Exercise absolutely can cause abdominal pain, and it happens far more often than most people realize. About 61% of active people across multiple sports report experiencing some form of exercise-related abdominal pain within the past year, and roughly one in five runners will feel it during any single race or training run. The pain ranges from a familiar side stitch to gut-level cramping, and while most causes are harmless and temporary, a few deserve closer attention.
Side Stitches: The Most Common Culprit
The sharp, stabbing pain in your side during a run or brisk walk is known as exercise-related transient abdominal pain, or a side stitch. Around 70% of runners say they’ve had one in the past year. It typically hits just below the ribs, more often on the right side, and can range from a mild cramp to pain sharp enough to force you to stop.
The leading explanation is friction between two layers of tissue lining your abdominal cavity. Your organs are wrapped in a smooth membrane, and a second layer lines the inside of your abdominal wall. During repetitive, bouncing movements like running, these layers can rub against each other. That friction irritates the tissue and produces the characteristic localized, stabbing sensation. Other proposed mechanisms include stress on the ligaments that suspend your organs from the diaphragm and temporary cramping of the abdominal muscles, but the friction theory best explains why side stitches feel the way they do and why they tend to worsen with jostling activities.
If you get one mid-workout, three simple steps help: slow your pace, take slow deep breaths (inhale for a few seconds, then fully exhale), and press your fingers into the painful spot. Most side stitches fade within minutes once you ease up. They’re not a sign of anything dangerous.
Blood Flow Shifts and Gut Distress
During exercise, your body redirects blood away from your digestive organs and toward your working muscles, heart, and lungs. This is a normal physiological response, but it leaves your gut temporarily short on oxygen and fuel. The cells lining your intestines, particularly at the tips of tiny finger-like projections called villi, already operate in a low-oxygen environment. When blood flow drops further during hard effort, those cells can lose integrity, triggering cramps, nausea, bloating, and diarrhea.
A study of over 800 recreational long-distance runners in China found that 26.1% reported gastrointestinal symptoms during races. The most common complaints were bloating (18.6%), an urgent need to use a bathroom (17.8%), stomach pain (16.5%), and side stitches (15.3%). The harder and longer the effort, the more pronounced the blood flow diversion and the more likely these symptoms become.
What You Eat and Drink Matters
Your pre-exercise meal and what you consume during a workout play a surprisingly large role in whether your stomach cooperates. Three nutrient types consistently increase the risk of abdominal pain during exercise: fiber, fat, and protein. All three slow digestion, meaning food sits in your stomach longer while your gut is already running on reduced blood flow. Eating a heavy or high-fiber meal within a few hours of a hard session is one of the most reliable ways to trigger cramping.
What you drink during exercise matters just as much. Highly concentrated carbohydrate beverages (those above about 6% carbohydrate content) slow the rate at which fluid leaves your stomach. In controlled trials, an 8% carbohydrate sports drink produced higher ratings of stomach upset and side aches compared to a 6% drink. Extremely sugary drinks pull water into the intestines rather than delivering it to the body, compounding bloating and cramping. If you use a sports drink, sticking to a 6% or lower carbohydrate concentration, or using a glucose-fructose blend at higher concentrations, tends to minimize problems.
A practical approach: keep pre-workout meals low in fat, fiber, and protein, focusing on simple carbohydrates. The closer you eat to your session, the lighter the meal should be. During exercise, sip moderate amounts of a dilute sports drink or plain water rather than gulping down concentrated energy drinks.
Muscle Strains and Hernias
Not all exercise-related abdominal pain comes from your digestive system. A sudden twist, change of direction, or heavy lift can strain the muscles of your core or groin. You’ll typically notice the moment it happens, sometimes feeling a pop, followed by pain that lingers for days or weeks. These injuries are sometimes called “sports hernias,” but that’s a misnomer. They’re muscle or tendon strains, and they heal with rest.
An actual inguinal hernia is different. It occurs when fatty tissue or a loop of intestine pushes through a weak spot in the abdominal wall. The telltale sign is a noticeable lump in the groin area, something you won’t feel with a simple strain. Hernia pain may come and go, but the defect in the abdominal wall doesn’t close on its own. If a hernia suddenly becomes extremely painful and is accompanied by nausea and vomiting, the trapped tissue may have lost its blood supply. That’s a medical emergency.
When Abdominal Pain Signals Something Serious
Most exercise-related abdominal pain resolves on its own within minutes to hours. A side stitch disappears when you slow down. Gut cramping from a hard race fades as blood flow normalizes. But certain symptoms point to something more than routine exercise stress.
Blood in your stool after intense exercise is one key warning sign. While mild, invisible blood loss is relatively common in endurance athletes, visible bloody diarrhea is less so, though one study found that 16% of runners reported it at least once after strenuous exertion. In some cases, this reflects ischemic colitis, where prolonged blood flow reduction actually damages a segment of the colon. A typical presentation involves severe lower abdominal cramping during or shortly after a run, followed by multiple episodes of diarrhea with visible blood. One documented case involved a recreational runner who developed cramping after a two-mile run, then had five bouts of bloody diarrhea. Colonoscopy revealed an ulcer at a vulnerable bend in the colon where blood supply is naturally limited.
Pain that persists for hours after you stop exercising, pain accompanied by fever, pain that worsens when you press on your abdomen and then release, or vomiting that won’t stop all warrant prompt evaluation. These symptoms can indicate problems ranging from a hernia complication to appendicitis that happened to surface during a workout. Exercise-related abdominal pain is overwhelmingly benign, but pain that doesn’t behave like a side stitch or routine gut distress deserves a closer look.