Field-measured drag area is a key correlate of level cycling time trial performance.

James E Peterman,Allen C Lim,Ryan I Ignatz,Andrew G Edwards,William C Byrnes

doi:10.7717/peerj.1144

Abstract

Drag area (Ad) is a primary factor determining aerodynamic resistance during level cycling and is therefore a key determinant of level time trial performance. However, Ad has traditionally been difficult to measure. Our purpose was to determine the value of adding field-measured Ad as a correlate of level cycling time trial performance. In the field, 19 male cyclists performed a level (22.1 km) time trial. Separately, field-determined Ad and rolling resistance were calculated for subjects along with projected frontal area assessed directly (AP) and indirectly (Est AP). Also, a graded exercise test was performed to determine n}{}dot {V}{O}_{2} peak, lactate threshold (LT), and economy. n}{}dot {V}{O}_{2} peak (n}{}mathrm{l}~min ^{-1}) and power at LT were significantly correlated to power measured during the time trial (r = 0.83 and 0.69, respectively) but were not significantly correlated to performance time (r = − 0.42 and −0.45). The correlation with performance time improved significantly (p < 0.05) when these variables were normalized to Ad. Of note, Ad alone was better correlated to performance time (r = 0.85, p < 0.001) than any combination of non-normalized physiological measure. The best correlate with performance time was field-measured power output during the time trial normalized to Ad (r = − 0.92). AP only accounted for 54% of the variability in Ad. Accordingly, the correlation to performance time was significantly lower using power normalized to AP (r = − 0.75) or Est AP (r = − 0.71). In conclusion, unless normalized to Ad, level time trial performance in the field was not highly correlated to common laboratory measures. Furthermore, our field-measured Ad is easy to determine and was the single best predictor of level time trial performance.

Highlights

A cyclist’s ability to produce and sustain mechanical power output is highly dependent upon physiological characteristics, V O2 max, lactate threshold (LT), and economy (Coyle et al, 1988; Coyle, 1995)
Because the AP was calculated with the rider only while the aerodynamic drag (Ad) was calculated for the entire bicycle and rider system, it would be technically incorrect to calculate a coefficient of drag (Cd) for the bicycle and rider system or rider alone
A cyclist’s mean field-measured power output normalized to our field-determined aerodynamic resistance (i.e., k or Ad) was the best correlate of level time trial performance time (r = −0.92, p < 0.001)

Summary

Introduction

A cyclist’s ability to produce and sustain mechanical power output is highly dependent upon physiological characteristics, V O2 max, lactate threshold (LT), and economy (Coyle et al, 1988; Coyle, 1995). How to cite this article Peterman et al (2015), Field-measured drag area is a key correlate of level cycling time trial performance. Measures of a cyclist’s ability to supply mechanical power do not always predict performance time in time trial racing (Hoogeveen & Schep, 1997; Balmer, Davison & Bird, 2000). Balmer, Davison & Bird (2000) demonstrated that while peak mechanical power output assessed during a graded exercise stress test does correlate highly (r = 0.99, p < 0.001) with average mechanical power output during a 16.1 km field time trial, neither the laboratory peak mechanical power output nor the average mechanical power output during the time trial correlated well with performance time (r = 0.46, p > 0.05). One possible explanation for these results is that the resistance impeding the forward motion faced by competitive cyclists is variable enough that mechanical power output alone may not predict performance (Jeukendrup & Martin, 2001)

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