| Summary: | 碩士 === 國立成功大學 === 醫學工程研究所碩博士班 === 96 === 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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