Perceived and Actual Grasp Forces on Cylindrical Handles

Abstract

Objective: To compare the grasp force and the perceived grasp force, as a percentage of the maximum voluntary contraction (MVC), on cylindrical handles and describe a functional relationship between the two. Background: Repeated forceful exertions during work are associated with musculoskeletal disorders, and direct measurement of those forces is often difficult. Estimates are frequently made based on the judgments of force relative to the maximum grasp force capability of the individual. Method: Participants exerted grasp forces on five sizes of cylindrical handles. Pressure values at 16 locations (12 on the fingers and 4 on the distal ends of the metacarpal bones) were measured. Participants were asked to exert what they perceived to be specific percentages (in 10% increments) of their maximum grasp force on each of the five handles. Results: A linear relationship between perceived and actual grasp force was found up to the point of about 80% of perceived MVC. Above that point, the relationship became quadratic. A piecewise regression model was developed to fit the entire range of perceived grasp forces in one model. Conclusion: Grasp force is linear and consistent up until the perceived percentage MVC reaches 80%. After that point the relationship becomes quadratic. Application: In actual application, for grasp on cylindrical handles, practitioners can use a linear relationship between perceived percentage MVC and actual percentage MVC for perceived percentages of 80% or less. Above 80%, the piecewise quadratic relationship should be used.