If you’ve been running long enough, you’ve either experienced it or lived in fear of it. The mid-run oh no moment. That sudden, undeniable urge to find a bathroom right now — otherwise known as runner’s trots.
Nobody wants to talk about it over coffee after a long run, but GI distress is one of the most common issues runners face — and one of the most misunderstood. The good news? You can absolutely reduce the chances of it happening, but first, you have to understand why it happens in the first place.
Why Runner’s Trots Happen
There isn’t one single culprit — it’s usually a combination of physiology, fueling, timing, and stress. Your gut is sensitive, your body is busy moving blood to your muscles, and you’re literally jostling your internal organs for miles. Of course things get… complicated.
Let’s break it down.
Blood Flow + Digestion Don’t Mix
When you run, your body prioritizes blood flow to working muscles, not digestion. Less blood to the gut = slower digestion and more irritation. For some runners, that means nausea. For others, it means the digestive system hits the eject button mid-run.
This effect tends to be stronger during hard efforts, long runs, and — fun fact — in perimenopause or menopause, when hormonal changes can affect gut motility. Lower estrogen can make your GI tract more reactive to stress, temperature, and fueling shifts.
Everything’s Literally Bouncing
Running is basically rhythmic impact over and over again. That movement can speed up intestinal transit time, especially if your system isn’t fully settled before you head out.
This is why that “it hit me at mile three” moment happens — your gut got the message that it’s time to move everything whether you wanted it to or not.
Hydration and Electrolyte Chaos
Too little fluid and your gut cramps. Too much, and you dilute electrolytes, which can trigger diarrhea. If you’re drinking plain water during long runs but not replacing sodium, potassium, and magnesium, your digestive system might be staging a protest.
And yes — this is where what you’re using to hydrate matters. Some sports drinks (especially ones with artificial sweeteners or excess fructose) can backfire.
Fueling Mistakes and Sneaky Triggers
That pre-run “healthy breakfast” might not be doing you any favors. High-fiber foods, heavy fats, and dairy are common culprits. Artificial sweeteners, gels with maltodextrin, or caffeine-heavy pre-workouts can be sneaky triggers, too.
And let’s be honest — sometimes it’s not even about what you ate today but how your gut’s been treated all week. If your nutrition, stress, and sleep are off, your GI system is more reactive across the board.
Stress, Nerves, and the Gut-Brain Connection
Ever notice how pre-race jitters send you sprinting to the porta-potty before you even start? That’s your enteric nervous system — your “second brain” — responding to cortisol and adrenaline.
Stress literally changes gut motility. When you’re anxious, your brain says “danger,” and your digestive system says, “Lighten the load.” Not ideal timing mid-race, but very on-brand for biology.
How to Stop the Mid-Run Panic
You can’t always eliminate GI distress completely (we’re human, not robots), but you can absolutely stack the odds in your favor.
Here’s how:
Time Your Meals (and Know Your Gut’s Schedule)
Give yourself 2–3 hours between your last meal and your run.
Need a pre-run snack? Go small and low-fiber — think banana, white rice, or toast with a little nut butter.
If your gut tends to be extra unpredictable, aim to eat and hydrate around the same time daily. Routine helps regulate digestion.
Train Your Gut Like You Train Your Legs
You wouldn’t try new shoes on race day — same rule applies to fueling. Practice taking in gels, electrolytes, and fluids during long runs so your GI system adapts.
“Gut training” actually teaches your body to absorb carbs more efficiently and reduces the shock of fueling under stress.
Balance Hydration and Electrolytes
Hydrate consistently throughout the day, not just before a run. Use an electrolyte mix that supports your sodium needs without overloading your gut with sugar or artificial sweeteners.
For a detailed look at options and how to match your needs, check out my Fueling + Hydration Guide — it breaks down popular products (like Maurten, LMNT, Skratch, and Tailwind) and how to pick the right one for your stomach and sweat rate.
Reduce Stress Before You Lace Up
A chaotic brain = a reactive gut.
Try a short warm-up walk, a few deep breaths, or even a minute of mindfulness before you start your run. The calmer your nervous system, the calmer your digestion.
Know Your Route and Have a Backup Plan
Even with perfect fueling, life happens. Know where bathrooms are, carry wipes, and don’t beat yourself up if you have to stop. Every runner has their story — most just don’t tell it until someone else admits it first.
Runner’s trots are a nuisance, not a character flaw. Your body’s not broken — it’s responding exactly as it’s designed to under stress, motion, and fuel shifts.
The key is to make your system less reactive through consistency: consistent meals, hydration, fueling practice, and pre-run routines.
And if you’re someone who deals with chronic GI issues, especially in menopause or after long-term endurance training, dig deeper into gut-brain regulation and fueling strategies inside my Fueling + Hydration Guide.
Because running shouldn’t feel like a sprint for the nearest bathroom — it should feel like freedom.