Effects of position of the handles and feed force on discomfort score and grip strength during hand drilling

摘要

This study was to investigate the effect of the position of the main handle and of feed-force on the perceived discomfort-score and on the change in maximum voluntary contraction (MVC) grip strength in a drilling task using a pistol grip hand drill machine. Three positions of the main handle and three feed forces (40, 60 and 80 N) were chosen to perform the study for a given experimental task (i.e., hand drilling). Multivariate analysis of variance (MANOVA) showed that the position of the handle significantly affected discomfort-score (p < 0.001) and MVC grip (p < 0.001), while the effect of feed force was significant only on the discomfort score. With increase in feed force, the vibration levels at the machine were reduced, indicating more vibrations were absorbed at higher feed force by the hand/arm system. The most stressful points were shoulder (84.7% cases), elbow (18% cases), forearm (14.5% cases) and wrist (11.1% cases).