Runners most often experience two distinct varieties of stomach pain after running: abdominal muscle cramps or "stitches," and gastrointestinal pain such as indigestion. Sometimes post-workout pain signifies serious medical issues such as ulcers and other inflammatory disease, so it is important to address stomach pain before it becomes chronic, disabling or fatal.
Studies at Rice University emphasize that adequate hydration while training significantly reduces post-run abdominal pain. Research has not fully realized water's many roles in physiological health, but one is that water naturally lubricates the gastrointestinal tract, optimizing both food transit and nutrient absorption. Another is that water is vital to metabolism as it balances potassium, sodium and other electrolytes governing muscle contraction and repair.
Abdominal cramping, or stitches, is perhaps the most widespread of all post-run complaints. A painful stitch can bring your workout to a screeching halt. Preventing stitches or cramps is a tricky task, but adequate preworkout water intake may decrease cramping because it promotes a "comfortable gut." Your stomach needs water for proper function, but take care not to drink too much water, as high water volume can also be uncomfortable. Breathing properly also discourages cramping. The Rice University report suggests that tight, rapid breaths cause abdominal muscle spasms. Therefore, relaxed, steady "stomach breathing" during a run is likely to delay cramping. If you do cramp, two actions help: take slow, powerful breaths and visualize sending them deep into the stitch; push air into the pain. A gentle fingertip massage can help unknot tissues.
Avoid bulky or slowly digested foods prior to running. As you train, you will become familiar with foods that stress your gut; a sensible approach means avoiding high-volume and high-fiber foods, and also foods high in protein and fat because, like fiber, protein and fat are digested slowly and tend to sit uncomfortably in your stomach. You should instead consume simple carbohydrates for energy and tissue support. Low-sugar beverages usually prove least distressing, and you should dilute by half any beverage of more than 100 calories per cup. Solid foods such as toast or bananas also provide simple carbs without promoting stomach pain.
Constrictive clothing and tight belts contribute to post-workout stomach pain. Be sure the waistband of your running outfit allows sufficient room for your stomach to expand when you breathe. You should be "belly breathing" anyway; it may feel unnatural, but accentuating breaths in your abdomen keeps your stomach relaxed and supple. An elastic belt or sufficiently loose waistband allows you to practice this style of breathing and thus dissipate stomach pain before it becomes disabling.
Serious Stomach Ailments
Stomach pain from illness includes appendicitis and inflammatory bowel disease such as Crohn's disease and colitis. Each contributes to pain after running and often requires professional treatment. According to the National Institutes of Health, if your appendix becomes infected and inflamed, it can burst, spreading infection throughout the abdominal cavity and causing toxic, sometimes fatal, peritonitis. Colitis and Crohn's disease are disorders of the immune system and manifest themselves as intestinal infection. Continual pain after running may indicate internal bleeding or ulcers and should be evaluated by a professional.