How Much Water Is Really in an Aid-Station Cup?

Why You Only Get About 100 mL From Each Cup

Most runners grab a cup at a table and count it as a drink. But, the cup you're handed is rarely full.

A good estimate is that each cup of water will provide you 100 mL (3.5 oz) of water.

That's because volunteers typically fill cups about half way to prevent water from splashing and you'll lose a good amount as you run with the cup and what spills as you drink.

So when you plan your fluids for a race, count every cup you take from a table as 100 mL (3.5 oz).

One Cup Isn't Enough to Wash Down a Gel

Research has shown that the best carbohydrate concentration is 6 to 8 percent. To achieve an 8% concentration, you need 100 mL (3.5 oz) of water for every 8 grams of carbohydrate.

A typical gel has 25 grams of carbohydrate in it, so you'll want about 300 mL (10 oz) of water with each one. That's 3 cups.

Researchers have tested where the top of that range is. In a 1999 study, a drink with 8% carbohydrate left the stomach more slowly than drinks with 4% and 6%.3

That means a 25-gram gel taken with a single cup is about 3 times stronger than the 8% your stomach can empty easily.

This matters on race day because blood flow to your gut drops about 20% in the first 10 minutes of running and by up to 80% after an hour at marathon effort.12

With less blood reaching it, your gut can't absorb as much at once. So a gel taken with one cup stays concentrated, leaves your stomach more slowly, and is more likely to cause cramping, bloating or nausea.

Gels can contain anywhere from 22 to 40 grams of carbs, so check the label on the one you plan to use. A 40-gram gel needs about 500 mL (17 oz), which is 5 cups.

Those cups have to be water. A cup of sports drink adds its own carbohydrate, so never take a gel with a sports drink.

For the full breakdown of how much water each gel needs, read our guide to how much water to drink with an energy gel.

CarbRate's course feature places each gel at an aid station on your course, so the water is there when you take it.

One Cup Per Table Leaves You Short on Fluid Too

Even at the tables where you don't take a gel, a single cup doesn't add up to much over a race.

Researchers have measured how much runners drink when the drinks are right in front of them. In a 2007 study, 18 experienced runners had a sports drink available every 2 miles and drank as much as they wanted.4

They replaced only about 30% of the fluid they lost in sweat. They also underestimated how much they had sweated by about 42%.

That means drinking whatever feels right at each table leaves most runners well short, even with a drink every 2 miles.

How much you need to drink each hour depends on your sweat rate. Our free fueling plan works out your fluid per hour, and dividing it by 100 mL (3.5 oz) tells you how many cups that is.

How to Get More Water Out of Each Cup

A few small changes get more of each cup into you instead of onto your shirt:

• Grab the cup and pinch it closed at the top. This makes one end into a funnel and keeps the water from splashing out as easily.
• Take your time while drinking and remember to breathe. You don't have to get all the water down in 5 seconds.
• Have your gel open before you reach the table, so you can take it with the first cup and still have time to grab another cup or two.
• If you're running over 4 hours, walk through the aid station while you drink. If you're running under 4 hours, run through it, but never skip the water to save a few seconds.

How to Practice Drinking From a Cup

If you're going to use the aid stations available on the course and plan on running through the water stops, I suggest heading to the store and picking up some paper cups so you can practice beforehand.

Fill the cups with water and set them up on a table. Practice running at a little faster than marathon pace, grabbing a cup, and taking a drink.

I guarantee that the first couple of times you run through your makeshift water stop, most of the water will end up on the ground or up your nose.

Practice also trains your stomach to handle the fluid. In a 2008 study, runners did 6 runs of 90 minutes, about a week apart, drinking enough to replace their sweat. They rated their stomach comfort better on the 5th and 6th runs than on the 2nd.5

That's why you should practice drinking from cups on the same runs where you practice your gels. CarbRate's practice schedule tells you which runs those are and what carb rate to target on each one.

Do You Need More Cups in the Heat?

The water each gel needs stays the same on a hot day: 3 cups for a 25-gram gel. What changes is how many cups you need between gels, because you sweat more.

Falling behind on fluid also slows how fast your stomach empties what you give it. In a 1990 study, people who had lost 4% of their body weight to dehydration emptied a carbohydrate drink more slowly while running at 86°F (30°C) than they did when hydrated.6

So on a hot day, take extra cups at the tables where you aren't taking a gel. Our guide to water with an energy gel covers how the heat changes your fluid.

How many extra cups depends on how much you sweat. CarbRate works out your fluid from your sweat rate and adjusts your plan when the race-day forecast comes in.