The scenario is all too familiar: You’ve trained diligently for months. Your fitness is peak. Your equipment is dialed in. Your nutrition plan has been tested on long training days. Yet somehow, 3 hours into your Ironman or 10 miles into your marathon, your stomach revolts. Nausea sets in. Cramping begins. The portaloo toilet stops multiply. Your carefully calculated pace slows to a walk, and your race goals begin slipping away.

Gastrointestinal issues represent one of the most common reasons endurance athletes fail to achieve their potential on race day. Studies suggest up to 90% of ultrarunners and 70% of triathletes experience some form of GI distress during competition. Even more frustrating, nutrition strategies that worked flawlessly in training can suddenly fail during events.

The good news? Many mid-race nutrition disasters can be troubleshot and corrected before they completely derail your performance. Let’s explore why these issues happen and how to address them when they strike.

Why Race Day Is Different

Understanding why your digestive system behaves differently during competition is the first step toward prevention and troubleshooting:

Race intensity often exceeds training intensity, redirecting blood flow away from the digestive system and toward working muscles. This reduced blood flow compromises digestive function.

Adrenaline and stress hormones spike on race morning, slowing gastric emptying and altering how your body processes nutrients.

Weather conditions may differ significantly from your training environment, changing sweat rates and electrolyte needs.

The cumulative fatigue of a long event creates a progressively more sensitive gut as the race continues.

Race morning routines often disrupt normal eating patterns and timing, throwing off your digestive rhythm.

Common GI Issues and Real-Time Solutions

Problem: Nausea/Feeling of Fullness

This often indicates that your stomach isn’t emptying properly, creating a backlog of fluid and nutrition.

Real-time fixes: Temporarily reduce intake concentration by drinking plain water for 15-20 minutes while continuing to sip very small amounts of your nutrition.

Switch to a different carbohydrate source. If using maltodextrin-based products, try glucose or fructose options instead, or vice versa.

Slow down your pace temporarily to allow more blood flow to return to your digestive system.

Try solid food if you’ve been using only liquids, or liquids if you’ve been relying on solids. Sometimes the change itself can trigger improved digestion.

Problem: Bloating and Gas

This typically signals either excess air swallowing, carbonation from sports drinks, or fermentation of certain carbohydrates in your gut.

Real-time fixes: Focus on your breathing pattern to reduce air swallowing, especially during high-intensity efforts.

Switch to different carbohydrate sources that may be easier for your body to absorb – often individual carbohydrates (just glucose or just fructose) are easier to process than blends when your system is stressed.

Try ginger chews, which naturally aid digestion and can reduce gas formation.

Take smaller, more frequent sips rather than large gulps of fluid.

Problem: Diarrhea or Urgent Bowel Movements

This is often caused by hyperosmolar solutions (too concentrated nutrition), excess magnesium or vitamin C in supplements, or simply the jostling motion of running.

Real-time fixes: Reduce the concentration of your sports drink immediately by adding more water.

Eliminate caffeine from your remaining nutrition plan.

Consider taking a fast-acting anti-diarrheal medication (only if you’ve tested this previously in training).

Temporarily switch to easily digestible solid foods like white rice or plain saltine crackers.

Focus on sodium intake, as sodium helps your intestines absorb water.

Problem: Cramping and Stomach Pain

These can have multiple causes, including electrolyte imbalances, dehydration, or consuming too much fiber or fat before or during the event.

Real-time fixes: Try taking additional sodium (600-1000mg) in concentrated form.

Sip flat cola which provides both easily digestible sugars and small amounts of caffeine that can aid absorption.

Apply gentle pressure or massage to cramping abdominal muscles.

For severe cramping, walk while tall with arms overhead for 30-60 seconds to create more space for your digestive system.

The Decision Framework: Push Through or Adjust?

When GI issues strike, athletes face a critical decision: try to maintain pace and original nutrition strategy, or make adjustments. Consider these factors:

Time remaining in the event: Early problems in long events almost always require adjustment rather than pushing through.

Severity of symptoms: Mild discomfort can often be tolerated, but significant pain or multiple bathroom stops require intervention.

Relationship to intake: If symptoms worsen immediately after consuming nutrition, that’s a clear signal to change your strategy.

The “15-Minute Rule”: If you make a nutrition change, commit to it for at least 15 minutes before judging its effectiveness or making additional changes.

Creating Your Nutrition Rescue Kit

Smart athletes prepare for potential GI issues by assembling a “rescue kit” of alternative nutrition sources. Consider including:

Different carbohydrate sources than your primary nutrition (if your plan relies on maltodextrin, include glucose or fructose alternatives)

Easily digestible real foods like boiled potatoes with salt, white rice, or saltine crackers

Ginger chews or capsules for nausea

Sodium tablets separate from your regular electrolyte sources

Liquid options if you normally rely on solids, and some solid options if you typically use liquids

Anti-diarrheal medication (only if pre-tested in training)

Prevention Through Simulation

The best way to handle race-day nutrition disasters is to prevent them entirely. In the months leading up to your key event:

Practice your exact nutrition strategy during race-simulation workouts at target intensity

Train your gut by using increasingly concentrated nutrition during specific training sessions

Experiment with your pre-race meal timing to identify your optimal window

Test your race-morning routine, including timing, food choices and bathroom schedule, multiple times

Practice your nutrition strategy under various conditions – heat, humidity, different intensities

When Disaster Strikes: The Mental Game

Perhaps the most critical aspect of handling mid-race nutrition problems is maintaining perspective. GI issues, while physically uncomfortable and performance-limiting, are temporary. Many champions have overcome significant stomach problems to finish strong.

Rather than catastrophizing (“My race is ruined!”), frame the situation as a problem-solving challenge: “This is a temporary setback. I have tools to address this.”

Remember that slowing down temporarily to fix nutrition problems often results in stronger performance later in the race compared to pushing through and suffering increasingly severe consequences.

Your Post-Race Learning Opportunity

If you experience GI issues during an event, document everything while it’s fresh in your mind. Note the specific symptoms, when they began, what you consumed before they started, and what interventions helped or hurt. This information becomes invaluable for preventing similar issues in future races.

Analyze the differences between your training environment and race conditions. Did weather, intensity, pre-race routine, or specific foods differ significantly?

GI issues are rarely random – they typically follow patterns that, once identified, can be addressed systematically.

Proper nutrition remains one of the most trainable aspects of endurance performance. With careful attention to troubleshooting when problems arise and dedicated practice to prevent future issues, you can transform this common race-day disaster into one of your competitive advantages.

Has a nutrition disaster affected your race performance? Reach out by email to share your experience or to inquire about personalized nutrition strategies for your next endurance challenge.