Why was temperature important for Ellen van Dijks' Hour Record?

The hour record is a unique athletic endeavour which demands so many performance factors that culminate into just 60 minutes and will prove whether the years of conditioning and the months of focus and preparation were enough. Unlike most cycling races and events where you have to beat your competitors on the day of the race, the hour record prize can only be won by athlete who can race within the rules and ride further than any other person in 60 minutes. Success relies on so many different aspects of training, preparation, and racing and here we take a closer look at the role of temperature in the hour record attempts. 

hour record heat temperature

Ellen van Dijk has now joined the Hall of Fame as the fastest ever women to beat the hour record, on Sunday 22 May 2022 in Grenchen, Switzerland. She achieved a new record of 49.254 km which is 849 m more than English rider Joss Lowden who set her record last year in September on the same track. The UCI rules for a valid hour record are strict and cover rider eligibility through to equipment design and even limiting transmission of data to the rider and support staff. Van Dijk from Team Trek Segafredo racing could rely on experience coaching staff and from Trek Bicycles who built a custom bike for her attempt along with support from partner brands and experts. 

bike aerodynamics hour record

Racing the Hour Record, the rules permitted only one of her support staff trackside while she races and communication is one-way and rudimentary, the coach shouts out lap times or blows a whistle to mark predetermined intervals (such as 10-minute intervals). The rider is not permitted to drink or take any nutrition. She is not permitted to view her rider data (though data can be recorded) and, as can be expected, any technical aides or modifications to the equipment or track to provide further advantages are excluded or strictly limited by the rules set by the UCI. 

Hour record data wahoo

Aerodynamics is a deciding factor (which we will touch on) and an athletic has the best chances when they have the most aerodynamic position and are also able to maintain this for 60 minutes. This alone is excruciating as the muscles and body is screaming to stop and it becomes a mental challenge to fight through the pain and to keep powering through. Over the hour record from van Dijk it was remarkable as she held a position with her head pointed directly down which is good for aerodynamics, but it also severely limits her vision and demands even more concentration to remain 'on track'. 

Heat and the Hour Record 

Beyond the obligatory ‘years of training and experience on the bike’, to be able to even consider the hour record, specific training usually begin a year or more in advance. Heat training is one fundamental part of training preparation and follows the straight-forward approach of conditioning the body to perform more efficiently when hot. As the power output is influenced by the core body temperature, heat training helps an athlete to increase their power output when they get hot plus improves the effectiveness of the body in cooling. 

core sensor hour record

Even after the fundamental heat training component covered, the next key consideration is attire. A lot of attention is directed towards the aerodynamic capabilities of the skinsuit which are custom tailored to the rider. Just like the rider position, the bike design and helmet, each fabric and panel of skinsuit is designed to minimise drag. Temperature is the other crucial factor for the skin suit, more specifically, the ability of the skinsuit to help keep the rider as cool as possible. 

At a speed of 50kmh, the cyclist can rely on wind speed for some cooling. Over the course of the hour record attempt with sustained high intensity, the core body temperature rises so better a skinsuit can aide in cooling the rider, the longer a rider can sustain their high-power output. 

The race strategy will also take into account rising body temperature and even through riders can physically ride for the first 30 minutes at a higher pace, this pushes them more quickly into their red zone from which they can't recover (without drastic slowing and cooling). Pacing is a balancing act. A conservative initial racing pace leaves provides a reserve to maintain the power output toward the end with a burst in the final five or ten minutes. 

temperature hour record

While the actual core body temperature of Ellen van Dijk remains closely guarded, it is assumed that the temperature would exceed 40ºC (104ºF) during an hour record attempt. The race commentator Jens Voigt noted after the event that van Dijk lost about 1.2 Litres of sweat during her successful ride. 

hour record core sensor

Notably, the ride preparation combines both a warm-up and simultaneous pre-cooling with ice-vests, slushies, and fans. Pre-ride cooling is designed try to cool the body as far as possible to start cooler and benefit from more power output for longer. This is fairly standard practice at track cycling events. For the long-distance hour record the initial pre-cooling 'wears off' fast though still creates an essential gap by delaying the rapid increase in core body temperature. 

Air temperature and environmental variables 

For hour record attempts, it is not uncommon that high altitude velodromes are preferred, the thinner air provides less resistance which means faster laps. In the case of the Hour Record for Ellen van Dijk in Grenschen, Switzerland, the velodrome is 454m above sea level. A nearby storm and associated low pressure system (1,004 mbar/29.65in) was welcome news although air pressure is a factor that can’t be controlled. When Victor Campenaerts achieved the current standing Hour Record in 2019 where rode 55.089 km at the high altitude (1,800m) velodrome in Aguascalientes, Mexico, the air pressure was 813.5 mbar. 

grenschen velodrome

Air temperature can be controlled in some velodromes and rather that setting a cooler temperature, a warmer temperature is preferable as this means the air is less dense and is favourable for speed. With respect to core body temperature, this appears counterproductive and in practice it is a balance between setting it the velodrome temperature high enough for the aerodynamic advantages, but not too high that it can significantly impact the rider’s body temperature. 

A key word for hour record attempts is 'wet bulb temperature'. Technically this is 'the lowest temperature to which air can be cooled by the evaporation of water into the air at a constant pressure'. In practice it is a calculation of humidity and air temperature to determine the temperature which the human body can still rely on sweat evaporation to cool them.

wet bulb temperature core body temperature

Sweat evaporation is responsible for cooling the body and the point at which the body can no longer evaporate sweat and is unable to cool becomes deadly. This is the reason why the WBGT (Wet Bulb Globe Temperature) was such an important measurement value at the 2020 Tokyo Olympic Games where the temperatures and humidity levels were high and thus increased the risk of heat related illnesses for competing athletes. 

The lower the humidity, the more easily the body can evaporate sweat and the better it can cool. Factoring for air pressure and the benefits of higher air temperatures for reducing wind resistance, it is a balancing act for hour record when choosing the location, predicting weather conditions, and even trying to manipulate some of the variables such as temperature which is possible to set in some velodromes. Riders and teams however are fond of keeping many of the details to themselves so that their expertise doesn't give the next challenger all the answers.

 Hour Record Ellen van Dijk