On metrics to assess road bicycle dynamic comfort during impacts

Abstract

A road bicycle's dynamic comfort relates to its capacity to filter vibration generated by the road surface. Typically, four quantities have been used to assess a road bicycle's dynamic comfort, acceleration, force, power, and energy; however, little has been done to compare the effectiveness of these in distinguishing between impact events. The aim of this study was to assess the ability of these four quantities when measured at a cyclist's hands, to discriminate between small changes in the level of an impact load applied at the front wheel of a road bicycle. With a rider seated on a bicycle, acceleration and force time signals were recorded at the left and right hands using instrumented brake hoods during a series of impacts at the front wheel on a bicycle treadmill. Six derived parameters of the acceleration, force, and power time signals were considered: discrete values: maximum, peak; mean values: root-mean-square, root-mean-quad; ratio values: crest factor, shock content quotient. Integral values were used for the energy. Various criteria were developed to assess the performance of these parameters and whether they should be recommended as road bicycle dynamic comfort metrics for impact events. The criteria were related to three characteristics: the consistency of the measurements, the parameter's statistical discrimination power, and how well changes in the parameter matched corresponding changes in impact level. The energy and root-mean-square value of power were found to be the top performers and are recommended as road bicycle dynamic comfort metrics for impact events. All acceleration-based parameters are not recommended. The remaining parameters demonstrated mixed results.