Diarrhea in the Endurance Athlete

It's race day. You've worked hard and you're pumped up to give this race (half marathon, marathon, triathlon, enter your race here) everything you've got. Things are going well, and then IT hits. Cramping, urgency. You spend the rest of your race port-a-potty hopping and praying you'll make it to the next one in time. Worse yet, you're home recovering from your race and the severe pain sets in and lingers. Maybe bloody or tarry stools fill your toilet bowl. This is scary stuff. But you love running, triathlon, racing. You don't want to quit! 

Runners diarrhea, the trots, GI distress. Call it what you want.  It can be a real bummer on race day.  These symptoms are actually very common in athletes, particularly runners.  They can lead to severe problems requiring hospitalization.  Let's break down what could be contributing and things you can do to reduce your risk. 

 

When you exercise, your sympathetic nerve system is in overdrive.  Remember "fight or flight" and "rest and digest" from grade school?  There are both hormonal and blood flow affects from sympathetic nerve stimuli.  In my opinion one of the biggest factors which causes runners diarrhea is that blood is shunted away from your GI tract to allow for more blood flow to the heart, lungs and skin (to cool you down).  Because of this, parts of your GI tract have what's called ischemia which is a lack of blood flow to supply nutrients and oxygen to a tissue.  One part of the left side of the colon is particularly susceptible to ischemia because of the anatomy of our blood flow.  In runners this can also happen in the small intestine and even stomach.  The ischemia can be mild in some cases but also can be severe and actually very dangerous in others.  Once there is ischemia it can bleed and also cause trouble with absorption of nutrients, water causing cramping, pain and diarrhea.

  Studies show the harder you are working (ie. faster and longer) the high risk for symptoms from ischemia.  It's common for symptoms to occur after the blood flow goes back to normal (when you are done exercising).

 Mechanically vibration to the intestine while running has also been reported to cause diarrhea.  There is a theory called the "cecal slap" that was described decades ago.  The cecum is the part of the colon where your small intestine joins the colon and appendix hangs off of it.  It can move about a bit, and the idea is running makes it bounce and hit the wall of your abdomen so much it can actually get bruised.  This also would cause irregular hormones to release and absorption problems temporarily. I'm not sure how valid this theory is, but it certainly could contribute. 

Hormones in the body are altered when we are exercising at high intensity.  Alteration of hormones can cause diarrhea and cramping as well. The good news is our bodies seem to be somewhat adaptable to these hormones, meaning if we train properly then our symptoms can improve.
 

 First things first, other causes of diarrhea and cramping should be ruled out by your doctor. 
If you are seeing blood, this is not normal and can potentially be serious, so please seek medical attention immediately. This blog does not substitute for a doctor-patient relationship and you should meet with a gastroenterologist in your area.

Ask your doctor to make sure you have normal blood flow to the colon when you are NOT exercising.  Assuming everything checks out fine with your GI doc, here are some tips to get you back to running.

*You may have anemia from heavy menstruation, iron deficiency or increased red cell distruction from the impact of running.  Anemia means there is less oxygen in the blood volume you have, so you want to maximize your oxygen carrying to the tissues.

**Constipation, Constipation, Constipation.  Just because you are having daily bowel movements, doesn't mean you are not constipated.  Not all bowel movements are created equal.  You would be amazed how many people are constipated to the point of severe pain and still don't believe they are constipated until they do a bowel cleanse and see how good they could actually feel.  If you are constipated and then during a long work out you have hormonal release and mild ischemia, all the more stool to be expelled once your bowels get moving.  Look out! 

 ***Eating and drinking during your exercise takes training.  Doing so keeps a little more blood flowing to the GI tract. I would recommend avoiding high fructose containing supplements and also lactose which may make things worse.

 I hope you find this helpful.  If this happens again, you may need to reduce your intensity for at least a few months and slowly resume in order to give your body some time to hopefully adapt.

Good luck to all the #INGNYCM Runners this weekend!