in median frequency (MF) with 20, 25, 30, 35 degree of inclined steps indicated that 30 degree step was identified as most effective for a decrease in feet muscle fatigue. In a department store, 80% of the workers are female standing sales workers. They work at standing on average 10 hours per day. They performed heavy duty jobs such as lifting, lowering. packing and carrying heavy materials. Furthermore, even though they have work shoes, they usually use various kind of high heels. Eventually, this situation develops low-back-pain (LBP) problems for female workers. In conclusion, it is recommended that a particular branch in a department store claimed this step can effectively to circulate blood and significantly decrease feet muscle fatigue in lower extremity.