Runners Trots
Can running/exercise induce IBS symptoms and why is this caused?
Moderate regular exercise prevents the build up of stress and tends to relieve symptoms in most runners. It also can relax the bowel and help to prevent constipation and induce a more regular bowel movement, but it does seem to depend on a person’s attitude to running and to life. If running and other aspects of life, work for example, and a healthy diet becomes a bit of an obsession, then this may be associated to a bowel that is too active. Several of my patients have ‘the running bowel of the running woman’. Also bear in mind that a high intake of fruit and veg may make the bowels looser.
Can you explain why runners commonly suffer from ‘runner’s trots’ before a race?
I suspect this is apprehension/nervousness in much the same way as people may need to go to the loo before an interview or public performance. An increase in emotional tension can make the rectum (and bladder) more sensitive encouraging an urge to go. There may also be effects on colonic peristalsis and secretion, especially if the race starts in the morning.
The twenty mile trots. Is this related to hitting the wall (bonking)?
As marathon runners know well, at about twenty miles, they can suddenly run out of energy as their carbohydrate stores get depleted and they ‘run on empty’, so their body switches to burning fat, which is a slower release form of energy and in any case, requires carbs to release its energy (fats burn in a carbohydrate flame!). 20 miles is also the time, runners may suddenly need the loo (but there are always queues and never enough loos). Why that occurs almost certainly has something to do with a shift in activity in the autonomic nervous system, perhaps the body switches to a more conservative mode of operating (less fight or flight) which would encourage bowel peristalsis. Or perhaps it’s the sugary drinks again. The advice given to avoid hitting the wall is to take sugary drinks, fruit juices, during the race to replenish carbs, but if those drinks contain too much sorbitol or fructose, then it’s not so much hitting the wall but not being able to find one!
Can you offer any advice for runners trying to manage the condition when training/racing?
Build running into your routine, so you always do it at the same time and approximately the same distance. Build up gradually within your limits of exhaustion. Make sure you have been to the loo before you start. Eat light and early the night before and skip (or have a very light )breakfast. Don’t have too much veg or fruit the night before. Be careful with energy/fruit drinks. Check the ingredients. Excess fructose, sorbitol may retain fluid in the bowel which may cause diarrhoea.
The Sensitive Gut 
This is a great post
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