• 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.

• PNF and Movement
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• v.20 no.1
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• pp.59-66
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• 2022

Purpose: The aim of this research was to verify the relationship between three-dimensional (3D) ground reaction force (GRF) and severity of leg length discrepancy (LLD) while walking at a normal speed. It used a 3D motion analysis system with force platforms in standing workers with LLD. Methods: Subjects comprising 45 standing workers with LLD were selected. Two force platforms were used to acquire 3D GRF data based on a motion analysis system during gait. Vicon Nexus and Visual3D v6 Professional software were used to analyze kinetic GRF data. The subjects were asked to walk on a walkway with 40 infrared reflective markers attached to their lower extremities to collect 3D GRF data. Results: The results indicated the maximal force in the posterior and lateral direction of the long limb occurring in the early stance phase during gait had significant positive correlation with LLD severity (r = 0.664~0.738, p <0.01). In addition, the maximal force medial direction of the long limb occurring in the late stance phase showed a highly positive correlation with the LLD measurement (r = 0.527, p <0.01). Conclusion: Our results indicate that greater measured LLD severity results in more plantar pressure occurring in the foot area during heel contact to loading response of the stance phase and the stance push-off period during gait.

• Korean Journal of Applied Biomechanics
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• v.16 no.3
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• pp.9-18
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• 2006

These studies show that I applied to functional insole (a specific S company) for minimizing shocks and sprain people's ankle arising from running. How to an effect on human body which studied a kinematics and kinetics from 10 college students during experiments. This study imposes several conditions by barefoot, normal running shoes and put functional insole shoes ran under average $2.0{\pm}0.24$ meter per second by motion analysis, ground reaction force and electromyography that used to specific A company. First of all, Motion analysis was caused by Achilles tendon angle, Angle of the lower leg, Angle of the knee, Initial sole angle and Barefoot angle. Second, Contact time, Vertical impact force peak timing, Vertical active force and Active force timing, and Maximum loading rate under impulse of first 20 percent and Value of total impulse caused Ground reaction force. Third. The tendon fo Quadriceps femoris, Biceps femoris, Tibialis anterior and gastronemius medials caused. electromyography. 1. Ground reaction force also showed that statically approximates other results from impact peak timing (p.001), Maximum loading rate(p<.001), Maximum loading rate timing (p<.001) and impulse of first 20 percent (p<.001). 2 Electromyography showed that averagely was distinguished from other factors, and did not show about that. Above experiment values known that there was statically difference between Motion analysis and Ground reaction force under absorbing of the functional insole shoes which was not have an effect on our body for kinetics and kinematics.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.341-354
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• 2003

The purpose of this study was to develop the uniaxial force plate system which is measured by the vertical force. The VGRF(vertical ground reaction force) 1.0 was composed of 2 bath digital scales, 2 indicaters, and analyzing software. This system was newly renovated to VGRF 2,0 which are 2 industrial digital scales, 2 adjustable indicators, and enforced analyzing software. Changes of the new system were as follows. First, the height of the plate was 75% lower than before. Second, sensing ability of the load cell was changed from 90 - 0.05kg to 300 - 0.1kg. Third, the speed of data processing was changed from 17 per second to 60 per second. Fourth, analyzing software was enforced to develop and calculate the data. For the test of the system, two different types(bare foot, high-heeled shoes) gait was adopted. highly skilled female walker(23yrs, height 165cm, body mass 46.8kg) participated for the experimental study. During the dynamic performance(gait analysis), the data of each load cell were very similar to the previous studies. Specifically, bare foot walking had less vertical force than high-heeled shoes. Consequently, VGRF 2.0 can sense the general dynamic movements as well as static load conditions.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.7
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• pp.641-646
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• 2011

A low cost gait analysis system, which can measure stride length, walking speed, and ground reaction force, is proposed. A gait analysis system is used for medical evaluation of patients and rehabilitation assistance. Low cost cameras are attached to a shoe and movement of a shoe is estimated using infrared LED landmarks. Ground reaction force is measured from pressure sensors, which are installed inside a shoe. Through experiments, it is shown that the proposed system can be used to obtain stride length, walking speed, and ground reaction force.

• Journal of the Ergonomics Society of Korea
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• v.11 no.1
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• pp.93-101
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• 1992

Gait parameters for the Korean normal adults were compared with sex and age. Time-distance measurements and ground reaction force parameters were studied in relation to walking speed. Regression analysis was performed to establish functional relations between walking speed and various gait parameters. It is found that cardence and stride length varied linearly with walking velocity whereas time of double support was inversely proportional to walking velocity. The amplitude of ground reaction force was increased with increasing velocities of gait due to the greater heel-strike force and toe-off forces associated with these higher velocities. The results of this study can be usefull utilized as basic data to design and evaluate prosthetic devices, and to detect abnormal gait performances.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.82-83
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• 1998

In this study, variation of ground reaction force and energy consumption are investigated while walking with four different AK prostheses in order to obtain basic biomechanical data for developing AK prosthesis for Korean. It is a important information to investigate ground reaction force(GRF) and energy consumption to evaluate efficiency and stability of the prostheses.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.733-738
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• 2014

We propose a new approach called as a peak time approach for faster detection of step initiation for the lower limb exoskeleton. As faster detection of step initiation is an important criterion in evaluating the lower limb exoskeleton, many studies have investigated approaches to detect step initiation faster, including using electromyography, the center of pressure, the heel-off time and the toe-off time. In this study, we will utilize vertical ground reaction force events to detect step initiation, and compare our approach with prior approaches. Additionally, we will predict the first step's heel strike time with vertical ground reaction force events from multiple regression equations to support our approach. The lower limb exoskeleton should assist the operator's movement much faster and more reliably with our approach.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.197-204
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• 2005

In this study, ground reaction force(GRF), absolute symmetry index(ASI) and coefficient of variation(CV) of fixed, single-axis and multi-axis prosthetic ankle assemblies were investigated to show the biomechanical evaluation for above knee amputees. In the experiments, 37 normal male volunteers, two male and two female AK amputees were tested with fixed, single-axis and multi-axis prosthetic ankle assembly. A gait analysis was carried out to derive the ratio of GRF to weight as the percentage of total stance phase for ten points. The results showed that fixed-axis ankle was superior to the other two ankle assemblies for the characteristic of forwarding and breaking forces. Multi-axis ankle was relatively superior to the other two ankle assemblies for gait balancing and movement of the center for mass. single-axis ankle was relatively superior to the other two ankle assemblies for CV and ASI of GRF.

• Korean Journal of Applied Biomechanics
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• v.13 no.2
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• pp.161-173
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• 2003

This study was performed to investigate the kinematic and kinetic differences between functional walking shoe(FWS) and general sports shoe(GSS). The subjects for this study were 4 male adults who had the walking pattern of rearfoot strike with normal feet. The movement of one lower leg was measured using force platform and 3 video cameras while the subjects walked at the velocity of 2/1.5 m/s. The findings of this study were as follows 1. The angle of lower leg-ground and angle of knee with FWS was greater than with GSS at the moment of strike the floor and the moment of second peak ground reaction force. The decreasing rate of angle of ankle was smaller in FWS from the strike phase to the second peak ground reaction force. These mean upright walking and round walking along the shoe surface. 2. The maximal Increased angle of Achilles tendon and the minimal decreased angle of rearfoot were smaller in FWS very significantly(p<0.001). Thus FWS prevent the excessive pronation of ankle and have good of rear-foot control. 3. The vortical ground reaction force and the rate of it to the BW were smaller in FWS statistically(p<0.001). The loading rate was smaller in FWS, too, and thess represent the reduction of load on ankle joint and prevention of injuries on it.