Special Cycle-Ergometer to Optimize the Rider Position through Force Measurement

This paper presents an original 7-degrees of freedom device to analyze, 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 optimal 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. This method considers only partially the relation between the positions of arms and torso for different physiques. This special device, adjusted through hydraulic cylinder actuators, allows to achieve optimum horizontal saddle position by measuring horizontal forces on saddle and handlebar. The aim of the research is to determine a quantitative method to establish the optimum rider position in order to minimize the muscular efforts in aerobic phase. Moreover special pedals, developed both for cycling sport performances and for clinical analysis, equipped with three-axial load cells, measure the effective pedalling force exerted by the rider in three orthogonal directions. In particular the lateral force components on the pedals, perpendicular to the para-sagittal plane are measured. Notwithstanding literature usually neglects the lateral components in pathological and non pathological subjects, these components provide meaningful information in rehabilitation treatment of pathological subjects and moreover the biomechanical analysis of pedalling through three-axial force measurements over each pedal allows to improve efficiency during cycling performance.