Does anyone know of any research or a general rule of thumb for the amount of strength used during grasp and push activities in relation to the force necessary to actually push the item. For example, it takes 1 lb of force to push a pencil into a pencil sharpener but how much grip force is necessary to maintain a solid grasp while doing this. I know there are a lot of variables but I just wondered if there were some rule out there. I may end up using some force gauges.
For the type of gripping involved in pushing the pencil into the sharpener, the amount of grip force required has a lot to do with the coefficient of friction between the fingers and the sides of the pencil. If you’re pushing in with 1 pound of force, and the coefficient of friction is 0.5, then it would take at least 2 pounds of force just to keep your hand from sliding down the pencil.
People do have a tendency to use more force than is required, especially when they’re new at a task. And coefficients of friction vary depending on how dry the skin is, the shape and surface of the object they’re grasping, etc. It may be easier to use force gauges, as you suggest.
As Rick Goggins mentioned, there are many variables that affect the gripping force. I am not aware of any rule of thumb but I did recently run across a data point that may give some guidance. Part of the research in the article noted below involved subjects holding a dumbell in a vertical orientation. The subjects were asked to hold a 4.5 kg dumbell with minimal grip force so that the dumbell would not slip down. The article notes that with clear instructions the estimated grip force required was 63.2 N. The force was estimated by force matching with a grip dynamometer. See the article for a full description and results from their trials with and w/clear instructions.
Article: Estimation of hand force in ergonomic job evaluations, S. Bao & B Silverstien, Ergonomics, Vol. 48, No. 3, 22 February 2005, 288-301
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