Runner's diarrhea

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 3, 2015
StartRunner's diarrhea

Exercising and physical activity can greatly help a person develop a healthy digestive tract and keep things moving along smoothly on a regular basis. Athletes who run regularly and in long distances can actually develop a condition called runner’s diarrhea, also known as runner's trots. While running can help maintain regular bathroom habits, it can also a quick dash to the bathroom in the midst of a run. In addition to diarrhea, gas, cramping and stomach upset can also occur.


Definition & Facts

Shockingly, as many as fifty percent of long distance runners can experience runner’s diarrhea at one time or another. Some runners experience the urge to use the bathroom while they are in the middle of a run while others can make it through a workout but will experience symptoms immediately upon stopping.

People with irritable bowel syndrome tend to be more susceptible to this issue but almost any runner can be faced with runner’s diarrhea consistently or occasionally. The most issues occur between approximately twenty miles and the finish line at 26.2 miles. Fifteen to twenty miles can be routine for many runners but that final few is really pushing the body to the extreme, no matter how well trained you think you may be. The body can begin to do interesting things to cope with these last few miles and runner’s diarrhea is one of these things.


Medical professionals are not completely positive why runner’s diarrhea occurs in the first place but there are some thoughts on the matter. For one, as a person runs, their body is constantly moving in an up and down series of motions. In certain people, this might cause some activity to engage in the bowels. Also, the blood flow that you usually have in the colon and intestines can sometimes be redirected to the legs or other parts of the body while in motion.

This can cause your stomach and intestines to start cramping up. If you continue along with your run, eventually diarrhea will begin. Dehydration can also cause diarrhea and depending on the length of the run and the weather conditions, this could also be a cause. Many runners take anti-inflammatory medications or pain relievers as a way to deal with soreness. This is especially true leading up to a run when a lot of training is going on.

The day of the run, nobody wants to be in pain as this will affect their time. Medications that can be purchased over the counter such as Tylenol® or ibuprofen can cause loose stools and diarrhea. They should be avoided at all costs at least a few days prior to a long distance run. Hot or cold therapy can often bring about just as much relief but these options are not taking internally and will not affect the bowels.

When to see a doctor

Any unexpected change in bowel habits warrants a visit to the doctor. While a runner might know of this condition and assume their issue is because of their running, but other possible issues should be considered as well. If the problem does seem to be runner’s diarrhea, then there are some instances where medical attention is needed.

Persistent diarrhea can quickly lead to dehydration. Running long distances can also cause dehydration so when this issue is present, it is important to seek medical attention if symptoms arise such as muscle cramping, lack of sweat, headache, dizziness, dry mouth and so on. Also, blood in the stools can be a sign of something more serious and should be investigated.

More often than not, it turns out that everything is ok and there may just be a simple issue such as lactose intolerance or gluten sensitivity. These issues simply require a change in diet and do not necessarily put a person’s life at risk. A trusted and reputable medical professional can help with alleviating symptoms as well as learning how to adapt to these medical discoveries.

Treatment & Therapy

It is important to take good care of the digestive system even when diarrhea is present. Rehydrating after a run is important especially when frequent bowel movements have taken place. Also, diarrhea can cause some stomach and intestinal upset for a few days. Following a diet such as the BRAT diet can help get things back on track. This includes eating the foods bananas, rice, applesauce and toast until symptoms subside.

After that, normal foods can be introduced back into the diet slowly. Food should never be avoided prior to a run or afterwards. The body needs nutrition especially for someone who is physically active. Running on an empty stomach or fasting before a marathon will land a person in the hospital quite quickly.

Prevention & Prophylaxis

Many long distance runners have found it beneficial to keep a food diary for a number of weeks in order to take a good look at their diet and see if what they eat on a given day is at all related to symptoms of runner’s diarrhea. A few changes to a person’s diet can very easily prevent an issue from happening while on the run.

Avoiding foods that are very high in fiber or fat can prevent diarrhea. There are other ingredients in products that can irritate a person’s digestive tract such as artificial sweeteners, which are often found in sport re-hydration drinks. A special diet does not have to be consistently followed as fiber and healthy fats are important, however a few days before a big marathon or event trigger foods should be avoided.

Simple foods such as white rice, white pasta, applesauce and bananas can help sooth the digestive tract and keep things in check. It is important to keep in mind that any food that is eaten will take approximately twenty-four to seventy-two hours to pass through the digestive system. Runners and people who exercise on a regular basis, tend to have a faster digestive system.