September 4th, 2025

Aero Isn’t Everything – Thermoregulation’s Role in Performance Apparel

The human body is only about 20% efficient. For every watt of power used by the muscles, roughly four watts of heat are generated. To stay efficient, the body must shed this heat through the skin via sweating, vasodilation, and vasoconstriction. What you wear plays a major role in this process. Performance fabrics and design features can either help or hinder how effectively you regulate heat and moisture.

Aerodynamics specialists often say: “the wind doesn’t like skin.” In practice, this means more coverage is usually faster. A skinsuit with sleeves, for example, is quicker than a sleeveless version. But is it cooler?

Today, the best apparel designers are no longer treating aerodynamics and thermoregulation as separate challenges. They’re integrating both into the performance equation, and using CORE technology to measure the results.

Designing Skinsuits for Team Q36.5 at La Vuelta

Ahead of this year’s La Vuelta, CORE joined Q36.5 Pro Cycling Team at their altitude camp in Andorra to test four prototype “extreme heat” skinsuits from the Dottore Clima range. Working alongside the team’s staff and riders David de la Cruz and Thomas Pidcock, CORE and Q36.5 monitored body temperature, fabric behavior, and rider feedback in real-world conditions, pushing the boundaries of what technical cycling apparel can achieve.

Optimizing Kristian Blummenfelt’s Surpas Tri Suit for the IRONMAN World Championships

CORE also partnered with Surpas to refine Olympic champion Kristian Blummenfelt’s new tri suit ahead of the IRONMAN World Championships in Nice. 

Field testing took place in Bergen, Norway and focused on both aerodynamics and heat management across different suit and helmet combinations. The winning combination resulted in a 9.6-watt aerodynamic gain – a decisive advantage in an event where every second matters.

For further analysis, the CORE team then tested the Surpas suits in their Zürich, Switzerland performance lab to replicate race day conditions, using a randomized, counterbalanced, within-subject crossover study. Multiple CORE sensors measured thermal power across the body, tracking how heat is produced and managed during exertion.

This lab-based approach allows us to quantify suit performance and better understand how design differences influence comfort and heat management under real-world conditions.

Thermoregulation for Everyday Athletes

Not everyone has access to world-class apparel designers or pro-level testing. But every athlete can still use CORE to build their heat awareness and make crucial decisions about things like training, apparel, and cooling strategies.

CORE's Heat Strain Index (HSI) gives athletes a live metric to track the impact that heat stress is having on their performance. This is useful for conducting heat training to make sure you are exposing yourself to the appropriate amount of heat stress in a given session. And on race-day, live HSI can be used to inform pacing, cooling strategies, and apparel decisions.

Explore our guide to the Influences on Heat Strain Index to learn how you can optimize your own thermoregulation and unlock better results.

Cooler Is Faster

SHOP CORE 2