Positional drafting in team pursuit: quantification of CdA reduction as a function of rider position

Over the past two decades, applied track cycling literature implicitly assumed that the reduction of the aerodynamic coefficient (CdA) produced by drafting in team pursuit operated homogeneously among subordinate riders. Research published since 2018 has invalidated this hypothesis. The exact quantification of CdA reduction per position now constitutes an unavoidable tactical design variable in the programming of the Olympic quartet.

Theoretical framework: drafting and aerodynamic coefficient in team pursuit

The aerodynamic coefficient CdA is defined as the product of the drag coefficient (Cd) and the projected frontal area (A) of the cyclist and bicycle. In track cycling, and specifically in team pursuit on a 250 m velodrome, the dissipated aerodynamic power obeys the classical relation P_aero = ½ · ρ · CdA · v³, where ρ denotes air density and v the instantaneous velocity. At the velocities sustained in team pursuit competition (60-65 km/h), this component accounts for between 87% and 92% of the total power demanded from the system (Grappe et al., 1997; Debraux et al., 2011).

Positional drafting is defined as the reduction of effective CdA experienced by a rider located in the wake of another. Its quantification requires rigorous experimental methodologies: wind tunnel measurements with instrumented mannequins (Íñiguez-de-la-Torre et al., 2009) or numerical computational fluid dynamics (CFD) simulations on realistic quartet geometries (Blocken et al., 2018).

Experimental results by rider position

Blocken et al. (2018) performed three-dimensional CFD simulations of a quartet in tight formation, with a wheel-to-wheel gap of 15 cm and a free-stream velocity of 65 km/h. Íñiguez-de-la-Torre et al. (2009) reproduced an analogous configuration in a wind tunnel. Both methodologies converge on the magnitude of the effect, with minor deviations for the second rider:

The data allow three relevant observations regarding track cycling aerodynamics to be formulated: (i) CdA reduction does not display a uniform distribution across the four positions; (ii) the maximum aerodynamic benefit is registered at the fourth position of the quartet; (iii) the relative difference between the second and third positions lies between 4% and 5%, a magnitude equivalent to approximately 20 W at 60 km/h and decisive in relay assignment.

Wake analysis: why the second rider does not maximise the benefit

The lower CdA reduction observed at the second position is attributable to the turbulent, not fully developed nature of the immediate wake behind the leader. In this region, the residual flow retains vortical components that raise local turbulent kinetic energy and limit the effectiveness of the draft. Riders located in the third and fourth positions benefit, in contrast, from a flow that has been partially reorganised through sequential interaction with the preceding wakes. This non-linear behaviour has been documented both in CFD simulations (Blocken et al., 2018) and in field observations with power meter instrumentation (Heimans et al., 2017).

Influence of wheel-to-wheel gap on drag reduction

The longitudinal distance between consecutive wheels significantly modulates the magnitude of positional drafting. Blocken et al. (2018) quantified this relationship for three representative configurations:

• 15 cm gap: 2nd −41%, 3rd −45%, 4th −46%.
• 30 cm gap: 2nd −34%, 3rd −38%, 4th −39%.
• 45 cm gap: 2nd −27%, 3rd −31%, 4th −32%.

An increase of 15 cm in gap represents a loss of 30-40 W per rider. Extrapolated to a quartet sustaining a mean power output of 480 W, this variation translates into a difference of approximately 5 seconds over the regulatory 4 km distance. Consequently, specific training of tight formation must be regarded as an aerodynamic component of performance, not as an aesthetic or disciplinary matter.

Optimisation of relay assignment based on physiological profile

The traditional heuristic that assigns the leading position to the rider with the highest critical power is incomplete when the actual asymmetries of positional drafting are integrated. The optimal quartet order depends on the distribution of individual capabilities.

Case 1. Homogeneous quartet

When the four riders exhibit similar values of critical power (CP) and anaerobic capacity (W'), rotation every half lap (125 m) maintains W' depletion in balance and maximises the exploitation of drafting. None of the riders undergoes premature exhaustion.

Case 2. Asymmetric quartet with a dominant engine

If a rider possesses a CP that exceeds the average of the group by 20 W, allocating approximately 40% of total time at the front (extended relays during the middle phase of the event) allows the physiological advantage to be exploited without compromising the metabolic homeostasis of the group.

Case 3. Start specialist

A rider with an elevated W' and a comparatively low CP may perform the role of initial leader during the first 30-45 seconds, subsequently transitioning to the fourth position to permit physiological recovery without returning to the front. This tactic, referred to as sacrifice, is common in teams that possess a recyclable sprint specialist.

Effective quartet CdA: a composite performance metric

The cruise velocity of the quartet does not depend linearly on the individual CdA of each component but on the time-at-front-weighted mean CdA. A team with deficient rotation is slower than one with lower raw power but tight formation. The following table illustrates the magnitude of this effect:

A quartet with an aerodynamically average leader but tight formation outperforms one with an aerodynamically optimal leader but open formation. Positional compaction constitutes a more cost-efficient route to aerodynamic performance improvement than individual optimisation of the leader's posture.

Practical implications for technical programme design

The reviewed findings justify the incorporation of specific tight-formation sessions within the velodrome training microcycle. The objective must be to maintain the wheel-to-wheel gap below 20 cm during extended relays and to constrain positional drift to magnitudes below 10 cm. Quantitative verification requires video instrumentation synchronised with individual power recording.

References: Blocken, B., Toparlar, Y., van Druenen, T., & Andrianne, T. (2018). Aerodynamic drag in cycling team time trials. Journal of Wind Engineering and Industrial Aerodynamics, 182, 128-145. Íñiguez-de-la-Torre, I., & Íñiguez, J. (2009). Aerodynamics of a cycling team in a time trial. European Journal of Physics, 30(6), 1365-1373. Boillet, A., Foissac, M., & Dorel, S. (2024). Modelling the pursuit start. Scientific Reports, 14, 12482. Heimans, L., Dijkshoorn, W., Hoozemans, M., et al. (2017). Optimising the team pursuit. Sports Engineering, 20, 63-70. Grappe, F., Candau, R., Belli, A., & Rouillon, J. D. (1997). Aerodynamic drag in field cycling. Ergonomics, 40(12), 1299-1311. Debraux, P., Grappe, F., Manolova, A. V., & Bertucci, W. (2011). Aerodynamic drag in cycling. Sports Biomechanics, 10(3), 197-218.