• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.187-194
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• 2007

The purpose of this study is to determine the characteristics of ground reaction force(GRF) in golf swing for various slopes of flat lie and uphill lies of 5 and 10 degrees. Five right-handed professional golfers were selected for the experiment and the 7 iron club was used. We used four forceplates to measure GRF and synchronized with the three-dimensional motion analysis system. Results showed that slope did not affect the total time for golf swing, but the time until the impact had a tendency to slightly increase for the uphill lie(p<0.05). The medial-lateral GRF of the right foot increased toward the medial direction during back swing, but less increases were found with the angle of uphill lie(p<0.05). The GRF of the left foot increased rapidly toward the medial direction at the uncocking and the impact during down swing, but decreased with the increase in the angle of uphill lie(p<0.05). The anterior-posterior GRF of both feet showed almost the same for different slopes. With the slopes, the vertical GRF of the right foot increased, but the vertical GRF of left foot decreased(p<0.05). Uphill lies would have negative effect to provide the angular momentum during back swing, restricting pelvic and trunk rotations, and to provide the precise timing and strong power during down swing, limiting movements of body's center of mass. The present study could provide valuable information to quantitatively analyze the dynamics of golf swing. Further study would be required to understand detailed mechanism in golf swing under different conditions.

• Journal of the Korea Convergence Society
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• v.9 no.8
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• pp.301-309
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• 2018

The aim of this study was to investigate the relationship between the neurocognitive ability and the risk factors of non-contact anterior cruciate ligament injuries during landing in female recreational athletes. Thirty-two female athletes participated in computerized neurocognition test and motion analysis for drop vertical jump. Pearson's linear correlation analysis was performed to analyze the relationship between the raw scores of neurocognition test and biomechanical variables including 3D joint angle, moment, power, vertical ground reaction force, loading rate, and support time. There were correlations between the scores of neurocognition test and biomechanical variables as high the neurocognition score, it also increase landing strategies were used to maintain posture of the lower extremity. Therefore, the neurocognitive test might be used as a good screening method to detect the risk factors before injury.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.3
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• pp.153-160
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• 2017

Gait analysis has been conducted in various environments, but the biomechanics during the transition from uphill walking to downhill walking have not been reported. The purpose of this study is to investigate the knee and ankle joint kinematics and kinetics during walking on a triangle-shaped slope compared with those during level walking. Kinematic and kinetic data of eighteen participants were obtained using a force plate and motion capture system. The greater peak ankle dorsiflexion angle and moment and the peak knee extension moment were observed (p<0.05) during both uphill and downhill walking on the triangle-shaped slope. In summary, uphill walking on a triangle-shaped slope, which showed a peak knee flexion of more than $50^{\circ}$ with greater peak knee extension moment, could increase the risk of patellofemoral pain syndrome. Downhill walking on a triangle-shaped slope, which involved greater ankle dorsiflexion excursion and peak ankle dorsiflexion, could cause gastrocnemius muscle strain and Achilles tendon overuse injury.

• 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.21 no.3
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• pp.327-334
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• 2011

The objective of this study was to develop a scientific approach for investigating Korean dance in detail, and to examine the intense expressions and various movements, which are based on Danjeon breathing. For the purpose, we analyzed the movement changes and distribution of forces resulting from the switch in movement between exhalation and inhalation while bending, which is the most basic movement in Korean dance. The following conclusions were drawn from this study. In Korean dance, bending with breathing involves less back-and-forth-movement and more up-and-down movement, as compared to bending without breathing; this indicates greater body stability and a wider range of movements while bending with breathing. In addition, less time is required for bending with breathing at the point of switching from exhalation to inhalation, and it involves less movement of the supporting leg; thus, vending with breathing involves faster switching from bending movements to extending movements. While bending, the raised leg goes through a less smooth curve while breathing, which indicates stronger movement of the toes. Bending with breathing requires a greater braking force than bending without breathing, and the vertical force, generated by switching from exhalation to inhalation, is transferred to extending movements using the ground load. The results of this study can be potentially employed to investigate the expressions used in Korean dance on th basis of its principle of forces. Korean dance has evolved into various creative forms, and basic analytical studies of these diverse forms and related breathing methods re required in the future.

• Korean Journal of Applied Biomechanics
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• v.21 no.3
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• pp.289-296
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• 2011

The purpose of this study was to quantify the biomechanical characteristics of the ground reaction force(GRF) during the Taekwondo's Apkubi, one of the basic movement in Taekwondo and the walking. The GRF profiles under the stance foot of Apkubi movement and walking were directly measured in sample of 20 healthy older persons. In the anterior-posterior and vertical direction, the GRF of the Apkubi movement reached to the peak braking force at 10% of the normalized stance time percent and the peak driving force at 90% of stance time, but that of the walking reached to the peak braking force at 20% of stance time and the peak driving force at 80% of stance time. In vertical force, the GRF of the walking showed two peak values, but that of the Apkubi movement seemed three peak values. Moreover the first peak vertical force was significantly(t=6.085, p<.001) greater in the walking(about 1.8 times of body weight) than the Apkubi(about 1.4 times of body weight). The walking velocity was affected significantly(over p<.05) by the braking impulse, the peak braking force and the first peak vertical force. Futhermore the peak braking force in the Apkubi showed a significant effect on the Apkubi's stride length(p<.01). So, we concluded that the braking force after the right touch down, the stance foot on the ground contributed to move the leg forward.

• The Journal of the Korea Contents Association
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• v.13 no.10
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• pp.523-532
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• 2013

When the golf club hits the ground prior to making contact with the golf ball, we define it as 'fat shot'. The aim of this research was to investigate the difference between normal shot and fat shot in golf. Five candidates playing as recreational golfer participated in this research and they were all right-handed people. Time phase between each event, wrist cocking angle, elbow extension-flexion angle, backswing height, pelvis angle, thorax angle, L-GRF, R-GRF, pelvis linear velocity, pelvis angular velocity and COG path were calculated. For statistical analysis the paired T-test was used. An early un-cocking, an early right elbow extension and impact with leaving their weight behind foot were not reasons of fat shot. Backswing height, X-Factor, pelvis angle and thorax rotation angle were not different between normal shot and fat shot. But we could find a pattern of abrupt pelvic movement and weight shift to target direction just before impact in case of fat shot. In addition fat shot showed time-delayed and small value of pelvis linear velocity pattern to upward during downswing phase as against normal shot.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1345-1350
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• 2010

Sit-to-stand movement is a basic movement in daily activities. On the basis of this movement, the biomechanical functions of a person can be evaluated. The study of the joint kinematics, moment, and muscle coordination is necessary to understand the characteristics of the sit-to-stand movement. We have developed a motion-based program for inverse dynamics analysis and the electromyogram-based program for muscle force prediction. The joint kinematics and the kinetic results estimated on the basis of obtained motion data, ground reaction force, and electromyogram signals were compared with those reported in previous studies, and the muscle forces determined by the two methods were compared with each other. The methods and programs developed in this study can be used to understand biomechanics and muscle coordination involved in basic movements in daily activities.

• The Journal of the Korea Contents Association
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• v.13 no.3
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• pp.109-118
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• 2013

The purpose of this study was to determine the effects of line dance programme on the balance ability during walking to reveal the exercise intervention for fall prevention. A 12-week line dance programme was applied to 18 elderly females who aged more than 65 years in the community. Balance ability during walking was evaluated by the range of center of pressure(cop), the velocity of cop, and free torque that calculated on the basis of ground reaction force data. The range and velocity of cop in the anterio-posterior were significantly reduced after performing(p<.01, p<.05, respectively), but change in those of cop in the medio-lateral and free torque were not found. It was demonstrates that 12-week line dance programme allows more effective in anterio-posterior stability of walking. It was suggested that the effect of fall prevention exercise should be studied more associate with fall frequency as future study.

• Korean Journal of Applied Biomechanics
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• v.14 no.2
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• pp.57-68
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• 2004

This study was to evaluate the consistency of the vertical force($F_z$) of the force platform and the impact force. Two experiments were performed. First, the force platform was vertically placed to hang to the wall. While the rotating iron body hit the force platform, $F_z$ was measured. Then $F_z$ was compared with the impact force of the rotating iron body that was precalculated by using the inertia moments and the rotating force. Second, six Taekwondo masters punched the force platform to show what a certain pattern the impart force has. They were asked to punch the target depending on target distances. The target distances were differed from the relative arm segment of subjects as 90%, 80%, 70%, 60%, and 50% (100% target distance equals the aim length of each subject). Pearson's correlations were used between $F_z$ and the impact force. Also the linear regression was also performed to show the linearity. At the first experiment, $F_z$ and the impact force had much correlations and showed linear characteristics. Therefore, $F_z$ could be regarded as the impact force. At the second experiment, the strongest impact force was measured at the target distance of 80% and the time taken to the maximum impact force was within 0.02 seconds. The result of this study recommends that it can help the comparative study between the impact forces and other hitting sports.