本研究之主要目的在探討跆拳道輕量級及重量級選手後踢動作過程生物力學變數之關係。研究以五名輕量級及五名重量級跆拳道運動員為實驗參加者，輕量級實驗參加者平均年齡22.2±3.3歲、身高171.0±2.5公分、體重60.3±5.5公斤、練習時間9.2±3.0年，重量級實驗參加者平均年齡21.8±1.3歲、身高181.3±4.7公分、體重78.0±10.4公斤、練習時間9.0±2.0年。使用Peak Performance 3D運動影像分析系統(60Hz)及F-scan鞋底測力系統(100Hz)，同步蒐集後踢動作過程的生物力學參數。以獨立樣本t考驗對兩組實驗參加者之運動學及動力學參數進行統計分析(顯著水準定為α=.05)，結果顯示：後踢時，實驗參加者重心速度最大值及重心速度最大值出現時間點與擊中目標物瞬時的時間差，兩組間未達顯著性差異(p>.05)。兩組實驗參加者動作時間(movement time)達顯著性差異(p<.05)，輕量級者動作時間明顯短於重量級者。兩組實驗參加者作用時間(action time)達顯著性差異(p<.05)，輕量級者作用時間明顯長於重量級者。綜合上述結果，本研究提出以下結論：以後踢的動作特性而言，適合速度快的輕量級選手從事主動攻擊或被動性的反擊；但是對於重量級選手而言，由於其動作時間較長，因此比較不適合從事主動性的攻擊；較佳的攻擊時機應該是在於對手攻擊之後的反擊動作，如此將可提高後踢的攻擊效果及得點的機會。

The main purpose of this research was to compare the biomechanical performances of Taekwondo back kick technique between lightweight and heavyweight players. The participants were five lightweights (age: 22.2±3.3 y, height: 171.0±2.5 cm, weight: 60.3±5.5 kg, practice time: 9.2±3.0 y) and five heavyweights (age: 21.8±1.3 y, height: 181.3±4.7 cm, weight: 78.0±10.4kg, practice time: 9.0±2.0 y). The Peak Performance 3D motion image analysis system and the F-scan sole dynamometer system were simultaneously used to collect the biomechanical data during the back kick. The comparisons were made using the students' t-test, and p <.05 was considered statistically significant. The results revealed that neither maximal velocity of the subjects' gravity nor lag of time (time to hit an object after the maximal velocity) differed significantly between lightweights and heavyweights. Movement time (time from onset of the attack to hit an object) was significantly shorter in lightweights than that in heavyweights, while action time (time from hitting an object to end of hit an object) in lightweights was remarkably longer than that in heavyweights. In conclusion, we suggested the initiative in attacking by the back kick for lightweight players; however, the best time to attack for the heavyweight players was after the competitor's attack.