• The Journal of Korean Physical Therapy
• /
• v.27 no.4
• /
• pp.196-200
• /
• 2015

Purpose: The purpose of this study was to examine the muscle activity of the trunk muscles during balance exercises on a stable and unstable surface in patients with stroke. Methods: Thirteen subjects (8 males, 5 females) with stroke were enrolled in the study. Muscle activity was recorded using surface EMG electrodes from the affected side of the erector spinae, external oblique, and internal oblique muscles. The exercise was performed under three conditions. For the first condition for balance exercise, subjects were instructed to sit on an exercise mat with legs extended. The second condition was to sit with legs extended, with a balance pad under their buttocks. The third condition was to sit with legs extended, have a balance pad under the buttocks and a balance cushion under the lower legs. Results: This study showed significant differences in EMG activities during both arm lifting exercise and weight shifting exercise between conditions. This study showed that the EMG activities of the erector spinae, external oblique, and internal oblique muscles were significantly higher when the trunk exercise was performed using the balance pad with balance ball than when using the stable surface. Conclusion: In conclusion, performing balance exercises using an unstable surface is a useful method for facilitating trunk-muscle strength and hence trunk stability.

• Tunnel and Underground Space
• /
• v.5 no.2
• /
• pp.104-113
• /
• 1995

Shear strength of the discontinuity on which the pre-failure of rock slope was occurred during surface excavation was measured through the direct shear test using core samples obtained in-situ. Internal friction angle was increased as the roughness of discontinuity surface(JRC) was increased. Results of the tilt test using core samples of higher JRC also showed very similar trend as those of the direct shear test. When the samples replicated from natural cores were used int he tilt test, results of friction angles showed almost perfect continuation of the residual friction angles from the direct shear test. However, when the gouge material existed in the discontinuity the internal friction angle strongly depended upon the rate of filling thickness to the height of asperity irrespective of the JRC. Based on the results of both direct shear test and tilt test internal friction angle and cohesion of discontinuity, which reflect the in-situ conditions fo pre-sliding failure and also can be used for the optimum design of support system, were assessed. Two kinds of support measures which were expected to increase the stability of rock slope were considered; lowering of slope face angle and installation of rock cable. But, it was found that the first method might lead to more unstable conditions of rock slope when the cohesion of discontinuity plane was negligibly low and in that case the support systems of any kind which could exert actual resisting force were needed to ensure the permanent stability of rock slope.

• Physical Therapy Korea
• /
• v.27 no.4
• /
• pp.250-256
• /
• 2020

Background: Unstable surface-based core training can significantly enhance core strength, but no studies have compared the effects of balance pad- and sling-assisted exercises. Objects: To study the effects of unstable surface-based balance pad- and sling-assisted core strength exercises on muscle activity. Methods: Twenty male students aged 20-25 years participated in this study. The effects of three types of core strength exercises, performed with a sling or balance pad, on the activities of three muscles, i.e., the right musculus obliquus externus abdominis (EO), right erector spinae (ES), and right gluteus maximus (GM), were examined. Results: 1) In the glute bridge exercise, the percentage of maximum voluntary contraction of the EO, ES, and GM were significantly different between the balance pad- and sling-assisted exercises. The relative contribution of the ES and GM activities to all muscle activity were not significantly different between the two training types, whereas that for EO showed a significant difference. 2) There was no significant difference in the percentage value of maximum voluntary contraction (%MVC) among the EO, ES, and GM during the "leg-lifting with flat support" exercise, and there were no significant difference in the relative contributions between the two training types. 3) In the "side bridge leg separation exercise", the %MVC of the ES, EO, and GM were significantly different between the two training types. Conclusion: Sling training for core muscles was generally better than balance pad assist training. The majority of physiotherapy patients require core training. Our results could guide physiotherapists in the choice of targeted exercises for these patients.

• Physical Therapy Korea
• /
• v.17 no.4
• /
• pp.16-25
• /
• 2010

The aim of this study was to determine the muscle activity of the abdominalis and erector spinae during bridging and unilateral bridging exercises on the firm surface, the sir-fit, and the foam roll. Eighteen healthy young subjects were recruited for this study. Surface electromyographic (EMG) activities were recorded from the both sides of the rectus abdominalis, external obliques, internal obliques, and erector spinae muscles during bridging and unilateral bridging-exercises. A one-way repeated analysis of variance was used to compare the EMG activity of each muscle according to the support surface condition. Differences in the EMG activities between the bridging and unilateral bridging exercises, and between the right and left side were assessed using a paired t-test. The study showed that the EMG activities of all of the muscles were significantly higher when the bridging exercise was performed using the foam roll or sit-fit than on the firm surface. The EMG activities of the right rectus abdominis, right external obliques, the right internal oblique, and both erector spinae were significantly higher during unilateral bridging ex exercise using the foam roll or the sit-fit than on the firm surface. The EMG activities of all of the muscles were significantly higher during the unilateral bridging exercise than during the bridging exercise. Based on these finding, performing the unilateral bridging exercise using the sit-fit or the foam roll is a useful method for facilitating trunk muscle strength and lumbar stability.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
• /
• v.29 no.1
• /
• pp.69-79
• /
• 2023

Purpose: This study examined the possibility of muscle strength and balance ability improvement through coordinative locomotor training by making a difference on the supporting plane using a resistance band for adolescent athlete of Taekwondo sparring athletes. Methods: A total of 22 students were selected as to the participants of the study, and 11 students each were randomly assigned to the control and experimental group for coordination locomotor training using a resistance band on stable and unstable supporting surface. The training period was 60 min, three times a week, for 8 weeks in total. To confirm changes on balance ability of each participant, balance assessment devices are used. Moreover, surface electromyography was used for muscle strength evaluation. Results: After coordinated locomotor training using a resistance band for 8 weeks, the difference bet ween groups was not significant; Also, the improvement in strength was no significant difference in other muscles in the between groups, but there was a significant in the muscle activity of the rectus muscle of the right thigh in the experimental group. Conclusion: The participants demonstrated that coordinative locomotor training using the elastic band on an unstable supporting surface was able to obtain junctional effects for the prevention of exercise injuries in youth taekwondo sparring athletes, and muscle activity exercise of the rectus muscle of the right thigh was particularly effective.

• The Journal of Korean Physical Therapy
• /
• v.32 no.3
• /
• pp.137-145
• /
• 2020

Purpose: The purpose of this study is to examine the effect of various bridge exercises on walking ability. Method: The subjects were 30 stroke patients. They were divided into a bridge exercise group on a stable support surface (Group I), a bridge exercise group on an unstable support surface (Group II), and a bridge exercise group combined with whole body vibrations (Group III). 10 subjects were randomly assigned into each group. The subjects of this study had 30 minutes of nervous system physical therapy including gait training and strength training. In addition, each group underwent a 30 minutes session five times a week for eight weeks. Before intervention, LUKOtronic was used to measure step width and step length, time was measured with a 10 m walking test, and time and number of steps were measured with the figure 8 walking test. After the intervention, remeasured and analysis was performed for each group. Results: As a result of comparing and analyzing the change of walking ability between groups, there was a statistically significant difference. As a result of the post hoc analysis according to the change of walking ability among groups, the change of walking ability was larger in Group III than in Group I and Group II. Conclusion: Based on these results, it is confirmed that the bridge exercise combined with whole body vibration was more effective for walking ability. Based on these findings, this study proposes an effective program for elite athletes as well as stroke patients.

• PNF and Movement
• /
• v.18 no.1
• /
• pp.45-53
• /
• 2020

Purpose: This study investigated the correlation between standing balance and head-forward posture in adolescents. Methods: The participants in this study were 15 female adolescents. We took photographs of the participants' craniovertebral angle with a digital camera to determine the degree of head-forward posture. Standing balance was evaluated using the 30-second Romberg test of BT4. The measurements were taken on a stable-support surface and on an unstable-support surface using a balance pad. The data measured in this study were analyzed using SPSS version 23.0, and the statistical significance level α was established as 0.05. Pearson correlation coefficient analysis was performed to identify the correlation between the degree of head-forward position of the participants and their balance ability. Results: When we measured 30 seconds of the Romberg test, we observed that, with their eyes open, the participants' head-forward posture and balance were not correlated. However, with their eyes closed, there was a strong correlation between the forward position of the head and the balance ability, which declined as the head position increased. Conclusion: Adolescents with severe head-forward posture exhibited problems with balance in posture control with closed eyes when visual information was not available. It can be inferred that an abnormality occurs in proprioceptor sensation due to their habitual head-forward posture. Education on correct posture and preventive activities should be recommended to improve the health of such adolescents and avoid possible future problems of physical deterioration.

• 한국연소학회:학술대회논문집
• /
• 1998.10a
• /
• pp.59-67
• /
• 1998

The aim of this study is to investigate advantages that the catalytically supported combustor can have. For this purpose, the catalytic combustor was prepared which consisted of the catalyst bed and the thermal combustor at the downstream of the catalyst bed. The catalyst bed consisted of two-stage. Pd catalyst was installed in the first stage of the catalyst bed, and Pt catalyst was placed in the second stage. Results showed that the catalytically supported combustion had some advantages. One was that auto-ignition occurred in the thermal combustor. This can give merit that an igniter is not necessary to start flame ignition. Other was that the catalytically supported combustion was stable for lean mixture. When combustion of lean mixture was not supported by surface reaction it became unstable so that big combustion noise was created. Therefore, it is desirable to support flame by catalytic surface reaction to obtain the stable combustion of lean mixture.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.2
• /
• pp.111.2-111.2
• /
• 2011

While many astrophysical disks are vertically stratified and obey a polytropic equation of state, most studies on gravitational instability (GI) of flattened systems consider isothermal, razor-thin disks by taking vertical averages of disk properties. We investigate local GI of rotating pressure-confined polytropic disks with resolved vertical stratification by performing linear stability analysis. We find that the GI of vertically-stratified disks is in general a combination of conventional razor-thin Jeans modes and incompressible modes. The incompressible modes that dominate in the limit of the maximal disk compression require surface distortion and are an unstable version of terrestrial water waves. Disks with a steeper equation of state are found to be more Jeans unstable because they tend to have a smaller vertical scale height as well as a steeper temperature gradient corresponding to lower pressure support. GI depends more sensitively on the vertical temperature than density distribution. The density-weighted, harmonic mean, rather than the simple mean, of the adiabatic sound speed well describes the dispersion relation of horizontal modes, and thus is appropriate in the expression for Toomre Q stability parameter of razor-thin disks. We generalize Q into vertically-stratified disks, and discuss astrophysical application of our work.

• Geomechanics and Engineering
• /
• v.25 no.1
• /
• pp.17-30
• /
• 2021

This paper develops a convenient approach for deterministic and probabilistic evaluations of tunnel face stability using support vector machine classifiers. The proposed method is comprised of two major steps, i.e., construction of the training dataset and determination of instance-based classifiers. In step one, the orthogonal design is utilized to produce representative samples after the ranges and levels of the factors that influence tunnel face stability are specified. The training dataset is then labeled by two-dimensional strength reduction analyses embedded within OptumG2. For any unknown instance, the second step applies the training dataset for classification, which is achieved by an ad hoc Python program. The classification of unknown samples starts with selection of instance-based training samples using the k-nearest neighbors algorithm, followed by the construction of an instance-based SVM-KNN classifier. It eventually provides labels of the unknown instances, avoiding calculate its corresponding performance function. Probabilistic evaluations are performed by Monte Carlo simulation based on the SVM-KNN classifier. The ratio of the number of unstable samples to the total number of simulated samples is computed and is taken as the failure probability, which is validated and compared with the response surface method.