標槍投擲時槍體受力型態及地面反作用力型態之探討

Reaction force analysis in javelin and the ground during javelin throw

目的：本研究主要在分析兩組不同等級標槍選手在最後出槍時之槍體受力及地面反作用力型態，除了探討兩組選手力學參數上差異外，也觀察槍體受力及地面反作用力之間的關係。方法：實驗儀器包括兩臺Redlake高速攝影機（250Hz）及一塊同步之Kistler測力板（1,250Hz）。透過標槍上不共線三點及三維動力學逆過程來計算槍體受力，程式的運算是以Matlab6.5來執行。結果：槍體受力方面，優秀選手之軸向及側向施力皆顯著地大於一般選手（p＜.05）；優秀選手之側向力矩比例顯著地大於一般選手（p＜.05）。測力板部分，優秀選手推蹬期前後方向之推蹬力量顯著地較一般選手為大（p＜.05），推蹬時間短且跳躍動作也較為明顯。出槍發生在制動期後半段，此時前後及垂直之地面反作用力並無明顯起伏變化。結論：制動腳在出槍時主要提供一個穩定之基底供軀幹動量傳遞及上臂扭轉投擲之用，故此時地面反作力並無明顯起伏變化。另外建議一般選手們推蹬動作要做完全且確實，並且可嘗試增加向後推蹬力量的比例，或許可以找出更好的推蹬型態。Purpose: To investigate the force applied to javelin and ground reaction force (GRF) during final thrust and the relationship between javelin applied force and GRF by comparing the two different classes of throwers. Methods: Two Redlake cameras (250 Hz) synchronized with a Kistler force plate (1,250 Hz) were used to collect the javelin kinematic data and GRF, respectively. The force applied to javelin was calculated by the 3D inverse dynamics with three non co-linear markers on the javelin. The Matlab version 6.5 software was used to computer variables. Results: The peak axial and lateral force of elite group was significant larger than those of general group (p < .05). The peak maximum GRFy of elite group was greater than that of general group in the propulsive phase. In addition, the elite group has a shorter duration of landing and more obviously jumping motion. The javelin release occurred in late breaking phase, at that moment and no significant change was observed on GRFy and GRFz. Conclusion: The breaking leg provides s a steady support base for transmission of the moment between ground and trunk, so no significant change on GRFs. It is suggested that after release, the general group should make the propulsive motion more completely during the following propulsive phase and try to increase the proportion of GRF on anterior-posterior direction.