Relaxed hand postures

Abstract

The objective of this study was to determine the relaxed hand postures in degree from a total of 14 finger joints including the thumb, index finger, middle finger, ring finger, and little finger without force exertions and constraints. Fifteen male students fully relaxed their right hands in 9 combinations of the hand positions of pronation, neutral, and supination at the shoulder flexion angles of 0 degree, 45 degrees, and 90 degrees. Vicon MX system was utilized to measure the joint angles with 8 cameras and 26 reflective markers. The hand position had more effects on the finger joint angles than the shoulder flexion angles. Overall, the fingers flexed with supination approximately 20% and 27% more than with neutral and pronation, respectively, due to the mass of the phalanges. For the same reason, the fingers were more flexed at the shoulder flexion angle of 90 degrees with the most hand positions except with the hand position of pronation because of the tensile force of the extensor muscles and connective tissues in the forearm.