Hand Torque Strength with Cylindrical Handles

Abstract

The relationship between the diameter of a smooth cylindrical handle and the torque that can be applied by the human hand has been analyzed. An analytical model has been derived for the maximum torque that can be developed before the hand slips on the handle. The model has been tentatively verified by torque measurements on 20 subjects using a series of smooth phenolic fiber cylinders ranging in diameter from 0.95 to 8.89 cm. The results of the analysis are: (1) Torque increases as the square of the handle diameter up to the point where the fingers and palm just touch without overlapping. This “grip-span diameter” is approximately 2.5 centimeters. (2) For larger diameters the torque continues to increase, but at a decreasing rate and reaches a maximum when the diameter is approximately 5 centimeters. (3) The maximum torque is approximately one and one-half times the torque obtainable at the grip-span diameter. (4) Female torque capability is about 40 percent of that of males. (5) The grip-span and maximum-torque diameters do not vary greatly between males and females. The analytical model is derived and discussed.