• Korean Journal of Applied Biomechanics
• /
• v.17 no.2
• /
• pp.197-205
• /
• 2007

The purpose of this study is to analyze the muscle activations and Ground Reaction Force(GRF) in university judo players, and provide the guide of training in Judo. Using surface electrode electromyography(EMG), we evaluated muscle activity in 5 university judo players during the Judo Uke Movements. Surface electrodes were used to record the level of muscle activity in the Tibialis Anterior, Rectus Femoris, Elector Spinae, Gluteus Maximus, Gastrocnemius muscles during the Uke. These signals were compared with %RVC(Reference voluntary contraction) which was normalized by IEMG(Integrated EMG). The Uke was divided into four phases : Kuzushi-1, Kuzushi-2, Tsukuri, Kake. The results can be summarized as follows: 1. The effective Uke Movements needs to short time in the Kake Phase 2. The Analysis of Electromyography of Uke Movements in Supporting Leg; TA(Tibialis anterior) had Higher %RVC in the Kuzushi Phase, RF(Rectus Femoris) had Higher %RVC in the Tsukuri Phase, GM(Gluteus Maximus) had Higher %RVC in the Kake Phase 3. The ground reaction force for Z(vertical) direction was showed increase tendency in Kuzushi phase, Tsukuri phase and decrease tendency in Kake phase.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.2
• /
• pp.126-132
• /
• 2009

This study examined the differences in spatio-temporal parameters, joint angle, ground reaction force (GRF), and joint power according to the changes of gait speed for trans-tibial amputees to investigate the features of the energy-storing foot for sports. The subjects walked at normal speed and at fast speed, wearing a single-axis type foot (Korec) and an energy-storing foot for sports (Renegade) respectively. The results showed that Renegade yielded faster gait speed as well as more symmetric gait pattern, compared to Korec. However, as gait speed was increased, there was no significant difference in kinematics, ground reaction force, and joint power between two artificial foots. This was similar to the results from previous studies regarding the energy-storing foot, where the walking velocity and gait symmetry have been improved. Nevertheless, the result of this study differed from the previous ones which reported that joint angle, joint power, and GRF increased as the gait speed increased except spatio-temporal parameters.

• Korean Journal of Applied Biomechanics
• /
• v.20 no.1
• /
• pp.49-55
• /
• 2010

The purpose of the study was to analyze kinetic factors required to the three-point jump shot of the basketball games through 3-D analysis and ground reaction force(GRF) analysis. Six university male players participated in this study. The results of the study were showed that (1) resultant velocity in the center of mass(COM) was $0.84{\pm}0.27\;m/s$ since a player didn't shot a ball in the highest peak and shot ball at the moment of going up forward and vertical movement. Therefore, it is necessary to find a proper timing to shot a ball; (2) the angular velocity was largely increased in upper arm and fore arm out of the upper-limb segments and the hands had the largest angular velocity since the body is in a fixed situation and angular speed is rapidly increased by the wrist' snap with the rapid movement of upper arm and forearm at the time of release a ball; (3) it is judged that a player can shot a ball at the accurate and high release point when the player collects power vertically to the maximum by keeping GRF to the right and the rear in a proper way and by keeping the body's balance so that a large power may not be dispersed.

• Korean Journal of Applied Biomechanics
• /
• v.14 no.3
• /
• pp.191-202
• /
• 2004

The batting performance in baseball is a repetitive movement. In order to make the stabilization of posture and the efficient shift of body weight, both the range of stance and stride are important. The previous studies explained that the consistent stride which included the amount of time, stance, and direction were needed. However, the batting performance is frequently changed according to the several speed of ball. Therefore, this study was to analyze the reaction time, the range of stance, the change of stride, and the change of GRF during the batting movement in three kinds of ball speed (120km/h, 130km/h, & 140km/h). Seven elite players are participated in this study. 1. The reaction time of the stride phase was short whereas the time of the swing phase was long according to the increasing ball speed. 2. The range of the stance was wide and the mediolateral direction of the stride was decreased according to the increasing ball speed. 3. In the three kinds of ball speed, the change of body weight was transferred to the center, the rear foot, and the front foot directions. The ball speed of 130km/h showed the high frequency of the suitable batting. At this ball speed, the movement of the body weight was shifted smoothly and the value of the Ground Reaction Force was large enough.

• Korean Journal of Applied Biomechanics
• /
• v.19 no.3
• /
• pp.581-592
• /
• 2009

The purpose of this study is to examine the effect of the functional shoes through the kinetic comparison of normal-design running shoes and spring-loaded running shoes. For this, 12 healthy females from the age from 30 to 40 years participated in the EMG and ground reaction force experiment with testing kinetic variables. 12 subjects walked at the velocity of 1.7m/s. After analyzing variables in the spring-loaded running shoes and normal-design running shoes, the following conclusions were obtained; For the ground reaction force, spring-loaded running shoes have larger antero-posterior GRF than normal-design running shoes in the first and second apexes of antero-posterior ground reaction force. For the analysis of EMG, spring-loaded running shoes showed the higher muscle activation of rectus femoris muscle than norma-design running shoes. So the spring-loaded running shoes help improvement muscle strength of knee extensor.

• Journal of Biomedical Engineering Research
• /
• v.22 no.6
• /
• pp.543-550
• /
• 2001

In this study, ground reaction force(GRF) and energy consumption of fixed. single-axis and multi-axis Prosthetic ankle assemblies were investigated to show the biomechanical evaluation for trans-tibial amputees. In the experiments. two male and two female trans-tibial amputees were tested with fixed, sin91e-axis and multi-axis Prosthetic ankle assembly. A three-dimensional gait analysis was carried out to derive the ratio of GRF to weight as the percentage of total stance Phase for nine Points Energy consumption of each Prosthetic ankle assembly was measured while subjects walked at 2km/h. 3km/h and the most comfortable walking speed on the treadmill The results showed that multi-axis ankle was superior to the other two ankle assemblies for the characteristic of forwarding and breaking forces. Fixed ankle was relatively superior to the other two ankle assemblies for gait balancing and movement of the center fur mass Compared to the other ankle assembly. sing1e-axis type showed lower energy consumption over 2.3km/h walking speed .

• Korean Journal of Applied Biomechanics
• /
• v.26 no.4
• /
• pp.413-420
• /
• 2016

Objective: The purpose of this study was to analyze and compare different kinds of outdoor walking shoes in terms of muscle fatigue and ground reaction force on walking, and to provide foundational data for developing and choosing outdoor walking shoes that fit the users. Method: The study subjects were 30 healthy men. The experiment was conducted by using outdoor walking shoes with different inner and outer harnesses of the midsole, and shapes of the outsole. For data collection, electromyography was used to measure the muscle fatigue of the anterior tibial muscle and gastrocnemii, which contribute to the dorsiflexion and plantarflexion of the ankle joint, and the biceps muscle of the thigh and lateral great muscles, which contribute to the flexion and extension of the knee joint. A GRF measurement device was used to measure the X, Y, and Z axes. Results: In the type A outdoor walking shoes, regarding the hardness of the midsole, the inner part was soft, while the outer part was hard. The vertical ground reaction force was the lowest, which means least impact while walking and light load to the knees and ankles. The type C outdoor walking shoes were intended to provide a good feel in wearing the shoes. The tibialis anterior, biceps femoris, and gastrocnemii indicate low fatigue, which means that during a long-distance walk, it will minimize the fatigue in the muscles of the lower limbs. Conclusion: To sum up the study results, the different types of outdoor walking shoes indicate their unique characteristics in the biomechanical comparison and analysis. However, the difference was not statistically significant. Thus, a systematic and constant follow-up research should be conducted to cope with expanding market for outdoor walking shoes. Lastly, this study is expected to present foundational data and directions for developing outdoor walking shoes.

• Korean Journal of Applied Biomechanics
• /
• v.16 no.1
• /
• pp.119-128
• /
• 2006

This study was performed to see ground reaction force with different soccer studs with twelve players in Human Performance Laboratory(University of Calgary). Running speed was $4.0{\pm}0.2m/sec$ in straight running as well as vcut running. By using four different kinds of shoes; three different pairs of soccer shoes and one pair of jogging shoes, I reached a conclusion as following. In case of right and left ground reaction force, on the assumption that the positive magnitude of power is inversion and the negative is eversion, vcut running did not occur any inversion, which in the aspect of kinetic mechanics, thought to be decelerating movement. Because when eversion happens, it arises component force of power on heading direction about 8.6 times more than in the movement of straight running. In case of front and rear ground reaction, on the assumption that the positive magnitude of power is suspension power and the negative is propulsion, vcut movement is thought to be decelerating movement in the aspect of kinetic mechanics. Because on heading direction, this movement occurs component force of power about 1.8 times more suspension and 2.2 more propulsion than in the straight running movement. In case of vertical ground reaction, on the assumption that the first peak is the magnitude of power in impact and the second peak is the magnitude of power in active, we judged that the straight running movement performed more efficiently than the vcut movement in the aspect of kinetic mechanics. On the next study, I suppose that vcut running would make up an interesting subject in the aspect of improving kinetic performance ability.

• Korean Journal of Applied Biomechanics
• /
• v.17 no.3
• /
• pp.69-80
• /
• 2007

The purpose of this study was to investigate the difference of ground reaction forces of swimming athletes during their starting motion and to find out the most effective starting motions which were used in swimming athletes. The subjects were 9 male and 8 female high school swimming athletes who were athletic career over 7 years and used three starting motions in competition. The ground reaction forces were measured from each athletes performing three starting motion each of the open grap starting motion, closed grap starting motion and track starting motion. For the measurement, the force platform of AMTI company was utilized, and the analysis on measured ground reaction forces were used of Biosoft(Ver. 1.0). The items measured were stance time, Fz max deceleration force and Fz max deceleration force time, Fz mid stance force and Fz mid stance force time, Fz max acceleration force and Fz max acceleration force time, Torque maximum and Torque maximum time, Torque average, Excursion along Y axis of center of pressure of foot, Excursion along X axis of center of pressure of foot, Length of center of pressure of foot, Average velocity of center of pressure of foot. The data measured by the closed grap starting motion, open grap starting motion and track starting motion were analyzed by one-way repeated ANOVA. The results were as follows ; 1. The Fz max deceleration force time, Fz mid stance force, Fz max acceleration force, Torque maximum and Torque maximum time, Excursion along Y axis of center of pressure of foot, Average velocity of center of pressure of foot were significantly fast and large in the closed grap starting motion then open grap starting motion and track starting motion. 2. The Excursion along Y axis of center of pressure of foot was significantly long in the closed grap starting motion then open grap starting motion and track starting motion.

• Korean Journal of Applied Biomechanics
• /
• v.30 no.1
• /
• pp.27-35
• /
• 2020

Objective: The purpose of this study was to investigate the influence of clubhead velocity through regression analysis on the magnitude and time difference of the forward-backward, mediolateral, and vertical ground reaction peak forces generated by force plate during golf swing. Method: 16 subjects (age: 20.5±4.2 yrs, height: 176.0±5.4 cm, weight: 77.8±5.9 kg, handy: 2.4±1.7) who is elite golf player in high school and university, participated in this study. The study method adopted three-dimensional analysis with 8 cameras and ground reaction force measurement with two force plate. The analysis variables were clubhead velocity, and ground reaction analysis variables set four events in each graph based on the peak forces commonly generated in Fx, Fy, and Fz graphs of the ground reaction data during the golf swing. Results: As a result of analyzing the influence of ground reaction magnitude difference on clubhead velocity, the influence on clubhead velocity was ym4, zm1, xm4, zm2. The larger ym4, xm4, zm1, the fasterthe clubhead velocity, but the smallerthe zm2, the faster the clubhead velocity. And in time difference, the influence on the clubhead velocity was in the order of xt4, zt1, zt3. The shorter xt4, zt1, zt3 showed faster clubhead velocity. Conclusion: The leftfoot played a leading role in increasing the velocity of the clubhead. Although the result was caused by the interaction of the right foot and the left foot during the swing, the role of the left foot is relatively large.