研究背景與目的：體感覺在站立平衡控制中是相當重要一種感覺訊息來源，因為它能夠提供神經系統包括：身體與外界的接觸感覺，和肢體與肢體間的相對位置感覺等訊息，而藉以維持身體的穩定狀態。過去文獻指出，當正常的體感覺輸入被改變後，站立平衡控制能力便會有惡化的情況產生，雖然這些研究利用實驗室方法改變了原本正常體感覺輸入，但多半是造成未知程度的體感覺改變(如：軟墊站立)，或是完全將體感覺輸入阻斷(如：缺血性阻斷)，因此體感覺的喪失程度和平衡控制能力改變之間的關係仍舊不甚明確。因此，本篇研究的目的便是要探討在不同程度的體感覺喪失情況下，對站立平衡控制的影響程度。

　　研究方法：共有21名健康的年輕受試者參與本實驗。整個實驗過程中，利用缺血性阻斷的方式，來阻斷受試者腳踝以下的體感覺輸入，並利用阻斷時間的不同，以製造以下三種不同程度的體感覺喪失情況：正常的體感覺輸入、部分體感覺喪失情況，和體感覺完全喪失情況。為了確認體感覺被阻斷的程度，受試者會接受二種不同的感覺測量，包括：1) 觸壓覺閾值，和2) 電流感覺閾值。觸壓覺閾值(反應受試者對觸壓感覺的敏感度)是利用Semmes-Weinstein單纖維尼龍絲來作測量；電流感覺閾值(反應受試者的大型神經纖維對電流刺激強度敏感度)則是使用神經感覺測試儀來作測量，此儀器能產生非侵入性的經皮電刺激，並以刺激電量的大小來量化受試者的電流感覺閾值。在平衡功能測試部分，受試者必須完成以下四種不同的平衡功能測試項目：1) 自然站立情況(同時在張眼和閉眼二種情況下)，和2) 較窄支撐底面的站立情況(同時在張眼和閉眼二種情況下)。在資料分析的部分，會利用壓力中心(center of pressure)的位移反應受試者的平衡控制能力，並計算以下幾個壓力中心的位移參數：位移軌跡、前後向位移幅度，和前後向位移速度。

　　結果：在體感覺測量部分，觸壓覺閾值和電流感覺閾值都隨著體感覺喪失的愈多，而顯著增加。在平衡控制能力部分，受試者不論執行那一種平衡功能測試項目，其壓力中心的位移軌跡和前後向位速度等二個參數，在體感覺部分喪失和完全喪失兩種情況各分別與正常體感覺輸入情況相較，都有顯著的增加。比較受試者在體感覺部分喪失和體感覺完全喪失等二個情況下的平衡控制能力時，受試者只有在較窄底面積站立，且閉眼的情況下，其壓力中心的位移軌跡和前後向位移速度，才有顯著的改變。

　　結論：體感覺輸入不論是部分喪失或完全喪失，都會影向我們的站立平衡控制能力。此外，平衡控制能力的惡化並不單只與體感覺所喪失的程度相關，它還與所剩餘可利用的其它週邊感覺輸入的多寡，和所執行的平衡功能項目的難易度有關。藉由這樣的結果，當我們在臨床上評估一個體感覺損傷的病人其平衡控制能力時，除了注意其感覺受損的程度之外，還必須同時著重其所能利用的剩餘週邊感覺輸入，和其所執行的平衡功能測試項目的難易度。

　　Background and Purpose：Somatosensation allows the nervous system to determine surface orientation as well as the relation between body segments, and thus provides essential sensory input for balance control. Previous studies have shown that experimentally induced changes in the function of the somatosensory system would be accompanied by deterioration in standing balance control. While some of the studies induced unknown degrees of altered sensory condition (i.e. standing on a compliant surface), others induced total sensory loss (i.e. ischemic blockage). However, the relationship between the degree of somatosensory loss and balance deterioration is still not clear. The purpose of this study was to investigate the influence of different degrees of somatosensation loss on standing balance control.

　　Methods：Twenty-one healthy young subjects were recruited. Three somatosensory statuses, intact, partial loss, and total loss, were manipulated by varying the duration of ischemic blocking of afferent inputs below the ankles. To identify the extent of somatosensory loss induced by ischemic blockage, two sensory tests were performed: 1) touch-pressure threshold (TPT), and 2) current perception threshold (CPT). TPT (reflected the sensitivity to the touch and pressure stimulation) was measured by Semmes-Weinstein Aesthesiometer; CPT (reflected the sensitivity of the large afferent fiber to electrical stimulation), was measured by Neurometer, which emitted a non-aversive transcutaneous electrical stimulus to quantify CPT values. Subjects were asked to perform the following balance tasks：quiet stance with eye open and eye closed；narrow space stance with eye open and eye closed, on a force platform. The following variables of the motion of center of pressure (to reflect the body sway during quiet standing) were calculated for analysis：trajectory, anteroposterior range (AP range), and anteroposterior mean instantaneous velocity (AP velocity).

　　Results：TPT and CPT were significantly increased according to greater extent of somatosensation loss. In all the balance trials, trajectory and AP velocity were significantly increased in both partial and total loss conditions when comparing to those in intact sensory condition. Between partial and total sensory loss conditions, the trajectory and AP velocity were changed significantly only in the narrow space standing trial, eye closed condition.

　　Conclusion：Both partial and total loss of somatosensation would deteriorate standing balance control abilities. In addition, deterioration of balance performance was not solely determined by the degree of somatosensory loss, but also by the availability of other sensory sources and the difficulty of the balance task. Thus, when evaluating balance performances of patients with somatosensory dysfunction clinically, attention should be also be given to the availability of other sensory inputs and task difficulty.

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