• The Korean Journal of Pharmacology
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• v.26 no.2
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• pp.113-120
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• 1990

Influences of trigger calcium on myocardial contraction from several sources were investigated on the frequency reduction-induced changes of contraction in rat left atria driven by electrical field stimulation. Rat atria elicited characteristic three phase-changes according to frequency reduction: the first rapid rise in twitch tension, the second transient fast decrease in tension and the third maintenance of twitch tension at about 200% of resting tension during high frequency. Caffeine treatment enormously suppressed the frequency reduction-induced twitch tension increase. The atrial contraction during high frequency vanished after verapamil treatment. But, during low frequency, atrial contraction revived in the presence of verapamil. Ouabain treatment and sodium depletion in superfusing solution abolished the characteristic second phase with slow frequency. These results suggest that slow calcium channel is an indispensable calcium entry route and calcium release from sarcoplasmic reticulum is an major source for trigger calcium in cardiac contraction. And sodium-calcium exchange has a modulatory roles in the regualtion of trigger calcium according to the changes of intracellular sodium concentration.

• Korean Journal of Applied Biomechanics
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• v.21 no.1
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• pp.77-83
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• 2011

In dance sport, hip movement is the most basic and essential technique, connecting the body movements to make the body move organically, and providing an overall balance of body movements. From that perspective, this study focused on the Cucarachas movement, representing a series of efficient hip movements in the center of gravity. For the purposes of this study, 4 dance sport participants who had won prizes at international contests were selected in order to analyze such variables as the radius of gyration (shift) on the hips and the shift of the center of gravity when scapula depression was performed and when it was not. To examine differences in these kinematic variables, a paired t-test was conducted, resulting in the following findings: First, the dancers were found to be able to control scapula depression, and a significant difference was observed in the vertical axis(Z) between the times when scapula depression was performed and when it was not. Second, when scapula depression was performed, shifts in the left-right axis(X) and anterior-posterior axis(Y) were found; the left-right axis showed a greater difference than the anterior-posterior axis. Third, scapula depression was found to have an influence on the shift to the left-right axis(X) of the center of gravity.

• Korean Journal of Applied Biomechanics
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• v.19 no.4
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• pp.719-728
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• 2009

In this study, a training program was conducted to improve the performance of the basic movement of the basket-to-handstand mount. After completion of the training program, the kinematic comparison of the before and after effects were investigated to provide scientific data about this technique. It is recommended that during P1, the center of body mass at the back should push the hip joint to flex quickly, and the shoulder joint should be maintained at a maximum angle. During P2, the body's center of mass must be accelerated so as to create enough momentum to rise efficiently for this, quick extension of both the hip and the shoulder is required. For safety during P3, it is advised that the speed upwards must be increased and that the hands, shoulders, and hip joint must be extended, as in the posture of a handstand. These results stress to coaches the importance of the bodies speed during the ascent in the motion.

• Korean Journal of Applied Biomechanics
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• v.14 no.1
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• pp.161-172
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• 2004

본 연구의 목적은 각기 다른 수직 점프 동작 시 근육의 길이와 근육의 수축속도 변화를 비교 분석하는데 있다. 피험자의 운동학적 변인들을 분석하기 위해 2대의 고감도 카메라를 (60 Hz, Panasonic AG455) 사용하여 점프 동작을 촬영하였다. 대퇴직근, 내측광근, 외측광근, 중간광근, 대퇴이두근(단두), 내측과 외측 비복근의 길이와 근수축 속도는 Brand et al. (1982)에 의해 제시되어진 하지근 기시 정지점의 3차원 좌표값과 동작분석을 통한 하지 분절간의 회전 및 변환행렬을 사용하여 측정되어졌다. 일반적인 근육 길이와 수축속도의 변화 형태는 각기 다른 점프간에 매우 유사한 형태를 보였다. 상승기 초기에 대퇴사두근의 길이가 최대인것으로 나타났으며, 이에 반해 대퇴이두근과 내외측 비복근은 공중 동작이 발생하는 시점에 근의 길이가 최대인 것으로 나타났다. 근육의 길이 변화 범위는 대퇴직근이 35.9에서 47.5 cm, 외측광근이 29.4에서 38.8 cm, 중간광근이 31.5에서 38.0 cm, 내측광근이 30.9에서 38.6 cm, 대퇴이두근이 21.3에서 39.1 cm, 외측비복근이 31.4에서 33.5 cm, 내측비복근이 30.5에서 33.2 cm인 것으로 나타났다. SQ와 CMJ에서는 대퇴사두근의 최대 단축성 수축 속도와 대퇴이두근과 내외측 비복근의 최대 신장성 수축이 공중동작이 발생하기 바로 전에 이루어졌다. 대퇴사두근의 최대 신장성 수축과 대퇴이두근과 내외측 비복근의 최대 단축성 수축은 일반적으로 피험자가 착지하는 순간에 발생되어졌다. 그러나 HJ와 DJ에서는 대퇴사두근의 최대 신장성 추축과 대퇴이두근과 내외측 비복근의 최대 신장성 수축이 하강기 초반에 발생되어졌다.

• The Korean Journal of Nuclear Medicine
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• v.33 no.1
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• pp.40-48
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• 1999

Purpose: The sensitivity of ST-depression in the electrocardiogram during exercise is influenced by the level of efforts. However, unlike the prevalence of ST-depression on exercise ECG, the degree of exercise is reported to do not influence the diagnostic ability of myocardial perfusion scan. Furthermore, the relation between the prevalence of myocardial ischemia and effort is still controversial. We evaluated the effect of the degree of exercise on the ability of SPECT imaging to detect coronary artery stenosis. Materials and Methods: The patient population was comprised of 111 patients (73 men and 38 women, mean age 56 years) who underwent an exercise test in conjunction with Tc-99m MIBI and cardiac catheterization within 3 months apart each other. The degree of exercise was classified into four groups according to the percentage of maximal predicted heart rate. The sensitivity and specificity was compared between each group. Results: The overall diagnostic sensitivity was significantly higher with Tc-99m MIBI SPECT than exercise ECG. The specificity was not significantly different between two tests. Sensitivity and specificity of Tc-99m MIBI was not different between four groups. Sensitivity for individual coronary stenosis seemed to be lower in subjects who had premature termination of exercise due to early appearance of ST depression. Conclusion: These results suggest that the overall diagnostic sensitivity of Tc-99m MIBI myocardial perfusion SPECT is not significantly affected by the degree of exercise in stable patients undergoing symptom-limited treadmill exercise testing. Myocardial perfusion SPECT imaging should be added to routine exercise stress testing for the detection of coronary artery disease.

• Journal of Astronomy and Space Sciences
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• v.25 no.2
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• pp.167-180
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• 2008

The resolution of Earth images taken from a satellite has close relation with satellite's altitude. If a satellite has lower altitude, it gets a picture having better resolution. However the satellite will be exposed to heavier air drag and will spend more fuel to maintain its altitude for a desired mission. Therefore, in this study, the required fuel to maintain very low earth orbit(LEO) with severe air drag is analyzed using optimization method such as collocation method. The required fuel to maintain the low altitude has significantly increased as the mission altitude is lowered and the solar activity is maximized. This study also shows that the fuel reduced by increasing the period of the satellite maneuver is very small, and that slightly increasing the satellite's mission altitude is much effective in reducing the amount of fuel to maintain its altitude. The calculated fuel to maintain very low earth orbit in this study would give useful information in planning the budget of fuel and cost for LEO satellites.

• Journal of Korea Entertainment Industry Association
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• v.13 no.4
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• pp.369-375
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• 2019

This study looked at the effects of teratainment taping and footpad exercise on the improvement of flat foot in a university student. We divided it into flexible flat foot taping group(n=13), flexible flat foot exercise group(n=14), rigid flat foot taping group(n=12), rigid flat foot exercise group(n=13) through a navicular drop test. After one hour's application of teratainment taping and footpad exercise, the height change of navicular, balancing ability and postural stability were evaluated. Change in the height of the navicular was measured before and after intervention, and the balancing ability was measured timed up & go test, and the postural stability ability was evaluated for stability limits in shoulder-width double leg stance, narrow base double leg stance, tandem stance. According to result, there was a statistically significant difference in the left and right foot of the flexible tapping group, right foot of the flexible tapping group, right foot of the rigid tapping group in the change in the height of the navicular in comparison pre- and post- intervention(p<0.5). There were no statistically significant differences in pre- and post- intervention comparisons intragroup and intergroup in balancing ability. There was a statistically significant difference in flexible flat foot exercise group and rigid flat foot taping group in tandem stance in comparison pre- and postintervention in the postural stability(p<0.5). And there was a statistically significant difference in tendem stance of the flexible flat foot exercise group compared to the rigid flat foot exercise group(p<0.5). The results of this study show that teratainment taping and footpad exercise have a significant effect on the improvement of flat foot in adults. Therefore, it is recommended to apply teratainment taping and footpad exercise to improve flat foot.

• Journal of Digital Convergence
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• v.13 no.8
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• pp.495-502
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• 2015

The purpose of this study was to investigating the effect of taping knee by testing the difference on kinetic variables of lower extremity when speed skating athletes jump on one leg. The results were as follows. The height of jumping after taping was higher, but the vertical height was not different according to taping. On take-off(TO), the horizontal and anterior-posterior maximum impulse force were decreased while the vertical maximum impact force was increased after taping. On landing(LD), the anterior-posterior maximum impulse force was decreased but the horizontal and vertical maximum impulse force were increased. TO, the impulse showed low after taping and the impulse dropped largely LD. The knee's moment of extension, eversion were reduced after tapping TO. LD, the flection moment of knee was decreased, but the inversion moment was increased after tapping. This study implies that the knee tapping helps injury prevention and performance enhancement, sports medicine convergence are needed.

• Korean Journal of Applied Biomechanics
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• v.15 no.3
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• pp.51-59
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• 2005

To examine the influence of aging on the mechanism of muscle fatigue, we compared the magnitude of central and peripheral fatigue in young and old women before, during and after a sustained submaximaI isometric contraction of elbow flexor muscles. Twelve women (6 young. $20.7{\pm}1.2$ years and 6 old, $68.8{\pm}29$ years) performed a contraction at 20% of maximal voluntary contraction (MVC) torque with their non-dominant arm. The old women were weaker than the young women, however their endurance time for the 20% contraction was longer compared with the young women ($1822{\pm}444$ vs. $1061{\pm}678$ sec, P <. 05). Both groups had a similar reduction in voluntary activation ratio (VA) during and after the fatiguing contraction. However, the old women showed much greater variability in VA before and after the contraction ($91.61{\pm}4.54%$ and $76.70{\pm}19.55\;%$ range of $79{\sim}99$ to $87{\sim}99%$ respectively) compared with the young women ($95.71{\pm}1.86\;%$ and $83.46{\pm}7.57\;%$ range of $39{\sim}75$ to $69{\sim}90%$, respectively). Furthermore, the EMG activity of the elbow flexor muscles and triceps brachii was greater for the old women compared with the young women throughout the fatiguing contraction, indicating different activation strategies with age. Indices of peripheral fatigue including twitch properties, showed that fatigue within the muscle was more rapid for the young women compared with the old women. These results suggest that although old women are weaker than young women, they have greater endurance due to mechanisms within muscle. Furthermore, old women showed great variability in their ability to optimally activate all muscle fiber compared with young women for an isometric contraction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.1-7
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• 2012

This paper introduces the mechanical design, fabrication, and control of a biomimetic fish robot whose driving motions resemble a real fish's flexibility and movement. This robot uses two motors create flexible movement like that of a fish. Several schemes, such as neutral buoyancy, fast underwater swimming, and direction changes, are introduced. The tail of the fish robot is made of a polymer material for flexible movement. The interior of the tail contains a joint and a wire. A sine wave command was applied to the tail to produce motion resembling a real fish swimming, and a buoy control device was installed. The up and down motion of the robot fish was controlled using this device.