So how is this possible? We know heat hinders performance. A 2016 review (Junge et al.) of 14 studies about the impact of heat on riders found mean power output during prolonged cycling time trials in ≥30°C/86°F conditions was on average reduced by 15%.
“How athletes tolerate heat is individual. Some riders can have a major performance drop in hot conditions — we have measured drops of more than 40 percent,” Olav Aleksander Bu, Head of Performance at Uno-X.
Through CORE’s partnership with eight of the World Tour teams, we are able to give an inside look at exactly how the peloton was handling the extreme heat at this year’s Tour. The above chart features CORE data averaged out across a handful of randomly selected riders from CORE partner teams.
Key Takeaways
- Overall, riders handled the intense ambient heat exceptionally well, likely due to thorough heat adaptation protocols and aggressive cooling strategies. In most stages, Heat Strain Index only peaked into Heat Zone 3 (where you start to see significant performance impact) for short periods of time.
- Heat strain increased with ambient temperature, but temperature alone did not fully explain riders thermal responses. While hotter stages generally produced greater heat strain, mostly due to elevated skin temperature values, substantial variability between stages indicates that factors such as workload, airflow, solar radiation, and race dynamics also influenced thermoregulatory demands.
- Interestingly, maximum core temperature remained relatively stable (around 38.5°C/101.3°F) despite an 11.7°C range in ambient conditions. This suggests riders were able to regulate core temperature despite hotter conditions. In contrast, skin temperature is directly exposed to the environment and therefore would be expected to rise more proportionally with increasing ambient temperatures. The resulting increase in skin temperature likely elevated cardiovascular and thermoregulatory strain, which is reflected in the higher HSI values observed on hotter stages.
Heat Adaptation
All of the CORE data above comes from teams that have placed a significant focus on heat training to prepare for the 2026 Tour de France, with most introducing indoor heat sessions as early as winter training camps. Teams then chose to pepper in additional heat prep throughout the season in different ways. Many teams leaned into the May/June heat wave in Europe to get natural adaptations from outdoor riding. Others continued with focused indoor heat blocks. And some used heat strategically to extend—and in some cases replace—the performance benefits from altitude training.
“This year, for Ilan Van Wilder, we replaced altitude with heat and saw very similar hemoglobin levels as he received last year with altitude.” -Koen Pelgrim, Soudal-Quickstep Trainer.
In all cases, teams used CORE to get an inside look into each riders’ individual physiology. Thermoregulation can differ significantly from rider to rider, and the only way to truly understand how each rider is responding is by individual monitoring. As Dr. Jeroen Swart, Head of Performance at UAE Team Emirates, explains:
"CORE sensors are integrated into our daily performance workflow to provide continuous insight into each rider's thermal strain during both training and competition."
Cooling Strategies
Besides heat training, another set of tools teams used to mitigate the intense conditions was cooling strategies. This year’s Tour featured the most diverse and widespread utilization of cooling strategies we’ve ever seen, including cooling towels, ice socks, cooling mitts, forearm ice-baths, ice slushies and more. Cooling strategies provide more substantial performance effects than just simple thermal sensation relief.
“Starting the stage with lower core temps gives the riders a longer buffer before reaching levels of heat stress that start to impact performance (CORE Heat Zone 3). This is why pre-cooling is so important,” explained Carles Tur, Head Coach of Pinarello-Q36.5 Pro Cycling Team.
Cooling was also used to aid in recovery. In a 21-stage race like the Tour, recovery is critical to maintaining performance across weeks of back-to-back racing. Although riders are exposed to high ambient temperatures, the airflow generated at race speeds provides substantial cooling through enhanced convection and sweat evaporation. However, when riders stop after the finish, this cooling effect is suddenly lost, causing skin temperature and heat strain to rise as stored body heat dissipates. This can cause heat strain to remain elevated for up to 30 minutes after each stage. Post-cooling is a very effective way to reduce this unnecessary additional strain and to aid in better recovery.
Mental Sharpness
As temperatures rise, the consequences extend beyond physical performance. Cognitive function, concentration, decision-making, and reaction time can all deteriorate under excessive thermal strain. It is very likely that the more heat-adapted riders were able to handle the complex and quick-moving dynamics of the pro peloton better than those who weren’t.
According to Xabier Muriel, Head of Performance at Movistar Team, "Heat adaptation is not only important for physical performance, but also to maintain a sharp mind and reaction time in fast descents, recognizing and following attacks, and other split-second decision-making moments."
In a race often decided by seconds, maintaining mental sharpness can be just as valuable as preserving physical power.
The Results Speak for Themselves
In the hottest Tour on record, CORE riders swept the GC podium, all 4 jersey wins, and 15/21 of the stages.
As global temperatures continue to rise, teams across the peloton are realizing they can’t stay competitive without dedicated heat-adaptation protocols, sophisticated cooling strategies, and real-time physiological monitoring to manage one of cycling's biggest performance limiters.
