The Influence of the Inter-Relationship of Leg Position and Riding Posture on Cycling Aerodynamics

Shibo Wang,Timothy Crouch,Christopher Brown,Mark C Thompson,John Pitman,Daniel Tudball Smith,David Burton

doi:10.3390/fluids7010018

Abstract

Aerodynamics is an important factor affecting cyclist performance, as at the elite level 90% of rider energy is used to overcome aerodynamic drag. As such, much effort has been channeled into understanding the detailed flow around cyclists, since small gains can produce large rewards. Previous studies have shown that cycling aerodynamic drag is sensitive to leg position during the pedaling cycle; however, a systematic analysis comparing the impact of leg position between different riding postures is yet to be undertaken. To address this question, we compare the impact of leg position for two elite-level riding postures: the standard sprint and pursuit body positions. The comparison shows that the effect of leg position on drag is not consistent between the two riding postures, as the altered flow associated with different leg positions is influenced by the wakes from and proximity of other upstream or nearby components, such as the arms. This study reveals the inter-relationship between leg position and riding posture; and suggests that the flow associated with varied leg position should include surrounding geometrical components to obtain and understand the full aerodynamic impact. Practically, the results are valuable for optimizing the posture and improving skin-suit design for drag minimization.

Highlights

Aerodynamics is an important factor that contributes to the outcome of many sporting events
The drag areas are firstly compared as a function of riding posture and leg position
The overall drag for each leg position is similar for each posture, the force distribution and flow over the cyclist’s body vary significantly for the different postures

Summary

Introduction

Aerodynamics is an important factor that contributes to the outcome of many sporting events. Substantial effort has been channeled to improve rider performance by optimizing the aerodynamic performance. These efforts are generally undertaken from two perspectives: (a) improving the aerodynamic performance of the equipment, and (b) optimizing the rider’s posture for a good balance between ergonomics and aerodynamics. Apart from aerodynamically optimizing the geometry of individual bike components and measuring the drag values for different rider configurations, few detailed studies had been undertaken to document the flow structures around a rider-bike system as a whole before Crouch et al [2] conducted a series of wind-tunnel experiments to systematically characterize the detailed wake structure. Griffith et al [4] conducted numerical simulations based on the rider geometry employed Crouch et al [3], and indicated that the leg position affects the local drag force and the drag on other body parts, for example, the torso

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