• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.455-461
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• 2014

The purposes of this study were to reveal the kinematic and kinetic difference of hard ground soccer shoe, firm ground soccer shoe and soft ground soccer shoe. Soccer players were shoes of varying stud designs with some preferring the bladed studs while others opting for the conventional studded stud. Statistics were used one way-ANOVA and Tukey's Honestly Significant Difference Method. Seven healthy college soccer players were attended a test. All parameters were recorded using the Zebris system. Spatio-temporal variables were no significant difference. Lateral symmetry was statistically significant differences (p<.05). Vertical GRF parameters were no significant difference. Medial midfoot pressure, lateral midfoot pressure and central forefoot pressure were statistically significant differences (p<.05). This study demonstrates that playing surface significantly affects difference soccer shoes during soccer game. Furthermore, epidemiological investigation is warranted to determine the effects of playing surfaces on sport specific injury mechanisms.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1653-1654
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• 2013

• Korean Journal of Applied Biomechanics
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• v.26 no.2
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• pp.143-151
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• 2016

Objective: The purpose of this study was to investigate the effect of fatigue induction on ground reaction force (GRF) components, postural stability, and vertical jump performance in Taekwondo athletes. Method: Ten Taekwondo athletes (5 men, 5 women; mean age, $22.30{\pm}2.62years$; mean height, $174.21{\pm}9.20cm$; mean body weight, $67.28{\pm}12.56kg$) participated in this study. Fatigue was induced by a short period of strenuous exercise performed on a motorized treadmill. The analyzed variables included vertical jump performance, static stability (mediolateral [ML], center of pressure [COP], anteroposterior [AP] COP, ${\Delta}COPx$, ${\Delta}COPy$, and COP area), postural stability index values (ML stability index [MLSI], AP stability index [APSI], vertical stability index [VSI], dynamic postural stability index [DPSI]), and GRF components (ML force, AP force, peak vertical force [PVF], and loading rate). To analyze the variables measured in this study, PASW version 22.0 was used to calculate the mean and standard deviation, while a paired t-test was used to evaluate the pre- versus post-fatigue results. Pearson's correlation coefficients among variables were also analyzed. The statistical significance level was set at ${\alpha}$ = .05. Results: Vertical jump performance decreased significantly after the induction of fatigue, while AP COP, ${\Delta}COPx$, COP area, APSI, VSI, and DPSI increased significantly. PVF and loading rate increased significantly after the induction of fatigue, while the postural stability variables (AP COP, ${\Delta}COPy$, COP area, APSI, VSI, DPSI) were similarly correlated with GRF components (PVF, loading rate) after fatigue was achieved (r = .600, $R^2$ = 37%). Conclusion: These results suggest that the induction of fatigue can decrease postural stability and exercise performance of Taekwondo athletes during training and competition sessions.

• Korean Journal of Applied Biomechanics
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• v.27 no.3
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• pp.189-195
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• 2017

Objective: The aim of this study was to examine the effect of foot landing type (forefoot vs. rearfoot landing) on kinematics, kinetics, and energy absorption of hip, knee, and ankle joints. Method: Twenty-five healthy men performed single-leg landings with two different foot landing types: forefoot and rearfoot landing. A motion-capture system equipped with eight infrared cameras and a synchronized force plate embedded in the floor was used. Three-dimensional kinematic and kinetic parameters were compared using paired two-tailed Student's t-tests at a significance level of .05. Results: On initial contact, a greater knee flexion angle was shown during rearfoot landing (p < .001), but the lower knee flexion angle was found at peak vertical ground reaction force (GRF) (p < .001). On initial contact, ankles showed plantarflexion, inversion, and external rotation during forefoot landing, while dorsiflexion, eversion, and internal rotation were shown during rearfoot landing (p < .001, all). At peak vertical GRF, the knee extension moment and ankle plantarflexion moment were lower in rearfoot landing than in forefoot landing (p = .003 and p < .001, respectively). From initial contact to peak vertical GRF, the negative work of the hip, knee, and ankle joint was significantly reduced during rearfoot landing (p < .001, all). The contribution to the total work of the ankle joint was the greatest during forefoot landing, whereas the contribution to the total work of the hip joint was the greatest during rearfoot landing. Conclusion: These results suggest that the energy absorption strategy was changed during rearfoot landing compared with forefoot landing according to lower-extremity joint kinematics and kinetics.

• Korean Journal of Applied Biomechanics
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• v.15 no.2
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• pp.1-10
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• 2005

G. B. LEE, A. S. GWON, The Research for Using methodof GRF (Ground Reaction Force) on Rotational Movement in Arabesque. Korean Journal of Sport Biomechanics, Vol. 15, No. 2, pp.1-10, 2005. As, in relation to all movements of a human being, the movements such as mutually walking, running, rotating, and jumping are attained endlessly through the ground amid the interaction with the ground, in terms of the harmonious movement of the upper limbs and the lower limbs, related to the basic movement in ballet, the type of a movement depends on the size and direction of the force that presses down the ground (Fz, Fx, Fy) amid the interaction with the ground. Therefore, aiming to correctly and efficiently perform a rotational movement in Arabesque, this study analyzed factors of the force manifestation through GRF (Ground Reaction Force), by dividing into preparing, stepping, standing, rotating, and finishing stages (events (1) ${\sim}$ (5)), targeting the subjects of 4 elite female students who majored in ballet. 1. At the No.5 position of the preparing stage, It is necessary that support the ground with left and right foot balance, 2. As the stepping stage is the phase ranging from the event (2), in which a plie movement of bending a knee is started, to the event (3) of stretching a knee, Rebunding motion is not good, and One have a position with ankle and knee flextion condition in order to stretch strengthly in event (3) position 3. At the event (1) position, It is necessary that exert the Fz reaction force at the event (3) position. Because large stretch force help to have a toe on position easily and show a active motion 4. In order to have a stand and rotation motion smoothly, One need a muscle strength training for ankle extension, knee extension, control horizental force

• Korean Journal of Applied Biomechanics
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• v.19 no.3
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• pp.449-455
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• 2009

The purpose of this study was to analyze the kinetics variables of GRF by dtance type during forehand stroke. Eight high school tennis players, who have never been injured for last six months, in Busan were chosen for the study. They performed horizontal swing and vertical swing that it was done each five consecutive trial in the condition of square, semi-open and open stance. It was filmed by 6 video camera and used with 3-dimensional motion analyzer system and GRF system. The following kinetic variables were analyzed in relation to left leg and right leg GRF. The conclusion were as follow: 1. In square and semi-open stances, the horizontal ground reaction force was decreased at impact in left leg regardless of swing type, whereas open stance was increased at impact to the tiptoe in both legs. 2. In square and semi-open stances, the vertical ground reaction force was increased at impact in left leg regardless of swing types, whereas open stance was decreased at impact to vertical direction in both legs.

• The Journal of the Korea Contents Association
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• v.14 no.9
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• pp.131-140
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• 2014

The purpose of this study was to kinetic analysis of using the skill of breathing korean dance movement will be to perform. To achieve the research objectives cheoyongmu Nakhwayousu the operation was performed. The selection of subjects like the following: Five people were skilled use of breathing and five unskilled person. The results are as follows. The skilled and the unskilled were no significant differences in the duration time. And the skilled and the unskilled z-axis position of the center of mass, there was a significant difference (p<.05). The skilled and the unskilled y-axis velocity of the center of mass, there was a significant difference of event 1 and event 4 (p<.05). And z-axis velocity of the center of mass, there was a significant difference of event 3 (p<.05). And the skilled and the unskilled Fx of GRF, there was a significant difference of event 2 and event 4 (p<.05). And Fy of GRF, there was a significant difference of event 1 and event 5 (p<.05). And Fz of GRF, there was a significant difference of event 4 (p<.05).

• Korean Journal of Applied Biomechanics
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• v.28 no.1
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• pp.29-35
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• 2018

Objective: The purpose of this study was to determine the asymmetry of vertical ground reaction force (GRF) components between dominant and non-dominant legs in rested and fatigued states in prolonged running. Method: Twenty healthy men, heel strikers, were included (age: $24.00{\pm}5.0years$; height: $176.1{\pm}6.0cm$; body mass: $69.0{\pm}6.0kg$) in this study. Subjects ran on an instrumented treadmill for 130 minutes. During treadmill running, GRF data (1,000 Hz) were collected for 20 strides at five minutes (rested) and 125 minutes (fatigued) running while they were unaware of collecting data. Asymmetry indexes (ASI) were calculated to quantify the asymmetry magnitude in rested and fatigued states. Paired t-test was used to verify the differences between dominant and non-dominant legs in rested and fatigued states. In addition, one-way repeated measure analysis of variance was applied for comparison of ASI of both states. The level of significance was set at p < .05. Results: Passive force peak magnitude, loading rate, and impulse affecting the development of running injury were found significantly greater in dominant leg than in non-dominant leg at rested state (p < .05). However, passive force peak time and active force peak magnitude were found significantly different between legs in fatigued state (p < .05). To determine changes in percentage of asymmetry between legs in both states, ASI was used. ASI for all variables increased in fatigued state; however, no significant differences were found between both states. Conclusion: This study found that fatigue did not affect differences in vertical GRF between dominant and non-dominant legs and asymmetry changes.

• Korean Journal of Applied Biomechanics
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• v.18 no.3
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• pp.71-82
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• 2008

W. S. CHAE, Ground Reaction Force Charateristics During Forward and Backward Walking Over 20 Degree Ramp. Korean Journal of Sport Biomechanics, Vol. 18, No. 3, pp. 71-82, 2008. The purpose of this study was to compare GRF characteristics during forward and backward walking over 20 degree ramp. Temporal parameters, GRFs, displacement of center of pressure (DCP), and loading and decay rates were determined for each trial. The results showed that the vertical GRF in BD during RTO was significantly greater than those found in FU. This reults indicated that GRF patterns may be changed by different walking conditions and altering position of ankle, knee, and center of mass throughout the walking cycle. The DCP during $RHC_2$-LHC in antero-posterior direction for downward was smaller than the corresponding value for upward condition. It' seems that the ankle and knee joints are locked in an awkward fashion at the toe contact to compensate for imbalance. Reducing the magnitude of loading rate can be achieved by walking in the backward direction. Accordingly, the results can be a benefit if one is suffering from an impact-type injury.

• Korean Journal of Applied Biomechanics
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• v.31 no.3
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• pp.220-225
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• 2021

Objective: The purpose of this study was to investigate the effect of levels of education on ground reaction force and center of pressure parameters during chest compression resuscitation. Method: Twenty male university students were divided into two groups; certified group (CG, n=10) and non-certified group (NCG, n=10). Two force plates were used to measure ground reaction force and center of pressure parameters during 30 times (three trials) chest compression resuscitation. Independent t-tests were used to compare ground reaction force and center of pressure parameters between two groups. An alpha level of 0.05 was used in all tests. Results: All chest-compression time parameters (total time, 1 systolic time, and diastolic time) in CG were significantly shorter than those in NCG (p<.05). Fy of the diastolic and Fz of the systolic in CG revealed significantly the larger GRF values and Fy of the systolic in CG showed significantly the smaller GRF value (p<.05). The standard deviation of Fz of the systolic and diastolic within the subject during 30 times chest-compression resuscitation revealed significantly the smaller values in CG (p<.05). Conclusion: First, CG performed chest compressions efficiently at an appropriate rate compared to NCG. Second, CG showed lower Fx and Fy values in both the mediolateral and anteroposterior axes compared to NCG, which reduced unnecessary chest-compression force consumption and minimized the movement in patients with cardiac arrest. Third, CG showed high Fz value of the systolic and low Fz value of the diastolic. Based on this, chest compression resuscitation was performed to increase the survival rate of cardiac arrest patients.