CORE’s mission is to unlock better performance and safety through thermal data. We are interested in understanding just how the extreme conditions of a stage like this impact riders at the physiological level. To that end, we analyzed the CORE thermal data from a Soudal Quick-Step rider from stage 15 and discovered four key insights into how the heat affected performance and recovery.
1. Pre-race skin temp
The rider's skin temperature was already quite elevated at 38.2°C/100.7°F during the pre-race period, likely from waiting around for the race start in the intense sun and heat. This meant the rider began the stage with a significant thermal load, contributing to a rapid rise in Heat Strain Index (HSI) once racing began.
2. Additional cardiovascular load
Heart rate reached a maximum of 183 bpm when HSI peaked at around 6/10. High heat strain like this will cause cardiac drift, otherwise known as heart rate decoupling, where heart rate continues to rise at a steady power output. Heat training can help lower the threshold at which this starts to happen, but no rider is safe from it at a certain point.
3. Elevated core temp
While wind convection helped lower the initially high skin temp and kept it at a manageable level throughout the race, core temp steadily rose to quite elevated levels throughout the stage. As a result, the rider spent much of the stage in Heat Zones 2–3, representing moderate to high heat strain and a likely negative impact on performance. For reference, Heat Zone 3 is where we recommend athletes conduct their heat training. It is incredibly uncomfortable and very difficult to sustain for long periods of time.
4. Post-race thermal strain
Core temp reacts slowly to external factors. This is while it can take a while to rise while racing. But this also means that it can continue to rise when the racing ends, especially when riders don’t immediately cool themselves. In this case, 15 minutes after the finish, the rider’s core temperature remained at an average of 38.2°C/100.7°F, indicating he was still carrying significant thermal load into the recovery period. This adds additional unnecessary strain on the body which can negatively impact recovery for the next day’s stage.
The takeaway
With global temperatures continuing to rise each year, individualized thermal data is becoming increasingly necessary to keep riders and staff informed about how rider physiology is handling the conditions. The teams that adapt well to racing in warmer conditions will be the ones who understand exactly how heat impacts physiology and adjust accordingly to maximize performance and safety.
