A comparative investigation of the influence of certain arm positions on hand pinch grips in the standing and sitting positions of dentists.

Hand pinch grips in the standing and sitting positions on a group of 46 healthy males of 20 to 26 years old were measured. The results were as follows: 1. Hand pinch grip forces are higher when the subject is standing than when he is sitting. 2. Hand pinch grip forces, depending on the position of the arm in the working space, are higher when the arm is supported than the corresponding forces of the unsupported arm. 3. There is an effect due to the position of the arm in relation to the frontal position of the subject's thorax. In the standing position, the forces are maximum when the forearm has a 60 degrees angle towards the frontal position, while in the sitting position pinch grip forces are maximum when the forearm is perpendicular (90 degrees ) to the frontal position. 4. A handle which permits all fingers to be spread in a pinch grip is capable of having an applied force 50% greater than if the thumb and either forefinger or middlefinger grips the handle. In such a handle each finger is required to apply less force to contribute to the total needed for the task, and therefore there is a diminished likelihood of the onset of fatigue.