• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.6
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• pp.613-619
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• 2017

Recently, the size of container ships has been progressively increasing, and much attention is required for safe navigation in shallow areas such as coastal waters and ports due to increases in draft. It is necessary to understand the characteristics of ship motion not only in still waters but also with waves. Especially in shallow regions, squat due to the vertical movement of the ship can be an important evaluation factor for the safe navigation, and wave drift force acting in the horizontal direction can have a great influence on the maneuverability of a ship. In this study, a numerical simulation using computational fluid dynamics has been performed for the wave exciting force acting in the vertical direction and the wave drift force acting in the horizontal direction for a very large container vessel sailing in shallow zone. As a result, it was found that total resistance in still waters greatly increased in shallow water. Wave drift force was shown to decrease given longer wavelengths regardless of water depth. It was observed that the wave exciting force in shallow water was considerably larger than at other water depths. As wave height against the central part of the ship lowered, the aft side rose.

• Journal of the Korea Society of Computer and Information
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• v.27 no.5
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• pp.215-224
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• 2022

The purpose of this study is to analyze how it affects functional movement and dynamic balance applying Czech get up exercise based on the principle of motor development of child for office worker women in 30s and 40s. Through random allocation, an Czech get up exercise group(n=15) and a control group(n=14) were formed to apply exercise for 12 weeks, 3 times a week, and 60 minutes a day, and the control group maintained daily life at the same period. As a result of the study, showed that Deep squat(p<.05), Hurdle step(p<.01), In-line lunge(p<.05), Trunk stability push-up(p<.001), Rotary stability (p<.01), Total score(p<.001), were significantly in the Czech get up Group, and Dynamic Balance of Lower Extremity(p<.001), Right Dynamic Balance of Lower Extremity(p<.001) were also significantly in the Czech get up Group. In conclusion, it is thought that Czech get up exercise based on the principle of motor development of child will have a positive effect on the functional movement and dynamic balance in office women, thereby increasing work efficiency as well as healthy life.

• Korean Journal of Applied Biomechanics
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• v.29 no.3
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• pp.185-196
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• 2019

Objective: The aim of this study was to suggest correct and effective way of squat through biomechanical analysis variables on the change of the toe-out angle. Method: 7 high school male weightlifter (age: $17.57{\pm}0.53yrs$, height: $174.0{\pm}3.93cm$, weight: $81.0{\pm}9.17kg$, 1RM: $164.29{\pm}20.7kg$) participated in this study. Results: Angle of the hip joint at E2 was smaller than toe-out angle was in $20^{\circ}$ than in $0^{\circ}$ (p<.05). Angular velocity of the foot joint at E1 and E3 was quicker that in $10^{\circ}$ than in $30^{\circ}$ (p<.05). Anterior-posterior stability index was greater that toe-out angle was in $30^{\circ}$ than in $0^{\circ}$ (p<.05). In average iEMG of flexion phase, VM of right, left leg showed high activity at toe-out angle $30^{\circ}$. In average iEMG of flexion phase, extension phase and in peak iEMG, RF of right leg, VM and VL of left leg showed high activity at all of the toe-out angles. In average iEMG of flexion phase, extension phase and in peak iEMG, all of the muscles activity of right leg showed high in $10^{\circ}$ and low in $0^{\circ}$, $30^{\circ}$. Conclusion: It is judged that setting the toe-out angle $10^{\circ}$ in squat help to efficiently use muscles and ensure stability.

• Korean Journal of Applied Biomechanics
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• v.30 no.4
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• pp.311-319
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• 2020

Objective: The purpose of this study was to examine of this study is to study the effect of squat exercise on muscle activation in a sling device using various types of ropes and to propose an effective sling exercise method for strengthening the lower extremity strength. Method: 20 adult male subjects (age: 25.2±2.4 yrs, height: 176.5±3.2 cm, weight: 77.2±4.5 kg) participated in this study. In the experiment, a total of four squats were conducted: squat [SE], sling squat using inelastic rope [IR], sling squat using elastic rope [ER], and sling squat using two elastic ropes [TER]. Squats were performed 5 times for each condition, and a 60-second break was given for each condition to minimize muscle fatigue. The activation of biceps brachii, rectus femoris, gastrocnemius, and tibialis anterior muscles was measured. Results: It was found that the activation of all muscles was the lowest during the squat exercise [SE]. During the sling squat using inelastic rope [IR], the muscle activation of the biceps brachii was the highest. During the sling squat using elastic rope [ER], the activation of the rectus femoris, gastrocnemius, and tibialis anterior muscles was found to be the highest. In the sling squat using two elastic ropes [TER], most of the muscle activation was similar to that of the sling squat using inelastic rope [IR]. Conclusion: Our results of the experiment, it was found that sling squat exercise using elastic rope had a positive effect on the activation of all muscles. It is thought that performing a squat exercise under moderate weight load and unstable conditions, such as sling squat exercise using elastic rope, can increase the muscle activity of the lower limbs and perform more effective exercise effect than performing a conventional squat exercise under stable conditions. In the future, if research is conducted not only on adult men, but also on various ages and patients, it will be able to provide positive help in improving balance, stability and stamina through squat exercise.

• Journal of The Korean Society of Integrative Medicine
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• v.10 no.2
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• pp.169-176
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• 2022

Purpose : The purpose of this study is to investigate the effect of squat, bracing and aerobic exercise on lung function, which is known to be effective for strength training, on lung function. Methods : The study was conducted with 33 students from Busan K university. Eleven students were assigned to squats, bracing, and aerobic exercise, six weeks three times a week. In order to measure lung activity, pony Fx manufactured the change amount of FVC (forced vital capacity), FEV₁ (Forced expiratory volume at one second), and FEV₁/FVC % (forced vital capacity/forced expiratory volume at one second) was analyzed after inputting the information of experimental group A and B controls. As a method of measurement, the difference between the three groups was analyzed using repeated ANOVA. Results : As a result of analyzing the effects of squat, bracing, and aerobic exercise for 6 weeks, all values of FVC, FEV₁, FEV₁/FVC % were increased from 0 weeks to 6 weeks except FEV₁/FVC %. There was no significant difference in FVC from week 3 to week 6. In the squat, bracing, and aerobic exercise, the changes in spirometry showed that the FVC, FEV₁, and FEV₁/FVC % values in bracing exercise were significantly increased with time than before exercise. As a result of analyzing the changes in the spirometry of squat, bracing, and aerobic exercise, the FVC, FEV₁, FEV₁/FVC % values in the squat exercise showed statistically significant difference according to the period, but the lowest increase among the three groups. Conclusion : In conclusion, aerobic, bracing and squat exercises all had a significant impact on improving lung function. Therefore, even without aerobic exercise, squat or bracing exercise alone can be expected to improve lung function.

• Korean Journal of Applied Biomechanics
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• v.34 no.2
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• pp.53-62
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• 2024

Objective: The purpose of this study was to analyze the differences in kinematic factors according to stretching treatment, myofascial release treatment, and static stretching treatment conditions during squat. Method: Twelve males with resistance training experience participated in this study. Participants performed squats without treatment (Pre-Test), and performed squats after treatment with the myofascial release technique (MRT) and static stretching (SS) on different days (post-test). Squat movements were captured using eight motion capture cameras (sampling rate: 250 Hz), and the peak joint angles of the ankle, knee, hip, and pelvis were calculated for each direction. One-way repeated ANOVA and Bonferroni post hoc analyses using SPSS 27 (IBM Corp. Armonk NY, USA) were used to compare the peak joint angle of the lower extremity joints and pelvis among the normal condition (squat without treatment), MRT condition (squat after MRT treatment) and SS condition (squat after static stretching). The statistical significance level was set at .05. Results: It was observed that the maximum ankle joint flexion angle during squats was statistically reduced under conditions of myofascial release and static stretching (p<.05), in comparison to the scenario where no stretching was performed. Furthermore, static stretching was found to enhance the maximum hip flexion angle during squat (p<.05), whereas the myofascial release stretching technique resulted in the minimal posterior pelvic tilt angle (p<.05). Conclusion: Employing myofascial release stretching as a preparatory exercise proved to be more efficacious in maintaining body stability throughout the execution of high-intensity squat movements by effectively managing the posterior tilt of the pelvis, as opposed to foregoing stretching or engaging in static stretching.

• Korean Journal of Applied Biomechanics
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• v.34 no.1
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• pp.25-33
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• 2024

Objective: The purpose of this study was to compare the lower extremity muscle activity and knee joint load according to movement speed conditions during the barbell back squat. Method: Nine males with resistance training experience participated in this study. Participants performed the barbell back squat in three conditions (Standard, Fast, and Slow) differing movement speed. During the barbell back squat, muscle activity of the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris long head (BFL), semitendinosus (ST), gluteus maximus (GM), gastrocnemius (GCN), and tibialis anterior (TA) was collected using an 8 channel wireless EMG system. The peak flexion angle of the lower extremity joints and the peak resultant joint force in each direction of the knee joint were calculated using eight motion capture cameras and ground reaction force plates. This study was to used the Friedman test and the Wilcoxon signed rank test, to compare lower extremity muscle activity and peak resultant joint force at knee joint according to movement speed conditions during the barbell back squat, and the statistical significance level was set at .01. Results: In the downward phase of the barbell back squat, the RF and TA showed the higher muscle activity in the fast condition, and in the upward phase, RF, VL, VM, BFL, ST, GM, and TA showed the higher muscle activity in the fast condition. As a results, analyzing of the load on the knee joint, in the downward phase, and in the upward phase, the higher peak compressive force of the knee joint was showed in the fast condition. Conclusion: The barbell back squat with fast movement speed was more effective due to increased muscle activity of lower extremity, but one must be careful of knee joint injuries because the load on the knee joint may increase during the barbell back squat with fast movement speed.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.6
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• pp.539-547
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• 2014

Ship squat is a well known phenomenon, which means an additional sinkage and a change of trim when a ship sails in shallow water. As a series of ship squat study, a HPMM(Horizontal Planar Motion Mechanism) test of KVLCC2 model ship to measure a sinkage and a trim in shallow water was conducted. Additionally a CFD(Computational Fluid Dynamics) analysis was carried out to simulate fluid flows around the ship surface. A change in ship speed, drift angle at three depth conditions(H/T = 1.2, 1.5 & 2.0) is considered for comparing these results. As a result, an increase of the ship speed and the drift angle caused an increase in ship squat in EFD(Experimental Fluid Dynamics), and created a lower pressure on the ship bottom area in CFD. Lastly the sinkage results of KVLCC2 by EFD and CFD are compared to results by three empirical formulas. The tendency of sinkage by EFD and CFD is similar to the results of empirical formulas.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.26 no.1
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• pp.47-54
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• 2020

Background: This study examined the changes in the leg muscle activities of 30 healthy subjects according to different pressures caused by isometric hip adduction during squat exercise. Methods: With their knee flexed at 60°, the subjects performed isometric hip adduction with a pressure of 0, 20, 40, and 60mmHg. Surface electromyography was used to measure their muscle activities. Changes in the activities of the muscles, such as the gluteus maximus (GMAX), Gluteus medius (GM), vastus medialis oblique (VMO), vastus lateralis oblique (VLO), biceps femoris (BF), and Tensor fasciae latae (TFL) muscles, were analyzed. Results: The activities of the VMO, VLO, GM, BF, and GMAX muscles were significantly different after exercise compared to that before exercise (p<.05). The activities of all the leg muscles measured were highest at a pressure of 60mmHg during isometric hip joint adduction. Conclusion: The pressure produced by isometric hip joint adduction during squat exercise increased the leg muscle activities of the subjects. These results will provide basic data on effective squat exercise to alleviate knee joint diseases.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.22 no.1
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• pp.9-15
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• 2016

Background: This study was conducted to investigate the effects of unstable modified wall squat exercises accompanied by abdominal drawing-in on the gait variables of healthy adults. Methods: The total number of subjects was 30, and 15 were randomly placed in the training group (TG) and 15 in the control group (CG). To determine the gait variables of TG and CG, step length difference (SLD) stance phase difference (STPD), swing phase difference (SWPD), single support difference (SSD), and step time difference (STD) were measured using OptoGait, a gait analysis system. Results: When the pre-intervention and post-intervention results of TG and CG were compared, statistically significant differences in SLD, STPD, SWPD, SSD and STD of TG were seen. Conclusion: Unstable modified wall squat exercises accompanied by abdominal drawing-in might help reduce the deviation between left and right gait variables during walking.