Optimum design of handle shape through biomechanical modeling of hand tendon forces

A biomechanical hand model was developed to estimate tendon forces of the main flexor muscles, flexor digitorum profundus and flexor digitorum superficialis, in each finger and to suggest optimal handle designs based on the user's hand and finger sizes. Experimental force data were collected from force sensitive resistors (FSR) which were placed on the palmar surface of the fingers. These data were then applied to the hand model in order to predict the tendon forces and also used to compare the magnitudes and distributions of the finger and phalange forces in maximum gripping and pulling tasks.; Two handle shapes (double frustum and oval), two hook positions (center and off-center) with small or medium and large sizes, resulted in a total of ten different handles which were evaluated. Force data and Borg's subjective ratings of perceived exertion (RPE) were recorded for each condition.; In the maximum gripping task, the finger force distributions showed that the middle finger exerted significantly more force and the little finger exerted notably less force than did the other fingers. There was no significant difference between the index and ring fingers. The results of the pulling task were different from patterns found with the maximum gripping task. The index and middle fingers contributed an average of 55.2% of total pulling force and the contribution of the ring finger was smaller, followed by the little finger with the smallest contribution. The contributions of the index and middle fingers were not significantly different. Phalange force distributions for the gripping and pulling tasks also indicated significant differences from each other. The force imposed by the distal phalange was significantly higher than that imposed by the middle and the proximal phalanges in the gripping task, while the force exerted by the proximal phalange was always higher than those exerted by the others in the pulling task.; Results of the finger tendon force showed that the average tendon forces of the small-double frustum handles were significantly lower than those of the other handles in both tasks. Large-double frustum handles always showed the largest finger tendon forces. Lower tendon forces were also demonstrated for the off-center hook handles rather than the center hook handles. These results were also supported by significantly lower subjective ratings. All subjects generally preferred the small and medium-double frustum handles and medium-oval handles over the large handles. Subjects also reported higher preference for the off-center hook handles for the gripping task. (Abstract shortened by UMI.)...