Special Bicycle Ergometer for Optimum Rider Position

This paper presents an original 7-degrees of freedom device to adjust, test and optimize different positions of a bicycle rider. The system allows data acquisitions of forces, angles and velocities during cycling performance. An overall of eight forces and three angles are simultaneously measured. An efficient position enables the rider to reduce the muscular effort for a given power produced. Basically good bike position presents three general parameters: saddle height, saddle-to-bar distance, and fore/aft saddle position. Determining the correct horizontal saddle position is of relevant importance in finding the correct fit for a road cyclist and the final frame geometry. Moreover saddle position determines seat tube angle as well as the top tube/stem length dimension. The traditional method consists of positioning the rider's saddle so that the knee (the tibial tuberosity) is over the pedal spindle with the crank in horizontal position. But this method does not consider the relation between the positions of arms and torso for different physiques. This special device, actuated with hydraulic cylinders, allows to achieve optimum horizontal saddle position by measuring horizontal forces on saddle and handlebar. Pedals, with three axial load cells, measure the effective pedaling force in three orthogonal directions exerted by the rider. The aim of the research is to determine a quantitative method to establish the optimum rider position in order to minimize the muscular efforts.