• Journal of the Korean Applied Science and Technology
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• v.37 no.2
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• pp.296-302
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• 2020

The purpose of this study was to assess knee joint loading in the target knee during a golf swing compared to loading rates of high impact activities such as cutting and drop landings. Nine healthy competitive golfers completed golf swings with the target foot both straight and externally rotated 30 degrees, as well as drop landings and cutting maneuvers. Motion capture data was collected at 240 Hz and ground reaction force data was collected at 2400 Hz. The frontal and transverse knee moments were examined using repeated measures ANOVA through SPSS. The abduction moments were higher in golf swings as compared to the other high impact activities (p=.010), while the external rotation moments were lower (p=.003). There were no significant differences between externally rotated and neutral golf swings. These results suggest moments applied to the knee during a golf swing are similar to those applied during a high impact activity.

• Korean Journal of Applied Biomechanics
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• v.14 no.2
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• pp.105-119
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• 2004

To enhance our understanding of the loads on the foot during treadmill running, we have used a pressure-sensitive insole system to determine pressure, rate of loading and impulse distributions on the plantar surface during treadmill running, both in minimally cushioned footwear and in cushioned shoes. This report includes pressure, rate of loading, impulse and contact time data from a study of ten subjects running on a treadmill at 4.0m/s. Among heel-toe runners, the highest peak pressures and highest rates of loading were observed under the centre of the heel and in the medial forefoot. The arch regions were only lightly loaded. Contact time was greater in the forefoot than in the heel. Two-thirds of the impulse recorded during the step was the result of forces applied through the forefoot, mostly in the region of the metatarsal heads. The distribution of loads in the shoe suggests that the load distributing properties of the cushioning system are most important in the centre of the heel, under the metatarsal heads and great toe. Shock attenuation is primarily required under the centre of the heel and to lesser extent under the metatarsal heads. Some energy dissipation may be desirable in the heel region because it causes shock to be absorbed with less force. All the 'propulsive' effort is applied through the forefoot. Therefore, this region should as resilient as possible.

• Journal of the Ergonomics Society of Korea
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• v.34 no.2
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• pp.167-177
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• 2015

Objective: The objective of this research is to develop evaluation checklist for personal office furniture and apparatus to shape comfortable and efficient worksite for workers' welfare improvement, productivity enhancement and labor force preservation, and to identify office work environment by applying the checklist. Background: Because most office workers work using computers in a sitting posture, the ratio of office workers among total musculoskeletal disorders patients is forecast to increase. In this regard, an effort to prevent and manage such musculoskeletal disorders is required. Method: This research developed evaluation checklist for personal office furniture and apparatus by examining 25 domestic and international ergonomic literature and anthropometric data. This research carried out a fact-finding survey targeting the A Office and B Office of one public agency using the checklist. Results: Although, the checklist items on desks, chairs, computers and other goods conformed to the checklist standards, the following items did not conformed: desk height adjustment, seat board depth adjustment, lumbar support depth, foot rest, wrist rest, mouse tray, headset, speaker phone and Bluetooth. Conclusion: The evaluation checklist for personal office furniture and apparatus and fact-finding survey results are considered to be used as basic data for office work environment and workers' welfare improvement. Application: The information drawn from this research can be helpful to manufacturers' design and manufacture of ergonomic furniture and apparatus.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.11
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• pp.1146-1154
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• 2008

This paper presents a method for the acceleration analysis of multi-legged walking robots in consideration of the frictional ground contact. This method is based on both unified dynamic equation for finding the acceleration of a robot's body and constraint equation for satisfying no-slip condition. After the dynamic equation representing relationship between actuator torques and body acceleration, is derived from the force and acceleration relationship between foot and body's gravity center, the constraint equation is formulated to reconfigure the maximum torque boundaries satisfying no-slip condition from given original actuator torque boundaries. From application of the reconfigured torques to the dynamic equation, interested acceleration boundaries are obtained. The approach based on above two equations, is adapted to the changes of degree-of-freedoms of legs as well as friction of ground. And the method provides the maximum translational and rotational acceleration boundaries of body's center that are achievable in every direction without occurring slipping at the contact points or saturating all actuators. Given the torque limits in infinite normsense, the resultant accelerations are derived as a polytope. From the proposed method, we obtained achievable acceleration boundaries of 4-legged and 6-legged walking robot system successfully.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.208-213
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• 2006

경사진 안창은 안창의 경사로 발의 자세를 교정함으로써 하지 통증을 완화시키는 데 사용되는 보조치료기구로 내측 경사진 안창(MWI: medially wedged insole)과 외측 경사진 안창(LWI: laterlly wedged insole)으로 나뉜다. 본 연구는 내/외측 경사진 안창이 족부압력에 미치는 영향을 정량적으로 분석하고자 한다. 분석변수는 압력중심(COP: center of pressure)의 궤적 변화, 발바닥 내 세 개 구획에 상대적으로 작용하는 수직 힘(RVF: relative vertical force) 그리고 여덟 개 해부학적 지점의 압력이다. 경사진 안창의 경사조건은 내/외측 각각 $5^{\circ},\;8^{\circ},\;15^{\circ}$이며, 경사가 없는 안창을 포함해 총 일곱 가지 안창이 실험에 사용되었다. 실험참여자로는 20대 성인 남성 10명이 참여하였다. 실험결과 앞발 누름기에서 MWI와 LWI는 모두 COP를 내측으로 이동시키고 외측 압력을 감소시켰다. 뒤축 접지기에서 MWI는 COP를 내측으로 이동 시키고 내측압력을 증가시키는 반면, LWI는 COP를 외측으로 이동시키고 외측압력을 증가시켰다. 그리고 RVF 분석결과 MWI와 LWI는 모두 앞발 부위 힘의 크기를 감소시켰고, LWI만이 발 뒤축 부위 힘의 크기를 증가시켰다.

• Journal of the Korean Society of Physical Medicine
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• v.9 no.3
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• pp.279-284
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• 2014

PURPOSE: This study intended to verify whether there was actual correlation between weight-bearing asymmetry and a limitation in hip joint rotation range in patients with low back pain. METHODS: Thirty five low back pain patients voluntarily participated this study. For each participant, hip joint medial rotation symmetry rate and the weight-bearing symmetry rate were calculated. The correlation between the two variables was investigated. RESULTS: A decrease in the left hip joint medial rotation range of motion (ROM) was observed more often than a reduction in the right hip joint medial rotation ROM. However, similar number between right and left side was observed in ground reaction force more weighted. The coefficient between the passive hip joint medial rotation symmetry rate and the weight loading symmetry ratio was -0.19 (p < 0.05). CONCLUSION: The present study demonstrated a weak correlation between the hip joint medial rotation ROM and the weight distribution of both feet. Such result suggests that careful evaluation by separating each element is needed in treating patients with low back pain. Future research should take into account asymmetric alignment and abnormal movement in different joints of the body as well as asymmetry in the bilateral hip joint rotation and the unilateral weight supporting posture.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.576-583
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• 2000

A robust position control using a sliding mode controller is adopted for the stable dynamic walking of the biped. For the biped robot that is modeled with 14 degrees of freedom rigid bodies using the method of the multibody dynamics, the joint angles for simulation are obtained by the velocity transformation matrix using the given Cartesian foot and trunk trajectories. Hertz force model and Hysteresis damping element which is used in explanation of the energy dissipation during contact with ground are used for modeling of the ground reactions during the simulation. By the obtained that forces which contains highly confused noise elements and the system modeling uncertainties of various kinds such as unmodeled dynamics and parameter inaccuracies, the biped system will be unstable. For that problems, we are adopting a nonlinear robust control using a sliding mode controller. Under the assumption that the esimation error on the unknown parameters is bounded by a given function, that controller provides a successful way to preserve stability and achieve good performance, despite the presence of strong modeling imprecisions or uncertainties.

• Korean Journal of Applied Biomechanics
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• v.22 no.1
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• pp.1-7
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• 2012

The purpose of this study was to investigate the pattern change of throwing in baseball after 15 weeks of participation in baseball class, by examining ball speed, trunk and upper body angles. The comparison was with 6 university students that haven't had any experience in baseball. 8 infra red cameras and 2 force platforms were used to collect the data. First, there was an increase in the speed of the ball after the class. Second, there was no significant difference in the allocated phases during the throw before and after class. Third, the release point was lower and more in front. Forth, there was an increase in the knee flexion at the left foot landing and release point. Finally, there was an increase in the maximum shoulder external rotation and pelvis angle. It is recommended that the coordination between the segments should be investigated to improve our understanding of the learning of throwing in future research.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.5
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• pp.257-263
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• 2000

One of the basic assumptions in the static gait design for a walking robot is that the weight of leg should be negligible compared to that of body, so that the total gravity center is not affected by swing of a leg. Based on the ideal assumption of zero leg-weight, conventional static gait has been simply designed for the gravity center of body to be inside the support polygon, consisting of each support leg's tip position. In case that the weight of leg is relatively heavy, however, while the gravity center of body is kept inside the support polygon, the total gravity center of walking robot can be out of the polygon due to weight of a swinging leg, which causes instability in walking. Thus, it is necessary in the static gait design of a real robot a compensation scheme for the fluctuation in the gravity center. In this paper, a body impedance control is proposed to obtain the total gravity center based on foot forces measured from load cells of a real walking robot and to adjust its position to track the pre-designed trajectory of the corresponding ideal robot's body center. Therefore, the walking stability is secured even in case that the weight of leg has serious influence on the total gravity center of robot.

• Journal of International Academy of Physical Therapy Research
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• v.7 no.2
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• pp.1037-1040
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• 2016

This study aims to investigate the effects of ankle foot orthosis(AFO) on the activities of tibialis anterior(TA), soleus(Sol), rectus femoris(RF) and biceps femoris(BF) during stairs descending. The activities of TA, Sol, RF and BF were initially measured while descending 4 stairs without using AFO. The activities of the same muscles were then measured again while descending 4 stairs while using AFO. Wilcoxon signed-rank tests were used to analyze the results in order to examine the differences between the with using AFO and without using AFO. Although the activities of TA, Sol and RF were relatively lower while using AFO than without using AFO, only the differences in Sol and RF activities were significant(p<0.05). The activity of BF was relatively higher while using AFO compared to the activity of BF observed without using AFO. However, difference was not significant(p>0.05). Conclusion of this study was observed since AFO's ground reaction force absorption during stairs descending reduced the need to use So and RF that is related to shock absorption. BF activity was increased with AFO than without during standing forward to correct the trunk stability.