Effects of Pinch Technique, Torque Direction and Sensation on the Pinch Force in Loaded and Unloaded Conditions

Many daily hand-related tasks require the ability to produce and control pinch forces to handle small objects. While there have been studies of various parameter effects on grip force, there appear to be no studies that investigate these effects on pinch force. This study aims to determine the effects of pinch technique, torque direction and sensation on pinch force with an emphasis on screw knobs under loaded and unloaded conditions. A total of 30 manual workers participated in the study. The workers were required to operate loaded and unloaded screw knobs in clockwise and counterclockwise directions to produce pinch forces using reduced and increased sensations and 3 types of common pinch techniques. The data was analysed using the analysis of variance via Minitab 16. Results for both conditions showed that pinch force is significantly affected by torque direction, sensation and pinch technique. However, the interaction effects of sensation and torque direction on pinch force appeared to be insignificant for both conditions. This is because the effects of increased sensation which reduce pinch force were neutralised by the effects of clockwise torque direction which increase force, while the effects of reduced sensation which increase pinch force were compensated by the effects of counterclockwise rotations which reduce pinch force. This study serves as a fundamental guideline for researchers and designers to improve hand tool designs operated with pinch grips so that they are safer and more ergonomic for manual tasks in the industry.