Study on the grip spans of combination pliers in a maximum gripping task

• Custom-made combination pliers with an adjustable grip span were applied.
• 50–60 mm was recommended as the most desirable grip spans of combination pliers.
• 80 mm grip span showed the least grip strengths and the most discomfort rating.
• The basic data for the manufacturing and designing of pliers were suggested.

A newly developed system was applied in this study to evaluate the effects of the grip spans (45–80 mm) of combination pliers on the total grip strength, individual finger force, resultant force, and subjective discomfort. A total of twenty-six males participated and were asked to exert their maximum grip strength with two repetitions. The highest and the lowest total grip strength and resultant force (311.8 N and 737.9 N vs. 210.1 N and 501.7 N) were obtained at a 60 mm and 80 mm grip spans, respectively. In general, the participants considered the 50 and 60 mm grip spans as being the least discomfort, whereas the 80 mm grip span was considered as the most discomfort grip span in a maximum grasping task. The results can be utilized as basic data for the manufacturing and design industries of two-handle hand tools, such as pliers and wrenches.Practitioners summaryCustom-made combination pliers were applied in this study to evaluate grip strength, resultant force, and subjective discomfort, relative to five grip spans. The authors expect that the results of the present study will provide valuable information for the designers and users of pliers.