The answer depends on the type of grip used. And, there is no universally accepted method to do so but here goes.

If the grip is for lifting, then measure the tare weight to lift the object from the floor using a force gauge and hook. The force will equate to the amount of grip needed to move the object.

If the grip is for tool use it is harder. You can do the method you spoke of but in doing so you should get a sample of 1/4 the workers performing that task and then take the average.

Or, if the object gripped is fixed you can push against the moving arm or handle to measure the force required to compress the handle (paddle switch, etc.).

A tool used dynamically (hammer, screwdriver, shovel) is tough to measure or estimate. I haven’t found a reliable method. Most often I use the observational method – see the attachment. (CPDs can email for attachment)

You can plug this data into the Moore-Garg or Rohmert’s ergonomics tools, etc.

If you happen to find a method in your search, I’d like to know. Good luck!

Vic Zuccarello, OTR/L, C.E.A.S. II, ABDA