Exercise Induced Nausea/Vomiting

A client of mine has a daughter that just finished her first year on the high school cross-country team.   One of girls on the team has had two races in which she vomited immediately afterwards.  My client thought it might be hydration related.  Water logging, another word for over-hydration, characterized by drinking too much water before, during, and/or after exercise (or at any time) can cause nausea, diarrhea, confusion, and muscle tremors.  If the overhydration is significant enough, it can be fatal.  Excessive water consumption reduces or dilutes electrolyte levels in the body. It is encouraged to control your level of water intake when working out, and also to eat salty snacks when you have consumed too much water (sodium and potassium are electolytes).  This is more likely to occur in long endurance events when athletes overhydrate throughout the race.  


This would be less likely for a 5K racer unless of course the runner is consuming copious amounts of fluid prior to the start of the race.  One possible explanation is ischemia - a restriction of blood flow - to the gastric mucosa, the membrane layer of the stomach.  Different types of stress (such as high intensity exercise) can breach this barrier, causing increased permeability of the gut lining and allowing entry of harmful bacterial toxins into the blood stream which could lead to nausea, vomiting, bloating, bloody diarrhea, and cramping.  

Intense anaerobic exercise (such as sprinting or lifting heavy weights) can also result in insufficient blood supply to the GI tract.  When this occurs, the GI tract simply can't function as designed and thus rejects its stomach contents, and in some cases the contents of the intestinal tract (diarrhea).  The ischemia achieved by athletes in long endurance events also compromises the intestinal barrier, contributing to and compounding the GI symptoms.


It has been suggested that exercise induced nausea could be caused by increased endorphin levels, which are released while exercising. Endorphins have been associated with nausea and vomiting, so this theory is plausible, but unsupported by evidence.


Other factors to consider include overheating due to hot and/or humid conditions, negative reactions to allergens, and food intake up to 24 hours prior to racing.  


Performance related mental stress has also been fingered as a vomit-inducing trigger.  Practicing coping mechanisms prior to and during a race can be just the trick to keeping those stomach butterflies from escaping through the top door.  


Often the urge to purge will subside after the body is conditioned to withstand extremely taxing exercise.  The conditioning effect combined with the ability to mentally distinguish where the proverbial red line lies.  


This is by no means meant to serve as medical advice, but certainly gives you some things to consider.  If vomiting continues more than a few times, certainly seek professional help.