• 대한물리치료과학회지
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• 제27권1호
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• pp.34-42
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• 2020

Background: The purpose of this study was to investigate the effects of ipsilateral and contralateral load changes during single-leg standing on the leg muscle activities of healthy people. Design: Randomized controlled trial. Methods: For all the subjects, a load was randomly applied to the ipsilateral or the contralateral side. While the load was applied, the subject raised a hand and then performed single-leg standing for 10 seconds using the dominant side. Results: During single-leg standing, the muscle activity of the gluteus medius, peroneus longus on the supporting side increased statistically significantly when an upper limb load was applied contralaterally, but no statistically significant differences were detected in the muscle activities of the tibialis anterior and the gastrocnemius using a test of within-subjects effects. Conclusion: It can be seen that muscle activities increase during exercise when the amount and frequency of a load are increased and when the same load is applied to different sides of the body. Such muscle activity increases may be applied to change the intensity of exercise when one is in a static posture, such as during single-leg standing.

• PNF and Movement
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• 제17권3호
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• pp.481-486
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• 2019

Purpose: This study examined the effect of calf muscle fatigue on postural sway according to foot posture (a pes cavus, a normal foot, and a pes planus). Methods: The subjects of this study were 12, 11, and 9 students of U University with a pes cavus, a normal foot, and a pes planus, respectively, according to a Navicular Drop Test. Postural sway was measured with a balance instrument (BioRescue, RM Ingenierie, France) while the subjects stood static on two legs as well as during one-leg standing using the dominant leg in two conditions (with the eyes open and with the eyes closed for 30 seconds). Muscle fatigue was then induced in the calf muscle of the dominant leg, and both muscle fatigue and postural sway were measured using an EMG. To compare the degree of postural sway between the three groups after muscle fatigue was induced, the change values were calculated. The results were analyzed using a Kruskal-Wallis test, and a post-hoc test was conducted using the Bonferroni correction. Results: Significant inter-group differences were detected for postural sway during two-leg standing with the eyes closed and during one-leg standing with the eyes open and with the eyes closed (p<0.05). The post-hoc test showed significant differences between the pes cavus and normal foot groups and between the pes planus and normal foot groups for all three variables (p<0.05). However, no significant difference was detected between the pes cavus and pes planus groups (p>0.05). Conclusion: The results of this study show that the pes cavus and pes planus cause more fatigue and postural sway than a normal foot. Therefore, attention should be paid to changes in balance caused by muscle fatigue.

• PNF and Movement
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• 제19권2호
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• pp.153-162
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• 2021

Purpose: The purpose of this study was to investigate the difference in the dynamic balance and leg muscle activity of adults in their 20s with or without shoes. Methods: In this study, seven male and 11 female university students in their 20s were randomized to determine the order of being with or without shoes, and the dominant foot was supported on the central platform of dynamic balance according to the order procedure. Using the opposite foot, the distance of leg stretching in the anterior, posterior medial, and posterior lateral directions and the muscle activity of the supporting leg were measured. Muscle activity measurement sites were attached to the dominant vastus medialis oblique muscle, vastus lateral oblique muscle, tibialis anterior muscle, peroneus longus muscle, and lateral gastrocnemius muscle. Results: As a result of this study, the distance of leg stretching was significantly increased in the anterior, posterior medial, and posterior lateral directions when barefoot rather than when wearing shoes (p < 0.05). The muscle activity of the vastus medial and lateral oblique muscles was significantly increased in all three directions when barefoot rather than when wearing shoes (p < 0.05). The muscle activity of the tibialis anterior was significantly increased in the anterior direction when barefoot (p < 0.05), the peroneus longus muscle was significantly increased when it was barefoot in the posterior medial direction (p < 0.05), and the lateral gastrocnemius muscle activity significantly increased when barefoot in the posterior direction (p < 0.05). Conclusion: The movement of the legs is freed when barefoot as compared to when wearing shoes, and being barefoot can effectively activate muscle activity and improve balance ability.

• 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.

• PNF and Movement
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• 제17권2호
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• pp.215-222
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• 2019

Purpose: The objective of this study was to investigate whether augmented low-dye taping treatment, which consists of low-dye, reverse-six, and calcaneal-sling taping, is effective in alleviating the collapse of the medial longitudinal arch, which is used for physical balancing during one leg standing. Methods: The subjects comprised 27 students in their 20s whose navicular bone height was lowered by 10 mm or more when evaluated using the navicular drop test. Those with interference factors like deformities, fractures, or traumas were excluded. Frequency-division multiplexing was used to measure one leg standing, and the method to avoir the average each time after 3 times of measurement was applied. Results: Significant differences in the center of pressure (COP) path length, COP average velocity, and forefoot force were observed during left leg standing (p<0.05), but for right leg standing, only changes in forefoot force were noted. Conclusion: Based on the changes to the non-dominant leg in terms of COP path length, COP average velocity, and forefoot force, the immediate effect of augmented low-dye taping, which combines three types of anti-pronation taping, on one leg standing balance in people with flat feet was confirmed.

• 한국정밀공학회지
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• 제30권10호
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• pp.1095-1101
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• 2013

The purpose of this study was to verify the effect on improvement of muscle strength unbalance according to load deviation protocol during whole body vibration exercise. Seventeen female volunteers (age $22{\pm}3$ years, height $160{\pm}4.9$ cm, weight $49{\pm}.8$ kg) participated in this experiment. The subjects performed squat exercise in WBV platform. Exercise were performed five set a day including 15 time a set, three days a week, and during 4 weeks. Vibration stimulus was 25Hz as frequency and intensity was dominant leg 1mm and non-dominant leg 4mm. The results in WBV group showed that the differences of peak torque in 16% were getting decreasing significantly after 4 weeks from 16.2% to 5.2%. This result means that WBV with load deviation protocol could provide muscle strength exercise for muscle strength balance. Our study found out that WBV of load deviation protocol could provide muscle strength exercise for improving muscle imbalance.

• 전기학회논문지
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• 제57권9호
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• pp.1669-1673
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• 2008

A new cycle ergometer using a Magneto-Rheological (MR) rotary brake system has been developed for rehabilitation of hemiplegia patients to reduce uneven pedaling characteristics. For this purpose, a control method to adjust the resistance of the MR rotary brake in real time based on the magnitude of the muscular force exerted by the subject has been devised so that the mechanical resistance to the pedaling can be minimized when the affected leg was engaged for pedaling. A series of experiments were carried out with and without the engagement of this real-time control mode of MR rotary brake at different pedaling rate to find out the effect of the real-time control mode. The characteristics of the pedaling for these specific conditions were analyzed based on the variations in angular velocities of the pedal unit. The results showed that the variations in the angular velocities were decreased by 42.9% with the control mode. The asymmetry of pedaling between dominant and non-dominant leg was 19.63% in non-control mode and 1.97% in the control mode. The characteristics of electromyography(EMG) in the lower limbs were also measured. The observation showed that Integrated EMG(IEMG) reduced with the control mode. Therefore, the new bicycle system using MR brake with the real time control of mechanical resistance was found to be effective in recovering the normal pedaling pattern by reducing unbalanced pedaling characteristics caused by disparity of muscular strength between affected and unaffected leg.

• 한국체육학회지인문사회과학편
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• 제56권5호
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• pp.665-677
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• 2017

이 연구는 U-12 유소년 축구선수를 대상으로 운동수행력과 의학적 평가를 상세히 분석한 후에 축구를 통한 운동수행력의 변화 및 의학적 문제점을 파악하는데 그 목적이 있다. 연구대상은 유소년 축구클럽에 참여하고 있는 초등학교 선수를 유소년 축구선수 집단(Youth football players group; YFG, n=15; $11.2{\pm}0.9$ 세)과 축구를 하지 않는 건강한 일반 유소년을 통제 집단(Control group; CON, n=15; $11.5{\pm}0.6$ 세)으로 각각 분류하여 운동수행력(건강관련 체력, 운동관련 체력, 기능적 움직임 및 동적 균형) 및 의학적 평가(하지정렬, 관절가동범위 및 도수근력검사)를 측정하였다. 왕복 오래달리기, 50-m 달리기, 눈 감고 외발서기, 능동적 하지직거상, 회전 안정성 및 비주측의 종합점수는 CON과 비교해서 YFG에서 긍정적인 결과를 보였다. 하지만, 하지정렬에서 주측 및 비주측의 Q각, 관절가동범위에서 비주측의 발목관절 발등굽힘, 주측 및 비주측의 발목관절 발바닥굽힘, 도수근력검사에서 주측의 엉덩관절 폄 및 벌림, 무릎관절 굽힘 및 폄, 비주측의 무릎관절 굽힘 및 폄은 CON과 비교해서 YFG에서 부정적인 결과를 초래하였다. 따라서 이 연구에서 U-12 유소년 축구선수는 부분적으로 운동수행력은 우수하게 나타났지만, 의학적 평가에서는 부정적인 결과를 확인하였다.

• 한국해양공학회지
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• 제35권5호
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• pp.347-359
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• 2021

This study aims to evaluate the dynamic responses of the jacket-type offshore wind turbine using FAST software (Fatigue, Aerodynamics, Structures, and Turbulence). A systematic series of simulation cases of a 5 MW jacket-type offshore wind turbine, including wind-only, wave-only, wind & wave load cases are conducted. The dynamic responses of the wind turbine structure are obtained, including the structure displacement, rotor speed, thrust force, nacelle acceleration, bending moment at the tower bottom, and shear force on the jacket leg. The calculated time-domain results are transformed to frequency domain results using FFT and the environmental load with more impact on each dynamic response is identified. It is confirmed that the dynamic displacements of the wind turbine are dominant in the wave frequency under the incident wave alone condition, and the rotor thrust, nacelle acceleration, and bending moment at the bottom of the tower exhibit high responses in the natural frequency band of the wind turbine. In the wind only condition, all responses except the vertical displacement of the wind turbine are dominant at three times the rotor rotation frequency (considering the number of blades) generated by the wind. In a combined external force with wind and waves, it was observed that the horizontal displacement is dominant by the wind load. Additionally, the bending moment on the tower base is highly affected by the wind. The shear force of the jacket leg is basically influenced by the wave loads, but it can be affected by both the wind and wave loads especially under the turbulent wind and irregular wave conditions.

• The Journal of Korean Physical Therapy
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• 제29권3호
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• pp.135-141
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• 2017

Purpose: This study was to identify the anticipatory postural adjustment (APA) mechanism which is represented by the onset time of trunk muscles and the displacement of the center of pressure (COP) according to the different base of support (BOS) during upper extremity movement. Methods: Thirty healthy subjects (14 males, 16 females) participated in this study. The movement was performed for 10 trials during each of various BOS (shoulder - width double leg stance, narrow base double leg stance, tandem stance, non-dominant single leg stance) at the 1.2 Hz frequency. Electromyography was used to measure muscle onset time and biorescue was used to measure characteristics of the displacement of COP. Surface bipolar electrodes were applied over the right deltoid anterior, right latissimus dorsi, both rectus abdominis, both internal oblique and both erector spinae. The data were analyzed by repeated one-way ANOVA and Duncan's post hoc test. Results: The study has revealed following. There were significant differences with muscle onset time in each BOS (p<0.01). There were significant differences in characteristics of the COP in each BOS (p<0.01). Conclusion: The study found that the more narrowed the basis requires the more rapid anticipatory postural control in contralateral postural muscle when the upper extremity movement is performed.