• Korean Journal of Applied Biomechanics
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• v.24 no.3
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• pp.229-238
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• 2014

This study comparatively analyzed the speed and segment coordination characteristics of Taekwondo hand techniques, while different attention focusing strategies were utilized. Ten elite Taekwondo poomsae athletes participated, and three different strategies (no focus, target focus, body focus) were utilized in random order. The hand velocity and upper body segment coordination characteristics were analyzed, with the following results. First, the maximum magnitudes of the hand velocity differed between the focus conditions for the Araenaereomakgi and Momtongjireugi techniques. Second, the angular velocity and kinetic energy transfer patterns of the segments differed between the focus conditions, and in the case of the body focus condition, the movement was more correct according to the theory. Third, the shoulder and elbow joint coordination patterns differed between the focus conditions, with more efficient movement shown with the body focus condition. In conclusion, we confirmed the potential of effectively using an attention focusing strategy in a taekwondo teaching situation. However, the effect on the movement coordination and results of the movement could be changed by a difference in the cue provided or the type of the task. In addition, depending on the task, the attention focusing strategy could affect the efficiency of the movement. Therefore, coaches and masters of Taekwondo will have to constitute determine the appropriate attention focusing cues based on the task.

• Korean Journal of Applied Biomechanics
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• v.24 no.3
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• pp.209-216
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• 2014

The purpose of this study was to explore the effect of 8 weeks after school classes of track sports on students' start motion through kinematic variables. 30 students in D National university of education participated for this study. These students divided into two groups, 17 students for experimental group and 13 students for control group. The two groups participated in general athletic class as common class, and the experimental group participated in after school class additionally. The general class taught track and jump skill for 3 hours a week, and the after school class taught only athletic running skill for 30 minutes a week. Pre and post test assessed to assess students' kinematic changes. Findings indicated that velocity and step rate were increased, and contact time, step length, displacement of center of mass were decreased in the experimental group. In the control group, early velocity, knee/hip angle velocity were increased, and contact time, step length, displacement of center of mass were decreased. In conclusion, the students who only participated in general class, could not maintain athletic skills obtained from the class. However, students who participated in both general and after school class accomplish athletic start skill. This is because Continuous learning effect helped students keep the skill and did not lose the skill. Thus, in order for students to learn specific sport skills, joining after school class with general class together is recommended.

• Korean Journal of Applied Biomechanics
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• v.24 no.3
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• pp.309-315
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• 2014

The aim of the present study was to investigate the effects of 6-week wrist resistance training on wrist torque control. Nineteen subjects were randomly assigned to either the wrist training group (n=9) or the control group (n=10). The training group performed wrist exercises for six directions (flexion, extension, pronation, supination, radial deviation, and ulnar deviation) while the control group did not. Testing for the isometric torque control error, one-repetition maximum (1-RM) strength, and isokinetic maximum torque (angular velocity of $60^{\circ}/s$ wrist movements) were conducted before and after six weeks of resistance training and after every two-week interval of training. The wrist training group showed significant decreases in isometric torque control error in all six directions after the 2-week resistance training, while the control group did not show significant increase or decrease. The training group showed significant increases in the maximum strength in all six directions assessed by 1-RM strength and isokinetic strength tests after the 4-week resistance training, while the control group did not show any statistically significant changes. This study shows that motor control ability significantly improves within the first two weeks of resistance training, while the wrist strength significantly improves within the first four weeks of resistance training in wrist training group compared to the control.

• Korean Journal of Applied Biomechanics
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• v.24 no.3
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• pp.277-285
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• 2014

Nakcyguri is one of the offensive weapons most often used in Taekkyon games, The purpose of this study was to investigate kinetic factors on two types of Nakcyguri, one of which uses hip bending and the other uses little it. 12 taekkyoners (males) who are the students of Y University participated in this study. They have been practicing on Taekkyon for five years or more. Positions of CoM, the elapsed time of each phase, ROM of joint and segment angles, ground reaction forces, joint moments of supporting leg were analyzed for this study. The results were as follows; in Nakcyguri with hip bending than without hip bending, anterior/posterior ROM of pelvis, head and swing foot were larger by flexing-extending more, and both vertical and posterior components of GRF were larger during phase 4. It was considered that hip bending produced posterior momentum as well as vertical momentum of trunk during Nakcyguri. In conclusion hip bending was essential and so useful to the successful attack.

• Korean Journal of Applied Biomechanics
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• v.24 no.3
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• pp.249-258
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• 2014

The purpose of this study was to investigate the different patterns of the lower limb between elderly and adult females to reduce the rate of falls. Ten old females(age: $73.1{\pm}2.69yrs$, height: $151.9{\pm}4.82cm$, mass: $57.36{\pm}5.36$) and ten adult females(age: $28\pm}4.76$ yrs, height: $160.6{\pm}6.83cm$, mass: $53.9{\pm}8.44$) were participated in this experiment. The gait motions were captured with Qualisys system and variables were calculated with Visual-3D. The following results were found. The elderly female group showed bigger inclination angle between COM and COP than the adult female group so that the dynamic stability was reduced in walking for the compensation with a bigger stride width. The elderly female group ensure for the necessary forward movement of COM in order to replace the decreased function of ankle and knee joint. If the distance between COM and COP is closer and the energy reduction of a specific joint is reduced, they could prevent the elderly female's falling rate by strengthening of muscles which were related the extension of ankle joint.

• Korean Journal of Applied Biomechanics
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• v.24 no.3
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• pp.259-267
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• 2014

The purpose of this study was to find the relationship between standing posture biomechanics and physical fitness in the elderly. Physical fitness variables and postural variables for 227 (140 women and 87 men) elderly individuals were tested. Physical fitness tests (Korean Institute of Sports Science, 2012) included 3m sit, walk, and return, grip test, 30 second chair sit and stand, sit and reach, figure 8 walks, and 2 minute stationary march. Postural biomechanics variables included resting calcaneal stance position (RCSP), shoulder slope, pelvic slope, knee flexion angle, leg length difference, thoracic angle, and upper body slope. In statistical analysis, multiple regression was conducted by using stepwise selection method via SAS (version 9.2). Analysis for both men and women revealed significant relationships between physical fitness and age, upper body slope, knee flexion angle, leg length difference. Pelvic and thoracic angle were only related to figure 8 walking and sit and reach in women, while RCSP and shoulder slope had no relationship with any physical fitness variables.

• Korean Journal of Applied Biomechanics
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• v.26 no.3
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• pp.257-264
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• 2016

Objective: The purpose of this study was to determine the periodicity of shank-foot segment coupling and free torque before and after fatigue induced by prolonged running. Method: Fifteen young healthy male participants with a rear-foot strike ran on instrumented dual-belt treadmills at 70% of their maximum oxygen uptake for 65 min. Kinematic and ground reaction force data were collected for 20 continuous strides at 5 and 65 min (considered the fatigued condition). The approximate entropy tool was applied to assess the periodicity of the shank internal-external rotation, foot inversion-eversion, shank-foot segment coupling, and free torque for the two running conditions. Results: The periodicity of all studied parameters, except foot inversion-eversion, decreased after 65 min of running (fatigued condition) for 80% of the participants in this study. Furthermore, 60% of the participants showed similarities in the change of periodicity pattern in shank internal-external rotation, coupling, and free torque. Conclusion: The findings indicated that the foot inversion-eversion motion may pose a higher risk of injury than the shank internal-external rotation, coupling, and free torque in the fatigued condition during prolonged running.

• Korean Journal of Applied Biomechanics
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• v.26 no.3
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• pp.309-314
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• 2016

Objective: There are no guidelines for choosing appropriate gait assistive devices. The aim of this study was to evaluate gait assistive devices in patients with Parkinson's disease. Method: We evaluated 15 individuals with Parkinson's disease who did or did not use one of two different devices including canes and two-wheeled walkers. Data were collected using the GAITRite system. Results: Participants in the group using canes and two-wheeled walkers had significantly increased double support time and decreased gait velocity, normalized gait velocity, and stride length compared with those who did not. Participants who used a two-wheeled walker had significantly decreased gait velocity, normalized gait velocity, and stride length compared with those who used a cane. Furthermore, participants who used a two-wheeled walker had significantly decreased coefficients of variation for step time, stride length, and swing time compared with those who used a cane. Conclusion: Our results indicated that the two-wheeled walker offered the most consistent advantages for decreasing the risk of falling.

• Korean Journal of Applied Biomechanics
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• v.17 no.4
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• pp.157-167
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• 2007

The purpose of this study was to analyze kinematic techniques in the woman's 100m hurdle. In order to find the kinematic parameters, a 3-D video system for kinematic analysis-kwon3d 3.1(Kwon3D Motion Analysis Program Version 3.1)-was used. Eight JVC video cameras(GR-HD1KR) were used to film the performance of Lee Yeon-Kyoung at a frame rate of 60fields/s. The kinematic characteristics from the first hurdle to last hurdle were analyzed at the clearing hurdle spots such as distance, velocities, heights and angles. The real-life three-dimensional coordinates of 20 body landmarks during each phases were collected using a Direct Linear Transformation procedure. After analyzing the kinematic variables in the 100m hurdle run, the following conclusion were obtained; Lee Yeon-Kyoung had to maintain constant stride lengths between hurdles and increase takeoff distance before clearance and shorter landing distance after clearance. She also had to hit the correct takeoff point in front of the hurdle and extend the lead leg at the moment of landing in order to minimize the loss of velocity. She had to sprint between hurdles as fast as possible over 8m/s and run powerful first stride and shortened third stride preparing for the following hurdle clearances.

• Korean Journal of Applied Biomechanics
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• v.17 no.4
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• pp.37-44
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• 2007

This study compared the Character Studio of 3ds Max and OpenGL to find an adequate modeling method of character animation to be used in motion analysis in the area of motor mechanics. The subject was one male golfer. We obtained the positional coordinates of marks needed by photographing the subject's golf swing motions. Because the method based on the Character Studio used meticulously designed character meshes, it enabled high.level animation but it took a long time in applying physique and demanded the repeated adjustment of each motion data. With the method based on OpenGL, a character completed once could be usable to almost every testee and desired program control was available, but because each character had to be created by making a computer program, it was hard to make characters delicately. Because the method using the Character Studio is actively studied not only in motor mechanics but also in many research areas, it is expected to be more usable in the near future. On the contrary, the method based on OpenGL is easily applicable and allows the convenient use of other mechanical data.