• Journal of Institute of Control, Robotics and Systems
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• v.11 no.1
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• pp.58-66
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• 2005

Usual human gait can be modeled as continual impact phenomenon that happens due to the topological change of the kinematic structure of the two feet. The human being adapts his own control algorithm to minimize the ill effect due to the collision with the environment. In order to operate a Humanoid robot like the human being, it is necessary to understand the physics of the impact and to derive an analytical model of the impact. In this paper, specially, we focus on impact analysis of the kicking motion in playing soccer. At the instant of impact, the external impulse exerted on the ball by the foot is an important property. Initially, we introduce the complete external impulse model of the lower-extremity of the human body and analyze the external impulses for several kicking postures of the lower-extremity. Secondly, a trajectory-planning algorithm of a ball, in which the initial velocity and the launch angle of the ball are calculated for a desired trajectory of the ball, will be introduced. The aerodynamic effect such as drag force and lift force is also considered. We carry out numerical simulation and experimentation to verify the effectiveness of the proposed analytical methodology.

• Korean Journal of Applied Biomechanics
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• v.22 no.1
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• pp.1-7
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• 2012

The purpose of this study was to investigate the pattern change of throwing in baseball after 15 weeks of participation in baseball class, by examining ball speed, trunk and upper body angles. The comparison was with 6 university students that haven't had any experience in baseball. 8 infra red cameras and 2 force platforms were used to collect the data. First, there was an increase in the speed of the ball after the class. Second, there was no significant difference in the allocated phases during the throw before and after class. Third, the release point was lower and more in front. Forth, there was an increase in the knee flexion at the left foot landing and release point. Finally, there was an increase in the maximum shoulder external rotation and pelvis angle. It is recommended that the coordination between the segments should be investigated to improve our understanding of the learning of throwing in future research.

• Journal of Korean Physical Therapy Science
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• v.11 no.2
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• pp.5-17
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• 2004

The purpose of this study was to investigate the relationship between normal adults' resting calcaneal stance position(RCSP) and postural sway. Subjects were 70 normal adults(34 men and 36 women) in their twenties who attend S. University. Postural sway during a single limb stance was measured using the CMS 10 Measuring System when subjects positioned on the balance trainer in their bare foot. RCSP while subjects were standing on the glass plate was measured using the angle tinder after subjects were positioned in prone to divide equally lower leg and calcaneus using the goniometer. The result was as follows. There were significant weak positive correlations between RCSP and postural sway(r=0.362, p<0.01), the leg of the small RCSP within a subject has the small postural sway index($X^2=43.758$, p<0.001). There was no significant difference between groups of rearfoot valgus(RCSp<$2^{\circ}$) and those of rearfoot varus (RCSp>$2^{\circ}$) in the postural sway. In conclusion, there is a weak relationship between increasing the absolute value of RCSP and increasing postural sway.

• Journal of Biomedical Engineering Research
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• v.30 no.3
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• pp.247-254
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• 2009

We studied the postural response induced by plantar sole vibration with various frequencies(20, 60, 100Hz) and vibration zone(the anterior and posterior foot zone) of both soles during standing. Eight healthy young adults were exposed to 15s periods of plantar sole vibration while blindfolded. Body sway(COM, center of mass), the angle of neck, trunk, hip, knee, ankle and EMG of four lower limb muscles(tibialis anterior, lateral and medial gastrocnemial, soleus muscle) were recorded during 15s plantar sole vibration using 3D motion analysis system. Simulating each zone separately resulted in spatially oriented body tilts; oppositely directed backward and forward, respectively, the amplitude of which was proportional to the vibration frequency. EMG activity of lower limb muscles also varied according to the direction of the vibration zone and linearly according to the frequency. These findings led us to consider the plantar sole vibration as useful method of postural balance control and adjustment.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.8
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• pp.506-509
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• 2003

This paper describes the possibility of analyzing gait pattern from the changes of the lower leg electrical impedance. This impedance was measured by the four-electrode method. Two current electrodes were applied to the thigh, knee, and foot., and two potential electrodes were applied to the lateral, medial, and posterior position of human leg. The correlation coefficients of the joint angle and the impedance change from human leg movement was obtained using a electrogoniometer and 4ch impedance measurement system developed in this study. We found the optimal electrode position for knee and ankle joint movements based on high correlation coefficient, least interference, and maximum magnitude of impedance change. The correlation coefficients of the ankle, knee, and the hip movements were -0.913, 0.984 and 0.823, respectively. From such features of the human leg impedance, it has been made clear that different movement patterns exhibit different impedance patterns and impedance level. This system showed feasibility that lower leg movement could be easily measured by impedance measurement system with a few skin-electrodes.

• Korean Journal of Applied Biomechanics
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• v.23 no.3
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• pp.235-243
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• 2013

The purpose of this study was to analyse scientific according to period of rehabilitation training of ACL patients. ACL patients seven subjects participated in this study. Gait (1.58 m/sec) analysis was performed by using a 3-D Cinematography, a Zebris system and a electromyograph system. The data were analyzed by paired t-test. The joint angles were recorded from the ankle, knee, hip joints. Peak max dorsi-flexion and peak max plantar-flexion identified significant differences (p<0.05). Another angles were no significant difference. Vertical force (Fz) and max pressure variables improved 6 month RTP better than 3 month RTP. EMG were collected from 4 muscles (rectus femoris, biceps femoris, gastrocnemius, tibialis anterior) with surface electrides in gait system. EMG signals were rectified and smoothed data. EMG signas were no significant difference but they also improved 6 month RTP better than 3 month RTP. More research is necessary to determine exactly what constitutes optimal rehabilitation training period for ACL patients.

• Korean Journal of Applied Biomechanics
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• v.29 no.2
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• pp.97-104
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• 2019

Objective: The aim of this study was to investigate the strategies for avoiding moving and stationary walker using body segments during walking. Method: Ten healthy young adults (10 males, age: $24.40{\pm}0.49yrs$, height: $175.80{\pm}5.22cm$, body mass: $70.30{\pm}5.22kg$) participated in this study. Each participant was asked to perform a task to avoid collisions with another walker who was moving or stationary during walking on the 10 m walkway. Both walkers were performed at natural self-selected walking speed. Results: Medio-lateral avoidance displacement of the trunk and the pelvis were significantly increased when avoiding a stationary walker (p<.05). There were no significant differences in medio-lateral center of mass trajectory. Rotation angle of trunk, pelvis and foot on the vertical axis were significantly increased when avoiding a stationary walker (p<.05). Conclusion: Based on our results, when another walker moves continuously, the walker recognizes another walker as the object of social interaction and performs the avoidance strategies while expecting the cooperative distance. On the other hand, when another walker is stopped, it is determined that the walker has an obligation to avoid, and the walker performs a relatively safer avoidance strategy.

• Korean Journal of Applied Biomechanics
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• v.28 no.4
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• pp.207-211
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• 2018

Objective: The purpose of this study was to examine the effects of an 8-week SMR, stretching, and band program on lower limb alignment (distance between the knees, Q angle) and gait (gait speed, stride length, impulse, and peak pressure) in female in their 20s who have genu varum. Method: The participants, female in their 20s who had genu varum, were randomly divided into the SMR, Stretching, and Band group (SSB, n=9), Stretching and Band group (SB, n=9), and Control Group (CG, n=9). Experimental group A (SSB) performed 3 50-minute sessions of the program per week for 8 weeks while the experimental group B (SB) performed stretching and band correctional exercise in 3 40-minute sessions per week for 8 weeks. The control group had no correctional exercise program. Results: Only the SSB group showed a significant increase in gait velocity and stride length in this study. The SSB and SB group showed a significant decrease of impulse on the forefoot after exercise program suggests that SMR and elastic band exercise had a positive effect on the distribution of foot pressure. Conclusion: We concluded that 8-week genu varum correctional exercise program had beneficial effects on the gait parameters (gait velocity, stride length, impulse, peak pressure) in 20s women with genu varum.

• Korean Journal of Applied Biomechanics
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• v.28 no.4
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• pp.219-225
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• 2018

Objective: Epidemiological research shows that 47 to 73% of athletes suffer from recurrent ankle sprains. Joint mobilization techniques (JMT) implemented in correcting may be beneficial in the management of ankle injuries. The purpose of this study is to examine the immediate JM on ankle complex as clinical measures in individuals with chronic ankle instability (CAI) through intervention. Method: Thirteen subjects with CAI (8 males and 5 females) participated in this study. Each subject tried total four alignments (Navicular drop test: NDT, Standing rearfoot angle: SRA, Tibia torsion: TT, and dorsiflexion range of motion: DFROM). The participants were performed the 10 meter shuttle run after JMT for post-task. Finally, it was tried to compare between pre-post tasks after shuttle run. Results: SRA and DFROM after intervention showed significant differences. SRA (p=.026), and DFROM (p=.034). Conclusion: We concluded that the JMT has resulted in improvement in SRA, DFROM. Increased DFROM and varus shapes of foot would be closed kinetic chain, indicating that reduce the risk factors of ankle sprain. Future study needs to be conducted in order to measure the effects of prolonged intervention of JMT.

• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.179-195
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• 2002

The purpose of this research is to provide a proper model by analyzing the sports biomechanical of physical movements on the basis of the two patterns(open-stance and cross-stance) at the ready-to-start pose. The subjects for this study are composed of five male handball players from P university and five female shooting players from S university. Three-way moving actions at start(right, left, and forward) are recorded with two high-speed video cameras and measured with two Force platforms and a EMG system. Three-dimensional action analyzer, GRF system, and Whole body reaction movement system are used to figure out the moving mechanisms at the start pose. The analytic results of the moving mechanism at the start pose were as follows. 1. Through examining the three-way moving actions at start, I have found the cross-stance pose is better for the moving speed of body weight balance than the open-stance one. 175 degree of knee joint angle at "take-off" and 172 degree of hip joint angle were best for the start pose. 2. The Support time and GRF data shows that the quickest center of gravity shift was occurred when cross-stanced male subjects started to move toward his lefthand side. The quickest male's average supporting time of left and right foot is 0.19${\pm}$0.07 sec., 0.26${\pm}$0.06sec. respectively. The supporting time difference between two feet is 0.07sec. 3. Through analyzing GRF of moving actions at start pose, I have concluded that more than 1550N are overloaded on one foot at the open-stance start, and the overloaded force may cause physical injury. However, at the cross-stance pose, The GRF are properly dispersed on both feet, and maximum 1350N are loaded on one foot.