The Effects of Running Shoes’ Midsole Properties on Impact and Lower Extremity Joint’s Dynamic Stability

( Sihyun Ryu ),( Ho-jong Gil ) 한국운동역학회 2021 한국운동역학회지 Vol.31 No.4

Objective: The purpose of this research is to examine the effects of three types of different running shoes with different properties on impact variables (PVRGF and VLR) and the lower extremity joint's dynamic stability variables (LyEs of DPA, IEA, FEA, DPAV, IEAV, and FEAV) during running. Method: The participants in this research were 12 males (Age: 22.0 ± 3.3 years, Height: 177.2 ± 4.1 cm, Weight: 74.3 ± 9.6 kg). One type of N company's running shoes and two types (FA, FB) of F company's running shoes were used. As for the properties of the running shoes, thickness (mm), dwell time (ms), peak acceleration (m/s2), and energy return (%) were measured. The motions running at 3.5 m/s on a treadmill (Instrumented treadmill, Bertec, USA) wearing each type of running shoes were analyzed. Results: Although the VLR of the thick running shoes (FB) was smaller than that of the other running shoes (N, FA), the LyEs of PVGRF and DPA were larger (p<.05). Even though the running shoes' dwell time (i.e., impact absorption time) and peak acceleration showed a positive correlation with the LyEs of DPAV, IEAV, and FEAV, the energy return showed a negative correlation (p<.05). Conclusion: Our results indicated that the running shoes with excellent impact absorption function are predicted to be suitable for running beginners who need to reduce the burden of the lower extremity joint during running. The running shoes with excellent energy return are expected to be suitable for mid-and long-distance running elite athletes or marathoners to whom stability and consistency are essential during running.

Industrial manipulator calibration with geometric and non-geometric parameters for the enhanced positioning accuracy

Sihyun Ryu,문형필 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6

Robot calibration is a fundamental problem of identifying robot’s kinematic parameters to improve the positioning accuracy. In this paper, we propose a practical method for industrial manipulator calibration to enhance positioning accuracy. Geometric parameters, as well as non-geometric parameters such as joint stiffness and backlash, are considered to account for the cause of the positioning error. However, these parameters have very complex dependencies with one another. Therefore, in order to estimate the parameters more accurately and reliably, the stiffness parameters are estimated through a separate process. The stiffness parameters are estimated by using the measured vector of the TCP (tool center point) position deformation due to changes in the tool load. For various configurations, the backlash effects for each joint based on the torque direction are estimated simultaneously with the geometric parameters through the least squares method. The advantage of the proposed method is verified through simulation analysis for noise and experiment with real robot. Experimental results show that our method outperforms conventional geometric approaches and is robust to the load variations. The maximum error and the deviation of the error by load condition are shown about five times more accurate with our proposed method than the conventional geometric calbration method.

Impact Signal Differences Dependent on the Position of Accelerometer Attachment and the Correlation with the Ground Reaction Force During Running

Sihyun Ryu,Young-Seong Lee,Sang-Kyoon Park 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.10

Attachment of an accelerometer on the tibia is widely applied in the studies of impact during running as peak acceleration (PA) is highly relevant to peak ground reaction force (PGRF) and loading rate (LR). However, there are no guide lines for the positioning of the accelerometer on the tibia. The purpose of this study was twofold: first, to compare the differences in acceleration during running depending on the positions of the accelerometer’s attachment to the tibia (i.e. the distal tibia vs. proximal tibia); second, to select the better accelerometer position between the two placements in order to measure impact from the ground based on the correlations with the major impact variables of ground reaction force collected by a force plate. The twenty participants ran on an instrumented treadmill. Two three-axis accelerometers were attached to the distal tibia and proximal tibia, respectively. PAs at the distal tibia were greater than those at the proximal tibia ( p < 05). PAs at the distal tibia had a greater effect on predicting PGRF and LR compared to those at the proximal tibia ( p < 05). Therefore, considering the purpose of this study, the position of the accelerometer should be carefully selected. These findings suggest that an accelerometer attached at the distal tibia would provide a better estimation of the measurement of impact during running.

Compromising Ties : Ch'oe Namsŏn's View on Culture and His Publication Activities around 1910s

Ryu Sihyun 고려대학교 한국사연구소 2003 International Journal of Korean History Vol.4 No.-

Immediate Effects of Real-time Visual Bio-feedback using Ground Reaction Forces on Gait Symmetry in Elderly Males

Sihyun Ryu,Jongbin Kim,Woo-Sub Kim,Sang-Kyoon Park 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.1

The purpose of this study was to investigate the effects of real-time visual bio-feedback during walking on the symmetry of the elderly gait. The subjects of this study were 16 elderly men (80.3 ± 4.6 years, 163.0 ± 4.7 cm, 64.7 ± 9.4 kg). They were asked to walk on a treadmill at the preferred speed, and later biofeedback was provided so that the subject could visually confirm the vertical ground reaction force of the both feet in real-time. The variables include three dimensional lower limb joint angle and bilateral symmetry index. As a result, the ROM of dorsi-flexion and plantar-flexion at the ankle joint was increased in the stance and swing phase after providing the visual biofeedback (p < .05). In addition, the symmetry index of double stance, single stance, ROM of hip AA at stance phase, and M/L COP range were decreased after providing the visual biofeedback (p < .05). The results suggested that the visual bio-feedback provided in real-time may have a positive effect on the symmetrical walking of the elderly. It is warranted whether gait exercise program using biofeedback would have a long term effect in future studies.

태권도 자유 품새에 적용하기 위한 뛰어 앞차기 착지 동작의 상해 예방 전략

Ryu, Sihyun 한국운동역학회 2020 한국운동역학회지 Vol.30 No.1

Objective: The purpose of this study was to investigate the injury factors of Taekwondo jumping kick during landing phase according to the experience of injury and to suggest a stable landing movement applicable to free style Poomsae. Method: The participants were non-injury group (NG), n = 5, age: 20.5±0.9 years; height: 171.6±3.6 cm; body weight: 65.7±4.4 kg; career: 5.0±2.7 years. Injury group (IG), n = 9, age: 21.0±0.8 years; height: 170.9±4.6 cm; body weight: 67.1±7.0 kg; career: 8.6±5.0 years. The variables are impact force, loading rate, vertical stiffness, lower limb joint angle, stability, balance, and muscle activity in the landing phase. Results: NG was statistically larger than IG in the gluteus medius (p<.05). The impact force, loading rate and vertical stiffness decreased as the landing foot angle, the ROM of lower limb joint angle and COM displacement increased (p<.05). Conclusion: Based on the results, it means that the landing foot angle plays an important role in the impact reduction during landing phase. It is required the training to adjust the landing foot angle.

태권도 자유 품새에 적용하기 위한 뛰어 앞차기 착지 동작의 상해 예방 전략

( Sihyun Ryu ) 한국운동역학회 2020 한국운동역학회지 Vol.30 No.1

Objective: The purpose of this study was to investigate the injury factors of Taekwondo jumping kick during landing phase according to the experience of injury and to suggest a stable landing movement applicable to free style Poomsae. Method: The participants were non-injury group (NG), n = 5, age: 20.5±0.9 years; height: 171.6 ±3.6 cm; body weight: 65.7±4.4 kg; career: 5.0±2.7 years. Injury group (IG), n = 9, age: 21.0±0.8 years; height: 170.9±4.6 cm; body weight: 67.1±7.0 kg; career: 8.6±5.0 years. The variables are impact force, loading rate, vertical stiffness, lower limb joint angle, stability, balance, and muscle activity in the landing phase. Results: NG was statistically larger than IG in the gluteus medius (p<.05). The impact force, loading rate and vertical stiffness decreased as the landing foot angle, the ROM of lower limb joint angle and COM displacement increased (p<.05). Conclusion: Based on the results, it means that the landing foot angle plays an important role in the impact reduction during landing phase. It is required the training to adjust the landing foot angle.

신발의 뒤꿈치 형태가 보행 시 충격과 생체역학적 특성에 미치는 영향

류시현(Sihyun Ryu),박상균(Sang-Kyoon Park) 대한인간공학회 2020 大韓人間工學會誌 Vol.39 No.3

Objective: The purpose of this study was to investigate the effects of a curved shoe design of the heel of a shoe on the impact variables, ankle joint angle, and COP (center of pressure) during walking. Background: Shoe design is one of important characteristics in the development of walking shoes as it has to be considered for the mechanism of human movement. Method: Twenty healthy male adults (age: 23.6±2.9 years, body mass: 71.0±8.7kg, height: 175.8±5.0cm) participated in the study. The data was collected using eight infrared cameras during walking at a speed of 1.3m/s and 1.7m/s on an instrumented treadmill. Results: The impulse and peak VGRF (vertical ground reaction force) were statistically smaller for the RHS and RLHS compared with the NS during walking of 1.3m/s & 1.7m/s (p <.05). The ankle plantarflexion angle at toe off, the ROM (range of motion) of dorsi-plantarflexion, and ROM of inversion-eversion were statistically smaller for the RHS and RLHS compared with the NS during walking of 1.7m/s (p <.05). The antero-posterior COP range and jerk were statistically smaller for the RHS and RLHS compared with the NS during walking of 1.7m/s (p <.05). Conclusion: It is concluded that RLHS is slightly effective in reducing shocks, RLHS and RHS help walk smoothly and naturally compared to NS, and RLHS improves the stability of the ankle joints compared to NS, and RLHS during walking. Application: The findings would be helpful when developing the walking shoes with biomechanical functions.

김대중의 역사인식과 한국사 이해의 특징

류시현 ( Ryu Sihyun ) 호남사학회(구 전남사학회) 2020 역사학연구 Vol.80 No.-

김대중은 한국 현대사를 대표하는 정치가이자 국정 책임자인 대통령을 지냈던 인물이다. 그의 활동과 영향력과 관련해서 외교와 통일을 포함한 정치 영역에서의 연구 성과는 많이 축적되어 있다. 하지만 상대적으로 정치적 활동과 결정의 기반이 되었던 그의 사상에 관한 연구는 적었다. 따라서 김대중의 정치활동에 기반이 되었던 그의 역사 인식이 어떠했는가에 관한 연구가 요구된다. 김대중은 아놀드 토인비와 그의 『역사의 연구』에서 많은 영향을 받았다. 인류문명사의 ‘도전과 응전’, ‘창조적 소수자’의 역할 등의 개념을 한국 역사 이해에 적용하고자 했으며, 민족사의 적용과정에서 형성된 역사 진행과정에 관해 ‘낙관’적 전망을 가지게 되었다. 또한 민중 주체의 개혁을 긍정적으로 이해했다. 세계사와 한민족사의 경험에 기초한 역사 발전에 관한 믿음은 민족주의에 관한 유연한 인식이 가능하게 만들었다. 그리고 민족사에 관한 이해는 민주주의와 통일이란 과제를 해결하기 위한 방안으로 활용했다. 역사를 좋아하고, 역사의 심판을 중요시 했던 김대중은 자신의 역사관을 그의 정치활동의 정신적, 사상적 자산으로 삼았다. Kim Dae-jung a politician who represents the modern Korean history and national responsibility, a former president. Reflecting his influence, many research achievements in the political area including diplomacy and unification have been accumulated. However there was less researches on his ideas which were relatively the basis of political activities and decisions. Therefore his A Study on the historical perception as well as Kim Dae-jung's political activities is required. Arnold Toynbee and his book A Study of History affected to Kim Dae-jung. He wanted to apply the role of "challenge and retort" and "creative minority" in the history of human civilization to understanding Korean history. The "optimistic" outlook on the progress of history, which was formed during the application of national history was given. And positively understood the reform of the people's subjects. Belief in the development of history based on the experience of world history and Korean history has made it possible to have a flexible perception of nationalism. And the understanding of national history was used as a way to solve the challenges of democracy and unification. Kim Dae-jung regards history as his mental, spiritual assets of his political activities.

발바닥 부위별 인솔 소재 및 경도 변화가 착화감과 충격 흡수에 미치는 영향

류시현(Sihyun Ryu),길호종(Hojong Gil),공세진(Sejin Kong),최용석(Yongsuk Choi),류지선(Jiseon Ryu),윤석훈(Sukhoon Yoon),박상균(Sang Kyoon Park) 대한인간공학회 2018 大韓人間工學會誌 Vol.37 No.4

Objective: The purpose of this study was to evaluate the biomechanical effects of insole material and hardness in different plantar regions on the comfort and impact absorption during walking and to analyze the correlations between comfort and impact variables. Background: It is necessary to apply materials tailored to the functionalities of different plantar regions during different phases of the gait cycle: the rearfoot portion should absorb the impact force during the heel-contact phase, the midfoot portion should support the entire arch, and the forefoot portion should enhance the swing efficiency during the toe-off phase. Method: Twenty men in their twenties were recruited for the study (age: 23.4±2.7yrs; height: 175.9±4.1㎝; weight: 72.9±9.4㎏). They wore insoles in random order. Pedar-X system (Novel GmbH, USA) and Treadmill (Instrumented treadmill, Bertec, USA) were used to measure the plantar pressure and ground reaction force. The walking speed was set at 1.3㎧ and 1.7㎧. The sampling rate was set at 50㎐ and 1,000㎐, respectively. For comfort testing, the subjects administered a questionnaire survey using the visual analogue scale (VAS) after walking 1km. Three insole models were tested: Insole A using a mixed material with shock-absorbing and anti-rebound components uniformly spread throughout the insole; Insole B and Insole C using sponge and ethylene vinyl acetate (EVA), respectively, as underlying material and strengthened with shock absorber in the rearfoot portion, high-hardness material in the midfoot portion, and anti-rebound function in the forefoot portion. The impulse, mean impact force, initial peak of ground reaction force, and loading rate were calculated. Results: First, Insole B significantly outscored Insole A in terms of the forefoot cushioning comfort (p <.05), with Insole B and C showing higher overall comfort scores compared with Insole A (p <.05). Second, Insole A showed higher mean impact force, initial and peak vertical ground reaction forces, and loading rate compared with Insoles B and C, but without reaching statistical significance. Third, Insole B and C showed statistically higher mean pressure in the midfoot portion compared with Insole A (p <.05). Conclusion: Positive effects in terms of comfort and impact absorption were demonstrated by the insoles fabricated with different materials and hardness tailored to the functionalities of different plantar regions in comparison with the conventional insoles using the uniform material throughout the insole. In particular, positive effects on overall comfort were found to be ascribable to the enhanced hardness in the midfoot portion, which supported the arch more efficiently and contributed to an even distribution of the overall pressure on the plantar. Application: The study results can be applied to insole development as follows: Insole material and hardness should be varied for different plantar regions, and shock absorber and high-hardness material should be used for the rearfoot and midfoot portions, respectively.