目的：以非線性方法分析觀察長時間戶外跑步疲勞後，各肢段動作的變異性。釐清因疲勞產生時，各肢段變異不規則性所增加的軸向與運動，並討論其含義。方法：招募 15 名受試者，將慣性感測器固定在四肢與軀幹，於跑道上執行75%最大跑速的快跑，時間達30 分鐘或運動自覺強度 (Rating of Perceived Exertion, RPE) 達18 即停止，並將其視為本次實驗的疲勞。擷取總時間10%與95%處，各10 秒鐘的資料做為疲勞前、後數據，使用非線性分析三軸加速度 (A) 與三軸角速度 (G) 訊號之變異性，並以相依樣本 t 檢定比較其差異。結果：跑步隨著疲勞介入，各肢段皆有特定軸向近似熵值顯著上升 (p < .05)，左腳為A-z (垂直軸)、G-x (額狀面)、G-y (矢狀面)、G-z (水平面)、右腳為A-x (前後軸)、G-x、G-y、軀幹為A-z、G-x，左手為 A-x、右手為A-y (左右軸)、G-y。結論：長時間跑步疲勞後，會增加各肢段動作變異不規則性，下肢在前後與側向的運動上不規則增加；軀幹則是上下晃動與左右擺動逐漸不一致；左右手動作不規則亦增加，但在方向上無重複；下肢與軀幹皆在側向擺動上會增加不規則性，可作為疲勞監控之參考。

Purpose: To observe the variability of the movements in each limb after long-time running fatigue by using a non-linear method. Moreover, we determined which axial and motion on each limb increase irregularity after fatigue and discussed its meaning. Methods: Fifteen healthy participants ran on the track at 75% of the maximum speed for 30 minutes or stopped when the rating of perceived exertion (RPE) was reported greater than or equal to 18, which was defined as fatigue in this study. Their limbs and trunk were set 5 inertial sensors. The data for 10 seconds at 10% and 95% of total time were analyzed as pre- and post-fatigue data. Triaxial acceleration (A) and triaxial angular velocity (G) signal variation (Approximate entropy value) was calculated by a nonlinear analysis method and was compared the differences between pre- and post-fatigue using dependent sample t test. Results: The approximate entropy value of several specific axials on each limb segment significantly increased after fatigue (p <.05). The specific axials were A-z (vertical axis), G-x (frontal plane), G-y (sagittal plane), and G-z (Horizontal plane) on left foot, A-x (front and rear axis), G-x, and G-y on right foot, A-z and G-x on trunk, A-x on left hand, A-y (left and right axis) and G-y on right hand. Conclusion: After long-time running fatigue, the irregularity of movement variation in each limb increase. Lower limbs movement increase irregularly in the forward, backward, and lateral direction; trunk is gradually inconsistent with vertical oscillate and left-right swing; although both hands also increase movements irregularly, there is no common feature. The movements irregularly of lower limbs and trunk increase in the lateral swing. These results can be used as a reference for fatigue monitoring.