How to Use 4 Hour Fuel in the Heat

Heat is one of the most challenging environmental factors to racing and exercise in general. Many, many people struggle in hot races - especially bigger folks (like me). Go hard for a few hours, sweat a few liters, supplement with not quite the right stuff, and all of a sudden you're facing many simultaneous problems that all compound: salt imbalance messes with your taste perception, nausea makes you unlikely to want to eat and drink, and hypovolemia (not enough blood) makes it much harder to deliver oxygen and nutrients to your muscles. Not fun.

It's taken us a while to have the confidence to do it, but the solution is pretty simple: keep the intensity down, stay cool, supplement salt, and stay way ahead of nutrition. Let's break down each of these.

Keep the intensity down: especially in hot races, I wear a heart rate monitor. For long, hot races, the intensity goal has to be a bit lower. I keep an eye on how much my heart rate goes up vs. my breathing. If the heart is pumping a lot, and I'm barely breathing, that means I've lost a lot of water, and I need to slow down and double down on hydration (salt + water!).

Stay cool: Why wait for sweat to cool you off? Just stay wet! It's much more efficient to keep yourself cool by applying water than it is to wait for your body to absorb and then sweat out the water. If I feel like I'm sweating a lot, I probably need to dial back the intensity, get wetter, or both.

Supplement salt: Salt is a key ingredient in hydration mixes for a reason! Sweat on average has 1g per L, so you need to replace about that. Interestingly, few sports drinks have enough, Gatorade for example is about half of what you need for ultra-endurance. I find it pretty difficult to consume enough salt when I can taste it, so I prefer taking salt caps, 1-2 per hour especially when it's hot (I drink 0.5-1L in the heat). Everybody has a favorite brand, but as long as you're consuming around to 1g of salt per liter of water when you're sweating, you're on the right track.

Stay way ahead of nutrition: This is where 4 Hour Fuel comes in. When I'm working out in the heat, the last thing I want to do is eat stuff. Staying on 200-300cal/hr with a squirt every half hour is pretty much all I want. If you get behind on food, it's incredibly difficult to get back, because your body is doing so many things at once. The last thing it wants to do is digest a big meal and go fast. In cold races, I'll often mix 4HF ahead of time, but since we don't use any preservatives, it can go bad if you leave it in the heat for a long time before you get to it, and that is definitely not going to help you stay fueled! We've never had it go bad in less than 6h, but have definitely had funky bottles after 12h in the heat.

Four Hour Fuel has transformed our hot-weather racing game. It is just so much mentally easier to stay on top of the many variables when it only takes ~30sec/hour to consume all the calories you need, and a minute or two every 3-4 hours to refill a fresh bottle. I love to have some savory bags (ramen and vietnamese pho) available, because in the heat especially I need a break from the sweet!