Effect of friction and load on pinch force in a hand transfer task

Abstract

The effect of friction and load on pinch force was studied in a simple hand transfer task using a repeated measures design and ten men. Subjects moved a container between two targets, 450 mm apart, at a slow, self-paced speed. The levels of mass in the container were set at 0.8, 2.5 and 4.2 kg (7.5, 24.5 and 41.5 N respectively). The handle materials were sandpaper and smooth aluminum. Applied pinch force was measured via a strain gauge mounted in a specially-designed handle attached to the container. Dependent variables were peak and 'steady-state' pinch force. The main and interaction effects of load and friction were significant. The friction effect was significant only for the highest load which, on average, elicited peak pinch forces of 16-70% of maximum voluntary force. This suggests that these men were not sensitive to friction effects at the lower loads. Results suggest that the use of tool handle friction enhancements may reduce required pinch forces for objects requiring upwards of 50% or more of maximum pinch strength.

A biomechanical analysis of applied pinch force during periodontal scaling

“…The first term of the equation, w/2m, is derived from the minimum pinch force required to resist the force of gravity, where w is the tool mass and m is the coefficient of friction between the gloved fingers and the tool (Frederick and Armstrong, 1995). The second term, F z /2m, acts along the axis of the tool and is the pinch force required to resist the force of pulling or pushing.…”

“…The tool blade is held parallel to the tooth surface during scraping and different surfaces of the same tooth are accessed by changing the dentist's wrist or torso posture or by changing the tool to one with a different tip. Previous studies have estimated pinch forces required to perform hand intensive tasks, but none have created a biomechanical model to predict peak pinch force (Frederick and Armstrong, 1995;Buchholz et al, 1988;Radwin et al, 1992). Developing a model that predicts pinch force may be useful in identifying jobs that pose high risks of injury and assisting in the design of safer tools.…”

Effect of dental tool surface texture and material on static friction with a wet gloved fingertip

“…He did not study a gloved or wet finger, but did note that static friction is important for dental or surgical tools to prevent sudden tool slippage under wet or contaminated conditions. Frederick and Armstrong (1995) tested the effect of static friction and load on pinch force. In their study a container was transferred between two targets by pinching a handle with bare fingers.…”

“…The pinch force applied during scaling can be reduced by using periodontal tools of larger diameter or tools of lighter weight (Dong et al, 2006a, in press). Increasing the static friction between the fingers and an object can reduce the pinch force required to lift and move the object (Johansson and Westling, 1984;Frederick and Armstrong, 1995). Modifying the texture of a flat surface can change the coefficient of friction with the finger by up to 50% (Bobjer et al, 1993).…”

Hand Grip Function Assessed by the Box and Block Test Is Affected by Object Surfaces

“…One study investigated the cycle time for repeated grip and release movements for different coefficients of friction (COFs) of object surfaces. 5 Yet, they found no significant effect of the COF conditions of grasped objects on the cycle time. In that study, however, subjects were instructed to move at a slow self-paced speed, unlike many clinical hand function tests, including the BBT, that instruct people to move as fast as possible.…”