罐子是在日常生活中很常使用到的一種包裝容器，在開罐的任務有困難的人不在少數。要設計有效保存內容物且易於取用的罐子，必須了解開關罐時最輸出扭矩和力量協調模式。本研究的主要目地在於研究開關罐時，各手指力量協調和扭矩貢獻值。此外對性別差異進行分析。
本研究利用自行設計的罐子模擬器(罐子直徑8.0cm，內含有三顆六軸荷重元及扭力計)，測量三十六位男性和三十六位女生上肢功能正常受測者分別在開罐和關罐動作時，手指所施的力量和總扭矩，分析出手指的施力點、力量和協調模式。
在關罐時，女性中指、食指和小指的合力施力點與拇指和魚際部份合力施力點的距離大於男性(男 160.1°，女166.9°)，女性拇指和魚際部份合力施力點與食指施力點的距離大於男性(男 126.0°，女119.6°)。女性在開罐(男 2.41 N-m，女1.98N-m)與關罐的扭矩絕對值都小於男性。除了中指、食指和小指的切線力開罐時沒有性別差異，其他部份不論在開關罐，女性的總合力、正向力和切線力都小於男性。長軸向力只有中指、食指和小指在開罐時，有顯著差異(男3.9N，女-0.6N)。女性的食指與中指、無名指和小指的在開罐貢獻較高。除了食指之外，女性在協調模式的正向力比值小於男性。女性的食指在開罐時，中指，食指和小指的在協調模式的切線力比值高於男性。女性的拇指和魚際部份和食指在關罐協調模式的長軸向力比值高於男性。相較於男性，女性對罐蓋施予的力量較小，卻更有效率的旋轉罐蓋，開罐動作時，更有效應用中指、無名指和小指產生扭矩，使開罐和關罐扭矩更接近。
在扭轉罐子時，拇指與魚際部份對扭矩貢獻最大，中指、無名指和小指次中，食指最少。.
以開罐為對照組，關罐時中指、食指及小指的施力點會遠距拇指和魚際部分的施力點。食指的施力點會遠離中指、食指和小指的施力點，向拇指和魚際部份靠攏。關罐的最大扭矩是開罐時的1.4倍。拇指和手掌魚際部份的總合力、切線力在協調模式比值和扭矩貢獻增加。中指、無名指及小指切線力在協調模式比值增加。食指在開關罐之間的變化異於其他手指，不但關罐時的總合力下降，協調模式中切線力比值也下降。表示食指的功能不只提供扭矩，還有維持穩定與協調功能。
此結果對手功能估評、復健、動作控制、及產品設計都提供具有參考價值的資料。

Jar is one of packaging containers usually used in our daily life. However, a large number of people are still not able to open the jar. In designing the jar for protection, preservation, and ease of access, the knowledge about maximum torque output and force coordination of the digits in jar opening and closing should be understood in advance. The purpose of this study was to investigate the applied force coordination and twisting torque contribution ratio of the digits in jar opening and closing. In addition, the gender difference was analyzed.
In this study, 36 male and 36 female subjects were recruited to measure the total twisting torque and applied loads of the digits in order to analyze their points of force application, and the force coordination using the custom jar simulator (diameter 8.0 cm, equipped with three six-axis load cells and one torque cell) when subjects opened and closed jars, respectively. The applied forces and moments of the thumb/thenar part, index, as well as the medial, ring and little fingers were measured by three six-axis load cells, respectively.
In female, the point of combined force application of the medial, ring and little fingers, 166.9° away from the thumb and thenar part, was greater from that, 160.1°, in male when subjects closed the jars. In female, the point of combined force application of the thumb and thenar part, 126.0° away from the index, was smaller from that, 119.6°, in male when subjects closed the jars. The maximum torque generated by male was greater that generated by female in jar opening (male 2.41 N-m, female 1.98 N-m) and closing (male 3.59 N-m, female 2.64 N-m). Except the tangential forces applied by the medial, ring and little fingers in jar opening, the magnitude of applied force and its components in all digits during turning jars were smaller in female compared with male. Compared with male, the twisting torque contribution of the index in female was also smaller, but the combined twisting torque contribution of medial, ring and little fingers in female was greater. Concerning the applied force ratio, the normal force ratio and longitudinal axial force ratio were smaller in female. Although the female applied the smaller force on the lid, their tangential force ratio used for twisting the lid was greater than that in male. While opening a jar, female subjects could generate the twisting torque efficiently using the combined medial, ring and little fingers to increase the torque up to similar magnitude used for closing a jar.
In turning a jar, the greatest torque contribution was from the thumb and thenar part, next the combined medial, ring and little fingers, and the index the least.
Compared with opening a jar, the point of combined force application of the medial, ring and little fingers was far away the thumb and thenar part in closing the jar. In addition, the point of force application of index finger was far away from the point of combined force application of the medial, ring and little fingers, and closer to the thumb and thenar part in closing the jar. The magnitude of total generated torque in closing a jar was 1.4 times greater than that in opening a jar. Also, the applied force, tangential force ratio, and torque contribution by the thumb and thenar part as well as the combined tangential force ratio of the medial, ring and little fingers increased in closing a jar. On the contrary, the function of index finger was different from other fingers in closing the jar. The applied force, the tangent force ratio and torque contribution by the index decreased in closing a jar. It indicated that the index finger plays an important role in force coordination and stabilization in addition to generation of twisting torque.
In conclusion, the studies provided important biomechanical information, especially in multi-digit force coordination and torque contribution, which may give valuable help for assessment of hand function and motor control as well as design of the jar with lid and related assistive devices.

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