2. Heart burn
This stinging sensation in your upper abdomen and chest can leave you gagging and belching during your run.
Possible causes:
Persistent heart burn could be gastro esophageal reflux disease, a condition that develops when acidic contents of stomach persistently seep into the esophagus.
Hard exercise easily stirs up those acids.
“The more strenuous the workout, the more commonly this occurs,” Fieseler says.
Heart burn-like discomfort can also be a sign of something more serious, including a heart attack or ulcer. If your pain is especially severe, see a doctor as soon as possible.
Treatment/prevention:
Chocolate, coffee and food and drinks with citrus and tomato may trigger acid reflux, so avoid them before a run.
You can also take Mylanta or chewable antacids.
“Antacids work the quickest and can be used during your workout if symptoms develop,” she says.
More potent medications, such as H2 blockers, are available over the counter or with a prescription.
3. Intestinal pain
In addition to being excruciating, lower belly cramps are notorious for sparking embarrassing sprints to the restroom.
"Most runners will deal with this at some point in their careers,” Fieseler says, and unfortunately, “some runners deal with this any time that they run more than a few miles.”
Possible causes:
Running can trigger a process called peristalsis, which is a series muscle contractions that moves food through the digestive tract. Stress and a poor diet can also contribute to intestinal pain.
“Cramping can be quite debilitating at times and may be accompanied by diarrhea,” she says, adding that symptoms usually ease after a bowel movement.
However, if you have blood in your stool, you should be evaluated by a doctor. It could be a sign of tissue damage in the intestines or inflammatory bowel diseases, such as ulcerative colitis and Crohn's disease.
Treatment/prevention:
“Modifying your diet is the first place to start,” Fieseler says. “Keep a diet diary for a few weeks. Is there a trend evident when symptoms develop? Avoid foods with a lot of fiber and fat the day prior to your long run. For some people, a liquid diet the day prior to a long run works.”
She also recommends avoiding sorbitol, an alcohol sugar that can have a laxative effect. Sorbitol, which is added to products to enhance sweetness, can be found in everything from chewing gum and mouthwash to candy and chocolate, according to the Mayo Clinic.
To avoid episodes of diarrhea, take Immodium before your runs.