The effect of seat-tube angle on biomechanical efficiency in cycling investigated by a new methodology: preliminary results on a new virtual sensor

Recent studies in Biomechanics are focused on postural optimization in cycling: among the numerous mechanical parameters the Seat Tube Angle (STA) is analyzed as the one that may influence the performance of cycling and triathlon athletes. In particular, it was conjectured that the STA may affect the biomechanical efficiency of a cyclist. The diffusion of this conjecture is testified by the frequent use of tuning techniques intending to get the ”optimal” STA angle by professional teams. In order to define a model of the biomechanical efficiency based on mechanical parameters, this paper presents a preliminary study aiming to confirm (or deny) this conjecture which asserts that a realistic biomechanical model has to include the STA as the independent (input) variable. The natural dependent (output) variable is the biomechanical efficiency measured by a new virtual sensor which hinges on both a dynamic and a static physiological model. In particular, those models where used to determine a range of mechanical and physiological values that guarantees a linear relationship between the biomechanical efficiency and the oxygen uptake. A two-phase experiment was designed to determine how changes in frame geometry during sub-maximal cycle ergometry have effects on the biomechanical efficiency. In particular, different STA positions were tested to argue if the STA is actually related to the cyclist performances. The methodology adopted was selected in order to keep constant all the major exogenous variables but the STA. The design of experiment results in a rigid protocol implemented on 14 subjects. The preliminary data analysis seems to suggest the existence of a relationship between the STA variation and the cycling efficiency. To prove an explicit relationship for all the athletes involved a more detailed statistical analysis is required. Further studies will investigate this particular aspect.