• Korean Journal of Applied Biomechanics
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• v.32 no.2
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• pp.43-48
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• 2022

Objective: The purpose of this study was to verify the effectiveness among simulating ski jumping trainings by comparing with actual ski jump. Method: Three healthy youth national athletes were recruited for this study (age: 13.70 ± 0.9 yrs, height: 169.30 ± 0.9 cm, jumping caree: 5.3 ± 0.9 yrs). Participants were asked to performed ski jumping with 3 simulating and one actual situation. A 3-dimensional motion analysis with 5 channels of EMG was performed in this study. Muscle activations of Rectus Femoris [RF], Tibialis Anterior [TA], Thoracis [TH], Gluteus maximus [GM], and Gastronemius [GL] were achieved with sampling rate of 2,000 Hz during each jump. Results: In the case of S1 in the actual jumping motion, the deviation of the muscle activity peak did not appear each trial, and the jump timing was consistent. For S2, the timing of the muscles peak activation which can maintain the posture of the upper body and ankles appeared at the beginning. In the case of S3, the part maintaining the ankle posture at the beginning appeared, but it could be expected that it would progress in the vertical direction due to the activation of GL at the time of jumping. Conclusion: The muscle activation peak before the take-off point showed a different pattern for each athlete, and individual differences were large. In addition, it was attempted to confirm the actual jump with simulation jump, and it was found that not only the difference in patterns but also the fluctuations in the timing of each muscle activation peak were large.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.57-62
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• 2014

Most analytical models of the human body have focused on conscious responses. A patellar tendon reflex, a representative example of spinal reflexes, occurs without a neural command. Muscle forces and activation of the quadriceps femoris muscles in healthy adults during patellar tendon reflex are identified in this study. The model is assumed to move in the sagittal plane, and the thigh and the trunk are assumed to be fixed in a sitting position so that the shank can move similar to a pendulum. The knee joint is modeled as a revolute joint, and the ankle joint is modeled as a fixed joint so that the shank and the foot can be regarded as one rigid body. Muscle forces are calculated following the inverse dynamic approach. Kinematic data obtained from an experiment (Mamizuka, 2007) are used as input data. Muscle activations are identified using a Hill-type muscle model. The obtained simulation results are compared with experimental results for validating the model and the underlying assumptions.

• Physical Therapy Rehabilitation Science
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• v.10 no.3
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• pp.244-250
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• 2021

Objective: The purpose of this study was to investigate the effect of sprinter pattern bridging exercise using theraband on activation of lower extremity and abdominal muscle and to find out postures that can effectively improve abdominal and lower extremity muscle strength and increase abdominal stability. Methods: This study was designed as a cross-sectional study. The following research was done with applicants attending S university in Seoul to compare the difference in muscle activity between one-leg-Support bridging exercise and sprinter-pattern bridging exercise using theraband. For 48 study participants, we first measured their MVC. Then, we applied one-leg-support bridging exercise and sprinter-pattern bridging exercise at random order. These data were expressed as the percentage of maximal voluntary contraction (%MVC).Electromyography analysis was performed by measuring the external obliques, internal obliques, biceps femoris, and gluteus maximus. Results: There was a statistically significant increment of muscle activity in external and internal oblique muscle(p<0.001)by sprinter-pattern bridging exercise using theraband. On the lower body, statistically significant increment of muscle activity in biceps femoris and gluteus maximus was found(p<0.05). On the other hand, on erector spinae, there was statistically significant decrease in muscle activity(p<0.05). Conclusions: Efficient treatment is expected when sprinter-pattern bridging exercise using theraband is applied clinically.For patients with chronic knee and ankle pain who have difficulty bearing weight, including low back pain and internal rotation of the femur, starting with a low weight bearing, we think it will be helpful in planning systematic training aimed at progressively strengthening the lower extremities.

• Journal of the Ergonomics Society of Korea
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• v.29 no.3
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• pp.357-364
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• 2010

This study proposes a lower-limb exoskeleton system that is controlled by a wearer's muscle activity. This system is designed by following procedure. First, analyze the muscle activation patterns of human leg while walking. Second, select the adequate actuator to support the human walking based on calculation of required force of knee joint for step walking. Third, unit type knee and ankle orthotics are integrated with selected actuator. Finally, using this knee-assistive system (KAS) and developed muscle stiffness sensors (MSS), the muscle activity pattern of the subject is analyzed while he is walking on the stair. This study proposes an operating algorithm of KAS based on command signal of MSS which is generated by motion intent of human. A healthy and normal subject walked while wearing the developed powered-knee exoskeleton on his/her knees, and measured effectively assisted plantar flexor strength of the subject's knees and those neighboring muscles. Finally, capabilities and feasibility of the KAS are evaluated by testing the adapted motor pattern and the EMG signal variance while walking with exoskeleton. These results shows that developed exoskeleton which controlled by muscle activity could help human's walking acceptably.

• Korean Journal of Applied Biomechanics
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• v.28 no.1
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• pp.37-43
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• 2018

Objective: The aim of this study was to analyze muscle activation of the lower extremities as a function of changes of the center of pressure (CoP) of the foot during squats in order to provide quantitative information to trainers who would like to teach correct movements for developing muscles. Method: Ten men with over three years of weight training experience participated in this study (age: $26.1{\pm}0.8yrs$, height: $171.2{\pm}3.9cm$, body mass: $71.1{\pm}5.7kg$, 60%RM: $84{\pm}9kg$, career: $4.0{\pm}0.7yrs$). The participants were instructed to perform a squat in each of 3 conditions, with different CoP's (the front, middle, and rear of the foot). Results: The position of the CoP showed significant differences according to instructions in both the eccentric and concentric contraction phases (p < .05). The range of movement of the hip and ankle joints showed significant differences corresponding to changes of the CoP position (p < .05). The rectus femoris and gluteus maximus muscle showed significant differences for different CoP positions only in the concentric contraction phase, while the gastrocnemius and anterior tibialis were significantly different in both the concentric and eccentric contraction phase (p < .05). Conclusion: When the target muscle of squat training is the gastrocnemius, the CoP should be located in the front of the foot for effective muscle training. When the target muscles of squat training are the gluteus maximus and quadriceps femoris, the CoP should be located on the rear of the foot.

• The Journal of Korean Physical Therapy
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• v.26 no.1
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• pp.27-32
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• 2014

Purpose: The purpose of the study was to comparison of trunk muscle activity during static standing position and standing position on therapeutic climbing wall of adult. Methods: Study subject is arbitrarily classified into 10 of experimental group and 10 control group among 20 of adult. Trunk activity measured as rectus abdominalis, external oblique, internal oblique, erector spinae. Control group maintains that center of gravity of trunk pass the front of shoulder, pelvis, knee and ankle on stable surface with putting legs apart more than shoulder width. Experimental group had static exercise on 4 by 3 meter, 90 degree of Therapeutic climbing wall. Starting position is that putting arms and legs apart more than shoulder width. In order to compare the effect of it between the groups, independent t-test was used. Results: According to the test result, significant difference between among rectus abdominalis, erector spinae the experimental groups. And external oblique, internal oblique muscle atvity is no significant difference experimental groups between among the control groups was observed. Conclusion: Trunk muscle activation is activated to standing position on the Therapeutic Climbing Wall more than static standing position.

• Journal of International Academy of Physical Therapy Research
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• v.7 no.2
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• pp.1037-1040
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• 2016

This study aims to investigate the effects of ankle foot orthosis(AFO) on the activities of tibialis anterior(TA), soleus(Sol), rectus femoris(RF) and biceps femoris(BF) during stairs descending. The activities of TA, Sol, RF and BF were initially measured while descending 4 stairs without using AFO. The activities of the same muscles were then measured again while descending 4 stairs while using AFO. Wilcoxon signed-rank tests were used to analyze the results in order to examine the differences between the with using AFO and without using AFO. Although the activities of TA, Sol and RF were relatively lower while using AFO than without using AFO, only the differences in Sol and RF activities were significant(p<0.05). The activity of BF was relatively higher while using AFO compared to the activity of BF observed without using AFO. However, difference was not significant(p>0.05). Conclusion of this study was observed since AFO's ground reaction force absorption during stairs descending reduced the need to use So and RF that is related to shock absorption. BF activity was increased with AFO than without during standing forward to correct the trunk stability.

• Journal of Biomedical Engineering Research
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• v.36 no.5
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• pp.235-239
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• 2015

The purpose of this study was to investigate the unstable plate system for the advanced balance ability. 7 male volunteers (age $33.7{\pm}1.2$ years, height $174.7{\pm}3.8cm$, weight $86.0{\pm}3.6kg$, BMI $28.2{\pm}2.0kg/m^2$) performed the partial squat motion on the shape of CAP type(${\cap}$) and BOWL type(${\cup}$) plate system. The range of motion (ROM) and muscle activation were acquired by the motion analysis system and the EMG system. Results of ROMs of the CAP type plate system were shown the widely range of the deviation in the ankle joint on the sagittal plane (sagittal plane - hip joint $10.7^{\circ}$ > $5.4^{\circ}$, knee joint $16.3^{\circ}$ > $6.4^{\circ}$, ankle joint $18.8^{\circ}$ > $6.3^{\circ}$ ; transverse plane - hip joint $3.5^{\circ}$ > $1.8^{\circ}$, knee joint $5.3^{\circ}$ > $3.4^{\circ}$, ankle joint $11.3^{\circ}$ > $5.3^{\circ}$ ; frontal plane - hip joint $0.9^{\circ}$ > $0.5^{\circ}$, knee joint $0.8^{\circ}$ > $0.6^{\circ}$, ankle joint $4.8^{\circ}$ > $3.7^{\circ}$). Muscle activation results of the CAP type plate system were indicated higher in major muscles for balance performance than the BOWL type plate system (vastus lateralis 0.90 > 0.62, peroneus longus 0.49 > 0.21, biceps femoris 0.38 > 0.14, gastrocnemius 0.11 > 0.05). These findings may indicate that the CAP type plate system would expect better effectiveness in perform the balance training. This paper is primary study for developing balance skills enhancement training device.

• Journal of Korean Physical Therapy Science
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• v.29 no.1
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• pp.47-54
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• 2022

Background: Plyometric exercise is an exercise exerting forceful power in a brief period using isotonic activation. It is effective to improve reaction of muscle, agility, endurance and athletics performance. Weight training is an exericse improving muscular strength, endurance and respirating ability applying diversely in frequency and load of exercise Plyometric exercise and Weight training is to facilitate the athletics performance though improving the function of lower limb muscle, there is a difference that Plyometic jump squats is the way to improve agility and Weight training is the way to improve muscular strength. Therefore, it is necessary to know how this difference effects on athletics performance as measuring ankle, ROM, and jumping ability. Design: Randomized controlled trial. Method: This study was conducted with the voluntary participation of 40 university students, who were randomly assigned to jump squat and calf raise groups (n=20 per group). For each subject, we measured the range of motion of the ankle joint before and after exercise, as well as a standing broad jump and vertical jump test performance. We compared the performance indices before and after exercises using paired t-tests, and between groups using independent-samples t-tests. Conclusions: Both jump squat and calf raise exercises improved ankle joint dorsiflexion and plantar flexion, as well as standing broad jump and vertical jump height performance. However, there were no significant differences before versus after exercise, or between exercise types. Although jump squats and calf raises have different purposes, it is thought that, in combination, these exercises improve performance more effectively than either alone, and that such a combined exercise program improves the quality of training in both the general public and athletes in various sports.

• Physical Therapy Korea
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• v.22 no.4
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• pp.8-16
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• 2015

The purpose of this study was to evaluate the effects of mobilization of the sciatic nerve on hamstring flexibility, lower limb strength, and gait performance in patients with chronic stroke. This study was a randomized clinical trial with a crossover design. Sixteen subjects were recruited for this study. The subjects were randomly divided into two intervention groups and underwent either of the following two interventions: sciatic nerve mobilization or static stretching of the hamstring. We assessed hamstring flexibility, lower limb strength, and gait performance using a digital inclinometer, a hand-held dynamometer, and the 10-meter walk test, respectively. Subjects had a 24-hour rest period between each session in order to minimize carryover effects. Measurements for each test were assessed prior to and immediately after the intervention sessions. Using a two-way analysis of variance test with repeated measures, data from the two trials were analyzed by comparing the differences between both techniques. The level of statistical significance was set at .05. Sciatic nerve mobilization resulted in significantly better knee extensor strength (p=.023, from $15.32{\pm}5.98$ to $18.16{\pm}6.95kg$) and knee flexor strength (p=.011, from $7.80{\pm}4.80$ to $8.15{\pm}4.24kg$) in the experimental group than in the control group. However, no significant effects of static stretching of the hamstring were observed on hamstring flexibility from the ankle plantar flexion (p=.966) and ankle neutral positions (p=.210) and on gait performance (p=.396). This study indicated that the sciatic nerve mobilization technique may be more effective in muscle activation of the knee extensor muscle and knee flexor muscle than hamstring static stretching technique in patients with chronic stroke.