• 한국운동역학회지
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• 제33권1호
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• pp.17-24
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• 2023

Objective: The purpose of this study was to investigate the effects of different frequency on of knee extensors muscle function during electrical muscle stimulation (EMS). Method: In this research, 40 subjects who have no musculoskeletal disorder, and less than a year workout experience were recruited in order to analyze effects of EMS with different stimulus frequency. Forty subjects were randomly divided into four groups of ten subjects in each group. A EMS training program with different frequencies (without EMS [WE], EMS with frequency 30 Hz [E30], EMS with frequency 60 Hz [E60], EMS with frequency 90 Hz [E90]) was assigned to each group. Throughout eight weeks of training, test subjects were simultaneously carried out knee extension exercises such as squat, leg extension, and leg-press while using EMS with different frequency (20 min, pulse width 250 ㎲, on-off ratio 1:1). Isokinetic knee extension strength, muscle activity of the rectus femoris (RF), the vastus medialis (VM), and the vastus lateralis (VL), and the median frequency of the RF, the VM, and the VL were collected and compared between pre and post training in order to find effects of applying EMS with different frequencies. For each dependent variable, a one-way ANOVA was to determine whether there were significant differences among four different conditions (p<.05). When a significant difference was found, post hoc analyses were performed using the contrast procedure. Results: When compared to WE and E90, E30 causes significant increase in isokinetic knee extension strength. No significant differences were found in EMG values across different EMS conditions. However, the median frequency of the VM in E30 was significantly increased than the corresponding value for WE. Conclusion: The results of this study showed that EMS training with 30 Hz frequency had positive effect on knee extensor. Based of the findings of the present study, EMS training with lower frequency may help the performer to focus on developing strength in knee extensor muscles.

• 대한정형도수물리치료학회지
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• 제29권2호
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• pp.49-57
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• 2023

Background: This study aims to investigate the effect of lower limb strengthening training combined with electro muscle stimulation on the quadriceps femoris muscle activity of soccer players. Methods: Thirty university soccer players were selected as study subjects and divided into a lower limb strengthening training group combined with EMS (Group I) and a general lower limb strengthening training group (Group II), and 15 subjects were randomly assigned. After receiving general soccer training, subjects in this study additionally mediated lower limb strengthening training combined with EMS and general lower limb strengthening training for 26 minutes, 3 times a week for 8 weeks. Quadriceps femoris muscle activity was analyzed before mediation. Vastus medialis, vastus lateralis, and rectus femoris were measured with maximum isometric contraction in the manual muscle test position in order to analyze leg muscle activity. The same items as above were re-measured and a between-group analysis was conducted after 8 weeks of mediation. Results: As a result of comparative analysis of lower extremity muscle activity between groups, the lower limb strengthening training group combined with EMS showed a statistically significant difference in lower extremity muscle activity compared to the general lower limb strengthening training group. Conclusion: As a result, it was found that lower limb strengthening training combined with EMS was more effective in improving quadriceps femoris muscle activity. Based on this study, we are going to provide basic data on the possibility of using EMS in the field of sports rehabilitation for soccer players.

• 대한의용생체공학회:의공학회지
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• 제44권5호
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• pp.336-345
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• 2023

The present study was designed to evaluate changes in neuromuscular properties and the structural and qualitative characteristics of muscles during submaximal isometric contractions at low-to-relatively vigorous target forces and to determine their influence on force steadiness (FS). Thirteen young adult males performed submaximal isometric knee extensions at 10, 20, 50, and 70% of their maximal voluntary isometric contraction using their non-dominant legs. During submaximal contractions, we recorded force, EMG signals from vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF), and ultrasound images from the distal RF (dRF). Force and EMG standard deviation (SD) and coefficient of variation (CV) values were used to measure FS and EMG steadiness, respectively. Muscle thickness (MT), pennation angle (PA), echo intensity (EI), and texture features were calculated from ultrasound images to assess the structural and qualitative characteristics of the muscle. FS, neuromuscular properties, and texture features showed significant differences across different force levels. Additionally, there were significant differences in EMG_CV among the quadriceps at the 50% and 70% force levels. The results of correlation analysis revealed that FS had a significant relationship with EMG_CV in VM, VL, and RF, as well as with the texture features of dRF. This study's findings demonstrate that EMG steadiness and texture features are influenced by the magnitude of the target force and are closely related to FS, indicating their potential contribution to force output control.

• 한국운동역학회지
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• 제34권1호
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• pp.25-33
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• 2024

Objective: The purpose of this study was to compare the lower extremity muscle activity and knee joint load according to movement speed conditions during the barbell back squat. Method: Nine males with resistance training experience participated in this study. Participants performed the barbell back squat in three conditions (Standard, Fast, and Slow) differing movement speed. During the barbell back squat, muscle activity of the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris long head (BFL), semitendinosus (ST), gluteus maximus (GM), gastrocnemius (GCN), and tibialis anterior (TA) was collected using an 8 channel wireless EMG system. The peak flexion angle of the lower extremity joints and the peak resultant joint force in each direction of the knee joint were calculated using eight motion capture cameras and ground reaction force plates. This study was to used the Friedman test and the Wilcoxon signed rank test, to compare lower extremity muscle activity and peak resultant joint force at knee joint according to movement speed conditions during the barbell back squat, and the statistical significance level was set at .01. Results: In the downward phase of the barbell back squat, the RF and TA showed the higher muscle activity in the fast condition, and in the upward phase, RF, VL, VM, BFL, ST, GM, and TA showed the higher muscle activity in the fast condition. As a results, analyzing of the load on the knee joint, in the downward phase, and in the upward phase, the higher peak compressive force of the knee joint was showed in the fast condition. Conclusion: The barbell back squat with fast movement speed was more effective due to increased muscle activity of lower extremity, but one must be careful of knee joint injuries because the load on the knee joint may increase during the barbell back squat with fast movement speed.

• 한국운동역학회지
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• 제25권1호
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• pp.103-111
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• 2015

Objective : The purpose of this study was to evaluate the effect for running shoes with resilience of midsole on biomechanical properties. Methods : 10 healthy males who had no history of injury in the lower extremity with an average age of 26.5 year(SD=1.84), height of 172.22 cm(SD=4.44) and weight of 67.51 kg(SD=6.17) participated in this study. All subjects ran on the treadmill wearing three different running shoes. Foot pressure data was collected using Pedar-X system(Novel Gmbh, Germany) operating at 100 Hz. Surface EMG signals for biceps femoris, rectus femoris, vastus lateralis, medial lateralis, tibialis anterior, medial gastrocnemius, soleus and peroneus longus were acquired at 1000 Hz using Bignoli 8 System(Delsys Inc., USA). To normalize the difference of the magnitude of muscle contractions, it was expressed as a percentage relative to the maximum voluntary contraction (MVC). The impact resilience of the midsole data was collected using Fastcam SA5 system(Photron Inc., USA). Collected data was analyzed using One-way ANOVA in order to investigate the effects of each running shoes. Results : TPU midsole was significantly wider in contact area than EVA, TPE midsole in midfoot and higher in EMG activity than EVA midsole at biceps femoris. TPE midsole was significantly wider in contact area than EVA midsole in rearfoot and higher in peak pressure than EVA midsole in forefoot. EVA midsole was significantly higher in EMG activity than TPU midsole at tibia anterior. In medial resilience of midsoles, TPE midsole was significantly higher than EVA, TPU midsole. Conclusion : TPU midsole can reduce the load on the midfoot effectively and activate tibialis anterior, biceps femoris to give help to running.

• 생명과학회지
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• 제14권3호
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• pp.484-489
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• 2004

인공관절은 21세기 정형외과 발전의 주요변화들 중의 하나이다. 1997년이래 전 세계적으로 무릎인공관절(Total Knee Arthroplasty: TKA)을 사용하는 사람들이 해마다 약 600,000명씩 증가하고 있는 추세이고 미국에서만 인공관절을 사용하고 있는 사람들이 210,000명에 달하고 있으며 그 시장은 대략 $5 billion을 넘고 있다(7). 무릎인공관절은 일상생활에서 의자에 앉았다 일어날 때 계단을 올라 갈 때 등, 무릎의 근 모멘트가 적당한 활동을 해서 무릎관절 근육에 지레와 같은 작용을 하게 하고, 완전한 무릎으로 정상인의 무릎과 같은 기능을 오랫동안 유지하게 한다. 이러한 목적을 달성하기 위해서는 무릎인공관절 디자인 시 정상적인 무릎 회전축(normal knee's axes of rotation)들의 정확한 위치를 파악하는 것은 중요하다. 인공관절 수술 후 무릎관절의 신전과 굴곡 운동을 하는 동안 하나의 회전축(single-axes)을 가진 하나의 회전 반경(single-radius)을 알아보는 것은 여러 축(multi-axes)으로 움직이게 된다는 다축 회전반경(multi-radius)을 분석하기에 앞서 중요한 연구이다. 따라서 본 연구에 서는 무릎이 신전운동과 굴곡 운동 시 신전과 굴곡 모멘트를 만들어내는 대퇴 사두근(quadriceps muscle)과 무릎 오금근 (hamstring)의 역할을 알아보았고, 또한 모멘트와 대퇴 사두근의 iEMG 형태를 파악하였다. 본 연구를 수행하기 위해 무릎인공관절 수술을 받고 1년과 3년이 지난 정상적인 생활을 하는 피검자(1년2명, 3년2명)를 대상으로 Isometric 테스트를 위한 KIN-COM III을 사용하여 60$^\circ$, 30$^\circ$의 무릎굴곡 측정을 하였고, Isokinetic concentric 테스트를 위해서 무릎굴곡각도의 $10^\circ$-80$^\circ$까지 움직임을 측정하였다 또한 15$^\circ$-75$^\circ$까지의 신전운동(sit-to-stand movement)과 굴곡운동(stand-to-sit movement)을 실시하여 시간의 차이, 내전과 외전의 차이 그리고 iEMG의 차이를 알아보았다. 본 연구의 데이터는 여러 번의 실험을 통하여 가장 일반적인 수치를 사용하였다. 이 때 16-channel BTS TELEMG를 사용하여 대퇴사두근과 무릎오금근의 근육활동모양을 알아보았다. 본 연구결과는 시술 후 3년이 지나면서 TKR (Total Knee Replacement)의 대퇴 사두근 토큐가 약해지는 것으로 나타났고, iEMG 실험에서는 N-TKR (Non-Total Knee Replacement)의 대퇴 사두근이 TKR의 대퇴 사두근 보다 근 수축력이 더 크게 발휘되는 것으로 밝혀졌다. 단축회전반경의 굴곡과 신전의 $10^\circ$-80$^\circ$까지의 각 속도는 굴곡동작이 1.19s, 신전 동작이 1.68s로 나타났다. 굴곡과 신전동작에서 다리의 외전(abduction)의 각도변화는 굴곡 시 5.5$^\circ$, 신전 시 5.2$^\circ$로 나타났고, 내전(adduction)의 각도변화는 굴곡 시 7.2$^\circ$, 신전 시 6.1$^\circ$로 나타났다. 대퇴 사두근의 iEMG변화에서는 15$^\circ$-60$^\circ$까지 vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF) 모두 굴곡동작에서 큰 값으로 나타났고, 61$^\circ$-75$^\circ$사이에서는 신전동작에서 iEMG가 큰 값으로 나타났다. 이와 같은 결과들은 인공관절 수술자들의 다축회전 반경을 분석하기에 앞서 중요한 선행연구가 될 것으로 생각된다.

• 대한물리의학회지
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• 제10권4호
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• pp.107-112
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• 2015

PURPOSE: This study investigated the effects of lower limb and trunk muscles activation on seat angle and height during sit to stand and stand to sit. METHODS: Subjects were instructed to sit and stand on different angles and heights; $0^{\circ}$(43cm), $5^{\circ}$(48cm), $10^{\circ}$(51cm) and $15^{\circ}$(58cm). Measurements were conducted from sit to stand and stand to sit for external oblique, transversus abdominis, rectus femoris, vastus medialis, vastus lateralis, tibialis anterior and gastrocnemius muscle activation by surface EMG. The muscle activation was measured three times for five seconds in each posture, and the %RVC value was calculated after the exclusion of one second before and after this measurement. This calculation standardized the data from each participant so it could be comparatively analyzed. RESULTS: The external oblique, tibialis anterior, and erector spinae muscles showed significant difference in $10^{\circ}$(51cm), $15^{\circ}$(58cm) and $0^{\circ}$(43cm), rectus femoris, in $15^{\circ}$(58cm) and $0^{\circ}$(43cm)(p<.05) during sit to stand. The external oblique, tibialis anterior, and rectus femoris muscles showed significant difference in $0^{\circ}$(43cm) and $15^{\circ}$(58cm), erector spinae and vastus medialis muscles showed significant difference in $10^{\circ}$(51cm), $15^{\circ}$(58cm) and $0^{\circ}$(43cm)(P<.05) during stand to sit. CONCLUSION: The present study findings indicate that the toilet seat angle and height could affect muscle activities of the lower limb and trunk.

• 수산해양교육연구
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• 제26권2호
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• pp.308-315
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• 2014

The aims of this study are to analysis about surface muscle activity of lower and upper musculus erector spinae according to walkers form. The subjects of the current step is inconvenient to use a walker and five people over the age of 65 valid samples were selected as final. All the subjects were measured in three forms. Wireless EMG muscle activity is a measure of surface measurements were measured using a system, both musculus vastus lateralis, outside the erector spinae muscle, musculus biceps femoris, gastrocnemius muscle was attached to the channel electrodes. According to the results, First, gastrocnemius muscle activity showed significant differences by type of gait. Second, the muscle activity of the erector spinae muscle walking showed significant differences by type, side grip type showed the lowest muscle activity. Consequently, the present study is the efficient use of the four-wheel walker will provide the baseline data.

• 대한인간공학회지
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• 제30권2호
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• pp.357-363
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• 2011

Objective: The aim of this study is to set the design direction of the lift chair's tilting seat for development. Background: Great attention has been shown to the development of senior friendly product, because of increasing elderly population rapidly in Korea. Therefore, we need to study on sit-to-stand(STS) motion of elderly systematically for developing lift chair that is one of senior friendly products. Method: In this study, we analyzed joint moment(knee, hip) and muscle activity (Erector spinae, Rectus femoris, Vastus lateralis) on STS motion of elderly(female, 60~70: 7) and young people(female, 20~30: 7) using 3 dimension motion capture camera, force plate, wireless EMG. Results: The results of muscle activity showed a similar trend but the results of joint moment were a lot of differences between the young and the elderly. Conclusion: The results of knee joint moment suggest the angle(10~30deg)-adjustable seat that can be better than to find the optimal seat's angle. Application: The method and results of this study are expected to develop senior friendly product and verification as well as be available to various application.

• 대한물리의학회지
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• 제9권1호
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• pp.55-62
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• 2014

PURPOSE: The objective of this study was to determine the effects of virtual reality training on muscle activation in the elderly. METHODS: The subjects were 32 healthy elderly people aged between 65 and 80, who were divided into the VR(virtual reality) training group(n=17) and the control group(n=15). The Virtual reality training group engaged in a 30-minute exercise session using Wii Fit three times a week for eight weeks. Virtual reality training group used the Ski Slalom, Table tile, Balance bubble programs. low-extremity muscle activation of the two groups were measured before and after the intervention. RESULTS: To investigate the effects of the training on lower-extremity muscle activation, biceps femoris, gastrocnemius, tibialis anterior, vastus lateralis were measured. The results revealed that the activation of gastrocnemius and tibialis anterior significantly increased(p<.05), which indicates virtual reality training is effective in improving the activation of the muscles involved in the movement of the ankle joint. CONCLUSION: Virtual reality training is effective in improving the healthy elderly's activation of the muscles involved in the movement of the ankle joint. Thus, virtual reality training can be proposed as a form of fall prevention exercise for the elderly.