A runner's laundry list of aches and pains is never-ending—there's the infamous side stitch, dreaded shin splints, and of course, those ungodly muscle cramps.

You've also no doubt heard that sometimes runners, um, don't quite make it to the bathroom. Hell, during a race, a lot of them don't even try.

If you've had a close call during a race (Chicago Marathon 2010, I'm looking at you), you know there's basically nothing more agonizing than the overwhelming need to poop while you're running. And while there are a bunch of potential catalysts for a code brown, the one that gets the most speculation is those colorful little packets of energy gel you see runners slamming mid-race.

What even are energy gels?

In 1992, Bill Vaughan, Ph.D., a biophysicist at UC Berkeley, recognized the need for portable and easily digestible nutrition for athletes when his daughter Laura struggled with fueling during a 100-mile race.

During activities of more than an hour, carbohydrate availability to both muscles and our central nervous system (which just controls the whole body, NBD) may be compromised if you're burning more carbs than you've stored. Studies recommend 30-60 grams of carbohydrates per hour of activity, combined with adequate re-hydration, to provide athletes the energy needed to sustain activity and endurance. Gels and other transportable carbohydrates are an easy way to get those in while running or cycling—unless, you know, you prefer to carry a sandwich instead.

But will these make me poop my pants?

The reason that you experience gastrointestinal distress from energy gels is actually pretty simple. When you consume more carbs at a rate faster than your stomach can handle, the residual carbs left in your gut lead to GI distress, says Michael Fredericson, M.D., a physiatrist at Stanford University School of Medicine.

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The good news, though, is that it's possible to prevent this. "Anecdotal evidence in athletes also suggests that the gut is trainable and that people who regularly consume carbohydrates or have a high daily carbohydrate intake may also have an increased capacity to absorb it," Fredericson says.

This is exactly what the phrase "don't try anything new before race day" means—you should be training your gut for race-day carb consumption as you simultaneously train the rest of your body to go the distance.

Fredericson recommends a product with a blend of glucose and fructose, such as PowerBar Performance Energy Gel or maltodextrin and fructose, like Gu Energy Gels. "The goal of multiple mixtures," he says, "is to bypass the usual limitation on gut uptake of glucose-based sugars. The gut can only process up to about 60 grams of glucose per hour, but a combination of energy is more effective than pure glucose-based products in maintaining gut comfort, promoting muscle carbohydrate oxidation, and enhancing performance."

Before you start overthinking the ingredient labels, know that regardless of the product, if you handle them properly, you're probably not destined for an embarrassing incident. "Gels should be consumed with water or other fluids, which will wash them down and reduce the net carbohydrate concentration to reduce risk of gut upsets." Science in Sport (aka SIS) gels don't require water, which is great if you hate the feeling of goop in your mouth. Just don't use that as an excuse not to drink water, because how you hydrate can make or break your race.

Also—slow it down! "One thing that can help with gels is to eat them slowly. There's often a tendency to eat the whole gel quickly in a few bites, but I'd suggest taking small nips of the gel for a mile or so," says Anne Mauney, MPH, RD.

So, to gel or not to gel?

Fredericson says to gel. He likes that they're a compact and portable source that can be consumed easily during or after exercise to meet recommended carbohydrate intake targets.

But Mauney disagrees, with caveats: "Gels are great, especially for faster races, but for longer distances like a full marathon, you may want to consider having something with just a little protein and fat as well. I often eat a pitted date stuffed with a little nut butter and sprinkled with salt every 30 to 45 minutes on really long runs—it can help you avoid hunger-induced nausea near the end of long runs."

So if you're training for a race distance of 10K or longer, rest a little easier about adding energy gels or blocks into your training. Just remember to take them with water, and the only sprinting you'll be doing will be to the finish—not the toilet. Then again, while this is one race day factor you can control, let's face it: Sh*t happens.

Theodora Blanchfield is an NYC-based writer, social media consultant, and fitness nut who also happens to be a NASM-certified personal trainer and RRCA-certified run coach. She can usually be found in search of either a cup of coffee or glass of wine, depending on the hour. She has been blogging at preppyrunner.com since 2009.

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