In this study, optimal grip span between a bicycle handlebar and a brake lever was determined by a twodimensionalbiomechanical hand model. A three-step process was applied: (1) develop a two- dimensionalbiomechanical hand model, (2) determine input data for hand model simulation, and (3) conductmathematical simulation. In the first step, in order to estimate tendon forces, joint constraint forces andtotal gripping support force at the metacarpal, a mathematical static hand model was developed based uponthe hand anatomy and static equilibrium conditions. In the second step, US 50%ile hand length wasselected as target population from the 1988 US Army data, and grip postures for five participants(averagehand length = 18.2 cm and SD = 0.8) were measured to get joint angles( θ_1, θ_2, and θ_3 ) which are requiredfor the hand model simulation, by using a dynamometer having adjustable grip spans such as 4, 5.2, 6.4,7.6, and 8.8 cm. In the third and final step, mathematical simulation was conducted to determine an optimalgrip span. Consequently, on given external load(grip force), 100 N, both total tendon forces and totalgripping support force of the metacarpal showed monotonically increasing trend while grip spanbroadening from 4 to 8.8 cm. Also, minimum of both total tendon force and total gripping support force atthe metacarpal was achieved at 4 cm grip span.
展开▼
