• Korean Journal of Applied Biomechanics
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• v.15 no.2
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• pp.185-196
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• 2005

Recently among several tennis techniques forehand stroke has been greatly changed in the aspect of spin, grip and stance. The most fundamental factor among the three factors is the stance which consists of open, square and closed stance and it is very important to know the patterns of plantar pressure distribution for the better understanding of forehand stroke. Therefore, the purpose of this study was to investigate the change of plantar pressure distribution according to close, square and open stance patterns during forehand stroke in tennis. Three high school tennis players were recruited for the study and required to perform forehand stroke five consecutive trials in the condition of open, square and close stance. The forehand strokes were filmed with two digital video cameras and measured with pedar system for plantar pressure. The plantar regions under the foot were divided into 3 regions, which were forefoot, midfoot, and rear foot.. In conclusion, the first hypothesis, "The plantar pressure of close stance during forehand stroke would be distributed more largely to the left foot.", was rejected and the result showed that The plantar pressure of close stance during forehand stroke was distributed transferring from right foot to left foot similar to square stance. The second hypothesis, "The plantar pressure of square stance during forehand stroke would be distributed transferring from right foot to left foot." was accepted. The third hypothesis, "The plantar pressure of open stance during forehand stroke would be distributed more largely to the right foot.", was accepted.

• Korean Journal of Applied Biomechanics
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• v.26 no.3
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• pp.285-292
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• 2016

Objective: This study collected data on muscle fatigue and ground reaction force during walking to provide a basis for development of custom-fitted outdoor walking shoes. The study analyzed an upright body exercise program using spine stabilization technique to determine the effect on foot plantar pressure in archers, demonstrate the effectiveness of upright body exercise, and develop a new, effective, and efficient training program. Method: A 12-week upright body exercise program was evaluated for the effect on plantar pressure in archers. Ten prize-winning archers (3 men, 7 women) in B metropolitan city, each with ${\geq}10years$ of experience, were given an explanation of the content and purpose of the program, and provided informed consent. Upright body exercise was performed 3 times a week for 12 weeks. A resistive pressure sensor was used to measure foot plantar pressure distribution and analyze quantitative information on variation in postural stability and weight shifting in dynamic balance during shooting, as well as plantar pressure in static balance with the eyes open and closed. Results: There were no significant differences in foot plantar pressure before and after participation in the exercise program. There was no statistically significant difference in foot plantar pressure in static balance with the eyes open or closed, or in foot plantar pressure in dynamic balance during shooting. Conclusion: An upright body exercise program had positive effects on foot plantar pressure in static and dynamic balance in archers by reducing body sway and physical imbalance during shooting and with eyes closed. This program is expected to help archers improve their posture and psychological state, and thereby improve performance.

• The Journal of Korean Physical Therapy
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• v.10 no.1
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• pp.127-138
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• 1998

This study was carried out tn invstigate and compare biomechanical characteristics during free speed gait in hemiplegic patients after stroke who took therapeutic exercise by analyzing kinematic and kinetic data in the sagital plane and electromyographic data. Six patients($41\~69$ years old) and age-matched six volunteers in good health(51-61 years old) wire studied. The patients were sorted into two groups, depending on their self-speed of walking : fast speed group(3 patients) and slow speed group(3 patients). The results were as fellows. : 1. In spatio-temparal parameters, affected and unaffected side of fast group showed symetry but blew group showed asymetry of single limb support, opposite foot contact and stance phase (p<0.05). Compared with normal group, patient group showed slower velocity, shoter stride length and longer double limb support (p<0.05). 2. In the pelvic anterior tilt, patient group showed lower valued than normal group. It. In the ground reaction force-vertical force, fast group showed similar double peak gragh compared with normal group, butvslow group showed lower values without double peak (p<0.05).

• Korean Journal of Applied Biomechanics
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• v.16 no.2
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• pp.145-151
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• 2006

A large interindividual variability and some abnormally kinematic patterns at the lower extremity were the main features of the gait in children with Down syndrome. The purposes of this study were to investigate the gait asymmetry and biomechanical difference between dominant leg and non dominant leg in children with Down syndrome. Seven boys with Down Syndrome(age: $120{\pm}0.9yrs$, weight $34.4{\pm}8.4kg$, leg length: $68.7{\pm}5.0cm$) participated in this study. A 10.0 m ${\times}$ 1.3 m walkway with a firm dark surface was built and used for data collection. Three-dimensional motion analyses were performed to obtain the joint angles and range of motions. The vertical ground reaction forces(%BW) and impulses($%BW{\cdot}s$) were measured by two force plates embedded in the walkway. Asymmetry indices between the legs were computed for all variables. After decision the dominant leg and the non dominant leg with max hip abduction angle, paired samples t-test was employed for selected kinematic and ground reaction force variables to analyze the differences between the dominant leg and the non dominant leg. The max hip abduction angle during the swing phase showed most asymmetry, while the knee flexion angle at initial contact showed most symmetry in walking and running. The dominant leg showed more excessive abduction of hip in the swing phase and more flat-footed contact than the non dominant leg. Vertical peak force in running showed more larger than those of in walking, however, vertical impulse showed more small than walking due to decrease of support time. In conclusion, the foot of dominant leg contact more carefully than those of non dominant leg. And also, there are no significant difference between the dominant leg and the non dominant leg in kinematic variables and ground reaction force due to large interindividual variability.

• Korean Journal of Applied Biomechanics
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• v.15 no.1
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• pp.143-153
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• 2005

J.Y. CHOI,S. J. KIM, E. L. LEE. Change of plantar pressure Distribution of Open Stance during Forehand Strke in Tennis. Korean Journal of Sport Biomechanics, Vol. 15, No. 1, PP. 143-153, 2005. Recently among several tennis techniques forehand stroke has been greatly changed in the aspect of spin, grip and stance. The most fundamental factor among the three factors is the stance which consists of open, square and close stance and it is very important to know the patterns of plantar pressure distribution for the better understanding of forehand stroke. Therefore, the purpose of this study was to investigate the change of plantar pressure distribution in open stance during forehand stroke in tennis. Three high school tennis players were recruited for the study and required to perform forehand stroke five consecutive trials in the condition of open stance. The forehand strokes were filmed with two digital video cameras and measured with pedar system for plantar pressure. The plantar regions under the foot were divided into 3 regions, which were forefoot, midfoot, and rear foot. In conclusion, The plantar pressure of open stance during forehand stroke was distributed more largely to the right foot. The plantar pressure of open stance during forehand stroke was distributed more weight loads on forefoot of right than heel of right

• Journal of the Korean Society of Physical Medicine
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• v.13 no.3
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• pp.113-120
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• 2018

PURPOSE: This study was conducted to investigate the characteristics of a specific functional shoe in terms of the range of motion (ROM) of ankle and foot joints during walking when compared to a standardized shoe. METHODS: Kinematic ROM data pertaining to ankle, tarsometatarsal, and metatarsophalangeal joints were collected from twenty-six healthy individuals during walking using a ten-camera motion analysis system. Kinematic ROM of each joint in three planes was obtained over ten walking trials consisting of two different shoe conditions. Visual3D motion analysis was finally used to coordinate the kinematic data. All kinematic ROM data were interpolated using a cubic spline algorithm and low-pass filtered with a cutoff frequency of 6 Hz for smoothing. RESULTS: The overall ROM of the ankle joint in the sagittal and coronal planes when wearing the specific functional shoe was significantly decreased in both ankles during walking when compared to wearing a standard shoe (p<.05). Significantly more flexibility was observed when wearing the specific functional shoe in the tarsometatarsal and metatarsophalangeal joints compared to a standard shoe (p<.05). CONCLUSION: Although clinical application of the specific functional shoe has shown clear positive effects on knee and ankle moments, the results of this study provide important background information regarding the kinematic mechanisms of these effects.

• Korean Journal of Applied Biomechanics
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• v.23 no.1
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• pp.25-35
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• 2013

This study examined 24 right-handed amateur baseball players. Twelve who had played baseball for more than 6 years were grouped as skilled players, while 12 who had played for 1-3 years were the unskilled player group. The swing motion was divided into four event phases: stance, backswing, impact, and follow-through. The mean and maximum plantar pressure, center of pressure, and ground reaction force were measured during each event phase. The mean and standard deviations for each variables were calculated and differences were validated with the independent sample t-test. A p-value <0.05 was considered statistically significant. The results were as follows. 1)The ideal stance is a stable, balanced position with more than 65% of weight on the right foot. There was significant difference in mean left plantar pressure, while the maximal plantar pressure and mean right plantar pressure did not differ significant. 2)The effective backswing of a skilled player is comprised a rightward shift in weight to build maximum energy. More than 90% of the weight was on the right foot. There was a significant difference in the mean left plantar pressure, while the maximal plantar pressure and mean right plantar pressure did not differ significantly. 3) For an effective impact, a rapid shift in weight to the left foot is essential, so that a power hit is obtained. Significant difference in the mean and maximum plantar pressures of both feet were observed. 4)Follow-through requires wight balance, more on the right than the left, without leaning leftward. There was no significant difference in the mean or maximum plantar pressure. 5)The center of plantar pressure should move from the center of the foot to the toe. 6)The analyses of the ground reaction force suggest that a good swing involves a gradual shift in weight to the right side and a rapid leftward shift at impact. Good balance, with the center of gravity on the right side at follow-through, is also required.

• Korean Journal of Applied Biomechanics
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• v.15 no.1
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• pp.29-44
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• 2005

The purpose of this study is to reveal the effects of two different kicks, the drop kick and the punt kick, into the kicking motion, through the kinetic comparative analysis of the kicking motion, which is conducted when one kicks a soccer goal. To grasp kinetic changing factors, which is performed by individual's each body segment, I connected kicking motions, which were analyzed by a two dimension co-ordination, into the personal computer to concrete the digits of it and smoothed by 10Hz. Using the smoothed data, I found a needed kinematical data by inputting an analytical program into the computer. The result of comparative analysis of two kicking motions can be summarized as below. 1. There was not a big difference between the time of the loading phase and the time of the swing phase, which can affect the exact impact and the angle of balls aviation direction. 2. The two kicks were not affected the timing and the velocity of the kicking leg's segment. 3. In the goal kick motion, the maximum velocity timing of the kicking leg's lower segment showed the following orders: the thigh(-0.06sec), the lower leg(-0.05sec), the foot(-0.018sec) in the drop kick, and the thigh(-0.06sec), the lower leg(-0.05sec), the foot(-0.015sec) in the punt kick. It showed that whipping motion increases the velocity of the foot at the time of impact. 4. At the time of impact, there was not a significant difference in the supporting leg's knee and ankle. When one does the punt kick, the subject spreads out his hip joint more at the time of impact. 5. When the impact performed, kicking leg's every segment was similar. Because the height of the ball is higher in the punt kick than in the drop kick, the subject has to stretch the knees more when he kicks a ball, so there is a significant affect on the angle and the distance of the ball's flying. 6. When one performs the drop kick, the stride is 0.02m shorter than the punt kick, and the ratio of height of the drop kick is 0.05 smaller than the punt kick. This difference greatly affects the center of the ball, the supporting leg's location, and the location of the center of gravity with the center of the ball at the time of impact. 7. Right before the moment of the impact, the center of gravity was located from the center of the ball, the height of the drop kick was 0.67m ratio of height was 0.37, and the height of the punt kick was 0.65m ratio of height was 0.36. The drop kick was located more to the back 0.21m ratio of height was 0.12, the punt kick was located more to the back 0.28m ratio of height was 0.16. 8. There was not a significant difference in the absolute angle of incidence and the maximum distance, but the absolute velocity of incidence showed a significant difference. This difference is caused from that whether players have the time to perform of not; the drop kick is used when the players have time to perform, and punt kick is used when the players launch a shifting attack. 9. The surface reaction force of the supporting leg had some relation with the approaching angle. Vertical reaction force (Fz) showed some differences in the two movements(p<0.05). The maximum force of the right and left surface reaction force (Fx) didn't have much differences (p<0.05), but it showed the tendency that the maximum force occurs before the peak force of the front and back surface (Fy) occurs.

• 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.14 no.1
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• pp.145-160
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• 2004

The purposes of this study to provide quantitative data in necessary to advance techniques kinematic analysis of Cucarachas which is an action of Rumba. Then, this study is performed on 5 female players who have won within the third prize at a national athletic meeting. When whole foot reached to floor, Displacement of right-left hip joint (until $E1{\sim}E3$ average moved 15.15cm)is found at right-left direction since the hip joint is turned to right back. On the other side, large displacement is shown because Rumba Cucaracha Movement is expressed by maximum shift of hip joint to right and left direction. Displacement of right hip joint(E3$57.40{\pm}7.46$) is found in front and in rear direction since hip joint is moved in rear and in front to turn the hip joint. It may be stated that this is ideal displacement expressed by movement of whole body with artistic poise and presentation because role of hip joint is very important in technical and artistic side. Angle of right shoulder joint E2($105.44{\pm}9.64$) is got wider. It may be stated that player shifts up and abduct elbow joint to right since center of gravity of player is exceedingly shifted to right in this motion of Cucarachas. On the other hand, since this motion is abducted right elbow and shrunk external abdominal oblique to him center of body to left front of hip joint, the angle becomes narrow. It is shown that angle of knee in right knee joint E4($75.44{\pm}2.61$) is large since right leg and hip joint is turned by foot using reaction of ground and so center of body is shifted to left. Large angle of ankle E4($134.40{\pm}10.50$) in Cucaracha Movement is shown by the action of twist force using narrow part of foot and compression force against ground with adduction speed of arm. The various kinematic analyses associated with motions of dance sport have not been sufficiently peformed so far, and thus a number of research projects for dance sport should be proposed and performed to be continuous.