Thursday, December 19, 2013

So I want to run a marathon: Am I going to sh*t my pants?

We were all new runners once. We naively pulled on our shiny new tech shirts and wiggled our toes in cotton socks (we didn't yet know the importance of non-cotton socks), and we shot out the door in a gallop.

Only to have that horrifying Oh-My-God-I-Need-To-Poop-NOW moment wipe the stupid happy off our faces.

Many of us (maybe all of us) have learned how to *ahem* control ourselves. We eat certain things (or don't eat certain things, as it were) and we plan our meal times around our running schedule. This makes things more predictable. Not perfectly predictable--there are still those moments when you're alone in the woods--but predictable enough that we don't give up running.

Then there's the beast that is the marathon. A 26.2 mile, 4 hour journey that strikes fear in the heart of anyone who suffers from runner's trots.

Is it inevitable that the marathon will make it happen?

I used to think that the runner's trots phenomenon was rare. That is, I thought that only a small minority of runners experienced it. Then I started talking with my friends about it (sorry, Oiselle teammates!) and I started to suspect that it's actually pretty common.

According to a 1988 study of 1,750 finishers at the Belfast Marathon, a whooping 83% of respondents reported that they occasionally or frequently felt "the urge to have a bowel movement or diarrhea" during or after a run.

83%. If you aren't in the club, you might not be in the game.

Your chances of being a victim are already high, but if you are (1) young and (2) a woman, then it's pretty much guaranteed. At least we have a reason to loo forward to old age, right ladies?

Another parameter that the researchers asked about was intensity: respondents reported a higher incidence of GI problems during "hard" runs than during "easy" runs.

There isn't a specification of what "hard" or "easy" means here. It could mean "longer" and "shorter" or it could mean "faster" and "slower". "Runners who performed larger weekly training mileages (> 37 miles/week) more frequently experienced darkened urine (p < 0.01) than those with lower training mileages. Better runners, i.e. those with a best marathon time below 3 h 34 min, suffered more from vomiting (p < 0.05) than poorer runners."

Longer and faster both seem to result in GI problems.

If you want to minimize your chances of sh*tting your pants, run (1) short distances (2) at a slow pace and be an (3) old (4) man.  Running a marathon violates the first of those four pieces of advice.

Still, another study puts the percentage of runner's trots sufferers at 36.4%-38.6%. This research also was done on data collected from marathoners. This time, it was 700 runners at the Trail's End marathon in Oregon responding.

So what gives? What's the actual percentage of runners who have to deal with this? 

Some researchers looked at the problem from a different angle. Instead of having runners self-report about their perception of when the problems occur and why, these scientist hypothesized that there was a certain cause. Specifically, they tested the idea that dehydration is at the root of the problem.

This study which allowed only male participants found that dehydration has an impact on the GI tract of runners. Once dehydration has set in, when we drink water again our stomachs get violent.

Of course, another thing that happens when we get dehydrated is that we lose weight. This study which was carried out on the same data that was used in the dehydration paper found that it is body weight loss that most directly corresponds with GI problems.

Body weight losses are more significant in marathons than in other distances (the study compares marathon runners with 25k runners). Among the 44 runners who participated, there was an average body weight loss of 3.2% with a range of 1.5%-6.2%. Men lose more than men.

Among those who lost greater than 4% of their body weight during the marathon, 80% experienced GI distress.

Dehydration is not the only problem associated with body weight loss, though. Decreased blood flow to the intestinal tract and a rise in body temperature could also be causing the GI problems.

In any case, there is a way to fight body weight loss. Drink plenty of water during your race!

So here's a fifth piece of advice: (5) Stay hydrated. 

Even if the second set of researchers is right about hydration not being the real cause of the problem, you'll be able to avoid a lot of the other problems they point to if you keep drinking water.

To satisfy my interests, I compared the average temperature of the Belfast marathon with the average temperature of the Trail's End marathon. Both races are held in May. The temperatures are cooler in Belfast and so the rate of body weight loss shouldn't be significantly higher there. So much for making sense of the discrepancy between the Belfast Marathon report that 83% of runners have GI problems and the Trail's End Marathon report that only ~37% have problems.

But I also came across something funny in the course of this little side excursion... The website for the Trail's End Marathon says that their 13th annual race had 247 finishers. That sounds about right for 1982, based on my not having any clue about how many people were running marathons back then. Plus, the registration even for this year says that the field is limited to 250.

But the study conducted on data collected from the Trail's End runners claims that there were 1,700 participants and that they collected surveyed from 707 of them.

What gives?

Okay, shady science aside, it looks like there is some scientific consensus on this issue of runner's trots. First, it is a real problem affecting real runners during real marathons. Second, it affects runners more at longer distances and faster paces (which are "harder").

The odds of you actually sh*tting your pants may not be very high, but the chances of you feeling like you're going to are relatively high.

If it's a big fear for you (as it is for me), then you should think long and hard about running a marathon. But you should definitely see how you feel if you stay well hydrated and maintain body weight (or minimize your loss) during training runs. That might be the key.
*I'm not a doctor or scientist. If you're reading this then you probably know that already. One day I'll be a doctor, but not *that* kind of doctor.


  1. This has definitely been an issue for me before. I have to say, it is not fun feeling like you have to go immediately!! Hadn't heard the hydration thing before, so maybe something for me to work on.

  2. Love reading about running and pooing! I had my first shit in the woods experience a few weeks ago and I really felt like I'd joined the club. Before you have done it you can't imagine ever doing it. Then after its just kinda like mehh.... SHIT HAPPENS.

  3. I've had runners' trots, but almost never during races and never during marathons (knock on wood). When I'm on my regular route, with accessible bathrooms, it's like my bowels know it's ok to let things process. On the other hand, during races, my body shuts down. Either that, or I'm so nervous beforehand that I go a bazillion times before the race. Same thing happens when I'm in a new or foreign place. My body is like, "Jen, you cannot poop here! Don't even think about it!"

    BTW I recently eliminated drip coffee from my diet and that has helped tremendously with runners' trots. Espresso is fine... my hypothesis is that drip is usually more acidic. Also, I have a history of having issues with stomach acidity (see also: tomato sauce).