Explaining Active Cooling and Cooling Watts

Like many aspects of endurance sport, cooling efficiency can be understood through a simple, practical concept: cooling watts.

In this article, we’ll break down what active cooling is, what cooling watts are, and why they matter to you as an athlete. More importantly, we’ll look at how you can generate more cooling watts efficiently by supporting your body’s natural cooling system.

 What are cooling watts? 

Cooling watts are straightforward: they represent the amount of heat energy your body is able to dissipate. The physiology behind this is well established. When you exercise, your body produces heat. For every 100 watts of energy you generate, roughly 80% is released as heat, while only about 20% contributes to actual mechanical power output.

That heat has to go somewhere. If it doesn’t, your body overheats. When that happens, performance drops fast.

There’s a clear relationship between core body temperature and efficiency. As core temperature rises, efficiency falls. This is a well-documented physiological response in sports science, and it’s one of the key reasons why managing heat is critical for endurance performance.

If you want to go deeper into the science, research into hyperthermia and induced fatigue shows just how closely heat buildup is tied to reduced performance.

So how does the body deal with heat? The process is simple. Excess heat is transported to the skin, where it’s removed through the evaporation of moisture, primarily sweat. The energy removed during this phase change is what we call cooling watts.

If you want to stay cool, you need to maximize those cooling watts.

Why your body stops cooling itself 

Here’s where things get interesting. Cooling efficiency drops when the evaporation process is disrupted. For example, if sweat is reduced, your ability to generate cooling watts is reduced. When sweat evaporates too quickly, and the system breaks down, you’re no longer sustaining effective cooling.

On the flip side, simply pouring water over your head or body isn’t the solution either. If that water runs straight off, it’s wasted. Every drop that hits the ground is lost cooling potential. They are cooling watts you never used.

 Active cooling to complement your body's natural process 

This is where active cooling comes in. Ultra Cool Tech develops active cooling technologies designed to complement your body’s natural cooling system. The principle is simple but powerful: add water, increase surface area, and enhance evaporation.

Ultra Cool Tech garments and accessories capture and retain water, whether it’s from sweat, a bottle, or an aid station, and convert that water into usable cooling energy through evaporation. By increasing effective surface area and maintaining optimal conditions for evaporation, these systems generate additional cooling watts beyond what your body can produce on its own.

 

At this point, it's important to highlight the difference between active and passive cooling. Passive cooling is about allowing your body to operate efficiently: good airflow, breathable fabrics, and letting sweat evaporate naturally. That works… up to a point.

But passive cooling doesn’t add fuel to the system. It relies entirely on your body’s sweat production, and that’s a limited resource. Once sweat production drops or conditions overwhelm evaporation, your cooling capacity declines rapidly. And when cooling fails, you know what happens next: rising core temperature, falling efficiency, and performance that fades faster than it should.

Active cooling changes that equation. It adds and manages water to sustain evaporation, even when your body alone can’t keep up.

Take this into your next session or race

Next time you train or race in the heat, indoors or outdoors, ask yourself:

• Am I producing enough cooling watts for these conditions?

• Where am I losing cooling potential?

• What active strategies can I use to improve this?

If you stay ahead of your cooling, you stay ahead in your effort. Think about it, plan for it, and use it to your advantage. That’s how you turn heat from a limiter into something you can manage for effective performance.