背景與目的：過去有關於等速膝關節測試時將髖關節角度改變對股四頭肌疲乏度的研究極少，且大部分是於坐姿（髖關節彎曲80°）狀況下測試。探討膝關節等速測試中，不同的髖關節角度與角速度對股四頭肌疲乏度之影響。方法：以15位健康男性，平均年齡241±22歲，接受四回膝關節等速運動疲乏度測試，每回測試中重複四十次最大努力向心收縮，四回間隔為一週，以比較二種髖關節彎曲角度（80°與10°）及二種角速度（240°/s與90°/s）對股直肌疲乏度的影響。以肌力疲乏指數(Muscle strength fatigue Index)、平均功率頻譜(mean power frequency, MPF)變化評估疲乏度。結果，肌力疲乏指數在二種角速度與兩種髖關節角度變化間均未達顯著差異(p>0.05)。平均功率頻譜變化在兩種髖關節角度測試下無顯著差異(p>0.05)；但在二種角速度變化以240°/s比90°/s較易疲乏且達顯著差異(p<0.001)。結論：髖關節彎曲80°與彎曲10°兩種姿勢下對膝關節等速向心收縮中疲乏度沒有顯著差異，可能原因為髖關節屈曲70°的改變主要影響在股直肌肌肉長度，但股直肌僅佔17%膝伸直肌之肌力，且其力臂之優勢在膝關節，故髖關節70°位置改變對膝關節等速肌力矩值的表現沒有顯著影響。在較高的角速度可能因為須較早徵召較多的快速運動單位，而快速運動單位是較易疲乏的，240°/s比90°/s其平均功率頻譜下降較明顯，表示經四十次收縮多元化的動作單元徵召方式開始轉向單調的動作單元徵召方式變化，使平均功率頻譜集中在較低頻頻帶

Purpose: In the context of isokinetic measurement, the change of hip position has been poorly studied. The few studies, which investigated peak torque change, did not specifically study fatigability test. The purpose of this study was to compare the fatigue of rectus femoris muscle at different hip angels with different angular velocities during isokinetic knee exercise. Method: Fifteen male subjects without any pervious knee injuries performed four fatigue tests at two angular velocities (90°/s and 240°/s) with two hip angles (flexion 10° and 80°), each set consisting of forty repeated maximal concentric knee extensions exercises Muscle strength fatigue index and mean power frequency (MPF) changes of rectus femurs muscle were recorded during exercise tests. Results: (l) The two fatigue indexes at the two hip angles without significanly different. (2) The changes of MPF decrease was greater at 240°/s than at 90°/s. Discussion: According to the results, we pumed that the rectus femoris contributes only about 17% of the total isokinetic maximal knee extension moment. The remaining vast majority of the total extensor moment generating capacity should have been unaffected by hip angle, as the lengths of the other knee extensors depend only on the knee angle. The greater decrease of MPF at 240°/s than at 90°/s reflects the MPF sensible to fatigability of fast twitch motor units.