Alongside stitch, knee pain and landing in a puddle that leaves your socks sodden, needing a poo – really, reeally needing a poo – is an agony experienced by every runner on a torturously regular basis.

Of course if you’re, saaay – just to pick a name at random – Paula Radcliffe, you can simply halt your stride, deal with the matter in hand and return to your run. But for us non-pros, pooping one off in a public place is simply not the done thing. We’re expected to grit our teeth, clench our bowels and pray to Jebus that we make it home before disaster strikes.

So is there any way we runners can gain some kind of advantage in our neverending war with turdkind? If anyone has the answer, it’s Peter Whorwell, Professor of Medicine and Gastroenterology at the University of Manchester.

Hi Peter. So, first off, are there any methods by which you can ‘train’ your bowels so that your movements become predictably scheduled – so you always poo at, say, 5pm every day? 

“No, is the short answer, I’m afraid! It’s an automatic function. But there are certain things that will stimulate the bowels to work.

“When you go to sleep, your gut goes to sleep, effectively. So when you wake up, your gut gradually becomes active. In a ‘normal’ person, eating breakfast will trigger their gut into something called the gastrocolonic response: their stomach fills with food, which stimulates the colon, which leads to defecation.

You’re more likely to run into trouble in the morning than later in the day

“That gastrocolonic reflex is at its height in the morning, so if you’re looking to stimulate it, the best time to do that is with your first meal of the day. Generally, after lunch or dinner you won’t need to open your bowels, as the gastrocolonic response is much less prominent later in the day.”

So if you were to shift your running schedule – rather than your pooing schedule – around, you’d be less likely to suffer bowel issues if you ran in the afternoon or evening? 

“Yes. You’re more likely to run into trouble in the morning, rather than later in the day when your gut is less likely to react.”

Is there any danger inherent in running while being badly in need of a poo? Could you rupture your bowel or something equally horrifying?

“No, you can’t rupture your bowel. It’s an incredibly strong bit of kit. There’ve been experiments in which a bowel has had air pumped into it, and you have to put it under under huge pressure before it gives.

People who run a lot tend to have a looser bowel

“So hanging on to a bit of stool for a while is not going to be a problem. You can’t damage yourself.

“Obviously though, when you’re running, it is going to be trickier to ‘hang on’ to that stool. The harder that stool is in consistency, the easier it’ll be. But people who run a lot tend to have a looser bowel, which can make hanging on to stools difficult.”

Oh. 

“Yes. But if a runner did have something of a loose bowel, a natural way to firm up their stools would be to reduce their fibre intake. Weetabix, Shredded Wheat, all those things, they really do significantly loosen up your stools.”

If you plan to head out for a run in a couple of hours, but you feel like your run may clash with a bowel movement, is there any way of hurrying that movement along a bit?  

“Some people, including a patient I saw today, will say that a cup of coffee always sets their bowels into action. And not that you should advocate this, but smoking also works for some of my patients with constipation.

Some people say that a cup of coffee always sets their bowels into action

“The problem is, if you do stimulate the gut with coffee, it may not stimulate it solely for the exact length of time you want it to. It may open your bowels, but they could remain hyper-responsive afterwards.”

And is there any way to delay the need for a poo – if, for example, you’re about to run a long-distance race? 

“I’d be a little reluctant to recommend it to ‘normal’ people, but you could take Imodium, which is a trade name for the medicine loperamide. We use that for patients with irritable bowel syndrome, because they’d otherwise need to defecate maybe ten times a day, and they couldn’t function without taking their loperamide.

“It’s not dangerous to take – loperamide is a very safe drug – but if you take it and you don’t have IBS or diarrhea then you risk being constipated for a day or two afterwards.”

Okay, so it’s a ‘swings and roundabouts’-type situation. Thanks, Professor Whorwell!