Heat and the Tour de France with EF Education-EasyPost
This year’s Tour de France has kicked off amid the most severe recorded heat wave ever to hit Europe. After the first few stages, it’s clear how heavily teams like EF Education-EasyPost are weighing the importance of thermoregulation.
In the first few stages, we’ve seen virtually every cooling protocol implemented including ice vests, ice slushies, dousing, palm cooling, forearm ice baths, ice socks, and more. But one hidden cooling strategy you won’t see at the tour (because it happened well before the first stage even started) is heat training.
Proven to lower core temp and heart rate and increase sweat rate and skin blood flow, heat training is the most effective hidden cooling protocol being used at the Tour. Best practices normally suggest athletes do heat training indoors in a controlled environment where variables like clothing, ambient temperature, and wind convection can be optimized for intense heat strain. However, given the northern hemisphere’s intense summer heat this year, many athletes and teams, pro peloton included, have elected to work heat exposure into normal training sessions outdoors.
“Historically we’ve done active blocks of heat training (with indoor riding or hot bathing protocols) in the second half of June as part of our final prep for the Tour,” explained EF Education-EasyPost’s Performance Manager, Nate Wilson. “If anything, with the very hot weather, we ended up removing some of the planned heat interventions and hypothesizing we’d get a significant adaptation to heat from the natural exposure given the heat wave across much of Europe.”
It’s an interesting theory, and one we hear a lot from athletes that reside in intensely hot climates year-round. So we investigated the data to see whether a normal training ride in baking summer heat causes enough heat strain to induce the same heat adaptations you’d get from a proper indoor heat training session.
Does a normal training session in intense summer heat count as “heat training”?
The chart below shows EF Education-EasyPost rider Max Walker’s data from a late-June training session in Mallorca a few days before the start of the Tour. Ambient temps rose to around 34°C/93°F that day, and Max’s CORE Heat Training Load measured a 10 out of 10.
So yes, Max absolutely experienced enough Heat Strain to contribute to his Heat Adaptation. But every ride is different, and there are several variables—effort, wind convection, humidity, sun exposure, clothing, hydration, road gradient—that end up affecting overall Heat Training Load. So just because you had a sweaty ride in the heat doesn’t necessarily mean it delivered a high quality heat session.
For example, on May 23, 2026 at EF Education-EasyPost’s team training camp in Sierra Nevada, Spain, ambient temps topped out identically to the day above (34°C/94°F), but Max’s data tells a different story. This session only earned Max a Heat Training Load of 5.8 out of 10. Still a decent heat session, but only 60% of the first session’s load.
So what changed?
The first ride had 3 substantial climbs. These correspond to the 3 spikes in heart rate and Heat Strain Index (HSI).
- The majority of the Heat Training Load (HTL) points accumulated during these climbs, with 4 points gained in the 20-minute climb. This was a big effort, with heart rate reaching 170bpm and HSI peaking at 4.5.
- Much of the rest of the ride was a moderately intense pace, with HSI often being above 2.0.
The second ride was a much less intense effort (steady heart rate in the 120s) with a flatter elevation profile and only one climb at the end.
- Thus, HSI stayed around 1.5 for most of the ride. At that level, HTL points accumulate slowly and are capped to a total of 1.4, reached only after 2 hours at that HSI.
- The one climb at the end saw HSI rise to 3.0, and this effort netted ~3 HTL points.
- The remaining HTL points accumulated from the few short excursions above HSI 2.0, and the longer continuous time around HSI 1.5.
In short, the HTL 10 ride saw 3 substantial hot efforts, with a number more of moderately hot efforts. In contrast, the HTL 5.8 ride was mostly ‘somewhat hot’ with one hotter effort at the end.
Using CORE data like this, EF Education-EasyPost were able to monitor and react to individual rider data throughout the lead up to the Tour and adjust heat training protocols accordingly.
“Having data from the CORE let us see what level of heat load we were actually getting from training in hot weather rather than just guessing,” said Wilson. “In the example of Max Walker in Mallorca, the CORE gave us the confidence to know we didn’t need to add extra load (via indoor riding, hot bathing, etc) to be prepared for the heat because we were getting sufficient stimulus from the hard training combined with the high ambient temperatures. Data based confidence to avoid adding extra load is invaluable to avoid errors in fatigue management prior to the Tour de France.”
What does this mean for an average rider?
Now, does that mean your weekend long ride (even in the summer) counts as heat training? Not necessarily. According to the CORE Sweatlabs team, amateur athletes should consider the following:
- Both data sets above were from 4-5 hour world tour training sessions in 34°C/93°F conditions.
- For such a long ride, most people will pick an exertion level that’s sustainable. Even if they feel hot and sweaty, Heat Strain Index will likely be below the threshold that yields heat adaptation. World Tour pros like Max are able to sustain intense power output across a 5-hour ride, and even then, their HSI only peaks into “heat training” territory on vigorous climbs or efforts. An amateur’s steady-state endurance ride, even in extreme heat, will likely yield a Heat Training Load less than 3.
- While a daily dose of HTL 3 will cause the Heat Adaptation Score to slowly rise, athletes will need some deliberate heat sessions to really boost the score. Once or twice per week, achieve a HTL of 5–10.
- To collect these higher HTL points, bouts of greater intensity are needed. On a hot day, either climbs or spirited tempo efforts will get HSI above 3.0 and yield more HTL points. This can be done during a shorter focused ride, or as a deliberate segment of a longer ride.
- Tracking your thermal vitals with the CORE sensor is the best (and safest) way to ensure you are getting sufficient heat training load.