THE CLINIC: Nausea During Distance Events

QUESTION:

I've been running for almost 20 years. When participating in endurance events, I have trouble with my stomach shutting down. At about the three-hour mark during a marathon, I am no longer able to intake a gel or other food without feeling nauseated. My recent Ironman competition went well for the first two legs, but by mile six of the run my stomach began cramping and that continued for the next hour and a half. I vomited during miles 19 through 24. What can I do to alleviate this problem? I'm a 33-year-old female weighing about 118 pounds.

Stacy Wrider

San Jose, CA

ANSWER:

The fact that these symptoms occur well into these extended events suggests that dehydration or electrolyte imbalance is affecting peristalsis. When peristalsis, the muscle contractions that propel food along the digestive tract, is interrupted, nausea and vomiting can result. There is a normal reduction of blood flow to the digestive tract during exercise, but this occurs early and remains so throughout the exercise, so it would not be the cause of a problem this late in the event. 

You should prehydrate with sports drink containing sodium, and continue to hydrate throughout the exercise period. Peristalsis is very sensitive to salt and water imbalance in the intestinal tract. Many runners restrict their nutrient intake late in the race to fluid-only. Be sure to experiment on long training runs with various foods—your intestinal tract needs to be trained for an endurance event in the same way your other muscles and organs do.

Dennis D. Daly, MD

Camillus, NY

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