Bike fit practices do not match scientific evidence

Abstract

Introduction Many bike technicians optimise bike fit using experience, look and feel, and 2D videos rather than 3D methods or scientific evidence. Therefore, cycling communities and scientists have different measures and views in regards to optimal bike configurations1. The most controversial component of bike fit is saddle height, leading to many studies on the topic. An optimal saddle height is vital as affects both performance and injury risk1. Aims • Compare 2D and 3D motion capture measures from road bike fit analyses (Fig 2). • Verify the alignment between current bike set ups in the cycling community and evidence-based recommendations. Methods Recreational road cyclists (8 males, 3 females; age 39.7 + 9.7 y; mass 72.4 + 14.1 kg; frame size 54.2 + 2.8 cm; cycling 7.1 + 4.4 h/week) cycled on a Cyclus 2 ergometer with their own bikes at 150 W for 90 s. Cycling motion was recorded at 120 Hz in 3D (Qualisys AB) and 2D (Sony RX10 II). Data were extracted using Visual 3D and Siliconcoach softwares, respectively. Bike fit measures were also recorded based on 4 methods used to set saddle height identified in a systematic search of the literature2,3,4 (Table 1). All 2D angles significantly differed from 3D (Fig 1). The most similar was the shoulder (3.1 + 1.9°) and the least was the ankle (27.9 + 4.0°). On average, the absolute difference between measured and recommended saddle heights was 3.4 + 2.0 cm (Fig 3). Measured heights most aligned with LeMond5 (2.1 + 1.8 cm) and least with ischial tuberosity4 (6.0 + 2.8 cm). Conclusions These findings indicate that 2D and 3D measures differ significantly, meaning that the two methods should not be used interchangeably. Further, current bike fit practices in New Zealand most aligned with the LeMond5 method, although the agreement was not perfect. Incorporating 3D methods into current bike fit practices and aligning saddle heights to match scientific evidence could optimise performance and reduce injury risk in recreational road cyclists. References 1 Bini, R. R., & Carpes, F. P. (2014). Biomechanics of Cycling. 2 Hamley, E. J., & Thomas, V. (1967). Physiological and postural factors in the calibration of the bicycle ergometer. J Physiol, 191(2). 3 Nordeen-Snyder, K. S. (1977). The effect of bicycle seat height variation upon oxygen consumption and lower limb kinematics. Med Sci Sports, 9(2). 4 Shennum, P. L., & deVries, H. A. (1976). The effect of saddle height on oxygen consumption during bicycle ergometer work. Med Sci Sports, 8(2). 5 Burke, E. R. (2002). Serious cycling (Vol. 2). Champaign, IL: Human Kinetics.