Understanding upper GI issues on race day

Gastrointestinal issues are very common among endurance athletes. Complaints are usually divided into two categories – upper GI and lower GI.

Most athletes are familiar with lower GI issues – gas, loose stool, urge to defecate, diarrhea, abdominal cramping. I’ve written several articles on the topic of GI issues, but most of the gastrointestinal issues I discuss involve the lower GI tract. In working with hundreds of endurance athletes on race day nutrition, the common culprits of lower GI issues include dehydration and concentrated or poorly applied sports nutrition consumption. I find this area fairly straightforward when it comes to prescribing well-formulated sports nutrition products to minimize or alleviate lower GI issues on race day.

When it comes to upper GI issues in endurance athletes, like belching, vomiting, reflux/heartburn, trouble swallowing and bloating, this area has been more challenging to fix. What makes it so difficult is that most of the athletes come to me for nutrition assistance only experience upper GI issues on race day, specifically in the half or full distance triathlon. With no common source of complaints, I’ve done a lot of research in this area and have come to a few conclusions as to why some athletes only experience upper GI issues on race day.

Before addressing some of the culprits of upper GI issues, it’s important to understand a few conditions that are related to upper GI issues.

1) GERD (gastro esophageal reflux disease) or heartburn.
GERD occurs when the cardiac sphincter relaxes and allows stomach acid to regurgitate into the lower part of the esophagus. The cardiac sphincter separates the lower part of the swallowing tube (esophagus) from the stomach.

Common symptoms of GERD include:

  • A burning sensation in the middle of the upper abdomen and chest.
  • Burping.
  • Regurgitation of food.
  • The taste of acid in the mouth.
  • Trouble swallowing.
  • Persistent cough/throat clearing or hoarse voice/sore throat
  • Asthma

2) Aerophagia – ingestion of air into the esophagus and stomach.

Aerophagia occurs when a person swallows too much air.

Common symptoms of aerophagia include:

  • Bloating
  • Belching
  • Decreased appetite
  • Diarrhea
  • Gas
  • Stomach noise
  • Uncomfortable distension of the stomach

In my experience, I believe that these are two of the primary causes of upper GI issues in endurance athletes. Based on the risk factors for aerophagia and GERD, it also makes sense why some athletes only experience issues on race day – and not in training.

3) Functional Dyspepsia – Indigestion.
Dyspepsia is a term for the intermittent signs and symptoms of indigestion that have no obvious cause.

Common symptoms of dyspepsia include:

  • Pain or discomfort in the upper abdomen
  • Bloating
  • Belching
  • Nausea
  • Early feeling of fullness/satiety when eating


  • When swimming, your body is placed in a horizontal position. It’s common to take big gulps of air when turning the head to breathe, especially in choppy conditions or at an effort higher than what you are used to. Seeing that the majority of triathletes do not swim before the bike but only on race day and the swim can be unpredictable and chaotic….it makes sense why so many athletes experience upper GI issues only on race day – after the swim.
  • Drinking from a straw (straw-based hydration systems). Each sip from the straw draws air into your mouth which is then swallowed.
  • Breathing rapidly and deeply (intensity) In the upright position (ex. bike or run), air rises above stomach liquids and expelled as a burp. In the horizontal position (swim/bike), air may get trapped behind stomach fluids and is sent into the small intestine, causing pain and gas.
  • Chewing gum or drinking carbonated beverages may cause you to swallow excess air. Gulping beverages (instead of sipping) may also cause you to swallow air.


  • Pre-race/race day stress and nerves – anxiety reduces pressure in the lower esophageal sphincter. Stress increases pressure around the stomach and pushes acid up. High anxiety may increase stomach acid production.
  • Eating too close to the race start or consuming food/sport nutrition while transitioning from swim to bike or bike to run. After a meal, it normally takes ~2-4 hours for food to move out of the stomach and into the small intestines. Allowing time for food to pass from the stomach to the small intestines will reduce the risk of reflux during exercise.
  • Exercise causes greater intra-abdominal pressure. Intense or jarring movements can force stomach acid into the esophagus, causing burning and irritation.
  • Bouncing and jostling can irritate the lower esophageal sphincter.
  • Tight fitting clothing, especially around the waist.
  • Full bending at the waist causes compression on the stomach and upper GI tract (aero position).
  • Lower esophageal sphincter (LES) losing its tone from the following substances:
    -peppermint, onions, garlic, chocolate, acidic citrus, tomato products
    -coffee (caffeinated or not) increases stomach acidity and the caffeine acts to relax LES
    -alcohol – relaxes the LES muscles and irritates the mucous membrane of the LES.
    -medications – some asthma inhalers, common pain relievers, blood pressure meds and over-the-counter medications.
    -adrenaline – a hormone secreted by the adrenal glands during times of stress
    -routine use of NSAIDs – inhibit protective prostaglandins and produce ulcerations in mucous membranes lining the stomach and the esophagus.

    Note: I’ve also looked into the citric acid in sports drinks as a culprit of upper GI issues and have not found a significant link. Even when I’ve switched athletes to a citric acid free drink, reflux still occurred.

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