自古以來，步行是人類日常生活中最常進行的動作，然而現實生活中並非條條大路均是坦途，是以步行中常需要跨越種種障礙物，如無法成功跨越過障礙物常會導致跌倒而造成傷害。成功地跨越障礙物取決於站立腳的穩定度與與跨越腳和障礙物之間的間隙，而膝關節中的前十字韌帶於此兩目的皆扮演重要的角色。因此本研究旨在探討正常人於跨越障礙時所採取之策略，同時藉由前十字韌帶損傷與前十字韌帶重建之病患跨越障礙物之研究，瞭解前十字韌帶之功能。
本研究選取12位正常受試者，及前十字韌帶損傷與重建之受試者各6位，每位受試者跨越障礙物高度各為其腿長的10%、20%與30%，並以三維動作分析系統（Vicon 370, Oxford Metrics, U.K.）量測跨越時之運動狀態，本研究另行開發一平面七連桿人體模型，配合多目標最佳控制的理論，以探討上述三個族群於跨越障礙物時所採取的控制策略。
本研究結果顯示上述三個族群於跨越障礙物過程皆非以能量最小化單一目標為其控制策略，而是在能量最小化與足部間隙最大化兩最佳妥協下的結果，兩者權重比為一定值。且不同障礙物高度並不影響其權重比例，顯示人類在跨越一障礙物時，所採取的策略是在中樞神經系統中預先編制的。惟前十字韌帶損傷和重建受試者之控制策略明顯與正常人不同，而前十字韌帶損傷與重建受試者之控制策略並無統計上之差異，顯示前十字韌帶的重建並未改變病人受傷後調適學習之控制策略。

Gait is the most common activity during human daily living and stepping over obstacles is an inevitable part of daily locomotion. Failure to negotiate successfully the obstacle will result in falls and injuries. A safe and successful obstacle-crossing requires stability of the body provided mainly by the stance limb and sufficient foot clearance of the leading limb. The anterior cruciate ligament (ACL) plays an important role in this activity, providing both the structural stability and sensory feedback of the knee joint. The purposes of the present study were to investigate the control strategies of normal subjects while crossing obstacles and to clarify the roles that the ACL plays in obstacle-crossing by studying ACL-deficient (ACL-D) and ACL-Reconstructed (ACL-R) subjects.
Twelve normal, 6 ACL-D and 6 ACL-R subjects participated in the study. They were asked to cross obstacles with 10%, 20% and 30% of their leg lengths while the kinematic data were collected with a three-dimensional motion analysis system (Vicon 370, Oxford Metrics, U.K.). A planar seven-link model combined with multiobjective optimal control theory was developed and used to simulate the motion of obstacle-crossing.
The model simulation results suggest that minimum energy was not the single objective the three subject groups used during obstacle-crossing. Instead, their control strategies were the best compromise between minimum energy and maximum foot clearance, with a unique fixed weighting ratio between the two objectives for each group. The weighting ratios were not influenced by the height of the obstacle (p>0.05), suggesting that the control strategy for negotiating with obstacles is preprogrammed in the CNS. However, the control strategies for the ACL groups were significantly different from that of the normal group (p<0.05) and there was no significant difference between the strategies for the ACL-D and ACL-R groups (p>0.05). This suggests that ACL reconstruction does not help change the control strategy in ACL-injured patients back to normal, possibly due to the incomplete sensory function of the ACL.

第1章 緒論 1
1.1 背景 1
1.2 下肢功能解剖構造 2
1.2.1 髖關節（Hip Joint） 3
1.2.2 膝關節（Knee Joint） 4
1.2.3 踝關節（Ankle Joint） 5
1.2.4 下肢關節周邊肌肉 6
1.3 文獻回顧 7
1.3.1 關節定義方式 7
1.3.2 下肢模型 9
1.3.3 跨越障礙物分析 11
1.3.4 現階段模型的限制 15
1.4 研究目的 15
第2章 實驗材料與方法 17
2.1 實驗對象 17
2.2 實驗儀器與設備 17
2.3 實驗流程與方法 20
2.4 實驗資料處理與分析 20
第3章 二維人體模型建立 26
3.1 二維人體模型之概述 26
3.2 模型之建立與座標系統之定義 27
3.3 正向與逆向動力學模擬：模型之驗證 32
第4章 跨越障礙之最佳控制模式 38
4.1 初始狀態與跨越障礙物控制策略的關係 38
4.2 下肢跨越障礙物的最佳控制 40
4.3 逆向動力學模型單目標最佳控制 45
4.4 多目標最佳控制 53
第5章 正常人與前十字韌帶病人跨越障礙物之控制策略比較 64
5.1 正常受試者 64
5.2 前十字韌帶缺損受試者 67
5.2.1 影響側跨越障礙物 67
5.2.2 健側跨越障礙物 70
5.2.3 前十字韌帶缺損受試者以不同側跨越障礙物之比較 73
5.3 前十字韌帶重建受試者 76
5.3.1 影響側跨越障礙物 76
5.3.2 健側跨越障礙物 79
5.3.3 前十字韌帶重建受試者以不同側跨越障礙物之比較 82
5.4 討論 85
第6章 結論 90
6.1 總結 90
6.2 未來研究方向 92
附錄A 93
參考文獻 95

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