• 대한의용생체공학회:의공학회지
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• 제33권3호
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• pp.135-140
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• 2012

Previous investigators have shown that the frequency compression is related to the muscle fatigue and the decreasing conduction velocity of muscle fibers. The aim of the present study was to investigate the relationship between endurance times and frequency parameters such as mean power frequency and median frequency in the surface EMG signal during isotonic contractions. Eight healthy subjects performed voluntary isotonic contractions of biceps Brachii muscle until their endurance times which were determined when the subject could no longer follow the contraction cycle. The regressive slopes of mean power frequency and median frequency were used to describe the frequency compression of the surface EMG signal, and to test the predictability of endurance time. As results of experiment, significant correlations were found between endurance time and the regressive slopes of mean power frequency and mean frequency computed over 50%Tend of endurance time.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1641-1648
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• 2017

Many researchers had examined the validity of using the high-to-low ratio between two fixed frequency band amplitudes (H/L-FFB) from the surface electromyography of a face and body as the first spectral index to assess muscle fatigue. Despite these studies, the disadvantage of this index is the lack of a criterion for choosing the optimal border frequency. We tested the potential of using the high-to-low ratio between two signal spectral moments (H/L-SSM), without fixed border frequencies, to evaluate muscle fatigue and predict endurance time ($T_{end}$), which was determined when the subject was exhausted and could no longer follow the fixed contraction cycle. Ten healthy participants performed five sets of voluntary isotonic contractions until they could only produce 10% and 20% of their maximum voluntary contraction (MVC). The $T_{end}$ values for all participants were $138{\pm}35s$ at 10% MVC and $69{\pm}20s$ at 20% MVC. Changes in conventional spectral indices, such as the mean power frequency (MPF), Dimitrov spectral index (DSI), H/L-FFB, and H/L-SSM, were extracted from surface EMG signals and were monitored using the initial slope computed every 10% of $T_{end}$ as a statistical indicator and compared as a predictor of $T_{end}$. Significant correlations were found between $T_{end}$ and the initial H/L-SSM slope as computed over 30% of $T_{end}$. In conclusion, initial H/L-SSM slope can be used to describe changes in the spectral content of surface EMG signals and can be employed as a good predictor of $T_{end}$ compared to that of conventional spectral indices.

• 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.

• 한국전문물리치료학회지
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• 제10권1호
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• pp.109-128
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• 2003

This study tested whether repeated measurement of median frequency (MDF)-related variables could express the muscle power changes during a 12-week DeLome strengthening program, by using consecutive overlapping FFT (Fast Fourier transformation) and integrated EMG (IEMG) from surface EMG data for isometric and isotonic exercise. To evaluate the effect of training, the following were recorded every 3 weeks for the elbow flexors and knee extensors of 5 healthy male volunteers: MVC, lRM, limb circumference, and surface EMG during isometric MVC or isotonic contraction at 10RM load. From the EMG data, IEMG and variables from a regression analysis between MDF and time were obtained. MVC, lRM, IEMG, and initial MDF increased linearly over the training period. The fatigue index and slope of the regression line increased temporarily until the 6th week and decreased thereafter. From these results, there appeared to be enhanced neural recruitment of fast twitch fibers in the first 6 weeks and continued enhancement in the recruitment and hypertrophy of fast twitch fibers, which led to increased fatigue resistance, over the last 6 weeks. Accordingly, the MDF and IEMG analysis technique could demonstrate the effect of the program detected significant changes in both isometric and isotonic contractions. EMG analysis methods can be used to estimate the electrophysiological and histological changes in skeletal muscles during a strengthening program.

• The Journal of Korean Physical Therapy
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• 제21권3호
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• pp.17-24
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• 2009

Purpose: The purpose of this study was to investigate the effects of a combination of isotonic (CI) technique on the balance, muscle fatigue and muscle activities of the quadriceps muscle in the paretic leg of hemiplegic patients. Method: All the subjects received a combined isotonic technique of proprioceptive neuromuscular facilitation (PNF) for about 30 minutes 3 times per week for 6 weeks. The root mean square (RMS) and mid frequency (MF) were recorded by surface electromyography (EMG)(EMG/EP system, OXFORD Medelec, UK) during maximal voluntary isometric contractions (MVIC). The balance ability was measured by a balance system (BIODEX, USA). Result: The RMS of the quadriceps muscle at post-treatment was significantly increased compared to that at pretreatment (p<0.05). Yet there was no significant difference among the three muscles. There were no significant difference in the MF of the vastus lateralis and rectus femoris between pre- and post-treatment, but the MF of the vastus medialis was significantly decreased (p<0.05). There was a significant difference in the vastus medialis and lateralis between pre- and post-treatment (p<0.05). Moreover, the overall stability index at post-treatment was significantly decreased compared to that at pre-treatment (p<0.05). But there was no significant difference between the anterior/posterior and medial/lateral stability indexes. Conclusion: The results of this study indicated that a CI technique of PNF had an effect to improve the balance and muscle activity in hemiplegic patients.

• 한국정보전자통신기술학회논문지
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• 제8권2호
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• pp.178-186
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• 2015

근지구력시간은 근피로를 평가하는 매우 중요한 지시자이다. 근지구력 시간을 직접 측정할 경우 근골격계 손상의 위험이 있다. 따라서 본 연구에서는 근지구력시간을 개인요소와 신체측정치수의 간접측정으로 예측할 수 있는 모델을 제시하려고 한다. 초기에는 개인요소인 성칭과 연령이 근지구력시간의 예측에 상관없다는 결과가 있었지만, 최근에는 팔의 중력토크(GTA, gravitational torque of the horizon arm, stretched arm)와 최대자율수축강도(MVC, maximum voluntary contraction) 등을 독립변수 또는 예측변수로 적용하여 근지구력시간을 예측하였다. 본 연구에서는 등장성 운동 시 개인요소와 신체측정치수를 이용하여 근지구력시간을 예측할 수 있는 변인들에 관하여 연구하였다. 총 25명의 피검자가 자원하여 10%,20%,30%,40% 그리고 50%MVC 강도의 등장성 운동을 수행하였다. 그 후 회귀분석을 통해 산출된 상관계수를 비교하였으며, 그 결과 다중회귀모델에서 유의성 있는 상관계수가 있었으며 근지구력시간을 예측하는 변인으로써 유용함을 알 수 있었다.