In endurance sports, we spend a lot of time talking about fuel. We carefully manage calories because we know our bodies convert that energy into mechanical power. As athletes, we invest countless hours optimizing that process through training and nutrition. But calories are not the only fuel your body needs. There is another type of fuel that often gets overlooked: water.
Water plays a critical role because it fuels your body’s cooling system.
The physiology behind it is actually quite simple, as we explained in a previous post. During exercise, only a small portion of the energy produced from calories becomes power. Most of it becomes internal heat. That heat continuously raises your core body temperature, and if it is not removed efficiently, performance begins to suffer.
To manage this, your body dilates blood vessels and transports more blood to the skin, where heat can be transferred away from the body and cooler blood can be recirculated. The main mechanism responsible for removing this heat is evaporation: sweat absorbs heat and carries it away as it changes from liquid to vapor.
The key point is that you need to keep fueling this cooling process. If you do not, your cooling system gradually becomes less effective, and you reach the performance decline associated with overheating much sooner.
However, this physiological system has limitations. Sweat is produced from body fluids and is constrained by your sweating rate and hydration status. There is only so much water your body can provide. Because of that, adding water directly to your skin can be a very effective strategy, especially when sweating becomes limited. That is why water can be thought of as fuel for cooling.
The science behind this is clear, and it helps explain why proper hydration is so important during training and racing. But it also highlights something athletes often overlook: not wasting cooling fuel.
Don't waste cooling fuel
A common example happens at aid stations. Athletes pour water over their heads and necks, but much of it immediately runs off and ends up on the ground. The intention is good, but in many cases a large portion of that cooling fuel is lost before it can actually contribute to heat dissipation. This is where smarter fueling for cooling becomes important.
Our cooling fabrics are designed to retain water and keep that fuel close to the skin, where evaporation can continue for longer periods. Instead of disappearing after a few seconds, the water remains available to support your body’s natural cooling process, especially in hotter conditions.
It sounds simple, but it can make a meaningful difference. You are not changing physiology; you are enhancing it. You are simply fueling your cooling system more effectively so it can continue working throughout the race.
So next time you line up for training or competition, think beyond calories alone. Ask yourself:
• Am I hydrating enough?
• Am I using water efficiently?
• Am I keeping enough cooling fuel available to support my body throughout the race?
The answers to these questions may be the difference between struggling through overheating and maintaining better thermal control from start to finish.
