• 한국운동역학회지
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• 제17권3호
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• pp.69-80
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• 2007

The purpose of this study was to investigate the difference of ground reaction forces of swimming athletes during their starting motion and to find out the most effective starting motions which were used in swimming athletes. The subjects were 9 male and 8 female high school swimming athletes who were athletic career over 7 years and used three starting motions in competition. The ground reaction forces were measured from each athletes performing three starting motion each of the open grap starting motion, closed grap starting motion and track starting motion. For the measurement, the force platform of AMTI company was utilized, and the analysis on measured ground reaction forces were used of Biosoft(Ver. 1.0). The items measured were stance time, Fz max deceleration force and Fz max deceleration force time, Fz mid stance force and Fz mid stance force time, Fz max acceleration force and Fz max acceleration force time, Torque maximum and Torque maximum time, Torque average, Excursion along Y axis of center of pressure of foot, Excursion along X axis of center of pressure of foot, Length of center of pressure of foot, Average velocity of center of pressure of foot. The data measured by the closed grap starting motion, open grap starting motion and track starting motion were analyzed by one-way repeated ANOVA. The results were as follows ; 1. The Fz max deceleration force time, Fz mid stance force, Fz max acceleration force, Torque maximum and Torque maximum time, Excursion along Y axis of center of pressure of foot, Average velocity of center of pressure of foot were significantly fast and large in the closed grap starting motion then open grap starting motion and track starting motion. 2. The Excursion along Y axis of center of pressure of foot was significantly long in the closed grap starting motion then open grap starting motion and track starting motion.

• 사회복지연구
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• 제43권1호
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• pp.59-87
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• 2012

본 연구는 여성 운동선수의 운동부 내 폭력 피해가 운동지속의사에 미치는 영향과 우울의 매개효과를 검증하고, 도움요청 경험유무에 따라 운동부 내 폭력, 우울, 운동지속의사의 경로에 차이가 있는지 파악하는 데에 목적이 있다. 이를 위해 중 고등학교 및 대학의 운동부와 국가대표팀, 실업팀, 프로팀에 속해 있는 여성 운동선수 총 345명을 대상으로 조사를 실시하였다. 주요 변수 간 인과관계 검증을 위해 구조방정식 모형을 사용하였으며 도움요청의 완충효과 검증을 위해 다집단 분석(Multi-Group Analysis)을 실시하였다. 연구결과, 운동부 내 폭력피해경험이 높을수록 우울수준이 증가하고 운동지속의사는 저감되며, 우울수준이 높을수록 운동지속의사가 저감되는 것으로 나타나 운동부 내 폭력피해가 운동지속의사에 미치는 영향이 우울을 매개로 이루어지는 것으로 파악되었다. 또한 다집단 분석을 통해 도움 요청을 하는 집단과 도움 요청이 없는 집단의 인과경로를 살펴본 결과, 도움요청을 하는 집단의 경우 운동부 내 폭력 피해가 우울에 영향을 미치지 않는 것으로 나타나 인과경로 상 도움요청이 없는 집단과의 차이가 있는 것으로 나타났다. 이에 따라 도움 요청이 운동부 내 폭력 피해와 우울의 경로에서 완충효과를 갖는 것으로 해석하였다. 이상의 연구결과를 바탕으로 운동부 내 폭력피해로 인한 운동중도탈락 문제를 예방하기 위한 개입 방안을 제언하였다.

• 한국운동역학회지
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• 제17권2호
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• pp.103-112
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• 2007

The purpose of this study was to investigate the kinematic characteristics during rising from a chair. Six stroke patients and three healthy subjects participated in the study. Three dimensional kinematic analysis was used to get the duration, center of mass, and lower extremity angle. The stroke patients performed longer duration(0.28sec) than the healthy subjects in rising from a chair. The stroke subjects stayed longer time than the healthy subjects did in phase 2(From the initiation of knee extension to the reversal of trunk flexion to trunk extension)(t=-1.01, p=.04). The healthy subjects showed longer time than the stroke subjects in phase 3(from the reversal of trunk motion to extension to full standing position). The healthy subjects displayed larger value of center of mass in anterioposterior direction than stroke subjects(t=5.79, p=0.05). The center of mass in the mediolateral direction did not change during the completion of movement. However, the center of mass in the anterioposterior direction began to increase throughout the completion of movement. The center of mass in the vertical direction increased extensively in phase 3. The significant difference was not found in the maximum dorsiflexion in ankle, the initiation angle of knee, and the minimum angle of hip between stroke and healthy subjects. Even though statistical results did not show any significant angle difference in the lower extremity, the patterns of the change in the knee and hip angle during rising from a chair were different. The stroke subjects showed smaller angle of knee extension than the healthy subjects in phase 3. The stroke subjects flexed their trunk more than the healthy subjects in phase 2.

• 한국운동역학회지
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• 제26권3호
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• pp.249-255
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• 2016

Objective: This purpose of this study was to analyze the relationship between dimensionless leg stiffness and kinetic variables during gait performance, and its modulation with body weight. Method: The study sample consisted of 10 young women divided into 2 groups (Control, n=5 and Obese, n=5). Four camcorders (HDR-HC7/HDV 1080i, Sony Corp, Japan) and one force plate (AMTI., USA) were used to analyze the vertical ground reaction force (GRF) variables, center of pressure (COP), low limb joint angle, position of pelvis center and leg lengths during the stance phase of the gait cycle. Results: Our results revealed that the center of mass (COM) displacement velocity along the y-axis was significantly higher in the obese group than that in control subjects. Displacement in the position of the center of the pelvis center (Z-axis) was also significantly higher in the obese group than that in control subjects. In addition, the peak vertical force (PVF) and dimensionless leg stiffness were also significantly higher in the obese group. However, when normalized to the body weight, the PVF did not show a significant between-group difference. When normalized to the leg length, the PVF and stiffness were both lower in the obese group than in control subjects. Conclusion: In the context of performance, we concluded that increased dimensionless leg stiffness during the gait cycle is associated with increased velocity of COM, PVF, and the change in leg lengths (%).

• 한국운동역학회지
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• 제20권2호
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• pp.221-230
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• 2010

The purpose of this study was to analyze biomechanical factors of trail running shoes applied to korean shoe-lasts. 10 healthy male subjects with an average age of 37.2 years(SD=8.28), weight of 69.6 kg(SD=10.56) and a height of 171 cm(SD=4.93) were recruited for this study. Ten males walked on a treadmill wearing four different shoes. Foot pressure data was collected using a Pedar-X mobile system(Novel Gmbh., Germany) operating at the 1000 Hz. Surface EMG signals for tibialis anterior, gastrocnemius, vastus lateralis and biceps femoris were acquired at 1000 Hz using Noraxon TeleMyo DTS system(Noraxon Inc., USA). Foot pressure and leg muscle fatigue were measured and calculated during walking. The results are as follows: After walking 60 minutes, Type A showed a lower MPF. MPF values were significantly different from each muscle(p<.05). Therefore, Type A shoe might decrease muscle fatigue in the legs while walking. In addition, Type It showed that Type A shoe has the highest contact area and the lowest maximum pressure. As a result of the analysis, Trail running shoes will use a new design to reduce muscle fatigue and are expected to increase comfort and fitting.

• 한국운동역학회지
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• 제16권1호
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• pp.11-17
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• 2006

The purpose of this study was to evaluate the smoothness of movement during various walking speeds. Based on the maximum smoothness theory (or the minimum jerk theory), we hypothesized that the walking speed at the maximum smoothness (or minimum normalized jerk) is the same as that at the minimum energy consumption. Eleven university students participated in treadmill walking experiment with 11 different walking speeds (1.11, 1.19, 1.25, 1.33, 1.56, 1.78, 1.9, 2, 211, 233, and 2.47m/sec). Normalized jerk at 15 markers and the center of mass was calculated. Results showed that there existed a quadratic relationship between the normalized jerk of the vertical direction at the center of mass and the walking speed As the walking speed increased, the normalized jerk of all directions at the heel decreased Our hypothesis that the previously published energetically optimal walking speed ($1.25\;{\sim}\;1.4m/s$) is the same as the minimum jerk speed (1.78m/s) did not agree with this result. The minimum normalized jerk at the center of mass occurred at the walking speed of 1.78m/s which was the preferred walking speed by subjects' questionaries. Further studies concerning the energetically optimal walking speed, preferred walking speed, and walk-run transition speed or run-walk transition speed are necessary based on actual energy consumption experiment and various multi-dimensional analysis.

• 한국운동역학회지
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• 제23권1호
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• pp.53-62
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• 2013

The methods of fitting a circle to measured data, geometric fit and algebraic fit, have been studied profoundly in various areas of science. However, they have not been applied exactly to a biomechanics discipline for locating the center of rotation of a human joint. The purpose of this study was to generalize the methods to fitting spheres to the points in 3-dimension, and to estimate the center of rotation of a hip joint by three of geometric fit methods(Levenberg-Marquardt, Landau, and Sp$\ddot{a}$th) and four of algebraic fit methods(Delogne-K${\aa}$sa, Pratt, Taubin, and Hyper). 1000 times of simulation experiments for flexion/extension and ad/abduction at an artificial hip joint with four levels of range of motion(10, 15, 30, and $60^{\circ}$) and three levels of angular velocity(30, 60, and $90^{\circ}$/s) were executed to analyze the responses of the estimated center of rotation. The results showed that the Sp$\ddot{a}$th estimate was very sensitive to the marker near the center of rotation. The bias of Delogne-K${\aa}$sa estimate existed in an even larger range of motion. The Levenberg-Marquardt algorithm of geometric fit and the Pratt of algebraic fit showed the best results. The combination of two methods, using the Pratt's estimate as initial values of the Levenberg-Marquardt algorithm, could be a candidate of more valid estimator.

• 한국운동역학회지
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• 제27권3호
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• pp.171-179
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• 2017

Objective: The purpose of this study was to perform a kinematic and kinetic analysis of double-under jump rope technique according to skill level and sex. Method: Participants comprised a skilled group of 16 (9 males, 7 females), and an unskilled group of 16 with 6 months or less of experience (9 males, 7 females). Five consecutive double-under successes were regarded as 1 trial, and all participants were asked to complete 3 successful trials. The data for these 3 trials were averaged and analyzed after collecting the stable third jump in each trial. The variables used in the analysis included phase duration, total duration, flight time, vertical toe height, stance width, vertical center of mass displacement, and right lower limb ankle, knee, and hip joint angles in the sagittal plane during all events. Results: The skilled group had a shorter phase and total duration and a shorter flight time than the unskilled group. The vertical center of mass displacement and ankle dorsiflexion angle were significantly smaller in the skilled group. The male group had a shorter phase duration than the female group. The vertical toe height was greater, the stance width was smaller, and the ankle and hip flexion angles were smaller in the male group. Conclusion: Variables that can be used to distinguish between skill levels are phase and total duration, flight time, vertical center of mass displacement, and ankle dorsiflexion angle. Differences between sexes in double-under jump rope technique may be related to lower limb flexion angle control.

• 한국운동역학회지
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• 제21권5호
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• pp.585-593
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• 2011

The purpose of this study was to analyze, from a kinematical point of view, the high jump techniques of three women's high jump winners at the IAAF World Championships, Daegu 2011. The trends for the techniques of the world's top high jumpers were examined, with a view toward adapting these techniques to the physical characteristics of Korean women's high jumpers. It was valuable that Di Martino, who was the shortest in height, was able to win a medal by using a single arm swing take-off technique, along with a half flexed leading leg swing to attain a deep arch and clear the bar. This showed that the world's top athletes used jumping techniques with no decrease in the run-up velocity at the take-off. Furthermore, It appeared that the knee joint angle at take-off had a direct effect on the body position at take-off (H1).

• 한국운동역학회지
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• 제21권5호
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• pp.573-584
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• 2011

The purpose of this study was to perform a kinematic analysis of the high jump techniques of the three men's medalists at the 2011 IAAF Championships in Daegu (August 27-September 4, 2011). In particular, a three-dimensional coordinates method was used to analyze the last three strides before touchdown, the touchdown techniques, and the movements after takeoff toward the bar. An analysis of the, data for the biomechanical characteristics of the world's best high jumpers could contribute to an improvement in the performance of a national high jumper. The first conclusion of the data analysis was that the arm movements of the gold medalist, J. Williams, had a single arm form, whereas the arm movements of the other medalists were a double arm form. Second, the difference in the knee joint angles upon touchdown and toe-off was $10^{\circ}$. Third, J. Williams achieved his maximum CM height after takeoff (1.26 m) using the maximum flexion of his knee joint. Fourth, the foot contact duration of A. Dmitrik (0.11 s) was the shortest among the medalists, and the ratio for his transformation of horizontal velocity to vertical velocity was the greatest (75.25%) among the three. Last, the maximum CM height of T. Barry was the greatest, and his foot contact duration was the longest.