手推輪椅使用者上肢傷害的發生率相當高，其發生原因是由於手推輪椅的主要動力來自於上肢的肌肉群，長時間及重複性的使用動作所產生的負荷累積易造成人體關節及周邊組織的傷害。同時，受到輪椅固有機構設計型態之侷限，造成輪椅使用者的上肢活動度以及輪椅推進過程中上肢運動軌跡皆會因輪椅型態而受限，使得輪椅推進成為一項效能相當低的動作，亦即在推進的過程中有相當多的能量耗損。瞭解輪椅設計參數對輪椅推進動作之影響將有利於降低累積性傷害。在過去有關人體動作分析的研究中，學者常利用一以生理參數為基本之分析模型來分析動作過程的生物力學參數；對於輪椅推進而言，建構此類分析模型將有助於探討輪椅與輪椅使用者之人機介面的相互影響。因此，本研究之主要目的為 (1)分析輪椅使用者於使用輪椅時其上肢受限於輪椅型態下所具有之活動空間並瞭解在此有限之活動空間中輪椅使用者選擇何種姿勢完成輪椅推進之動作；(2)探討輪椅使用者於不同手肘位置推進輪椅時上肢關節之受力及效能；(3)建構一分析模型預測輪椅推進之動態過程中之手推輪施力。
本研究於實驗部分，利用動作分析擷取系統以及一特製手推輪收集輪椅使用者於靜態與動態動作過程中上肢之運動學表現以及手推輪施力表現。整體實驗同時徵召有經驗的輪椅使用者以及無輪椅使用經驗的男性受試者參與完成。於探討手肘活動空間部分，受試者必須在五個不同手握輪圈位置下，盡可能移動手肘以獲得上肢活動空間。進一步，受試者分別以自覺最舒適之位置、最內側以及最外側位置三個不同手肘位置在五個不同手握輪圈位置上施力推動輪椅。最終，本研究建立了一個平面四連桿的機構模擬輪椅使用者之上肢及輪圈，此模型藉由提升效能並降低關節負荷的目標函數及上肢關節所能承受之生此模型藉由提升效能並降低關節負荷的目標函數及上肢關節所能承受之生理限制條件以最佳化模組來預測輪椅推進過程中之手推輪施力。而此分析模型所需之輸入參數則來自於當受試者以平均1 m/s的速度推進時所收集之運動學參數。
研究結果顯示固定手腕及肩膀位置時，手肘的活動軌跡會形成一弧狀，其活動空間由於生理機構受限使得其所涵蓋角度隨著手握於輪圈之不同位置而有所差異，弧之最小角度為62.1度，最大角度為83.4度。若以手肘最外側位置做為起始點，最內側為終點，輪椅使用者之自覺最舒適位置座落於整個可動範圍的2/3處，亦即較為靠近身體的位置。輪椅使用者選擇最舒適推進位置時之考量主要為降低上肢關節負荷同時提升有效推力。當我們以此特徵作為分析模型之條件來預測手推輪施力時，除了起始階段外，皆能有效預測手推輪施力。其中，預測有經驗與無經驗使用者之推力結果發現，由於無輪椅使用經驗的受試者在輪椅推進過程中之有效分力較高，因此模型預測之結果較佳。然而對於輪椅推進期的起始階段，由於未考量肌肉收縮動力學以致無法獲得準確之力量預測。
本實驗探究了輪椅使用者在侷限的輪椅型態下，上肢之活動空間以及在此有限之活動空間中輪椅使用者選擇何種姿勢完成輪椅推進之動作及其效能。同時，所建立之分析模型得以預測動態過程中之手推輪施力。當輪椅設計相關參數改變時，藉由模型的預測，可以進一步瞭解對輪椅使用者之影響，並能進一步對輪椅使用者選擇輪椅時提供資訊，選擇正確適合的輪椅，以降低傷害率並提高輪椅推進效能，同時提供輪椅使用者以及輪椅設計生產者設計客製化輪椅時的參考指標。

Wheelchair users suffer a limited range of motion of the upper extremities due to the confining wheelchair configuration. This is a key factor affecting the efficiency of wheelchair propulsion and upper extremity loading. Researchers of wheelchair propulsion have usually suggested that a wheelchair be properly designed using anthropometrics to reduce high mechanical load and thus reduce pain and damage to joints. A model based on physiological features and biomechanical principles can be used to determine anthropometric relationships for wheelchair fitting. Therefore, with a view toward further understanding the interaction between the user and wheelchair, the optimal position for wheelchair propulsion and the mechanism through which propulsion performance been enhanced, this study attempted to (1) to identify the total accessible workspace of the elbow while shoulder and hand are in positions demanded by conventional wheelchair and to identify the subset of the total accessible workspace used spontaneously by the elbow during wheelchair propulsion in novice and experienced wheelchair users; (2) to examines changes in propulsion forces and joint kinetics with varied elbow positions in a confined workspace to clarify the kinetic factors which determine preferred elbow position in novice and experienced wheelchair users; (3) to develop and validate a two-dimensional model to verify applied handrim forces during dynamic wheelchair propulsion for novice and habitual wheelchair users.
Male experienced wheelchair users and inexperienced wheelchair users participated in this study. Participants under standardized conservative wheelchair-sitting position moved their right elbow as widely as possible at five different wheel angles while elbow positions were recorded, thereby establishing the maximum possible elbow workspace. Actual positions of the right elbow were recorded during wheelchair propulsion. In addition, participants were instructed to propel a stationary wheelchair at three elbow positions: the inner position, preferred position, and outer position. An eight-camera motion analysis system recorded the kinematics of 14 non-experienced wheelchair users. An instrumented wheel and a motion capture system were used to collect kinetic and kinematic data from the subjects. To verify propulsion forces with an analytical model, kinematic data obtained from ten able-bodied and ten wheelchair-dependent users during level propulsion at a velocity of 1 m/s was used as the input of a planar model with the criteria of increasing efficiency and reducing joint load.
The arc angles of the elbow workspace range from 62.1 to 83.4 degrees and are located at the lateral and posterior quadrant of the circle on which the elbow trajectories located. The preferred positions for propulsion are located approximately 2/3’s of the way through the total workspace. Propulsion at outer positions exposed joints to greater loads as opposed to inner and preferred positions. Reducing joint loads together with increasing force effectiveness is a major consideration for users when choosing their preferred propulsion positions. Model computed results showed that for both experienced and inexperienced users, computed hand-rim contact forces agree with experimental data through an extensive range of the push. Significant deviations that were mostly observed in the early stage of the push phase might result from the lack of consideration of muscle dynamics and wrist joint biomechanics.
The obtained data will be useful for improved wheelchair design and biomechanical modeling of the wheelchair/user system. Additionally, findings in this study will be useful for identifying factors associated with upper extremity kinetics, prescribing a custom-fit wheelchair and improving wheelchair design.

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