• The Journal of Korean Physical Therapy
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• v.35 no.5
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• pp.125-131
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• 2023

Purpose: This study examined the acute effects of static and dynamic stretching on the flexibility of the hamstring, dynamic balance ability, and function of the lower extremities in healthy adults. Methods: Thirty participants were assigned randomly to three groups: static stretching group (SSG), basic dynamic stretching group (BDSG), and 5 sec dynamic stretching group (5DSG). SSG performed three sets of 30 seconds of static stretching. BDSG performed a single-leg deadlift (SLD) at the same time as SSG, and 5DSG performed SLD held for five seconds. Hamstring flexibility, dynamic balance ability, and lower extremity function were evaluated before and after intervention. Results: The hamstring flexibility significantly improved in all groups (p<0.05). The dynamic balance ability improved significantly after intervention in all groups except BDSG in the anterior direction (p<0.05). There were significant differences in the posterolateral and posteromedial direction in all groups. The function of the lower extremity showed significant improvement over time only in BDSG (p<0.05). Conclusion: This study suggested that basic dynamic stretching and 5 sec dynamic stretching positively affect the hamstring flexibility, dynamic balance ability, and lower extremity function. Therefore, it is recommended to include dynamic stretching in a program for improving the hamstring flexibility, dynamic balance ability, and the lower extremity function. In addition, it is recommended to apply it at different times depending on the purpose.

• Structural Engineering and Mechanics
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• v.13 no.4
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• pp.437-453
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• 2002

In this paper, dynamic stiffness and flexibility for circular membranes are analytically derived using an efficient mixed-part dual boundary element method (BEM). We employ three approaches, the complex-valued BEM, the real-part and imaginary-part BEM, to determine the dynamic stiffness and flexibility. In the analytical formulation, the continuous system for a circular membrane is transformed into a discrete system with a circulant matrix. Based on the properties of the circulant, the analytical solutions for the dynamic stiffness and flexibility are derived. In deriving the stiffness and flexibility, the spurious resonance is cancelled out. Numerical aspects are discussed and emphasized. The problem of numerical instability due to division by zero is avoided by choosing additional constraints from the information of real and imaginary parts in the dual formulation. For the overdetermined system, the least squares method is considered to determine the dynamic stiffness and flexibility. A general purpose program has been developed to test several examples including circular and square cases.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.629-634
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• 2000

Dynamic behavior of an automatic dynamic balancer is analyzed by a theoretical approach. Using Lagrange's equation, we derive the non-linear equations of motion for an automatic dynamic balancer equipped in a rotor with the bending flexibility with respect to the rectangular coordinate. Considering the rotor bending flexibility we analyze out-of-plane vibrations as well as in-plane vibrations of the automatic dynamic balaner. The time responses are computed from the non-linear equations by using a time integration method. We also investigate the effect of rotor flexibility on the behavior of the automatic dynamic balancer

• Physical Therapy Rehabilitation Science
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• v.11 no.2
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• pp.259-268
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• 2022

Objective: The purpose of this study was to measure the immediate effect of hip hinge exercise stretching on hamstring flexibility, pelvic tilting angle, proprioception, and dynamic balance in individual with tightness of the hamstring. Design: A randomized controlled trial. Methods: A total of 35 healthy young adults (27 males, 8 females) volunteered for this study and randomly divided into three groups (Hip hinge exercise stretching group, passive stretching group, and PNF stretching group). The hamstring flexibility, pelvic tilting angle, knee joint proprioception, dynamic balance was conducted for 3 times. In order to evaluate the hamstring flexibility, the active knee extension test was performed. Forward bending test was performed to examine pelvic tilting angle.The proprioception was tested by the joint position sense test and dynamic balance was evaluated by Y balance test. Results: The hamstring flexibility, pelvic tilting angle and dynamic balance were significantly improved between three groups before and after intervention (p<0.05). Dynamic balance was significantly difference between the three groups in the posterolateral direction (p<0.05). Conclusions: This study result showed that hip hinge exercise stretching was the most effective method for increasing hamstring flexibility, pelvic tilting angle and dynamic balance. In addition, it is necessary to study whether hamstring stretching is effective in low back pain patient with hamstrings tightness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1125-1130
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• 2001

Dynamic behaviors of an automatic dynamic balancer are analyzed by a theoretical approach. Using the polar coordinates, the non-linear equations of motion for an automatic dynamic balancer equipped in a rotor with the bending flexibility are derived from Lagrange equation. Based on the non-linear equation, the stability analysis is performed by using the perturbation method. The stability results are verified by computing dynamic response. The time responses are computed from the non-linear equations by using a time integration method. We also investigate the effect of the bending flexibility on the dynamics of the automatic dynamic balancer.

• Wind and Structures
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• v.16 no.1
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• pp.93-115
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• 2013

This paper describes a study of the influence of a dynamically flexible building structure on pressures inside and net pressures on the roof of low-rise buildings with a dominant opening. It is shown that dynamic interaction between the flexible roof and the internal pressure results in a coupled system that is similar to a two-degree-of-freedom mechanical system consisting of two mass-spring-damper systems with excitation forces acting on both the masses. Two resonant modes are present, the natural frequencies of which can readily be obtained from the model. As observed with quasi-static building flexibility, the effect of increased dynamic flexibility is to reduce the first natural frequency as well as the corresponding peak value of the admittance, the latter being the result of increased damping effects. Consequently, it is found that the internal and net roof pressure fluctuations (RMS coefficients) are also reduced with dynamic flexibility. This model has been validated from experiments conducted using a cylindrical model with a leeward end flexible diaphragm, whereby good match between predicted and measured natural frequencies, and trends in peak admittances and RMS responses with flexibility, were obtained. Furthermore, since significant differences exist between internal and net roof pressure responses obtained from the dynamic flexibility model and those obtained from the quasi-static flexibility model, it is concluded that the quasi-static flexibility assumption may not be applicable to dynamically flexible buildings. Additionally, since sensitivity analyses reveal that the responses are sensitive to both the opening loss coefficient and the roof damping ratio, careful estimates should therefore be made to these parameters first, if predictions from such models are to have significance to real buildings.

• PNF and Movement
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• v.7 no.2
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• pp.11-20
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• 2009

Purpose : The purpose of this study is to find out which method is efficient to enhance the flexibility of lower back between PNF(Proprioceptive Neuromuscular Facilitation), static and dynamic stretching. Methods : Subjects were 30 young people between the ages 17 and 19. They were randomly divided into three groups; static group(n=10) performed a static stretching, dynamic group(n=10) performed a dynamic stretching, and PNF group(n=10) performed a PNF stretching. Intervention was provided 5 days per week for 4 weeks. For each case, Trunk flexion forward, trunk flexion backward, trunk left lateral bending, trunk right lateral bending, trunk flexion forward a measuring instrument and tapeline were performed to measured the flexibility of lower back at different times(before starting the exercise, after 4 weeks). Results : The results of the study reveal that the lower back flexibility was a statistically significant difference in all groups(p<.05). There was statistically significant difference between PNF group and static group, PNF group and dynamic group. Conclusion : The finding indicated that PNF may be preferred technique for improving flexibility, and that flexibility training results in an increased consistency of flexibility scores.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.2
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• pp.80-86
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• 2002

Previous method of computer simulation to predict the dynamic response of a vehicle has been based on the assumption that vehicle structure is rigid. If the flexibility of the vehicle structure becomes too large to ignore, rigid body assumption will no longer give good estimation of the dynamic characteristics. Therefore, in order to predict more precise vehicle dynamic characteristics, flexible multi-body dynamic analysis of a vehicle is necessary. This paper investigates dynamic characteristics of vehicle systems with flexible frames numerically. Joint reaction forces, vertical accelerations, pitch accelerations are analyzed for the vehicle systems with various flexible frames using multi-body dynamic analysis code and finite element analysis code.

• Journal of Korean Clinical Health Science
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• v.4 no.3
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• pp.644-651
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• 2016

Purpose. This study was to investigate the change of dynamic balance and flexibility for normal group, using skater and sprinter exercise program of PNF pattern. Method. In this study it was participated twenty-one subjects. Experimental group worked skater and sprinter pattern exercise with Thera-band or without Thera-band each 40 times. Evaluation of dynamic balance and flexibility(using the Functional Reach Test and Fingertrip To Floor Test) were carried out before and after the exercise. Result. In dynamic balance it was observed to significant change except first measure and flexibility was observed to all measures significantly(p<.05). Conclusion. Skater and Sprinter pattern exercise is effective to improve for dynamic balance and flexibility. However, the experimental group is small sample size of normal adult. therefore, It should be carefully considered in generalizing the results to disabled person.

• Journal of International Academy of Physical Therapy Research
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• v.11 no.2
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• pp.2042-2051
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• 2020

Background: Many trials have been conducted the methods and types of intervention of form rollers, but no research has been done yet that mixes the methods and types of intervention. Objectives: To analyze the effects of myofascial release on the improvement of range of motion (ROM), flexibility, pain pressure threshold, and balance. Design: Randomized controlled trial. Methods: All subjects measured ROM, flexibility, pressure pain threshold, and dynamic balance by pre-test. After pre-test, subjects were randomized that static-vibration foam rolling group (n=12), dynamic-vibration foam rolling group (n=12), general foam rolling group (n=12). For the intervention, 3 sets of 90 seconds were applied to each group, and rest time was set to 60 seconds between sets. In the post-test and follow-up test after 10 minutes, all three groups were measured the ROM, flexibility, pressure pain threshold, and dynamic balance. Results: The results of comparing ROM, flexibility, pressure pain thresholds, dynamic balance ability appeared higher significant difference in the pre-post-10 minutes follow up test in comparison between time in the intragroup (P<.001). As a result of comparing the change of pre-post-10 minutes follow up, static vibration foam rolling showed higher significant difference compared to control groups (P<.001). Conclusion: Through this study, when foam rolling is applied within the same intervention time, static foam rolling can be expected to have a better effect than the existing dynamic foam rolling as well as vibration foam roller can expect better effect than general foam rolling.