OPTIMIZING HANDLE SIZE BASED ON NORMALIZED HAND SIZE IN A MAXIMUM GRIPPING TASK

Six cylindrical handles were evaluated for the effect of handle size (diameter) on handle comfort, finger force capability and muscle activity in a maximum gripping task. Optimal handle size was calculated based on a ‘normalized hand size, NHS’, which was defined as the ratio of handle circumference to a user’s hand length. A pressure sensitive glove was used to measure finger force capability and surface electromyography was recorded from flexor digitorum superficialis and extensor digitorum to analyze muscle activity while participants performed maximum isometric grip exertions. The 35mm handle was rated as the most comfortable handle size followed by the 40mm. The 30 and 25 mm handles were associated with the highest finger force capability followed by the 35 and 40mm handles. The muscle activity of the flexor showed that 25, 30, and 35mm handles had high flexor muscle activities, whereas 45mm and 50mm handles represented low flexor muscle activities in this study. A 64 % NHS ratio was applied to obtain recommended handle sizes for comfort as a function of users ’ hand size in a maximum gripping task