MODELING ROAD-CYCLING PERFORMANCE

This paper presents a complete set of equations for a ''first principl es'' mathematical model of road-cycling performance, including correct ions for the effect of winds, tire pres;sure and wheel radius, altitud e, relative humidity, rotational kinetic energy, drafting, and changed drag. The relevant physiological, biophysical, and environmental vari ables were measured in 41 experienced cyclists completing a 26-km road time trial. The correlation between actual and predicted times was 0. 89 (P less than or equal to 0.0001), with a mean difference of 0.74 mi n (1.73% of mean performance time) and a mean absolute difference of 1 .65 min (3.87%). Multiple simulations were performed where model input s were randomly varied using a normal distribution about the measured values with a SD equivalent to the estimated day-to-day variability or technical error of measurement in each of the inputs. This analysis y ielded 95% confidence limits for the predicted times. The model sugges ts that the main physiological factors contributing to road-cycling pe rformance are maximal O-2 consumption, fractional utilization of maxim al O-2 consumption, mechanical efficiency, and projected frontal area. The model is then applied to some practical problems in road cycling: the effect of drafting, the advantage of using smaller front wheels, the effects of added mass, the importance of rotational kinetic energy , the effect of changes in drag due to changes in bicycle configuratio n, the normalization of performances under different conditions, and t he limits of human performance.