• Title/Summary/Keyword: GRF

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Number of Trials for the Reliable Golf Swing Ground Reaction Force Data Collection and Its Characteristics (골프 드라이버스윙 시 지면반력 반복측정 횟수와 지면반력 특성)

  • Park, Young-Hoon;Youm, Chang-Hong;Seo, Kuk-Woong;Seo, Kook-Eun
    • Korean Journal of Sport Biomechanics
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    • v.17 no.4
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    • pp.115-125
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    • 2007
  • Grould Reaction force(GRF) is important in human movements and GRF measurements are one of the most frequently used tool in biomechanical studies. In the studies of the golf swing motion, people refer to GRF as weight transfer. A successful golf swing motion requires many segments activation sequences which are controled by the nerve system. Due to the inter- and intra-individual variability of the human movement and the movement strategies, reliability of the measurements are important in human movement studies. Previous golf researches were based on group studies and certain events' values were analyzed. The purposes of this study were to determine the number of trials for the reliable golf swing GRF data collection, to reveal the variability level of the meaningful components of the golf swing GRF, and to classify the types of the golf swing GRF patterns. Twenty three male professional golfers($26.4{\pm}6.6$ years, $174.3{\pm}5.2\;cm$, $71.3{\pm}6.5\;kg$) signed an informed consent form prior to participation in this study. GRFs of driver swings were collected with Kistler 9285 force platform and 9865A amplifier, and calculated by the KwonGRF program(Visol, Korea). Sampling frequency was 1080 Hz. GRF data were trimmed from 1.5 s prior to the impact to 0.5 s after the impact. The number of trials for the reliable GRF collection was determined when the change in floating mean overs the 25 % of the standard deviation of that variable. Variabilities of the variables were determined by the coefficient of variation(CV) of 10 %. The types of GRF patterns were determined by visual inspection of the peak GRF shapes. The minimum number of trials for the reliable golf swing GRF data collection was five. Ten-trial seems more conservative. The value of the peak GRF was more reliable than the value of the impact GRF. The CV of the peak GRF and impact GRF were 7.4 %, 15.2 %, respectively. Because of the +/- sigh of the peak GRF appearance time, it was impossible to calculate CV of the peak GRF appearance time. Golf swing GRF patterns were classified as sing peak type, double peak type, and plateau peak type. This classification suggests the presence of the different golf swing weight transfer strategies.

Biological roles and an evolutionary sketch of the GRF-GIF transcriptional complex in plants

  • Kim, Jeong Hoe
    • BMB Reports
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    • v.52 no.4
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    • pp.227-238
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    • 2019
  • GROWTH-REGULATING FACTORs (GRFs) are sequence-specific DNA-binding transcription factors that regulate various aspects of plant growth and development. GRF proteins interact with a transcription cofactor, GRF-INTERACTING FACTOR (GIF), to form a functional transcriptional complex. For its activities, the GRF-GIF duo requires the SWITCH2/SUCROSE NONFERMENTING2 chromatin remodeling complex. One of the most conspicuous roles of the duo is conferring the meristematic potential on the proliferative and formative cells during organogenesis. GRF expression is post-transcriptionally down-regulated by microRNA396 (miR396), thus constructing the GRF-GIF-miR396 module and fine-tuning the duo's action. Since the last comprehensive review articles were published over three years ago, many studies have added further insight into its action and elucidated new biological roles. The current review highlights recent advances in our understanding of how the GRF-GIF-miR396 module regulates plant growth and development. In addition, I revise the previous view on the evolutionary origin of the GRF gene family.

Variability of GRF Components between Increased Running Times during Prolonged Run (오래달리기 시 시간 경과에 따른 지면 반력 성분의 Variability)

  • Ryu, Ji-Seon
    • Korean Journal of Sport Biomechanics
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    • v.24 no.4
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    • pp.359-365
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    • 2014
  • A study was conducted to investigate the possible effects of fatigue which was resulted from increased running time on the stability during a prolonged run. The purposes of this study were twofold: first, to determine the discrete and non-linear variability of GRF (ground reaction force) components between running times to know the body stability, and second, to determine the pattern between discrete and non-linear variability. Nineteens healthy young adult males served in this study as subjects who ran at their preferred running speed. GRF data for twenty strides were collected at 5, 65, and 125 minutes during run. Variance coefficient and Lyapunov Exponent techniques on the GRF data were used to calculate variability index for each of the running time conditions. There were no difference between discrete variabilities of three components of GRF, but non-linear variability of the Fz component of GRF was decreased by increasing running time (p<.01). No relationship was found between discrete and non-linear variability.

Study on Hepatoprotective and Antioxidant Activities of Korean Red Ginseng-Mixed Formula (홍삼복합제의 보간 및 항산화 작용에 대한 연구)

  • Kang, Chang-Hee;Kim, Dong-Hee;Ryu, Shi-Yong;Kim, Sung-Hoon
    • Korean Journal of Pharmacognosy
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    • v.31 no.4
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    • pp.383-389
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    • 2000
  • GRF (Korean Red Ginseng mixed formula) consists of six herbs such as Ginseng Radix rubra Koreana, Lycii Fructus, Artemisiae Capillaris Herba, Poria, and Glycyrrhizae Radix and Hoveniae Fructus. For the evaluation of hepatoprotective effect of GRF, the study was performed on protective effect against hepatic damage induced by galactosamine in vitro and ccl4 in vivo and also elucidate antioxidant activity. In vitro assay with 1.1 mM galactosamine, protection (%) was 44% (GR), and 58% (GRF-A) at 50 ug/ml. GRF effectively protected fatty degenertion and necrosis in murine hepatic damage induced by ccl4. For the -antioxidant study, GRF inhibited hemolysis of erythrocyte and decolored DPPH (2,2-diphenyl-l-picrylhydrazyl) free radical in a dose dependent manner more effetively than GR alone in vitro. GRF and GR significantly suppressed the time course $(1\;hr{\sim}6\;hr)-level$ of MDA (malondialdehyde) following AAPH (2,2'-azo-bis-(2-amidino -propane) dihydrochloride) treatment in vivo as compared with control data. From the results it can be concluded GR and GRF exerted the hepatoprotective effect by dint of antioxidant activity.

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Urine Analysis in Transgenic Mice Expressing the Growth Hormone-releasing Factor (성장호르몬 방출인자를 발현하는 형질전환 생쥐에서 소변분석)

  • Cho, Byung-Nam;Jung, Hoi-Kyung;Yoon, Yong-Dal;Mayo, Kelly-E
    • Development and Reproduction
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    • v.6 no.1
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    • pp.31-35
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    • 2002
  • The major urinary proteins(MUPs) of mice that bind hydrophobic molecules known as pheromones are regulated in part by the actions of growth hormone. The expression of the MUPs was therefore investigated in transgenic mice that express a human growth hormone-releasing factor gene from a metallothionein gene promoter(MT-GRF) and as a result have elevated growth hormone levels. MUPs were severely down-regulated in the urine of these animals compared to normal mice or to control transgenic mice expressing another gene(the inhibin a subunit) from the same metallothionein promoter(MT-Inh) and more MUPs disappeared in male mice than female ones. MUPs were also down-regulated in the urine of the UT-GRF-injected mice. In addition, it was observed that the urine of the MT-GRF mice included a high molecular weight protein that co-migrates with the major serum protein albumin, indicating an impairment in glomerular filtration within the kidney. The urinary loss of serum proteins was more severe in male MT-GRF mice than female ones. Thus the overexpression of human GRF mimics changes observed in MUP protein expression and glomerular function in other models of growth hormone hypersecretion with sex-dependent differential effects.

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Investigation of the Ground Reaction Force Parameters According to the Shoe's heel Heights and Landing Distance during Downward Stairs on Bus (버스계단 내리기 시 구두 힐 높이와 착지거리에 따른 지면반력 파라미터 조사)

  • Hyun, Seung-Hyun;Ryew, Che-Cheong
    • Korean Journal of Sport Biomechanics
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    • v.24 no.2
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    • pp.151-160
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    • 2014
  • The purpose of this study was to investigate the GRF(ground reaction force) parameters according to the shoes's heel heights and ground landing distances during downward stairs on bus. Participants selected as subject were consisted of young and healthy women(n=9, mean age: $21.30{\pm}0.48$ yrs, mean height: $164.00{\pm}3.05cm$, mean body mass: $55.04{\pm}4.41kg$, mean BMI: $20.47{\pm}1.76kg/m^2$, mean foot length: $238.00{\pm}5.37mm$). They were divided into 2-types of shoe's heel heights(0 cm/bare foot, 9 cm) and also were divides into downward stairs with 3 types of landing distance(20 cm, 35 cm, 50 cm). A one force-plate was used to collect the GRF(AMTI, USA) data from the sampling rate of 1000 Hz. The GRF parameters analyzed were consisted of the medial-lateral GRF, anterior-posterior GRF, vertical GRF, loading rate, Center of Pressure(${\Delta}COPx$, ${\Delta}COPy$, COP area) and Dynamic Postural Stability Index(MLSI, APSI, VSI, DPSI) during downward stairs on bus. Medial-lateral GRF and vertical GRF didn't show significant differences statistically according to the shoe's heel heights and landing distance, but 9 cm shoes heel showed higher vertical GRF than that of 0 cm bare foot in landing distance of 50 cm. Also anterior-posterior GRF didn't show significant difference statistically according to the shoe's heel heights, but landing distance of 20 cm showed higher than that of landing distances of 35 cm and 50 cm in anterior-posterior GRF. Loading rate didn't show significant difference statistically according to the landing distance, but 9 cm shoe's heel showed higher than that of 0 cm bare foot during downward stairs. The ${\Delta}COPy$ and COP area didn't show significant differences statistically according to the shoe's heel heights and landing distance, but 0 cm bare foot showed higher than that of 9 cm shoe's heel in ${\Delta}COPx$. Dynamic Postural Stability Index(MLSI, APSI, VSI, DPSI) didn't show significant differences statistically according to the landing distance, but 9 cm shoe's heel showed decreased value than that of 0 cm bare foot in dynamics balance. Considering the above, parameters of GRF showed different characteristics according to the shoe's heel heights and ground landing distances during downward stairs on bus.

The Effects of Gel-type Insole on Patients with Knee Osteoarthritis during Gait (겔-타입 인솔이 무릎 골관절염 환자의 보행에 미치는 영향)

  • Eun, Seon-Deok;Yu, Yeon-Joo;Shin, Hak-Soo
    • Korean Journal of Sport Biomechanics
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    • v.17 no.3
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    • pp.181-188
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    • 2007
  • The purpose of this study was to investigate the biomechanical effects of wearing different type of insole shoes on gait characteristics in patients with knee osteoarthritis. Seven patients with knee osteoarthritis (Grade 3 & 4 by Kellgren & Lawrence) were participated in the study. They wore two different type of shoes (with Gel-type Insole: GIS, with Normal insole: NIS) during gait. Three dimensional cinematography and Ground Reaction Force(GRF) data were used to get the maximal value of horizontal distance between the center of pressure in GRF and knee joint center, GRF in mediolateral direction, peak value of GRF in frontal plane, vertical compressive force and adduction moment in knee joint. The results were as follows: The maximal value of horizontal distance between the center of pressure in GRF and knee joint center was smaller in GIS than NIS. The peak value of GRF in mediolateral direction was found in 30% of gait cycle, five subjects wearing GIS showed lower value of peak GRF in mediolateral direction than wearing NIS. The peak value of GRF in frontal plane and vertical compressive force in knee joint did not show any difference between GIS and NIS. The adduction moment in GIS decreased in the late stance of gait and the mean value of the adduction moment in GIS smaller than that in NIS. GIS may help to move quickly knee joint center to the center of pressure in GRF, therefore it may prevent increasing the adduction moment in knee joint.

The Theta Analysis on the Components of Ground Reaction Force According to the Ground Conditions During Gait (보행 시 지면조건에 따른 지면반력 성분의 세타 분석)

  • Ryew, Che-Cheong;Hyun, Seung-Hyun
    • Korean Journal of Sport Biomechanics
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    • v.25 no.3
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    • pp.241-248
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    • 2015
  • Objective : The purpose of this study was to investigate the theta on the components of ground reaction force according to the ground conditions during gait. Method : Six healthy women(mean age: 22 yrs, mean height: $166.14{\pm}2.51cm$, mean body weights: $56.61{\pm}4.58kg$) participated in this study. The medial-lateral GRF(Fx 1), anterior-posterior GRF(Fy 1, Fy 2), vertical GRF(Fz 1, Fz 2, Fz 3), and impact loading rate were determined from time function and frequency domain. Also, GRF theta were time function and forces. Results : Fx 1, Fy 1 and Fy 2 of stair descending showed significant statistically higher forces than that of level walking, and ascending. Fz 1 of stairs descending showed significant statistically higher forces than that of level walking and stairs ascending(theta $88.62^{\circ}$). Also, Fz 2 of level walking showed significant statistically higher forces than that of stairs ascending and descending(theta $65.78^{\circ}$). Fz 3 of stairs ascending showed significant statistically higher forces than that of level walking and stairs descending($65.26^{\circ}$). Impact loading rate of stairs descending showed significant statistically higher forces than that of level and ascending walking. The GRF showed similar correlation with GRF theta(r=.603) according to the ground conditions during gait. Conclusion : These results suggest that the GRF theta can be used in conjunction with a gait characteristics, prediction of loading rate and dynamic stability.

Relationship between Ground Reaction Force and Attack Time According to the Position of Hand Segments during Counter Attack in Kendo

  • Hyun, Seung Hyun;Jin, HyeonSeong;Ryew, Che Cheong
    • Korean Journal of Sport Biomechanics
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    • v.27 no.1
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    • pp.1-7
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    • 2017
  • Objective: The purpose of this study was to analyze the relationship between ground reaction force (GRF) and attack time according to the position of hand segments during counter attack in Kendo. Method: The participants consisted of 10 kendo athletes (mean age: $21.50{\pm}1.95yr$, mean height: $175.58{\pm}5.02cm$, mean body weight: $70.96{\pm}9.47kg$) who performed standard head strikes (A) and counter attack with a preferred hand position of +10 cm (B), 0 cm (C), and -10 cm (D). One force-plate (AMTI-OR-7., USA) was used to collect GRF data at a sample rate of 1,000 Hz. The variables analyzed were the attack time, medial-lateral GRF, anterior-posterior GRF (AP GRF), peak vertical force (PVF), and loading rate. Results: The total attack time was shorter in types A and C than in types C and D. The AP GRF, PVF, and loading rate had significantly higher forces in types C and D than in types A and C. The attack time (bilateral and unilateral leg support and total) was positively correlated with the GRF variables (vertical GRF and loading rate) during the counter attack in Kendo (r = 0.779 [$R^2=0.607$], p < 0.001). Conclusion: The positions of the hand segments can be changed by various conditions of the opponent in Kendo competitions; however, the position preferred by an individual can promote the successful ratio of the counter attack.

A Method for Analyzing and Evaluating the Golf Swing Using the Force Platform Data (지면반력분석기를 이용한 골프 스윙의 분석 평가 방법)

  • Sung, Rak-Joon
    • Korean Journal of Sport Biomechanics
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    • v.20 no.2
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    • pp.213-219
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    • 2010
  • The purpose of this study is developing a method to analyze and evaluate a golf swing motion using the ground reaction force (GRF) data. Proper weight shifting is essential for a successful shot in golf swing and this could be evaluated by means of the forces between the feet and ground. GRF during the swing were measured from 15 low-handicapped male golfers including professionals. Four clubs(driver, iron 3, iron 5, and iron 7) were selected to analyze the differences due to different characteristics of club. Swings of each subject were taken using a high speed video camera and GRF data were taken simultaneously by two AMTI force platforms. To simplify the GRF data, forces of the three major component of GRF(vertical, lateral, anterior-posterior force) at 10 predefined temporal events for each trial were selected and the mean of each event were calculated and evaluated. Analyzed vertical GRF (VGRF) data could be divided into two different styles, one-legged and two legged. One-legged style shows good weight transfer to the target leg and most of the previous study shows this style as a typical pattern of good players. Therefore the data from the iron 5 swing obtained from 10 one-legged style golfers are provided as criteria for the evaluation of a swing.