The sceptical medic – Toilet Breaks

Q: I have started to run longer distances – to the point that I am now having to think about toilet breaks. What is the best way to stop yourself from needing to go when you are out for a couple of hours?
A: It is not uncommon for entire running clubs to disappear into the bushes when out for longer runs (famously, Paula Radcliffe had no bushes to hide in). This experience of loose, sometimes urgent bowel motions during or immediately after a longer run is known as runners’ diarrhoea or "dumping syndrome" and as many as 50% of long-distance runners feel the urge.
There are various theories about this phenomenon. Hormones released by the constant "jiggling" of running may cause the bowel to speed up. And prolonged exercise diverts blood from the bowel to the legs, delaying absorption and causing fluid to build.
Some simple strategies may help. The most important is not to change your routine on race day. On the day before avoid overloading with high-fibre foods such as rice, bran, beans and fruit. If you are not used to them, shun artificial sweeteners, high-fat foods and energy bars, as all may fire things up. In the hours before a race, make time for ablutions and perhaps omit solid food. Dehydration and overheating can also promote diarrhoea so regular fluid with only 4-8% carbohydrate at 30mls per hour fluid is key.
If none of this works, medications such as loperamide an hour before a race may help. However, they may also interfere with sweating so use with caution in hot weather. If the problems are severe consult your doctor as exercise can bring conditions such as irritable bowel syndrome and lactose intolerance to light. It is rare not to be able to sort out the problem so don’t stop running.
Dr Nicholas Peirce is the ECB’s chief medical officer and a lead physician for the English Institute of Sport. To ask a question, email


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