Comparison of comfort, discomfort, and continuum ratings of force levels and hand regions during gripping exertions

The goal of this study was to compare three different evaluation systems of comfort, discomfort, and a continuum for the force levels and hand regions when gripping hand tools. Seventy-two participants were assigned to three groups, each group testing a different evaluation system. Each participant exerted ten levels of submaximal voluntary contractions on hand tools and used their assigned evaluation system to evaluate comfortable or uncomfortable feelings for the force levels and five different regions of the hand. The participants generally rated higher discomfort as required forces increased, but the discomfort and continuum evaluation systems were better than the comfort evaluation system because gripping exertion was related to the physical aspects of the hand tools and their users. Based on the results of the continuum evaluation system, the feeling changed from comfort to discomfort at 65% maximum voluntary contraction. The palm was the region of the hand with the most discomfort. Other design factors affecting comfort need to also be considered in order to better understand hand tool use.