Objective: The purpose of this study is to investigate the finger functions while accomplishing the active operation of using a prismatic object. We measured each finger pressure toward the object when the center of gravity changes the position toward distal, proximal, thumb side and finger side.

Method: The Maximal Voluntary Prehension Power (MVPP) was measured for 10 female volunteers respectively. Also, the finger pressure when changing the positions of center of gravity was also measured. The loads were set at 200 g and 400 g, and were suspended at five positions. The fingers pressures were measured over all trials and the %MVPP was calculated and analyzed.

Result: When the loads were changed from the center position to the distal and proximal side, %MVPP of index finger especially increased in the distal side. In the proximal side, %MVPP of little finger increased more than center position. When the load positions were changed from center to thumb side and finger side, %MVPP of the little finger increased in the thumb side of center of gravity and %MVPP of the index finger increased in the finger side of center of gravity due to the rotation torque toward pronation and supination.

Discussion: From the results, we found that each finger had an interaction of finger function and finger coordinated motion control from the temporal changing of finger pressure and %MVPP. The change in center of gravity direction correlated with providing patterns of each finger pressure and %MVPP.

Finger function, Active manipulation, Center of gravity