# A question on involuntary defecation (TMI) **URL:** \ **Category:** Factual Questions\ **Created:** [June 14, 2016, 4:45am UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328 "2016-06-14T04:45:01Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [June 14, 2016, 4:45am UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328/1 "2016-06-14T04:45:01Z")
A friend of mine recently had a mountain biking accident where he was attempting to do a “manual” (a wheelie without pedalling) and overbalanced so he fell on his back. He didn’t fall hard and only has minor injuries, but he tells me, with some embarrassment, that as he hit the ground a small amount of faeces was expelled from his rear. He had recently evacuated his bowels voluntarily so there won’t have been a whole lot in there, though enough to cut the ride short. Question is, what is the most likely mechanism that caused this? He’s not been in the habit of shitting his pants when he’s had other more serious accidents so we don’t think it was a “fear poo”. All we can think is that maybe the sphincter was relaxed at the exact moment of impact and, like an open tube of toothpaste hit with a mallet, the body was squeezed briefly and the faecal matter took the path of least resistance. Any insights? ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [June 14, 2016, 5:01am UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328/2 "2016-06-14T05:01:17Z")
How recently had he gone voluntarily, before this incident occurred? Is it possible there could have been something that didn’t quite make it out the first time, but was right there waiting when the impact occurred? ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [June 14, 2016, 5:12am UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328/3 "2016-06-14T05:12:05Z")
Earlier that morning, 2 - 3 hours prior to the event. ---
**Author:** ![harmonicamoon](https://avatars.discourse-cdn.com/v4/letter/h/65b543/32.png) [@harmonicamoon](https://boards.straightdope.com/u/harmonicamoon)\ **Post date:** [June 14, 2016, 6:34am UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328/4 "2016-06-14T06:34:32Z")
Does he take Flo-Max, or the generic Tamsulosin? They relax the sphincter. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [June 14, 2016, 6:54am UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328/5 "2016-06-14T06:54:34Z")
I will ask… No, he does not. He doesn’t take any medication at all. ---
**Author:** ![usedtobe](https://avatars.discourse-cdn.com/v4/letter/u/ec9cab/32.png) [@usedtobe](https://boards.straightdope.com/u/usedtobe)\ **Post date:** [June 14, 2016, 8:50am UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328/6 "2016-06-14T08:50:22Z")
Inertia? If he landed on his back, the poo was moving downward. His body stopped, but the poo kept moving down. Maybe the force moving the poo was stronger than the sphincter that tried to stop it. And: Trying to second-guess “When will my body invoke ‘fight or flight’?” is not really a fool-proof way of approaching the situation. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [June 14, 2016, 9:25am UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328/7 "2016-06-14T09:25:58Z")
> [@usedtobe](#): > > Inertia? > > If he landed on his back, the poo was moving downward. His body stopped, but the poo kept moving down. > Maybe the force moving the poo was stronger than the sphincter that tried to stop it. Wouldn’t that be more applicable if he landed on his bum with his spine vertical? ---
**Author:** ![cwthree](https://avatars.discourse-cdn.com/v4/letter/c/9de0a6/32.png) [@cwthree](https://boards.straightdope.com/u/cwthree)\ **Post date:** [June 14, 2016, 3:42pm UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328/8 "2016-06-14T15:42:11Z")
Did he land on his lower back? The impact may have been hard enough to shock the nerves that control the rectum and anus, leading to a brief spasm and the observed defecation. ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [June 14, 2016, 3:51pm UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328/9 "2016-06-14T15:51:32Z")
Although it’s considered poor form to cite [Bill Cosby](http://tvtropes.org/pmwiki/pmwiki.php/Creator/BillCosby) these days, he did cover this in his standup routine, decades ago (emphasis added.) > [@](#): > > And mothers are always more interested in the condition of your underwear than your body if you’re ever in an accident. And they tell you that; “I hope for my sake if you’re ever in an accident, you have on clean underwear.” Well, I thought that’s what an accident was! Look; you’re driving a truck. Here comes another truck, gonna hit you. Now, whether you hit the truck or not, you’re going to have soiled underwear. **Because first you say it, then you do it!** ---
**Author:** ![muldoonthief](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muldoonthief/32/3188_2.png) [@muldoonthief](https://boards.straightdope.com/u/muldoonthief)\ **Post date:** [June 14, 2016, 3:57pm UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328/10 "2016-06-14T15:57:17Z")
> [@Richard\_Pearse](#): > > I will ask… > > No, he does not. He doesn’t take any medication at all. You do know you’re not fooling anyone 😉 ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [June 14, 2016, 3:59pm UTC](https://boards.straightdope.com/t/a-question-on-involuntary-defecation-tmi/757328/11 "2016-06-14T15:59:27Z")
The only time it happened to me was in Bolivia,when I was afflicted by some kind of intestinal disorder, which left me ambulatory and with seemingly relatively normal bowels, but feeling discomfiture… I went to take a piss, and when I released, I shit my pants. Much to my surprise, as it wasn’t even diarrhea. So I suppose, under conditions that are outside the ordinary, body parts can function with a mind of their own.