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The uphill struggle - IRONMAN's decision to move away from Kona.

Updated: May 2

Gustav Iden at the IRONMAN World Championships in Kona, Hawaii

Hawaii - famous for its volcanic landscape, surfing hot spots and of course home to the IRONMAN Triathlon World Championships. Since 1978, the competition has been held annually in Hawaii (with the exception of 2020 & 2021 due to COVID) originating as a 2 day event covering the Waikiki Roughwater swim (3.86km), the Around-Oahu Bike Race (185km) and the Honolulu Marathon (42.195 km). Popularisation led to a move to the Big Island and a new home in the bay of Kailua-Kona.

With so much history of the sport carved into the island’s volcanic rock it seems like an impossible choice to move the championship away from such an iconic location. In recent weeks, IRONMAN announced that the 2023 World Championships will be held at two separate venues. The women’s championships will remain in Kona while the men’s race is set to be held elsewhere on a separate day. Whilst the official 2023 men’s World Championships course is yet to be confirmed, industry professionals have touted Nice, France as the heavy favourite as host.

The current IRONMAN Nice course boasts an ocean swim, an exceptionally hilly and technical bike course and a flat promenade run. With that in mind, we spoke with our Lead R & D Engineer , Jordan Bolland to find out how competitors' aerodynamics will be impacted on a much hillier course like Nice.

What impact does riding uphill have on aerodynamics?

A good starting point when you want to begin to determine how environmental conditions can impact cycling performance is to fully understand what the rider (and bike) are up against and need to overcome. Once you know the forces involved you should start to be able to quantify how much of an impact each one has on performance. There are three main forces a cyclists has to overcome:

  1. Drag force (usually depicted as Fd)

  2. Rolling resistance/friction (usually depicted as Fr)

  3. Gravity (usually depicted as g)

When specifically looking at the aerodynamic component of above it is also worth noting how the Fd is calculated:


Fd = Drag Force

p = Density of Fluid

v = Velocity

Cd = The Drag Coefficient

A = The reference area

So from this equation you can see velocity (speed in a given direction) will indeed have an influence on the drag force. The relationship is actually exponential, meaning the velocity of the cyclist has a huge impact on the drag force.

In terms of tucking in and reaping the aero rewards, at slower speeds these rewards are of diminishing return. There's the flip side, when going downhill, minor positional changes can have a huge effect on the rider's speed.

Image courtesy of BMC

When climbing we experience environmental changes such as a change in temperature, humidity and air density. All of these factors will affect performance but to a much smaller level than the speed of the cyclist due to not being a squared function. This is one of the reasons why a lot of the UCI world hour record attempts are located at Aguascalientes velodrome in Mexico – it sits at 1887m above sea level.

What impact does ‘sitting up’ have on aerodynamics compared to in the TT bars?

When starting our journey to validate our system in wind tunnels we spent quite a bit of time looking at how large positional changes affect your CdA value. We did this for two reasons - we could start to identify large positional changes in our system and start to see correlations between our datasets and the wind tunnels data sets; and secondly we found it interesting! My Drag Force in Newtons at 13m/s in a time trial position is around 17.5Ns, and when I'm upright (hands actually on the elbow pads) is around 30.8Ns. It’s worth noting the faster the speed, the higher the delta was between those two positions – but as above,velocity is an exponential component so it shouldn’t surprise us!

What can riders do to minimise drag whilst climbing?

  • Zip up. If you are wearing a jacket,try to leave it zipped fully to ensure it’s not creating unnecessary turbulence.

  • IF you can produce good power whilst on a climb stay in the aerobars.

  • When climbs get too steep and you can’t maintain a good cadence, stand up. While temporarily less efficient aerodynamically, you’ll be able to clear the steeper section quicker at the expense of greater effort.

Ultimately, the deliberation continues for the team at IRONMAN while they determine the new course for the men’s IRONMAN Triathlon World Championships 2023 but the impact of a hilly course is clear. Maintaining an aero position will be important when climbing, so long as competitors are able to produce the required power; meaning the best performances will require careful calculation, planning and reconnaissance. On any longer descents, the importance of aerodynamics will increase exponentially so expect to see athletes take that into consideration in their equipment and position choices.


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