The influence of the environment on the calculation of drag area in cycling: Contrasting results between indoor and outdoor field tests

Abstract

This study analyzes two methods of calculating drag area (C_DA) in cycling, Notio and Martin, in indoor and outdoor environments, to determine if C_DA is consistent regardless of the testing environment. In addition, we assess the practical utility of both methods in both environments for selecting the most aerodynamic equipment. Twelve trained cyclists rode on an indoor cycling track and an outdoor road with four different settings combining different equipment. Each cyclist performed 4 attempts with each setting, completing a total of 32 segments of 1500 m, 16 segments in each environment. We calculated C_DA using both Notio and Martin methods. We then evaluated the repeatability and reliability of each method in both environments. C_DA comparison revealed significant differences between indoor and outdoor environments for Martin (MD = 0.006 m²; SD = 0.009; p < 0.001), but not for Notio (MD = 0.001 m²; SD = 0.005; p = 0.569), with indoor C_DA being consistently higher. Standard error of measurement (SEM) was similar across environments: Notio (±0.004 m² indoor, ± 0.003 m² outdoor), and Martin (±0.005 m² indoor, ± 0.006 m² outdoor). Notably, the 95% confidence interval of the SEM (SEM95), exceeded the C_DA changes observed in all settings relative to the baseline, for both methods and in both environments. Although Notio, unlike Martin, calculates C_DA consistently regardless environment, neither method demonstrated sufficient sensitivity to detect changes in C_DA in either environment, limiting their practical utility for selecting the most aerodynamic equipment.