Balance will help stave off the runs

Have you ever suffered from diarrhoea after a hard training session or marathon? I experienced this not too long ago, just after the SEA Games marathon this year. I ended up making multiple pit stops to the toilet throughout the day immediately following the race.

I had a chat with Dr Low How Cheng, a senior consultant with the division of gastroenterology and hepatology of the National University Hospital, to find out more.

In one of the earliest studies in 1984, American researchers found that out of 707 athletes, up to a third of them had the urge to defecate, both during and immediately after running. According to Dr Low, such symptoms are not uncommon among endurance athletes who have shown other gastrointestinal (GI) symptoms, such as diarrhoea, abdominal cramps, bloatedness, nausea and flatulence.


There is still a paucity of medical literature on this condition, but one commonly accepted explanation is that during intense exercise, precious oxygen-carrying blood cells are shunted towards the contracting muscles in our arms and legs, and fewer are delivered to the gut.

This may also explain why these GI symptoms occur even more frequently in warm environments - where blood has to be shunted to the skin to promote heat loss, thus further reducing flow to the gut.


A study published by the Journal of American College of Sports Medicine in 2010 found a direct correlation between carbohydrate intake during exercise and GI symptoms across three different Ironman races - the higher the intake, the higher the chance of the symptoms occurring.

However, much still depends on how well each individual's body is able to break down, absorb and eliminate carbohydrates.

It would be best that athletes find their own unique balance. Remember, more is not necessarily better.


There has also been some scientific evidence that well-trained runners are less prone to suffering from such GI symptoms - but I, from my own experience, beg to differ. However, it does make sense that if you turn up at an event untrained, you will be bound to face some problems, GI-related or not. So it is crucial to train regularly to prepare your body well for a race.


Dr Low, an avid runner who clocks 40km weekly, also said that the fluids one consumes before and during a race can affect GI responses.

What is important is to find what works for you personally and stick to it during your race day.

For example, if you have been using a certain brand of isotonic drink for your training, stick to it on race day so that your body will not be thrown off guard by the different concentration of ions in a new drink. The same applies for energy gels.


Dr Low strongly emphasised that although GI symptoms after runs are common, they may simply be a red herring and may in fact indicate something more serious.

It is therefore vital to seek professional help should these symptoms be accompanied by bleeding, unexplained weight loss, excessive fatigue and poor appetite.

Listen to your body and take care of those bowels.

A version of this article appeared in the print edition of The Straits Times on November 18, 2017, with the headline 'Balance will help stave off the runs'. Subscribe