此研究之目的為測試痙攣雙邊麻痺型腦性麻痺兒童於不同伸手動作限制下的動作表現(手部伸手活動結果、姿勢調整以及動作模式)；同時檢驗伸手活動表現與兒童姿勢控制能力之關連性。十二位痙攣雙邊麻痺型腦性麻痺兒童以及17位一般發展兒童參與此研究。他們坐在凳子上從事一個伸手碰觸到一個位於120%的手長距離之玩具後再回來的活動任務，伸手的速度是根據節拍器所發出的頻率(46次/分鐘)而調整。玩具的位置包含身體正前方、往旁40度以及往內40度。本研究使用一套動作分析系統、兩塊力板以擷取兒童伸手活動過程中肢體的運動學、力板反作用力以及壓力中心 (center of pressure)的資料與變化情形；也以兒童伸手測試(Pediatric Reach test)方式評估兒童的姿勢控制能力。以伸手動作時間、手部筆直率(hand straightness ratio)、手部最大峰值速度、手部動作單位(hand movement unit)、絕對最大壓力中心峰值速度、前後方向地板反作用的平均力(分為手部加速與減速期)、姿勢排列(手動作前的300ms)以及關節角度變化(手部加速與減速期)等變項陳述伸手活動情形，使用多變項分析(MANOVA)方式分析組間效應、任務效應以及組間任務的交互作用。以皮爾森積差相關係數檢驗伸手活動表現與姿勢控制能力間之相關性。
就手部伸手表現的結果而言，痙攣雙邊麻痺型腦性麻痺兒童相較於一般發展兒童表現出較長的動作時間(組間效應F = 4.29, p = 0.017)、較大的手部筆直率(組間效應於伸手期：F = 16.32, p < 0.001；回復期：F = 6.53, p = 0.014)、較多的動作單位(組間效應F = 4.38, p = 0.016)。此外痙攣雙邊麻痺型腦性麻痺兒童於從事往外以及往內側的伸手活動時，手部筆直率會變大而一般發展兒童卻不受動作任務限制的影響。兒童手部的筆直率、動作單位表現與其姿勢控制能力呈現中度的相關性(相關係數介於-0.326與-0.735)。
就壓力中心與力板反作用力的結果而言，痙攣雙邊麻痺型腦性麻痺兒童相較於一般發展兒童於往前與往外的伸手活動中，呈現出較大的內外側壓力中心速度的絕對最大峰值(組間效應F = 4.74, p = 0.015)、較小的壓力中心晃動比率(較寬廣的壓力中心晃動模式)(組間效應F = 6.48, p = 0.002)以及較大的力道調整(誇張的姿勢控制)。例如：有較多比例的痙攣雙邊麻痺型腦性麻痺兒童於手部加速期時，表現出較明顯的力板前後向反作用力(往外伸手：Fisher exact, p =0.024；往內伸手：Fisher exact, p = 0.008).就關聯性而言，伸手過程中壓力中心的晃動比率與兒童姿勢控制能力呈現中等相關的關係(相關係數介於0.478與0.618)；而椅子的壓力中心晃動比率也與手部的動作單位呈現負向的相關性(相關係數介於-0.445與-0.474)。
就動作模式(關節的角度變化情形)而言，痙攣雙邊麻痺型腦性麻痺兒童在從事伸手活動時，不能很好地協調各個不同關節間的動作，他們容易單獨先動某一關節再動下一個，造成關節間的動作變化曲線出現崎嶇或者突然轉折的現象。他們徵召了較多的軀幹與下肢的不同關節活動度來完成伸手活動。研究也發現在手部加速期或減速期中，軀幹各角度變化上、骨盆左右傾斜以及髖關節的外展/內展動作變化上均呈現顯著的組間與任務的交互作用；就身體軀幹角度變化上而言，於手部加速期，痙攣雙邊麻痺型腦性麻痺兒童比一般發展兒童沒法有效率調整身體轉動角度去適應不同動作任務(痙攣雙邊麻痺型腦性麻痺兒童：往前伸手的平均角度變化為-3.48度、往外伸手的平均角度變化為-1.29度、往內伸手的平均角度變化為-7.63度；一般發展兒童依序為-3.48、-0.04以及-10.04度；組間任務交互作用為F = 4.240, p = 0.025)；他們會在伸手動作開始之前，就先轉動身體以減少活動中所需調整的角度變化(組間效應F = 3.080, p = 0.046；組間任務交互作用F = 4.092, p = 0.029)。這樣的現象在往內伸手活動時，更形明顯！或許痙攣雙邊麻痺型腦性麻痺兒童感知自己在平衡能力上限制，因而產生不一樣的動作模式以解決伸手活動所產生的動作問題；此外痙攣雙邊麻痺型腦性麻痺兒童在處理伸手活動時，明顯使用了身體與下肢互相抗衡(counterbalance)的方式來平衡自己，他們在處理不同伸手方向時，不像一般發展兒童一樣可以有效率的調整身體轉動角度，他們會先在伸手前轉動身體，以減少活動中身體轉動需求，並改用其他關節的活動度來完成活動。所以痙攣雙邊麻痺型腦性麻痺兒童的確會根據自己狀況而呈現出不同的動作模式，但是當其活動挑戰到他們的姿勢控制能力時(需同時出現身體調整方向與手部往前伸手)，這些方式有可能是效率較差、不協調地，故臨床工作者應多注意這樣的伸手活動特性，多讓動作障礙孩童練習這類型的動作任務，以期減少未來平衡不穩的危險。

The purposes of the study were to examine the effect of reach task constraints on the reaching performance in terms of outcome of hand reach, postural adjustment, and motor patterns in children with spastic diplegic cerebral palsy (di-CP) and to examine the correlations between the reaching performance and postural control ability. Twelve children with di-CP and 17 typically developing (TD) children participated in the study. They performed a reach-and-return task with a seated posture on a stool. The target of a toy for reaching was set at a 120% arm length distance in three directions of the children (anterior, medial, and lateral). Reaching speed was modulated with a metronome at a rate of 46 beats/min. A motion capture system and 2 force platforms, with a sampling rate of 150 Hz, were used to measure the kinematic data, ground reaction force (GRF) and center of pressure (COP). Postural control ability was assessed with a Pediatric Reach Test (PRT). Movement time (MT), hand straightness ratio (hand_SR), hand peak velocity (PV), hand movement unit (hand_MU), absolute peak COP velocity, COP sway ratio (COP_SR), mean GRF in the anterior posterior direction during the acceleration and deceleration segments of reaching, postural alignment (300 ms before hand reached), and angular changes of joint movement during acceleration and deceleration segments were compared between groups and among task conditions with MANOVA method. Pearson’s product–moment correlation coefficients were used to examine the correlations between reaching performance and postural control ability.
For hand reach performance, children with di-CP presented longer MT (group effect, F = 4.29, p = 0.017), larger hand_SR (group effect, F = 16.32, p < 0.001) and more hand_MUs (group effect, F = 6.53, p = 0.014) than did TD children. Further, the children with di-CP showed larger hand_SR while reaching medially and laterally than anteriorly. But TD children were not affected by these task constraints. Moderate correlations between postural control ability and SR and MUs were noted (r = -0.326~-0.735).
For COP and GRF information, children with di-CP showed a greater absolute peak COP velocity in the medial lateral direction (group effect, F = 4.74, p = 0.015), a smaller COP_SR (wider COP pattern) (group effect, F = 6.48, p = 0.002), and greater amplitude of force modulation (exaggerated postural adjustments) than TD children in lateral or medial reaches. Greater proportion of children with di-CP showed a greater mean AP_GRF than TD children did during hand acceleration segments (lateral reach: Fisher exact, p =0.024; medial reach: Fisher exact, p = 0.008). There was a moderate positive correlation between COP_SR and postural control ability (total PRT score) (r = 0.478~0.618). The chair COP_SR was also negatively correlated with the hand movement units (r = -0.445~-0.474).
For motor patterns in terms of angular changes of joints, children with di-CP could not well coordinate different joints to finish a reach task. They moved body segments separately (cranky, sharp curved angular displacement between joints). Children with di-CP recruited different degrees of freedom in axial body and lower extremities to complete the reach task, especially the medial reach. Interaction effects of trunk motions, pelvis motion in the frontal plane and hip motion in frontal plane during hand acceleration or deceleration segments were noted in the study. Apparently, children with di-CP did not efficiently adjust the range of trunk rotation in accordance with reaching condition compared with TD children did during hand acceleration segment (di-CP: anterior reach = -3.48, lateral reach = -1.29, and medial reach = -7.63; TD: anterior reach = -3.48, lateral reach = -0.04, and medial reach = -10.04; interaction effect: F = 4.240, p = 0.025). Furthermore, children with di-CP prepared their trunk alignment in advance in order to decrease the need of postural adjustment during the task (group effect: F = 3.080, p = 0.046; interaction effect: F = 4.092, p = 0.029).
Children with di-CP and TD presented different motor patterns during reach, especially during reaching medially. Children with di-CP may perceive their individual constraints (e.g. insufficient postural control ability), then adopted different motor solutions. Children with di-CP showed apparently counterbalance force between trunk and feet as reaching out. We also noted that children with di-CP would rotate the trunk toward the reach direction in advance but TD children did not. The results confirmed that children with di-CP did not significantly adjust trunk rotation, according to the reach direction, as TD children. Instead, they recruited different degrees of movements to complete the task, such as pelvis rotation motion at lateral reach or trunk sidebending and extension at medial reach. Therefore, children with di-CP did adjust their personal constraint to manage the task demands. However, the motor solutions could be inefficient and inadequately coordinated when the task demands challenge individual’s postural control ability. In our study, the results showed that the medial reach with a seated posture on a stool, which involved trunk rotation, could be challenging in children with di-CP. Clinicians should pay attention to this kind of reach task (involving trunk-oriented adjustment and hand reach at the same time) and manage children with di-CP to practice this kind of tasks frequently in order to function in daily activities safely.

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