The Hour Record – Nuances Abound (Part 1)

Perspective on Victor Campenaerts’ new benchmark

Join Tom Helleman for a deep-dive into the makings of a new UCI Hour Record. This three-part series will explore the factors that combined to see Victor Campenaerts break Sir Bradley Wiggins’ 2015 record of 54.526km.

April 16th, 2019. In Aguascalientes, central Mexico, Belgian professional cyclist Victor Campenaerts climbs aboard his custom-made Ridley bike and settles himself for the effort to come.

What follows is 60 minutes of metronomic efficiency around the high-altitude Mexican velodrome.  The gun finally goes off and after a few seconds the screen flashes up a number.  It’s a big one.  55.089 kilometres.  A new UCI Hour Record.

It was official, Campenaerts had ridden 563 metres further than Sir Bradley Wiggins’ record-setting 2015 attempt.  He became the sixth person to break the record since the ‘unified rule change’ of 2014 which had effectively reset the record to Ondrej Sosenka’s 49.7km of 2005*.  We have seen a significant amount of innovation and development since a retiring Jens Voigt reset the modern benchmark to 51.11km in September 2014.  However, there still remains a large gap to Sir Chris Boardman’s ‘Best human effort’ of 56.375km set in 1996.  Campenaerts has pushed the modern record one step closer, eclipsing one of the greatest cyclists of the modern era in the process.

*Ondrej Sosenka failed doping controls in both 2001 (elevated haematocrit) and 2008 (methamphetamine).

So how did he do it?  Did he produce more power?  Improved aerodynamics?  Aggregation of marginal gains? 

There are quite a number of performance factors to unpack despite the seemingly simple event format.  In this discussion I am to identify some of differences between the record-setting efforts of Campenaerts and Wiggins, as well as consider the technical aspects and future possibilities of this prestigious record.  Read on for some insight into this exciting chapter of the UCI Hour Record arms race!

Environmental Factors

Let us begin by comparing the venues used for the two best attempts in the current era, as this is a key piece of the puzzle.  Campenaerts selected the Bicentennial Velodromo in Aguascalientes, central Mexico for his record bid.  Known for its altitude at 1887m (6191ft) above sea level, it is an indoor, wooden 250m velodrome with steep 48-degree banking.  The track has a pressurized ‘bubble’ style roof but does not have an internal climate control system, and the temperature can fluctuate up to 20 degrees Celsius through the day.  This particular venue is notable for other world record cycling performances in recent years, including Francois Pervis’ 1km TT world record of 56.303 seconds set in 2013, and Ashton Lambie’s 4km Individual Pursuit world record of 4:07.251 set in 2018.  Although seemingly an excellent choice for this type of performance, it is interesting to note that it had not been the host for any of the previous five successful hour record attempts since the unified rule change in 2014.  Not for a lack of trying though, as Thomas Dekker, Tom Zirbel, Martin Toft Madsen and Dion Baukeboom have all made unsuccessful world record attempts at the track.

The Bicentennial Velodrome, Aguascalientes, Mexico.

In contrast, Wiggins made his attempt at the Lee Valley Velopark in London, which is barely 30m above sea level.  Constructed for the 2012 Olympic Games, the track is also an indoor, wooden 250m velodrome but with shallower 42-degree banking and does feature an internal climate control system.  It uses specially designed and asymmetrically banked corners to encourage the highest speeds possible (Thomas, 2011).  The Lee Valley track has hosted several of its own record-setting performances.  Team GB stormed to a Team Pursuit World Record of 3:51.659 in the men’s 4000m and 3:14.051 in the women’s 3000m at the London Games.  Some commentators have suggested Wiggins’ choice of venue may have been down to the largely British-based sponsorship of his attempt, as well as the push to sell tickets and showcase the performance to a home crowd.

A packed Lee Valley Velodrome on the night of Wiggins’ record attempt

There are several ways that the weather can influence an hour record attempt, despite it being held indoors.  The characteristics of the air inside the velodrome on the day will have a significant effect.  Though we tend not to notice it in our day to day existence, atmospheric air has a mass like any other fluid.  The density (mass per volume) of the air that the rider is passing through is directly related to the power required to overcome that resistance- this is why it is critically important (but not necessarily always possible) for a record attempt to be held under low air density conditions.

Air density is determined by three variables: Barometric pressure, temperature and humidity.  Let’s look at these three factors individually and examine how they influenced both Campenaerts’ and Wiggins’ record attempts. 

Barometric Pressure

Air density is directly proportional to barometric pressure.  This means that lower barometric pressure gives lower air density, and that means less drag and more speed for cyclists.  Barometric pressure naturally fluctuates with the weather.  For example, the highest and lowest pressures ever recorded at sea level are 870hPa and 1084hPa respectively.  Wiggins rode on a day with an above-average barometric pressure of 1036hPa, which reduced the distance he was able to cover.  The day prior to Wiggins’ attempt UK cycling aerodynamicist Xavier Disley posted the chart below, which neatly illustrates the effect of barometric pressure on the distance ridden in the weeks leading up to the attempt.

As you can see by looking at the ‘Distance lost’ on the vertical axis, fluctuation in barometric pressure alone is a massive variable, even before the influence of temperature and humidity are considered.  Disley’s data suggest that Wiggins may have ridden in excess of 55km in his sea-level attempt had the conditions been favourable.

For Campenaerts, the conditions were indeed much more favourable.  At the time of his attempt, the barometric pressure at the nearby Aguascalientes airport was recorded at 813.5hPa (Weather Underground, 2019).  This is 21.5% lower than it was for Wiggins in London.


Warmer air is less dense than colder air.  Due to the unfavourable climatic conditions on the day of Wiggins’ attempt, the decision was made to increase the ambient air temperature of the velodrome above the theoretically ideal (on balance of physiological and aerodynamic properties) ~28 degrees to 30 degrees Celsius.    

The average temperature of Aguascalientes in May is 21.7 degrees Celsius.  Reports suggest that the attempt was timed such that the temperature within the velodrome for the attempt was around 28 degrees Celsius, slightly cooler than it was for Wiggins.

Dew Point (Humidity)

Humidity has the least impact on air density.  Counterintuitively, dry air is actually more dense than moist air.  This is because the molecular weight of water vapour is lower than both of the most common gas molecules in the air, i.e. nitrogen and oxygen.  The resulting change in air density between 0% and 100% relative humidity is only around 1% (at a certain temperature and pressure).  More importantly, the effect of humidity on athlete thermoregulation is significant (Zhao et al., 2013).  Hot and humid conditions impair evaporative cooling, meaning core temperature is likely to rise due to the limited ability to remove heat produced by the working muscles.

Air density

Wiggins’ conditions gave an air density of 1.176kg/m3.  For Campenaerts, our best estimates are around 0.940kg/m3. This is a 20.1% reduction in density and would translate to a 20.1% reduction in drag.  Does that mean that Wiggins would have gone 20.1% further if he rode in Campenaerts conditions? No!  Aerodynamic drag is not directly proportional to velocity; it is proportional to the square of the velocity.  This is why riding at 40km/h requires double the power output to 32km/h.

As it stands today, the hour record may be attempted whenever and wherever the rider chooses (assuming all UCI regulations and anti-doping controls are complied with), which is something that any future attempts cannot afford to ignore if they are serious about challenging the record.

Stay tuned for Part 2 of this series, where we discuss differences between athletes, strategy and technique.


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