• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.1062-1065
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• 2002

We have evaluated the ability of a time-delayed artificial neural network (TDANN) to predict muscle forces using only eletromyographic(EMG) signals. To achieve this goal, tendon forces and EMG signals were measured simultaneously in the gastrocnemius muscle of a dog while walking on a motor-driven treadmill. Direct measurements of tendon forces were performed using an implantable force transducer and EMG signals were recorded using surface electrodes. Under dynamic conditions, the relationship between muscle force and EMG signal is nonlinear and time-dependent. Thus, we adopted EMG amplitude estimation with adaptive smoothing window length. This approach improved the prediction ability of muscle force in the TDANN training. The experimental results indicated that dynamic tendon forces from EMG signals could be predicted using the TDANN, in vivo.

• 한국운동역학회지
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• 제31권2호
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• pp.104-112
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• 2021

Objective: This study aimed to analyze the effects of consecutive whole body vibration through heel raise posture on the center of pressure and electromyography of anterior tibial muscle, lateral gastrocnemius and soleus muscles during single-leg stance. Method: The subjects of this study included 30 healthy males in their 20's, with the following inclusion criteria: no history of orthopaedic medical history, no participation in regular exercises, no history of whole body vibration exercise, and right leg being the dominant leg. The experimental procedure involved pretreatment measurement of eye open single-leg stance, application of whole body vibration for 30 seconds, post-treatment measurement (3 measurements in total). Static and dynamic movements have been measured over 2 separate experiments, with 72 hours gap between the experiments. Static movement involved maintaining single-leg heel raise posture for 30 seconds while applying whole body vibration, and dynamic movement involved heel raise (15 repetitions over 30 seconds) while applying whole body vibration. The strength of applied whole body vibration was 35 Hz frequency and 2~4 mm amplitude. Results: As the single-leg posture after static heel raise posture, mediolateral velocity of the center of pressure at post 2 and post 3 were significantly reduced compared to the pre-treatment measurement. In addition, the percentage for reference voluntary contraction in anterior tibial muscle and soleus and median frequency at anterior tibial muscle and lateral gastrocnemius muscle at post 3 were significantly decreased compared to the pre-treatment value. As the single-leg posture after dynamic heel raise posture, the mediolateral 95% edge frequency of the center of pressure and median frequency at anterior tibial muscle, lateral gastrocnemius muscle, and soleus muscle at post 3 were significantly reduced compared to the pre-treatment value. Conclusion: Acute whole body vibration via static and dynamic heel raise posture have positive effect on mediolateral posture control during single-leg stance.

• The Journal of Korean Physical Therapy
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• 제29권1호
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• pp.39-43
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• 2017

Purpose: This study was to investigate the effects of unilateral muscle fatigue in knee and ankle joints on balance and gait in healthy adults. Methods: Exercise inducing muscle fatigue in the knee joint consisted of concentric and eccentric contraction of dominant knee extensors in healthy adults by using the Leg Extension Rehap exercise machine (HUR, Finland). Exercise inducing muscle fatigue in the ankle joint was composed of voluntary contractions and forced contractions of the dominant plantar flexors in healthy adults. Exercises to induce muscle fatigue in the knee and ankle joints were performed until the subject complained of fatigue or pain, the occurrence of muscle fatigue was confirmed by electromyography. We measured static and dynamic balance using the Good Balance system and gait performance by RS-scan. Results: Static and dynamic balance ability and spatial-temporal gait decreased significantly after muscle fatigue in knee and ankle joint. Conclusion: These results show that unilateral muscle fatigue of the lower extremities affected postural control and gait. Therefore, therapists and sport trainers should minimize the risks of fall and injuries related to unilateral muscle fatigue.

• The Journal of Korean Physical Therapy
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• 제27권4호
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• pp.207-213
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• 2015

Purpose: The aim of the current study was to investigate EMG activity on dynamic balance of subjects with functional lumbar instability following fatigue of low back. Methods: The subjects (24 university students) were divided into 2 groups; functional lumbar instability group (6 males and 6 females) and lumbar stable group (7 males and 5 females) who could complete a questionnaire and undergo a prone instability test. All participants were evaluated for distribution of muscle activity using the TeleMyo DTSTM system. Dynamic balance was tested by Y balance test. This study was conducted for measurement of EMG activity on dynamic balance with the difference between FLIG and control group following muscle fatigue. Results: The functional lumbar instability group (FLIG) showed a significantly lower YBT score (%) of anterior, posterolateral direction on Y-balance test (YBT) in dynamic balance than the lumbar stable group (LSG) (p<0.05). The FLIG was significantly lower than the LSG in anterior direction in EMG activity(%) of MF, RA, ES, GMX, GME, RF, and posteromedial direction in EMG activity(%) of IO, ES and then posterolateral direction in EMG activity(%) of IO, ES in dynamic balance (p<0.05). There was significant correlation of MF, RA, and GMX in anterior reach direction (p<0.05) and ES, GME (p<0.01) and IO, ES in posteromedial reach direction (p<0.05) and EO, ES, GMX in posterolateral reach direction (p<0.05) there was positive correlation. Conclusion: This study showed that FLIG effected EMG activity by dynamic balance following muscle fatigue. Further study is needed for measurement of various ages and work with lumbar instability for clinical application.

• 대한의용생체공학회:의공학회지
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• 제31권4호
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• pp.310-315
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• 2010

Estimation of muscle forces is important in biomechanics, therefore many researchers have tried to build a muscle model. Recently, optimization techniques for adjusting muscle parameters, i.e. EMG-driven model, have been used to estimate muscle forces and predict joint moments. In this study, an EMG-driven model based on the previous studies has been developed and isometric and isokinetic contraction movements were evaluated to validate the developed model. One healthy male participated in this study. The dynamometer tasks were performed for maximum voluntary isometric contractions (MVIC) for ankle dorsi/plantarflexors, isokinetic contraction at both $30^{\circ}/s$ and $60^{\circ}/s$. EMGs were recorded from the tibialis anterior, gastrocnemius medialis, gastrocnemius lateralis and soleus muscles at the sampling rate of 1000 Hz. The MVIC trial was used to customize the EMG-driven model to the specific subject. Once the subject's own model was developed, the model was used to predict the ankle joint moment for the other two dynamic movements. When no optimization was applied to characterize the muscle parameters, weak correlations were observed between the model prediction and the measured joint moment with large RMS error over 100% (r = 0.468 (123%) and r = 0.060 (159%) in $30^{\circ}/s$ and $60^{\circ}/s$ dynamic movements, respectively). However, once optimization was applied to adjust the muscle parameters, the predicted joint moment was highly similar to the measured joint moment with relatively small RMS error below 40% (r = 0.955 (21%) and r = 0.819 (36%) and in $30^{\circ}/s$ and $60^{\circ}/s$ dynamic movements, respectively). We expect that our EMG-driven model will be employed in our future efforts to estimate muscle forces of the elderly.

• 한국응용과학기술학회지
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• 제35권3호
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• pp.905-913
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• 2018

본 연구는 필라테스 동작 시 폼롤러의 적용과 움직임에 따른 몸통과 하지의 근활성도 차이를 알아보는 것이 목적이다. 피험자로 남자 8명을 선정하여 필라테스 네발자세, 교각자세, 코어컨트롤 동작을 매트위에서 정적동작, 폼롤러 위에서 정적동작, 폼롤러 위에서 동적동작으로 무선배정하여 1주 간격으로 수행하였다. 각 동작의 수행 시 척추세움근, 배곧은근, 배바깥빗근, 중간볼기근, 넙다리두갈래근과 넙다리곧은근의 근활성도를 측정하여 일원분산분석으로 분석하였다. 유의수준은 ${\alpha}=.05$로 설정하였다. 첫째, 네발기기 동작에서 폼롤러 동적동작에서는 배곧은근, 배바깥빗근, 중간볼기근, 넙다리두갈래근의 근활성도가 높게 나타났으며(p<.001)(p<.05), 폼롤러 정적동작에서는 넙다리곧은근의 근활성도가 높게 나타났다(p<.001). 둘째, 교각자세 동작에서 폼롤러 동적동작에서는 넙다리두갈래근의 근활성도가 높게 나타났다(p<.001). 셋째, 코어컨트롤 동작에서 폼롤러 동적 동작에서는 배곧은근, 척추세움근, 중간볼기근의 근활성도가 높게 나타났으며(p<.001)(p<.01), 정적 동작에서는 배바깥빗근의 근활성도가 높게 나타났다(p<.05). 필라테스 운동시 근활성도를 고려하여 방법과 난이도를 적용하면 더욱더 효과적일 것이라 사료된다.

• 한국산학기술학회논문지
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• 제13권10호
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• pp.4676-4685
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• 2012

본 연구는 저강도 원심성 운동과 동적 스트레칭이 지연성 근육통에 미치는 효과를 비교하고자 시행하였다. 본 연구의 대상자는 연구에 참여하기 5개월 전부터 하지에 규칙적인 운동을 하지 않았던 18명의 20대 건강한 여성을 대상으로 하였다. 대상자들은 전체 3그룹인 대조군, 저강도 원심성 운동군 그리고 동적 스트레칭군에 무작위로 배정되었다. 측정변수로는 최대 수의적 등척성 수축력, 초음파 영상을 통한 근 두께, 근 통증 척도, 무릎관절 가동범위이며 지연성 근육통 유발 전, 유발 후 24시간, 48시간, 72시간에 각각 측정되었다. 저강도 원심성 운동군과 동적 스트레칭군의 운동 프로그램은 지연성 근육통 유발 4주 전에 일주일에 3회씩 각각 시행되었다. 본 연구의 결과 최대 수의적 등척성 수축력과 근 통증 척도에서만 그룹간 유의한 차이가 있었으며(p<.05), 저강도 원심성 운동은 동적 스트레칭에 비해 근 통증 척도가 유의하게 감소하였다(p<.05). 그러므로 저강도 원심성 운동과 동적 스트레칭이 지연성 근육통의 증상 중 근 통증에 효과적임을 제시하며 또한 저강도 원심성 운동이 동적 스트레칭보다 근 통증을 빠르게 감소시킴으로써 근 통증에 더 효과적임을 제시하고자 한다.

• 한국정밀공학회지
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• 제23권7호
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• pp.152-158
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• 2006

The objective of this work is to develop the knee joint model for representing various pendulum motions and quantifying the spasticity. Knee joint model included the extension and flexion muscles. The joint moment consists of both the active moment from the stretch reflex and the passive moment from the viscoelastic joint properties. The stretch reflex was modeled as nonlinear feedback of muscle length and the muscle lengthening velocity, which is Physiologically-feasible. Moreover, we modeled the spastic reflex as having dynamic threshold to account far the various pendulum trajectories of spastic patients. We determined the model parameters of three patients who showed different pendulum trajectories through minimization of error between experimental and simulated trajectories. The simulated joint trajectories closely matched with the experimental ones, which show the proposed model can predict pendulum motions of patients with different spastic severities. The predicted muscle force from spastic reflex appeared more frequently in the severe spastic patient, which indicates the dynamic threshold relaxes slowly in this patient as is manifested by the variation coefficient of dynamic threshold. The proposed method provides prediction of muscle force and intuitive and objective evaluation of spasticity and it is expected to be useful in quantitative assessment of spasticity.

• 한국정밀공학회지
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• 제24권7호
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• pp.133-138
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• 2007

It is important to understand the characteristics of amputee gait to develop more advanced prostheses. The aim of this study was quantitatively to analyze the stair climbing task for the above-knee amputee with a prosthesis and to predict muscle forces and joint moments at musculoskeletal joints by dynamic analysis. The three-dimensional musculoskeletal model of lower extremities was constructed by gait analysis and transformation software for one above-knee amputee and ten healthy people. The measured ground reaction forces and kinematical data of each joint by gait analysis were used as input data during inverse dynamic analysis. Lastly, dynamic analysis of above-knee amputee during stair climbing were performed using musculoskeletal models. The results showed that summed muscle farces of hip extensor of amputated leg were greater than those of sound leg but the opposite results were revealed at hip abductor and knee flexor of amputated leg. We could also find that the higher moments at hip and knee joint of sound leg were needed to overcome the flexion moment caused by body weight and amputated leg. In conclusion, dynamic analysis using musculoskeletal models may be a useful mean to predict muscle forces and joint moments for specific motion tasks related to rehacilitation therapy..

• The Journal of Korean Physical Therapy
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• 제34권4호
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• pp.187-191
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• 2022

Purpose: The purpose of our study aimed to identify the effect of static and dynamic bridge exercise with gym ball using gym ball on muscle activation of trunk and lower-limb in healthy individuals. Methods: A total of 20 healthy adults participated in this study. The individuals performed general bridge exercise, static and dynamic bridge exercise using gym ball. During the three methods of bridge exercises, electromyography (EMG) data (% maximum voluntary isometric contraction) of the rectus abdominis, erector spinae, biceps femoris, and gastrocnemius were recorded using a wireless surface EMG system. Results: Rectus abdominis activation showed significantly greater during dynamic bridge exercise compared with general bridge exercise and dynamic bridge exercise. Erector spinae, biceps femoris, and gastrocnemius were greater during static and dynamic bridge exercise compared with general bridge exercise. Conclusion: Based on our results, bridge exercise using gym ball, particularly integrating lower-limb movement, could be a useful method to enhance muscle activation of trunk and lower-limb (rectus abdominis, erector spinae, biceps femoris, and gastrocnemius).