• Title/Summary/Keyword: gravity center

Search Result 886, Processing Time 0.032 seconds

Comparison of the Limitation of Stability between Flatfeet and Neutral Feet (편평발과 정상발의 무게중심한계 비교)

  • Han, Jin-Tae
    • PNF and Movement
    • /
    • v.15 no.3
    • /
    • pp.311-316
    • /
    • 2017
  • Purpose: Flatfeet are one of the risk factors of foot dysfunction and postural imbalance. The purpose of this study was to compare the limitation of stability (LOS) for the center of gravity (COG) between flatfeet and neutral feet on stable and unstable support surfaces. Methods: The study included 26 healthy, adult male participants: 14 with normal feet and 12 with flatfeet. The subjects were asked to incline the trunk maximumly to the left, right, anterior, and posterior directions and were asked to keep their feet on the floor with the knee extension. The subjects had 30 seconds of rest time between the tasks. The LOS (anterior, posterior, left, right) of COG was measured by Balance Trainer (BT4, Hur-labs, Tampere, Finland). An independent t- test was used to compare the LOS of COG between flatfeet and normal feet on stable and unstable support surfaces, respectively. Results: The LOS of the flatfeet group was generally decreased on stable support surfaces as compared to that of neutral feet, but it was not significantly different (p>0.05), while the LOS of the flatfeet group was significantly decreased compared to that of neutral feet on unstable support surfaces (p<0.05). Conclusion: This study suggested that the LOS of individuals with flatfeet may be decreased on unstable support surfaces and the postural balance of the flatfeet group may easily be disturbed on an unstable support surface.

A Review of Pregnancy Related Low Back Pain (임신 중 요통에 관한 고찰)

  • Cho Mi-sook;Park Rae-joon
    • The Journal of Korean Physical Therapy
    • /
    • v.15 no.4
    • /
    • pp.431-441
    • /
    • 2003
  • Pregnancy and puerperium are associated with significant changes in pschological and physiologic health status. Back and pelvic pain is common in pregnancy with prevalence figures in the range of $48\%-90\%$. The pain starts during pregnancy and often disappears soon after childbirth. But the prevalence of such pain four to six months post postpartum is report to be $25-40\%$. In $10-15\%$ of the case the pain become chronics, that is persisting for more than three months after childbirth. Low back pain and pelvic pain maybe caused by several factors related to changes that occur naturally during pregnancy. Changes in the center of gravity can create a strain on weight-bearing structures in bone. Pregnancy related hormones, relaxin, create general laxity of collagenous tissue. Another factor found to be a possible primary or contributing cause for law back and hip symptoms are leg length inequality, weight gain and changes in foot function. This article outlines the physiological and biomechanical changes that occur during pregnancy which have been reported to be possible causes of low back and pelvic pain And then, examination, diagnosis, evaluation and treatment of the woman during pregnancy are described. Standard treatment for low back pain and pelvic pain in pregnancy includes education in anatomy and kinesiology, back-strengthening exercise, training of the abdominal muscles and body posture correction. So, most woman during pregnancy require individual consultation and physiotherapist.

  • PDF

A Kinematic Analysis of Glide Kip Motion on the Uneven Bars (이단 평행봉 차오르기 동작의 운동학적 분석)

  • Kim, Seung-Kwon;Kim, Seoung-Eun;Jang, Dae-Sun
    • Korean Journal of Applied Biomechanics
    • /
    • v.23 no.4
    • /
    • pp.307-318
    • /
    • 2013
  • The purpose of this study was to analyze the kinematic variables of glide kip motion on the uneven bars through a two-dimensional cinematography. Three expert female gymnastics players were involved in the data gathering process. The followings were concluded according to the results. The arm, trunk and leg segments were fully extended throughout the kip movement. The whole body center of gravity showed the biggest changes during 66 to 87% of the kip motion. During the kip phase, the horizontal displacement of the leg was greater than the vertical displacement the leg. Glide kip motion should be done in orders of upward movement of leg, forward movement of leg, upward movement of trunk and forward movement of trunk segment. It was found that trunk segment and hip joint movements showed bigger changes than those of leg segment and shoulder joint in the glide kip motion. The largest angular velocity of hip joint was shown in the middle of the kip Phase. In conclusion, effective kip movement could be resulted when the trunk was displaced posterior-upward direction with fast hip joint extension after the leg segment was elevated upward and thrusted forward in advance.

Relationship between Leg Stiffness and Kinematic Variables According to the Load while Running

  • Hyun, Seung Hyun;Ryew, Che Cheong
    • Korean Journal of Applied Biomechanics
    • /
    • v.27 no.2
    • /
    • pp.109-116
    • /
    • 2017
  • Objective: This study aimed to investigate the relationship between leg stiffness and kinematic variables according to load while running. Method: Participants included eight healthy men (mean age, $22.75{\pm}1.16years$; mean height: $1.73{\pm}0.01m$; mean body weight, $71.37{\pm}5.50kg$) who ran with no load or a backpack loaded with 14.08% or 28.17% of their body weight. The analyzed variables included leg stiffness, ground contact time, center of gravity (COG) displacement and Y-axis velocity, lower-extremity joint angle (hip, knee, ankle), peak vertical force (PVF), and change in stance phase leg length. Results: Dimensionless leg stiffness increased significantly with increasing load during running, which was the result of increased PVF and contact time due to decreased leg lengths and COG displacement and velocity. Leg length and leg stiffness showed a negative correlation (r = -.902, $R^2=0.814$). COG velocity showed a similar correlation with COG displacement (r = .408, $R^2=.166$) and contact time (r = -.455, $R^2=.207$). Conclusion: Dimensionless leg stiffness increased during running with a load. In this investigation, leg stiffness due to load increased was most closely related to the PVF, knee joint angle, and change in stance phase leg length. However, leg stiffness was unaffected by change in contact time, COG velocity, and COG displacement.

The change of vowel characteristics for the dysarthric speech along with speaking style (경도 마비말장애 환자의 발화 유형에 따른 모음 특성 비교)

  • Kim, Jiyoun;Seong, Cheoljae
    • Phonetics and Speech Sciences
    • /
    • v.8 no.3
    • /
    • pp.51-59
    • /
    • 2016
  • The purpose of present study is to examine differences between habitual speech (HS) and clear speech (CS) in individuals with mild dysarthria. Twelve speakers with mild dysarthria and twelve healthy control speakers read sentences in two speaking styles. Formant and intensity related values, triangular area, and center of gravity of /a/, /i/, and /u/ were measured. In addition, formant-ratio variables such as vowel space area(VSA), vowel articulatory index (VAI), formant centralization ratio (FCR) and F2i/F1u ratio (F2 ratio) were calculated. The results of repeated-measures ANOVA showed a significant difference in F2 of vowel /i/ and F2 energy of vowel /a/ between groups. Regarding formant energy, F2 energy of vowel /a/ were observed as meaningful variables between speaking styles. There were significant speaking style-by-group interactions for F2 energy of vowel /a/. These findings indicated that current parameters could discriminate healthy group and mild dysarthria group meaningfully and that speaker with dysarthria had larger clear speech benefit than healthy talkers. We also claim that various acoustic changes of clear speech may contribute to improving vowel intelligibility.

Korean and English affricates in bilingual children

  • Yu, Hye Jeong
    • Phonetics and Speech Sciences
    • /
    • v.9 no.3
    • /
    • pp.1-6
    • /
    • 2017
  • This study examined how early bilingual children produce sounds in their two languages articulated with the same manner of articulation but at different places of articulation. English affricates are palato-alveolar and Korean affricates are alveolar. This study analyzed the frequencies of center of gravity (COG), spectral peak (SP), and the second formant (F2) of word-initial affricates in English and Korean produced by twenty-four early Korean-English bilingual children (aged 4 to 7), and compared them with those of monolingual counterparts in the two languages. If early Korean-English bilingual children produce palato-alveolar affricates in English and alveolar affricates in Korean, they may produce Korean affricates with higher COGs, SPs, and F2s than English affricates. The early Korean-English bilingual children at the age of 4 produced English and Korean affricates with similar COGs, SPs, and F2s, and the COGs, SPs, and F2s of their Korean affricates were similar to those of the Korean monolingual counterparts. However, the early bilingual children at the age of 5 to 7 had lower COGs and SPs for English affricates with higher F2s compared to Korean affricates, and the COGs, SPs, and F2s of their English affricates were similar to those of the English monolingual counterparts.

The Effect of Meridian Massage on Muscle Power, ROM, and ADL in Persons with Cerebral Palsy (경락 마사지가 뇌성마비장애인의 근력, 관절운동범위 및 일상생활활동에 미치는 영향)

  • Oh Mi-Jung;Choi Kyong-Hee
    • Journal of Korean Academy of Fundamentals of Nursing
    • /
    • v.10 no.1
    • /
    • pp.68-77
    • /
    • 2003
  • Purpose: This study analyzed the effects of meridian massage on the muscle power, ROM, and ADL in persons with cerebral palsy. Method: A non-equivalent pre-test/post-test design was used. The data were collected from August to October, 2000 from 10 persons with cerebral palsy (a control group of 5 and an experimental group of 5). Muscle power was evaluated with the Brunnstrom-Dennen gravity test, ROM with a goniometer, and ADL with a self developed ADL scale. T-test, repeated measure ANOVA were used for statistical analysis. Result: The results are; 1. For muscle power, both time series group difference (F=10.66, p=0.000) and the total period group difference (F=72.67, p=0.000) were significant between the two groups. 2. ROM was not significantly different between the two groups. 3. For ADL, both time series group difference (F=7.09, p=0.001) and total period group difference (F=35.99, p=0.000) were significant between the two groups. Conclusion: Overall, this study shows that Meridian massage is effective for muscle power, ROM, and ADL in persons with cerebral palsy person. So it can be used to develope effective nursing programs to improve the function of motion of persons with cerebral palsy.

  • PDF

Analysis on Stable Grasping based on Three-dimensional Acceleration Convex Polytope for Multi-fingered Robot (3차원 Acceleration Convex Polytope를 기반으로 한 로봇 손의 안정한 파지 분석)

  • Jang, Myeong-Eon;Lee, Ji-Hong
    • Journal of Institute of Control, Robotics and Systems
    • /
    • v.15 no.1
    • /
    • pp.99-104
    • /
    • 2009
  • This article describes the analysis of stable grasping for multi-fingered robot. An analysis method of stable grasping, which is based on the three-dimensional acceleration convex polytope, is proposed. This method is derived from combining dynamic equations governing object motion and robot motion, force relationship and acceleration relationship between robot fingers and object's gravity center through contact condition, and constraint equations for satisfying no-slip conditions at every contact points. After mapping no-slip condition to torque space, we derived intersected region of given torque bounds and the mapped region in torque space so that the intersected region in torque space guarantees no excessive torque as well as no-slip at the contact points. The intersected region in torque space is mapped to an acceleration convex polytope corresponding to the maximum acceleration boundaries which can be exerted by the robot fingers under the given individual bounds of each joints torque and without causing slip at the contacts. As will be shown through the analysis and examples, the stable grasping depends on the joint driving torque limits, the posture and the mass of robot fingers, the configuration and the mass of an object, the grasp position, the friction coefficients between the object surface and finger end-effectors.

Verification of Thermal Characteristics and Overturning Moment for Lateral Vibration System (수평가진 시스템의 열 특성 및 모멘트 성능 검증)

  • Eun, Hee-Kwang;Im, Jong-Min;Moon, Sang-Moo;Moon, Nam-Jin;Lee, Dong-Woo;Choi, Seok-Weon
    • Aerospace Engineering and Technology
    • /
    • v.8 no.2
    • /
    • pp.113-121
    • /
    • 2009
  • Shaker system is used to simulate the vibration from the launch environment. The vibration tests are performed in the vertical and lateral direction. For the lateral vibration test, the slip table system is used with shaker system. For the latest large satellite, vibration test adaptor is made of the steel. But slip table of lateral vibration is made of magnesium, so there is big difference of thermal expansion ratio between slip table and vibration test adaptor. This paper encompasses the following items; verification process of thermal characteristics and overturning moment and a solution for lateral vibration test with steel vibration test adaptor.

  • PDF

Experimental and Numerical Study on the Dynamic Stability of a Cantilevered Beam Subjected to a Rocket Thrust (로켓 추진력을 받는 외팔보의 동적 안정성에 관한 수치 및 실험적 연구)

  • ;;Sugiyama, Y.
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.17 no.11
    • /
    • pp.2762-2772
    • /
    • 1993
  • The paper deals with the flutter of a cantilevered beam subjected to a rocket thrust generated by a solid rocket motor. It is saaumed that the rocket thrust is to be a constant follower thrust, and produced by the installation of a solid rocket motor to the tip end of the cantilevered beam. The rocket motor is considered to be a rigid body having finite sizes, but not a mass point as it has been assumed so far. Governing equations are derived through the extended Hamilton's principle, and finite element method is applied to obtain the theoretical prediction for critical follower thrust. The maximum follower thrust is also calculated through the change of shear deformation parameter of the beam in the numerical simulation. The theoretical prediction for flutter or stability is verified by experiment. The experimental results show that critical follower thrust in theory agrees well with the experimental value taking account of the magnitude, rotary inertia of the rocket motor and the distance from the tip end of the beam to the center of gravity of the rocket motor.