• 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.17 no.2
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• pp.31-40
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• 2007

Proper weight shifting is essential for a successful shot in golf swing and this could be described by means of the ground forces between the feet and ground. It is assumed that the ground forces would different according to the club used because the length and swing weight of each club is different. But, in present, it is not clear what changes are made by the change of clubs and this affect the swing motion. Therefore this study focused on the investigation of the changes of the ground forces and ground reaction forces (GRF) by the change of club length. The subjects were three professional male golfers. Four swings (driver, iron 3, iron 5, and iron 7) for each subject were taken by two high speed video cameras and two AMTI force platforms were used to measure the GRF simultaneously. Kwon GRF 2.0 and Mathcad 13 software were used to post processing the data. Changes of the three major component of GRF (Vertical, lateral, anterior-posterior force) at 10 predefined events were analyzed including the maximum. Major findings of this study were as follows. 1. Vertical forces; - There were no significant changes until the top of backswing. - Maximum was occurred at the club horizontal position in the downswing for both feet. The shorter club produced more maximum forces than longer ones in the left foot, but reverse were true for the right foot. - Maximum forces at impact shows the same patterns. 2. Lateral forces; Maximum was occurred at the club horizontal position for both feet, but there were no lateral forces because the direction of two forces was different. Maximum force pattern by different clubs was same as the vertical component. 3. Anterior-posterior forces; - This component made a counter-clock wise moment about a vertical axis located between two foot until the club vertical position was reached during the backswing, and reverse moment were produced when the club reached horizontal at the downswing. - Also this component made a forward moment about a horizontal axis located in the CG during the fore half of the downswing, and a reverse moment until the club reached vertical at the follow through phase. Maximum was occurred at the club vertical in the downswing for both feet. The longer club produced more maximum forces than shorter ones for both feet.

• Journal of the Korean Society of Physical Medicine
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• v.6 no.4
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• pp.447-454
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• 2011

Purpose : The purpose of this study was to identify the effects of circuit class training on the performance of locomotor tasks in chronic stroke. Methods : The study included 45 patients with chronic stroke randomly divided into experimetal group and control group. Both groups participated in exercise classes three times a week for 8weeks. The experimental group had 10 workstation of circuit class designed to improve walking. The control group practiced fitness exercises by equipment in health center. Walking performance was assessed by measuring walking speed(timed 10-meter walk and TUG), GAITRite analysis and peak vertical ground reaction force through the affected foot during walking. Results : The experimental group demonstrated significant improvement(p<.05) compared with the control group in 10-meter walking and vertical ground reaction force after training. The experimental group showed significant improvements in the walking velocity and cadence by GAITRite system(p<.05). Conclusion : Task- oriented circuit class training leads to improvements in locomotor function in chronic stroke. Further studies are necessary to occur in usual environments to improve walking performance.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.145-151
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• 2012

In this study, finite element analysis is carried out to estimate horizontal forces needed for the required power calculation and vertical forces applied on the structural analysis model for the development of automatic serrated surface at metal gasket core machining system. By considering of elasto-plastic material characteristics, nonlinear contact analysis was conducted to compute these loads according to the change of roll reduction, frictional coefficient and core thickness. As the result, horizontal and vertical reaction force variations are found according to parameters and maximum reaction force is also confirmed to be most affected by roll reduction.

• Physical Therapy Rehabilitation Science
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• v.9 no.4
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• pp.281-286
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• 2020

Objective: This study examined the effects of dynamic tape applied to the patellofemoral joint on the knee valgus angle, muscle activity, and ground reaction force during a single leg squat (SLS) and single leg landing (SLL). Design: Cross-sectional study. Methods: Twenty-four subjects (11 male, 13 female) who met the inclusion criteria were screened by the knee palpation and patella compression tests. First, the knee valgus angle and muscle activity during SLS were measured. Second, the knee valgus angle and ground reaction force during SLL were measured. For the intervention, a patella joint loop using dynamic tape was used. The knee valgus angle, muscle activities in SLS and SLL after the intervention, and the ground reaction force were measured in the same way. A paired t-test was used to examine the difference between before and after the intervention. Results: The knee valgus angle showed a statistically significant improvement after dynamic taping application in SLS and SLL (p<0.05). The differences in muscle activity of the VL/VMO and ground reaction forces were not statistically significant after dynamic taping application in SLS and SLL. Conclusions: This study showed that dynamic taping applied around the patellofemoral joint was effective in improving the knee valgus angle in SLS and SLL and had a reduced risk of secondary injury during sports activity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.14-14
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• 2003

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.226-232
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• 2020

Repetition of landing with visual control in sports and training is common, yet it remains unknown how landing with visual control affects postural stability and lower limb kinetics. The purpose of this study was to test the hypothesis that landing with visual control will influence on lower limb control for intrinsic dynamic postural stability. Kinematics and kinetics variables were recorded automatically when all participants (n=10, mean age: 22.00±1.63 years, mean heights: 177.27±5.45 cm, mean mass: 73.36±2.80 kg) performed drop landings from 30 cm platform. Visual control showed higher medial-lateral force, peak vertical force, loading rate than visual information condition. This was resulted from more stiff leg and less time to peak vertical force in visual control condition. Leg stiffness may decrease due to increase of perturbation of vertical center of gravity, but landing strategy that decreases impulse force was shifted in visual control condition during drop landing. These mechanism explains why rate of injury increase.

• 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.

• The Journal of Korean Physical Therapy
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• v.22 no.1
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• pp.9-17
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• 2010

Purpose: The purpose of this study was to compare the effects of Tai-Chi exercise (TCE) and resistance exercise (RE) when used as part of a community-based exercise program on improvement of physical function in elderly women with knee arthritis. Methods: Forty-seven women with knee arthritis participated in this study. They were assigned to one of two groups: the TCE group (n=22) or the RE group (n=25). Tai-Chi exercise and resistance exercise sessions were held for 1 hour per session, twice per week, for 8 consecutive weeks. At pre-treatment and post-treatment, subjects were tested using the following measurements: one-legged stand test (sec), a functional reach test (cm), a test of the strength of the knee extensor and flexor muscles, determination of the pathway of center of foot pressure and vertical ground reaction force for stance phase at pre and post treatment time points. An independent t-test and a ${\chi}^2$ were used to determine the significance of differences between group means using SPSS 12.0. Results: After 8 weeks of participation in the exercise programs, there were significant improvements for both groups in joint pain, difficulty of performing activity, muscle strength of knee extensor and flexor. Also, vertical ground reaction force increased at the loading response phase for both groups. The RE group was significantly different from TC group on the eyes-closed one-legged stand test (sec). Conclusion: Tai-Chi exercise and resistance exercise programs improve physical functioning and reduce pain and locomotion difficulties.

• Physical Therapy Korea
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• v.9 no.3
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• pp.39-46
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• 2002

In this study, vertical acceleration of center of mass was observed along normal gait phases in 9 healthy male volunteers (aged $25.7{\pm}2.18$). The developed wireless accelerometric device was attached on the intervertebral space between L3 and L4 using a semi-elastic waist belt. A three-dimensional motion analysis system, synchronized with the accelerometry, was used for detecting gait phases. There was no significant correlation between the body weight and the acceleration. The first peak curve covered loading response phase. The second downward peak point was matched accurately with the opposite toe-off. In mid-stance and terminal stance, the acceleration curve highly resembled the vertical ground reaction force curve. There was no significant difference in timing between the final upward peak point and the initial contact. Therefore, the developed accelerometry system would be helpful in determining determine temporal gait pattems in patients with gait disorders.