您是否曾經想過手在日常生活中的重要性？那您又是否思索過受傷後的手，其傷害對於手的抓握功能有多大的影響，甚至嚴重影響工作和日常生活的執行？您是否曾經思考過僅僅一隻受傷的手指，無論是感覺或動作上的損傷，也可能是造成日常規律活動執行不佳的重要因子。事實上，人類的手由於其精緻的結構和複雜連結系統，我們將它視為十分高階的身體組成部分，由於其本身的複雜性，現今的評估系統很難精準地評量手指協調性(hand coordination)。文獻回顧指出協同模式(synergy pattern)被稱作是協調的基礎並且可以用量化的方式量測，其中一種協同模式稱為肌肉協同(muscle synergy)或稱做力量協同(force synergy)，也就是說在某個特定的手部姿勢下每隻手指的出力程度，因為協同模式的緣故可以形成特定的力量分佈。在本研究中，我們欲觀察柱狀握罐(cylindrical grasp)動作下各指力量的貢獻度(力量分佈)，並設計正常握罐和缺單指握罐姿勢以供檢測錯誤補償(error compensation)的概念和各指力量間的相關係數來檢測協同模式的強度，主成分分析(principle component analysis)同樣也在本研究中拿來檢測各指力量的變化趨勢的一致性，最後藉由獲得的基礎資料來建立正常人協同模式的力學模組。
研究中收集二十四位健康受試者和一位手部缺食指和中指的男性受試者的手部資料，我們設計了一個客製化的握罐模擬器，其中可裝載五個六軸荷重元以便量測五指的出力值。在實驗過程中，受試者被要求只能以五指的指腹觸及罐身以便量測到正確的抓握總力。除了缺指的受試者外，其餘的受試者必須執行正常握罐(normal grasp)和缺單指握罐(amputation-like grasp)的姿勢：正常握罐表示五指抓握罐身；缺單指握罐表示四指抓握罐身，依序從缺食指到缺小指姿勢，總共有四種缺單指的姿勢(缺食指T-MRL；缺中指 T-IRL；缺無名指T-IML；缺小指T-IMR)，缺指的受試者只需執行缺食指中指握罐姿勢即可(T-RL)。力學參數包含抓握力值、握力的變異程度、握罐指力貢獻度和指力彼此間的關聯強度。
結果顯示不同的握罐姿勢有不同的指力分佈型式，姆指總是貢獻大約50%的總握力，此外，五指的正向力(Fz)符合錯誤補償的概念，也就是說，缺指的鄰近手指增加力量貢獻度來代償缺指的損失，在握罐姿勢下，中指、無名指和小指形成一個特定的群組，會彼此互相代償其中一指的缺損；然而，五指的抗地心力(Fy)並沒有和正向力一樣形成一個特定分佈模式，而且也不適用錯誤代償的概念來解釋缺指後的力量分佈情形，事實上，每個人在抗地心力上的力量分佈情況有很大的變異性。相關係數和主成分分析的結果也同樣顯示正向力相較於抗地心力擁有較佳的協同程度，正向力顯示姆指總是與其餘各指擁有較高的相關程度(r>0.8)，另外鄰近的指力也傾向於擁有較高的相關程度，例如食指－中指和中指－無名指。關於正向力的主成分分析，第一主成分高達97%，如此顯示出五指間的正向力擁有極佳的協同趨勢。
本研究呈現了柱狀握罐姿勢下手指的力量分佈模式，包含正向力和抗地心力的分佈模式，各指間的正向力表現無論是靜態力量分佈和動態力量平衡中都擁有較高的協同模式表現，因此我們建議未來的研究可以繼續針對其他的手部動作，進行手指指力的協同模式做探討，評估正向力是否相較於其他方向的指力向量擁有高度的協同趨勢，以提供臨床研究一個手部協調評估指標和復健活動的建議。

Have you ever thought about the importance of your hand in your daily life? Could you imagine what a great influence of your hand grasp functions after suffering from hand injuries while working or performing daily activities? Most of people do not take this issue seriously. Actually, human hand is an advanced part of human body due to its’ refined structures and splendid connection systems. However, it’s hard to define the hand coordination ability through a quantitative method. In fact, synergy pattern which was said to be the basic mechanism of coordination could be measured in validity way. One of the synergetic patterns called muscle synergy could be referred as the muscles co-activation in the time serious. In other words, by measuring force produced by each finger in the specific multi-finger movement, the time series force data could be applied to identify the level of force synergy in specific hand movement. In the present study, we would like to construct a kinetic model about digit contribution pattern during cylindrical grasp movement. Other ideas about error compensation, the strength of relationship among digit force had been applied to explain the quality of synergetic pattern and coordination of the common multi-finger movement. Correlation matrix about digit force and principle component analysis would be processed to represent the strength of finger coordination in the study. Moreover, we would like to examine the force synergy change after finger being restricted.
Twenty-four healthy subjects and one male patient with index and middle finger amputee were recruited in the present study. A custom design glass simulator was designed to record the applied loads of the thumb and four fingers. Five six-axis force transducers were equipped on the glass simulator to record the applied loads. During the experiment, subjects were asked to perform a cylindrical grasp movement with finger pads only in order to get correct grasp force. Except the patient, Normal grasp posture and amputation-like posture were both performed by all subjects in the study. Holding the glass simulator with one finger restricted would be considered as the amputation-like trial. Four different amputation-like trials would be performed (T-MRL, T-IRL, T-IML and T-IMR). Patient would be asked to perform T-RL trial only. Parameters including grasp force, force distribution pattern change due to single finer restricted and force coefficient of variance would be processed. Correlation coefficients and principle component analysis (PCA) would be especially applied to estimate the strength of coordination.
Results showed that a specific digit force distribution pattern remaining in different holding postures. Thumb always account for 50% of total grasping force. Furthermore, in Fz (normal force) concerning, the adjacent finger would compensate for the absence finger which could match the principles of error compensation. Middle, ring and little finger formed a special group that each digit in the group would compensate for any missing finger in the group. However, Fy displayed a diverse distribution pattern as Fz. Fy distribution pattern were in great variability in subjects. Error compensation was not suitable for explaining the force change in anti-gravity direction (Fy) after finger been restriction. PCA results showed Fz of five digits presented strongest coordination, but not Fy. Actually, the first principle component of Fy contained variable contribution from thumb to little finger. After all, thumb presented highly relationship with other fingers in both normal grasping posture and amputation-like trials as compare to other fingers. Index finger-middle finger (IM) and middle finger-ring finger (MR) were other two groups demonstrate higher relationship (r>0.8).
The present project revealed the specific forces distribution pattern of digits in cylindrical grasping in both normal force and anti-gravity force concerning. Normal force synergy performance could be approached in both stationary and dynamic situations. Furthermore, we would like to recommend that future studies should focus on normal force synergistic performance but not anti-gravity force due to great force synergistic performance in normal force concerning.

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