• 한국운동역학회지
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• 제21권4호
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• pp.411-420
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• 2011

The purpose of this investigation was to determine whether correlations exist between balance and impact velocity, angular position, and maximum velocity of a club during drive swing. Twelve skilled golfers were recruited in this study. They were asked to perform ten swing trials and two trials were selected for analysis. Balance parameters were calculated via the force platform while kinematic variables were determined by using the Qualisys system. The results of the present study demonstrated that the average of COP velocity was faster in the medio-lateral direction rather than the anterio-posterior direction. Also, left foot's COP velocity and free torque were greater than the right foot's before impact. The range of the right foot's COP in the anterio-posterior direction before impact were correlated with the club velocity and angular position at impact. There was a negative correlation between the left foot's COP velocity before the impact and the velocity at impact. Additionally, the range and RMS of the left foot's free torque affected on the club angular position at impact and the maximum velocity at release, respectively. Finally, a negative correlation existed between the range of the right foot's free torque after the impact and club's maximum velocity at release.

• 한국정밀공학회지
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• 제24권1호
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• pp.118-125
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• 2007

In this study, we analyzed the plantar shear stress and normal pressure in lateral heel diabetic foot patients during walking by using in-shoe local shear stress and plantar pressure measurement systems. The shear force transducer based on the magnetic-resistive principle, was a rigid 3-layer circular disc. Shear transducers were mounted on the locations of four metatarsal heads and heel in the insole. Twelve normal subjects and three diabetic foot patients with diabetic neuropathy in the lateral heel participated in this study. The center of pressure in lateral heel diabetic foot patients moved more medially and directed toward the first, medial to the second metatarsal heads, and the hallux during late stance, making pressure at the medial heel and the second metatarsal head significantly larger than in the normal. Shear stress at the heel changed significantly in early stance and the magnitude of shear stresses in each metatarsal head also changed. Further studies would be very helpful to design foot orthoses in patients with diabetic neuropathy or other diseases.

• 한국정밀공학회지
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• 제24권1호
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• pp.85-92
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• 2007

In the present study, three-dimensional motion analyses were performed to determine biomechanics of the lower extremity in unexpected missing foot steps for ten healthy young volunteers. In unexpected missing foot steps, the whole plantar surface of the foot or the heel contacted to the ground. A rapid ankle dorsiflexion was found right after missing foot steps and an increased plantarflexion moment was noted during loading response. After the unexpected situation, the breaking force increased rapidly. At this time, both tibialis anterior and soleus were simultaneously activated. Moreover, the range of motion at ankle, knee and hip significantly decreased during stance. In pre-swing, rectus femoris and biceps femoris prevented the collapse of the lower limbs. During late stance, propulsive forces decreased and thus, both plantarflexion moment and power generation were significantly reduced. On the opposite side, hip extension and pelvic upward motion during terminal swing were significant. Due to the shortened pre-swing, the energy generation at the ankle to push sufficiently off the ground was greatly reduced. This preliminary study would be helpful to understand the biomechanics of unexpected dynamic perturbations and valuable to prevent frequent falling of the elderly and patients with gait disorders.

• 대한족부족관절학회지
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• 제24권4호
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• pp.165-167
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• 2020

Failure to achieve stable fixation during surgery for a Lisfranc joint injury leads to subtle instability that causes dysfunction and posttraumatic osteoarthritis. Therefore, it is important to check for appropriate fixation during surgery. This paper reports a test that evaluates the joint instability dynamically during the open reduction of the Lisfranc joint and checks the stability after fixation. a Freer elevator was inserted into the interosseous area between the medial cuneiform and second metatarsal base, and a twisting force was applied to evaluate the dynamic instability of the Lisfranc joint. After fixation of the Lisfranc joint, the stability of the fixation could be tested by trying this maneuver with the Freer elevator. Overall, the Freer test can be considered a valuable test in open surgery for a Lisfranc joint injury.

• 한국운동역학회지
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• 제24권2호
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• pp.151-160
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• 2014

The purpose of this study was to investigate the GRF(ground reaction force) parameters according to the shoes's heel heights and ground landing distances during downward stairs on bus. Participants selected as subject were consisted of young and healthy women(n=9, mean age: $21.30{\pm}0.48$ yrs, mean height: $164.00{\pm}3.05cm$, mean body mass: $55.04{\pm}4.41kg$, mean BMI: $20.47{\pm}1.76kg/m^2$, mean foot length: $238.00{\pm}5.37mm$). They were divided into 2-types of shoe's heel heights(0 cm/bare foot, 9 cm) and also were divides into downward stairs with 3 types of landing distance(20 cm, 35 cm, 50 cm). A one force-plate was used to collect the GRF(AMTI, USA) data from the sampling rate of 1000 Hz. The GRF parameters analyzed were consisted of the medial-lateral GRF, anterior-posterior GRF, vertical GRF, loading rate, Center of Pressure(${\Delta}COPx$, ${\Delta}COPy$, COP area) and Dynamic Postural Stability Index(MLSI, APSI, VSI, DPSI) during downward stairs on bus. Medial-lateral GRF and vertical GRF didn't show significant differences statistically according to the shoe's heel heights and landing distance, but 9 cm shoes heel showed higher vertical GRF than that of 0 cm bare foot in landing distance of 50 cm. Also anterior-posterior GRF didn't show significant difference statistically according to the shoe's heel heights, but landing distance of 20 cm showed higher than that of landing distances of 35 cm and 50 cm in anterior-posterior GRF. Loading rate didn't show significant difference statistically according to the landing distance, but 9 cm shoe's heel showed higher than that of 0 cm bare foot during downward stairs. The ${\Delta}COPy$ and COP area didn't show significant differences statistically according to the shoe's heel heights and landing distance, but 0 cm bare foot showed higher than that of 9 cm shoe's heel in ${\Delta}COPx$. Dynamic Postural Stability Index(MLSI, APSI, VSI, DPSI) didn't show significant differences statistically according to the landing distance, but 9 cm shoe's heel showed decreased value than that of 0 cm bare foot in dynamics balance. Considering the above, parameters of GRF showed different characteristics according to the shoe's heel heights and ground landing distances during downward stairs on bus.

• 한국운동역학회지
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• 제30권1호
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• pp.37-49
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• 2020

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.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.733-740
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• 2016

To achieve bipedal walking in real human environments, a bipedal robot should be capable of modifiable walking both on uneven terrain with different heights and on flat terrain. In this paper, a novel walking pattern generator based on a 3-D linear inverted pendulum model (LIPM) is proposed to achieve this objective. By adopting a zero moment point (ZMP) variation scheme in real time, it is possible to change the center-of-mass (COM) position and the velocity of the 3-D LIPM throughout the single support phase. Consequently, the proposed method offers the ability to generate a modifiable pattern for walking on uneven terrain without the necessity for any extra footsteps to adjust the COM motion. In addition, a control strategy for bipedal walking on uneven terrain with unknown height is developed. The torques and ground reaction force are measured through force-sensing resisters (FSRs) on each foot and the foot of the robot is modeled as three virtual spring-damper models for the disturbance compensation. The methods for generating the foot and vertical COM of 3-D LIPM trajectories are proposed to achieve modifiable bipedal walking on uneven terrain without any information regarding the height of the terrain. The effectiveness of the proposed method is confirmed through dynamic simulations.

• 대한인간공학회:학술대회논문집
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• 대한인간공학회 1993년도 춘계학술대회논문집
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• pp.1-9
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• 1993

A human gait study is required for the biomechanical design of running shoes. A tow-dimensional dynamic model was developed in order to analyze lower extremity kinematics and loadings at the right ankle, knee, and hip joints. The dynamic model consists of three segments, the upper leg, the lower leg, and the foot. Each segment was assumed to be a rigid body with one or two frictionless hinge joints. The lower extremity motion was assumed to be planar in the sagittal plane. A young male subject was involved in the gait test and his anthropometric data were measured for the calculation of segement mass and moment of inertia. The experimental data were obtained from three trials of walking at 1.2m/s. The foot-floor reaction data were measured from a Kistler force plate. The kinematic data were acquired using a three-dimensional motion measurement system (Expert Vision) with six markers, five of which were placed on the right lower extremity segments and the rest one was attached to the force plate. Based on the model and experimental data for the stance phase of the right foot, the calculated vertical forces reached up to 492, 540, and 561 N at the hip, knee, ankle joints, respectively. The flexion-extension moments reached up to 155, 119, and 33 Nm in magnitude at the corresponding joints.

• 한국운동역학회지
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• 제17권4호
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• pp.191-200
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• 2007

The purpose of this study was to analyze the foot-pressure distribution of trekking boots for assessing their functionality. Subjects participated in this study included 10 university male students who had no injury experience in lower limbs and a normal gait pattern. The size of all subjects was 270mm. Five models of trekking boots, most popular in Korea (A, B, C, D & E company), were selected for the test. Using the PEDAR-X system and PEDAR-X insoles, 5 different walking stages were analyzed for the foot-pressure distribution: (a) straight gait; (b) $45^{\circ}$ turn gait; (c) $25^{\circ}$ uphill gait; and (d) $25^{\circ}$ downhill gait. Results of the foot-pressure distribution and functionality on each stage were as follow; 1. Straight gait - In case of Max ground reaction force, mean plantar pressure and Max plantar pressure, there was not a distinct tendency; however, products manufactured by E and A company showed relatively lower pressure distribution. 2. $45^{\circ}$ turn gait - In Max ground reaction force, mean plantar pressure and Max plantar pressure, there wasn't a distinct tendency; however, products manufactured by E and A company showed relatively lower pressure distribution. Results also revealed that the products manufactured by E and A company were superior to those by other companies in terms of functionality. 3. $25^{\circ}$ uphill gait - In Max ground reaction force, mean plantar pressure and Max plantar pressure, there wasn't a distinct tendency; however, products manufactured by E and C company showed relatively lower pressure distribution. Results also revealed that the products manufactured by E and C company were superior to those by other companies in terms of functionality. 4. $25^{\circ}$ downhill gait - In Max ground reaction force, Mean plantar pressure and Max plantar pressure, there wasn't a distinct tendency; however, products manufactured by E company showed relatively lower pressure distribution. Results also revealed that the products manufactured by E company were superior to those by other companies in terms of functionality. Overall, five pairs of trekking shoes selected in this study showed the excellent performance in several conditions. The findings above may provide us with the important criteria for choosing trekking boots.

• 한국정밀공학회지
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• 제24권1호
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• pp.27-36
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• 2007

This paper describes the development of 6-axis ankle force/moment sensor for the intelligent feet of a humanoid robot. When the robot walks on uneven terrain, the feet should perceive the applied forces Fx, Fy, Fz and moments Mx, My, Mz from the attached 6-axis force/moment sensor on their ankles. Papers have already been published have some disadvantages in the size of the sensor, the rated output and so on. The rated output of each component sensor (6-axis ankle force/moment sensor) is very important to design the 6-axis force/moment sensor for precision measurement. Therefore, each sensor should be designed to get the similar rated output under each rated load. Also, the size of the sensor is very important for mounting to robot's feet. Therefore, the diameter should be below 100 mm and the height should be below 40mm. In this paper, first, the structure of a 6-axis ankle force/moment sensor was modeled for a humanoid robot's feet newly, Second, the equations to predict the strains on the sensing elements was derived, third, the size of the sensing elements was designed by using the equations, then, the sensor was fabricated by attaching straingages on the sensing elements, finally, the characteristic test of the developed sensor was carried out. The rated outputs from the derived equations agree well with the results from the experiments. The interference error of the sensor is less than 2.94%.