Working out can make you need to poop more frequently or with greater urgency. This common phenomenon is a direct result of the complex changes that occur in your body’s digestive system during physical activity. The experience is widely reported, especially among endurance athletes, and is a normal physiological response as the body prioritizes energy and blood flow to working muscles. This exercise-induced change in gastrointestinal function is a challenge that many active individuals learn to manage.
Why Exercise Speeds Up Digestion
Physical activity triggers sympathetic nervous system activation, often called the “fight or flight” response. This process immediately begins to reroute resources to the muscles, heart, and lungs in preparation for exertion, shifting priorities to support performance rather than digestion.
A primary mechanism behind this shift is the shunting of blood flow away from the gastrointestinal (GI) tract. During intense exercise, blood flow to the splanchnic region, which includes the stomach and intestines, can be reduced by 80% or more. This lack of adequate blood supply can lead to temporary tissue irritation and intestinal ischemia. The reduced blood and oxygen supply impairs the gut’s ability to function normally, affecting nutrient absorption and overall motility.
The physical movement of certain exercises also contributes to increased gut activity. High-impact activities, such as running, cause mechanical agitation or a “jostling” effect on the internal organs. This movement combines with the body’s natural contractions, known as peristalsis, to push contents through the intestines faster. The combined effect of reduced blood flow and mechanical stimulation accelerates the transit time of waste, leading to a quickened urge for elimination.
Understanding Exercise Related Bowel Urgency
The physiological changes in blood flow and mechanical movement manifest as symptoms commonly referred to as “Runner’s Trots” or exercise-induced diarrhea. This condition is characterized by an urgent need for a bowel movement, often resulting in loose or watery stools during or immediately following a workout. The prevalence of this gastrointestinal distress is high, with estimates suggesting that between 20% and 80% of endurance runners experience some form of gut issue.
Symptoms include diarrhea, abdominal cramping, nausea, bloating, and gas. The severity of these symptoms correlates with the intensity and duration of the physical activity. High-impact and long-duration endurance sports, like marathon running, are more likely to induce severe GI distress compared to lower-impact activities such as swimming or cycling. This difference is due to the more pronounced mechanical stress and greater blood flow shunting that occurs during prolonged, high-intensity efforts.
The irritation caused by reduced blood flow can temporarily compromise the protective lining of the gut, increasing its permeability. This compromised barrier function may allow substances to pass into the bloodstream, potentially worsening the digestive symptoms. While mild urgency is inconvenient, severe symptoms like persistent diarrhea or fecal incontinence can significantly impair an individual’s ability to train or compete. The symptoms usually resolve within a few hours of stopping the activity.
Strategies to Manage Gut Distress
Managing exercise-related gut distress involves focusing on dietary timing and strategic consumption of specific nutrients. Adjust the timing of your last substantial meal to allow for adequate digestion before your workout. Most experts recommend eating a meal one to four hours before exercise to ensure the stomach has largely emptied its contents before activity begins.
The composition of the pre-exercise meal is important for preventing bowel urgency. Foods high in fat, fiber, or protein should be limited or avoided in the hours leading up to an intense workout. These nutrients are more difficult to digest and slow down gastric emptying, leaving food in the stomach and intestines when blood flow is being redirected. Instead, focus on easily digestible, lower-fiber carbohydrates, which provide readily available energy and pass through the digestive system more quickly.
Hydration must be managed carefully to avoid worsening symptoms. Dehydration can exacerbate GI distress, but consuming highly concentrated sugar drinks can also be problematic. Beverages with a high osmolality can draw water into the intestines, potentially leading to loose stools and cramping. Sports drinks should contain a balanced concentration of carbohydrates and electrolytes to promote absorption without causing digestive upset.
The gut itself can be trained to better tolerate the demands of exercise. This “gut training” involves gradually increasing the intake of carbohydrates and fluids during training sessions. Repeated exposure helps the stomach improve its rate of emptying and encourages the intestines to become more efficient at absorbing nutrients. For long-duration activities, utilizing multiple transportable carbohydrates, such as a combination of glucose and fructose, can enhance absorption and reduce the likelihood of gut issues.