Browsing by Author "Guo-Hong Gu"

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The biomechanical analysis of the taekwondo front-leg axe-kick
(2005-08-27) 黃長福; Yeh-Jung Tsai; Guo-Hong Gu; Chia-Jung Lee; Chen-Fu Huang; Chien-Lu Tsai
The purpose of the study was to analyze the biomechanics of taekwondo front-leg axekick. One force plates, two synchronized high-speed cameras were used to measure biomechanical parameters in each phase of the front-leg axe-kick. The results included: 1. The average reaction time and movement time were 0.423 sand 0.327 s, which respectively occupied about 56% and 44% of attack time. 2. The maximum velocity of hip, knee and ankle were 1.74 m/s, 5.25 m/s and 7.43 m/s respectively. When the kicking leg touched the target, the velocity of knee and ankle were 0.78m/s, 1.72m1s, and 4.64m1s respectively. 3. The peak vertical GRF and impulse were 0.96 SW and 77.57N-s. For decreasing the movement time, it's suggested that an athlete should increase the power and flexibility of lower extremities during the training section.
The calculation on the rotational kinematics about the longitudinal axis of javelin by three methods
(2005-08-27) 黃長福; Guo-Hong Gu; Yeh-Jung Tsai; Chen-Fu Huang
The motion of javelin is complicated after it is released. Itis necessary to use some skills to calculate the rotation kinematics about the longitudinal axis of javelin. In this study, the Euler angle, the Cardan angle and the screw axis methods were used to calculate these kinematic variables. Two synchronized Redlake high-speed cameras (250 Hz) and a javelin with three fixed reflective markers were used in the experiment. Generally the results by three methods were close, and all of the three methods are suitable for the calculation on these variables. In the Euler angle and Cardan angle methods, the order of rotation sequence needs to be taken account, however no similar problem occurred in screw method. The results suggested that the longitudinal axis should be set as second axis in either Euler angle or Cardan angle methods to avoid Gimbal Lock (singularity) problem.
The dynamic analysis of the applied force on javelin during final thrust by an elite javelin thrower
(2006-07-18) 黃長福; Guo-Hong Gu; Yeh-Jung Tsai; Chenfu Huang
According to the javelin rules, a throw is valid only if the tip strikes the ground before any other part of the javelin. So it is important to precisely control the applied force on javelin for further distance and tip-first landing. Two synchronized Redlake high-speed cameras (250 Hz) were used to videotape an elite thrower; a javelin with three fixed non-collinear markers was used in experiment. The aerodynamics and Newton-Euler equation were taken into account in the 3D inverse dynamic analysis. The results showed that the force was mainly on the axial direction as the whole hand gripped the javelin. However, as the portion of hand touching the javelin became lesser, the direction of force was changed from axial to lateral direction. The lateral torque was significantly larger than axial torque during the whole phase, and their maxima were 24.08 and 1.31 Nm, respectively. The results measured by this method were similar to those by force sensor, and it could be suitable for use in further researches.
兩組不同等級標槍選手之生物力學分析
(2006) 古國宏; Guo-Hong Gu
本研究希望透過兩組不同水準選手之比較，除了找出動作技術的關鍵點也幫助一般選手更進一步。受試者為大專男子選手，優秀選手組最佳紀錄平均為68.04±5.68 m，一般選手組為55.74±7.17 m。利用四台同步之Redlake高速攝影機（兩台125 Hz拍攝人體動作，另兩台250 Hz拍攝槍體）與一塊Kistler測力板（1250 Hz）來擷取資料；以Kwon 3D軟體處理資料並以Butterworth 4th order修勻（6 Hz）。以三維動力學逆過程計算槍體及下肢各關節受力情形，槍體受力程式以Matlab 6.5版來執行。經由比較分析後發現：（一）優秀選手出槍前最大軸向力平均194.6±19.6 N，一般選手平均為147.81±18.54 N，優秀選手顯著地大於一般選手。（二）優秀選手前後傾的角度比一般選手來得大，另外成績越好的選手肩關節的角速度也有越大的現象。（三）制動腳剛著地時，優秀選手之左膝角度（166.3±4.9 deg）顯著地大於一般選手（154.4±10.4 deg）。另外助跑時身體質心速度方面，不管是在推蹬腳著地、制動腳著地及出槍時優秀選手之身體速度皆顯著地大於一般選手（四）標槍在腳跟剛著地時地面反作用力會急速上升，造成一2000 ~ 2222 N左右的最大垂直力量峰值；且由測力板之前後分力來看，出槍瞬間是發生在制動期階段，非推蹬期階段。