Tour de France riders are facing some of the hottest racing conditions in the event’s history .
As a heatwave swept across western Europe last week , temperatures in southern France approached 40°C. Organisers shortened Stage 9 by 30 kilometres to reduce heat exposure.
As climate change accelerates the frequency and intensity of heatwaves, questions are increasingly being asked about whether current approaches are sufficient.
Cycling in the heat
The Tour is held in France, with the start often taking place in neighbouring European countries. Over its 21 stages, riders cover roughly 3,500km and accumulate between 45,000 and 55,000 metres of elevation gain.
Competing in cycling’s premier event under extreme heat places significant strain on the human body. Riders must cope with both the demands of professional racing and the environment.
During professional road cycling races, core temperature can exceed 40ºC and, in exceptional circumstances, reach 41.5ºC . Such temperatures place substantial strain on the cardiovascular system, increase the sense of effort, and contribute to declines in performance.
More importantly, the rise in body temperature increases the risk of heat-related illnesses such as muscle cramps and heat exhaustion. In the most severe cases, riders can suffer exertional heat stroke, a life-threatening condition in which intense exercise causes the body’s core temperature to rise above 40°C.
What changes have been made?
In 2024, the Union Cycliste Internationale (UCI), global cycling’s governing body, launched a new high temperature protocol to protect rider health.
This requires race officials and team representatives to assess heat risk using wet-bulb globe temperature , an index that combines the effects of air temperature, humidity, solar radiation and wind.
Under the protocol’s highest heat-risk category, when wet-bulb globe temperature reaches or exceeds 28°C, countermeasures include the provision of extra shade during warm-up, cooling and hydration during racing, and even shortening, altering or cancelling a stage.
During this year’s Tour de France, the use of feeding bags in zones where only bottles are usually allowed was permitted on specific climbs. This was intended to get riders to drink more water on days with forecasted extreme heat.
Organisers also extended the stage time limit by 2% on Stage 9 in response to requests from the riders’ union, the Association of Professional Cyclists . This reduced the likelihood of riders dropped from the peloton – the tightly packed main group of riders in a road cycling race – in the heat would be eliminated from the race.
How can we protect riders long term?
Riders have called for additional measures to be considered, including changing start times to protect their performance and health.
Earlier start times could substantially reduce heat exposure at the Tour de France and other major races such as the Vuelta a España , where stages typically begin around midday. This would help riders avoid the hottest part of the day.
But questions remain about whether current approaches are sufficient.
While recent measures adopted by the UCI and Tour de France organisers are a positive step, relying on wet-bulb globe temperature has limitations.
One limitation is that the evaporation of sweat – the body’s primary mechanism for dissipating heat during exercise – is restricted at any given wet-bulb globe temperature when humidity is high or air movement is low. Consequently, the same wet-bulb globe temperature can be associated with different levels of heat strain, depending on the specific environmental conditions experienced by riders.
While the wet-bulb globe temperature index provides a measure of environmental heat stress, it does not account for the metabolic heat produced by riders. Nor does it factor in the clothing they wear, which can impede sweat evaporation.
This is particularly important in road cycling, where the demands on the body can change dramatically within a single stage. For example, climbing uphill results in slower speeds and less airflow across the body at a time when metabolic heat production is soaring.
Together, these factors suggest that wet-bulb globe temperature alone may not provide a complete picture of the thermal challenge experienced by riders during competition.
Competitive but safe
As global temperatures continue to rise, heat strain – the stress placed on the body by the combination of intense exercise and hot weather – is likely to become an increasing determinant of performance in professional cycling.
Future policies may need to move beyond broad environmental indices to capture the unique demands professional cyclists put on their bodies if the sport is to remain competitive and safe in a warming world.
