• Korean Journal of Applied Biomechanics
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• v.18 no.3
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• pp.11-21
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• 2008

The purpose of this study was to investigate the most optimum way of performing the bandal chagi during Taekwondo Kyorugi competition. By analyzing the EMG data and the kinematic data it was hoped that scientific data would be provided to instructors and players about the optimization of the Bandal Chagi. The results of the analysis are as follows: During competition while performing the Bandal Chagi the most important factors that affect the impact point are the range of motions of the upper body hyper extension and knee joints. Through the measurement of the muscles EMG activity of a well performed Bandal Chagi with the right leg it was observed that the left side erector spinae muscle was highly activated and so it was concluded that this muscle should be trained to improve the performance of the Bandal Chagi. Likewise it was observed that for the right side of the abdominal muscle's EMG there was a high activity level and thus showed that there was a large contribution of this muscle for the optimum performance of the Bandal Chagi.

• Journal of Biomedical Engineering Research
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• v.32 no.2
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• pp.165-176
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• 2011

The femoral nerve innervates the quadriceps muscles and its dermatome supplies anteromedial thigh and medial foot. Paralysis of the quadriceps muscles due to the injury of the femoral nerve results in disability of the knee joint extension and loss of sensory of the thigh. A child could walk independently even though he had injured his femoral nerve severely due to the penetrating wound in the medial thigh. We measured and analyzed his gait performance in order to find the mechanisms that enabled him to walk independently. The child was eleven-year-old boy and he could not extend his knee voluntarily at all during a month after the injury. His gait analysis was performed five times (GA1~GA5) for sixteen months. His temporal-spatial parameters were not significantly different after the GA2 or GA3 test, and significant asymmetry was not observed except the single support time in GA1 results. The Lower limb joint angles in affected side had large differences in GA1 compared with the normal normative patterns. There were little knee joint flexion and extension motion during the stance phase in GA1 The maximum ankle plantar/dorsi flexion angles and the maximum knee extension angles were different from the normal values in the sound side. Asymmetries of the joint angles were analyzed by using the peak values. Significant asymmetries were found in GA1with seven parameters (ankle: peak planter flexion angle in stance phase, range of motion; ROM, knee: peak flexion angles during both stance and swing phase, ROM, hip: peak extension angle, ROM) while only two parameters (maximum hip extension angle and ROM of hip joint) had significant differences in GA5. The mid-stance valleys were not observed in both right and left sides of vertical ground reaction force (GRF) in the GA1, GA2. The loading response peak was far larger than the terminal stance peak of vertical ground reaction curve in the affected side of the GA3, GA4, GA5. The measured joint moment curves of the GA1, GA2, GA3 had large deviations and all of kinetic results had differences with the normal patterns. EMG signals described an absence of the rectus femoris muscle activity in the GA1 and GA2 (affected side). The EMG signals were detected in the GA3 and GA4 but their patterns were not normal yet, then their normal patterns were detected in the GA5. Through these following gait analysis of a child who had selective injuries on the knee extensor muscles, we could verify the actual functions of the knee extensor muscles during gait, and we also could observe his recovery and asymmetry with quantitative data during his rehabilitation.

• Journal of the Ergonomics Society of Korea
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• v.30 no.5
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• pp.605-611
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• 2011

Objective: The aim of this study was to investigate the influence of seat heights for optimizing the ingress/egress performance in the elderly people. Background: Recently elderly users have been increasing in number and the ease of ingress/egress of the vehicle becomes an important issue. Method: Seven elderly subjects participated in this study(age: 71.7${\pm}$3.6yr, height: 167.7${\pm}$5.4cm, weight: 68.1${\pm}$11.5kg). Each subject performed the sitting and rising task from comfortable seated position on the chair under the following conditions: (1) with a lumbar support and (2) without a lumbar support. We measured EMG activities of seven muscles(tibialis anterior, soleus, gastrocnemius, vastus lateralis, rectus femoris, biceps femoris and erector supinae) and ranges of motion in lower limb during sitting and standing from three different heights (400mm, 500mm and 600mm from ground) of slide-up seat. Results: Muscle activities and angular movements of hip and knee joints during standing-up and sitting-down with a high seat height(600mm) were reduced mean 30.4% in extensor muscles, 57.11% in flexor muscle, 18.74% in erector muscle and 31.0% in joints compared with a low seat height(400mm). Conclusion: Muscle activities and joint movements in hip and knee were reduced when rising/sitting from a high seat height(600mm) compared with a low seat height(400mm). Application: This study can be used to design vehicle that are easy to get in and out of by older peoples with or without impairments.

• Physical Therapy Rehabilitation Science
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• v.8 no.2
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• pp.61-66
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• 2019

Objective: The purpose of this study was to investigate the effects of resistance applied in various directions on lower extremity muscle activity and balance during squat exercise performance. Design: Cross-sectional study. Methods: Forty-one adults (19 males and 22 females) agreed to the study purpose and procedures. All subjects randomly performed squat exercises with an intensity of overcoming 10% of body weight resistance pulled forward, backward and general squats with $60^{\circ}$ of knee joint flexion. Electromyography was used to measure muscle activity of the vastus medialis oblique (VMO), rectus femoris (RF), vastus lateralis oblique (VLO), biceps femoris (BF), and semitendinosus (ST) muscles. The Wii Balance Board was used to assess balance during the three-method squat operation. Each operation was measured three times for 10 seconds. Results: There were significant differences in muscle activities of the VMO, RF, VLO, ST and balance ability with the application of three directions of resistance (p<0.05). Post hoc comparisons revealed that squats performed with resistance pulled in the backward direction resulted in higher VMO, RF and VLO activity than with the resistance placed in a pulled forward direction (p<0.05). In the ST, resistance applied in the pulled forward direction showed greater muscle activity compared to the pulled backward direction (p<0.05). With balance, squats performed with resistance pulled in the forward direction showed greater muscle activity than with resistance applied in the pulled backward direction and during general squat performance (p<0.05). Conclusions: In this study, squat exercises performed with resistance applied in the direction of pulling backwards was found to be the most effective in improving quadriceps muscle strength and balance. It is effective to provide resistance that is placed in the forward when it is difficult to perform a general squat due to weakness of the quadriceps.

• Physical Therapy Rehabilitation Science
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• v.10 no.1
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• pp.16-21
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• 2021

Objective: To control the rate at which body weight drops, forefoot initiates floor contact with the limb relatively extended at each joint. However, when the knee joints could not extend enough with going down the stairs, the forefoot cannot be contact initially. The purpose of this study was to investigate the differences between forefoot and whole foot in initial contract on soleus and tibialis anterior for health young adults when descending stairs. Design: A cross-sectional observational study design. Methods: Fifteen healthy young adults participated in this study. To compare between forefoot and whole foot in initial contact when going down the stairs, this study measured muscle activation on soleus and tibialis anterior. This study used the paired t-test to analyze the collected data and compare the supporting conditions. Results: After analyzing, the muscle activation of soleus was not statistically significant difference as 25.16% at forefoot initial contact and 24.37% at whole foot initial contact when descending stairs (p>0.05). However, the muscle activation of tibialis anterior muscle was significantly difference was 49.19% at forefoot contact and 71.55% at whole foot contact. Conclusions: The results of this study was that the muscle activation of the tibialis anterior was a higher at whole foot contact than that at fore foot contact when descending stairs. This study suggests that the landing strategy of the initial contact is a beneficial effect at the forefoot contact to maintain the postural balance and the muscle performance effectively when descending stairs in individuals with healthy young adults.

• Korean Journal of Applied Biomechanics
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• v.29 no.3
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• pp.129-135
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• 2019

Objective: The purpose of this study is to present the scientific and quantitative data by finding the common points and differences of the side-kick according to the height change through the difference of the side kick motion performance according to the three target height changes and the function of the lower limbs muscle in side kick motion of Taekwondo Poomsae. Method: For this, total 14 players were selected who were registered in Korea Taekwondo Association and skilled group 7 players who had a medal from national competition and 7 players who did not have Taekwondo experience from department of physics. 4 video cameras to the feature on side kick per target height, and the subjects' support foot was located on the ground reactor and the practice was conducted 3 times: waist, chest, and head as the target height. the basic materials were collected by using Kwon 3D XP program and the T-test was conducted to verify the statistic difference between groups (SPSS 24.0). At this time, the statistics significance level was set as .05 and the following conclusion was obtained. Results: The lower the proficiency and the higher the height, the more the joint coordination between the hip and the knee. Conclusion: Summary of the result shows a common point that the change of target's height makes the lower the proficiency and the higher the height, the more the joint coordination between the hip and the knee. Also, the higher the target's height became, the greater angular momentum of thighs, shanks, foot became in common.

• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.465-477
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• 2018

The purpose of this study is to analyze the effect of three - week high altitude ski training on the myocardial performance of cross - country skiers and to provide basic data for the future improvement of cross - country skiers'. The subjects were 6 cross - country skiing male college athletes. To investigate the effects of periodic and high altitude training on cross - country skiers, a general linear model ANOVA with repeated measure And analyzed using the Paired Samples t-test. In high altitude ski training for 3 weeks, the body composition did not change but the isokinetic muscular function of the shoulder joint, hip joint, knee joint, and ankle joint was decreased. Therefore, further study is needed if it is considered that continuous strength training should be performed during the ski training period such as SP period.

• Korean Journal of Applied Biomechanics
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• v.26 no.1
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• pp.11-20
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• 2016

Objective: This study aimed to compare biomechanical data between elite and beginner cyclists during cycle pedaling by performing a comparative analysis and to provide quantitative data for both pedaling performance enhancement and injury prevention. Methods: The subjects of this study included 5 elite cyclists (age: $18{\pm}0years$, body mass: $64.8{\pm}9.52kg$, height: $173.0{\pm}4.80cm$) and 5 amateur cyclists (age: $20{\pm}0years$, mass: $66.6{\pm}2.36kg$, height: $175.6{\pm}1.95cm$). The subjects pedaled on a stationary bicycle mounted on rollers of the same gear (front: 50 T and rear: 17 T = 2.94) and cadence of 90. The saddle height was adjusted to fit the body of each subject, and all the subjects wore shoes with cleats. In order to obtain kinematic data, 4 cameras (GR-HD1KR, JVC, Japan) were installed and set at 60 frames/sec. An electromyography (EMG) system (Telemyo 2400T, Noraxon, USA) was used to measure muscle activation. Eight sets of data from both the left and right lower extremities were obtained from 4 muscles (vastus medialis oblique [VMO], vastus lateralis oblique [VLO], and semitendinosus [Semitend], and lateral gastrocnemius [Gastro]) bilaterally by using a sampling frequency of 1,500 Hz. Five sets of events ($0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, and $360^{\circ}$) and 4 phases (P1, P2, P3, and P4) were set up for the data analysis. Imaging data were analyzed for kinematic factors by using the Kwon3D XP computer software (Visol, Korea). MyoResearch XP Master Edition (Noraxon) was used for filtering and processing EMG signals. Results: The angular velocity at $360^{\circ}$ from the feet was higher in the amateur cyclists, but accelerations at $90^{\circ}$ and $180^{\circ}$ were higher in the elite cyclists. The amateur cyclists had greater joint angles at $270^{\circ}$ from the ankle and wider knee joint distance at $0^{\circ}$, $180^{\circ}$, and $360^{\circ}$ than the elite cyclists. The EMG measurements showed significant differences between P2 and P4 from both the right VLO and Semitend. Conclusion: This study showed that lower body movements appeared to be different according to the level of cycle pedaling experience. This finding may be used to improve pedaling performance and prevent injuries among cyclists.