Opening Jars: An Anthropometric Study of the Wrist-Twisting Strength of the Elderly

Abstract

The purpose of this study was to measure the wrist-twisting strength among the elderly. The subjects were 100 men and 100 women whose ages ranged from 62 to 92 years. To measure their wrist-twisting strength a device was developed that consisted of a modified torque-wrench which would accept 8 different container lids whose diameters ranged from 27 mm to 123 mm. Each subject performed the wrist-twisting task on each lid 4 times – twice clockwise and twice counter-clockwise. The results showed that men were stronger than the women, that there was no difference in the torque from a clockwise or a counter-clockwise twist, and that a greater amount of torque could be applied to large diameter lids than to smaller diameter lids. When age, body weight, height, grasp, lateral prehension, and hand length, breadth, and spread were correlated with the wrist-twisting strength it was found that for the men, age, grasp and hand length contributed to torque and for the women, body weight, grasp, and lateral prehension were the main determinants of torque. In addition the torque required to open various commercial products was measured so that by comparing these torque values with those of the wrist-twisting strength it was able to estimate the percentage of men and women who could open a jar of a given diameter and torque.