As thousands prepare for the London Marathon on 26 April, a gastroenterologist has shed light on why many runners suddenly need the bathroom around mile 18. Known as 'runner's trot', this common phenomenon occurs during or after intense exercise, causing an urgent need for a bowel movement.
What Happens to Your Gut During a Marathon?
Dr Trisha Pasricha, a Harvard doctor and author of You've Been Pooping All Wrong, explained the science behind the urge. In an Instagram video, she stated: 'When you run, blood flow to your gut can drop to 20% of its baseline. That is literally just your body choosing your legs over your intestines.'
This reduction in blood flow explains why many runners struggle to keep food down and feel ill at mile 18. 'Your gut is screaming that it is not getting enough blood,' she added.
How to Predict and Manage Symptoms
Dr Pasricha advised using a smartwatch or fitness tracker to monitor heart rate. Symptoms often cluster when heart rate hits a certain threshold. 'When you're training, pull up that heart rate data and see how high it goes before you start to get symptoms,' she recommended. Runners can then adjust training to stay below that threshold.
She also urged runners to stay hydrated but avoid sugary drinks, opting for electrolytes instead. 'Honestly, I'd probably skip the coffee the morning of the race too,' she said, as it can 'rev up your colon'. The goal is to keep the colon as calm as possible before and during the race.
Runner Reactions
Many runners thanked Dr Pasricha for the explanation. One commented: 'Ah, thank you. Another reason half marathons seem like a better option.' Another wrote: 'Thanks for this information!'
