# Why do you spit up 'mucus' and feel pain in your right side when running? **URL:** \ **Category:** Factual Questions\ **Created:** [November 7, 2003, 4:19am UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823 "2003-11-07T04:19:34Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [November 7, 2003, 4:19am UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/1 "2003-11-07T04:19:34Z")
Feeling shy tonight? 🙂 About the second part of the question, get ready, it´s gasses building up in a corner of your large intestine, gasses accumulate in that particular bend increasing the pressure there, producing that characterisitc pain. In Spanish is called “flato” (hint: flatulence), I don´t know in English though… ---
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [November 7, 2003, 4:21am UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/2 "2003-11-07T04:21:49Z")
Uhhh, just to clear things up for people dropping by, the original thread didn´t have an OP, my post is actually a reply to the thread title. ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [November 7, 2003, 1:27pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/3 "2003-11-07T13:27:58Z")
Odd. where’d the original post go? here is a synopsis. When running sometimes a person will start to spit up some kind of clear mucus like substance. What is it exactly and why is it produced? also why does someone start to feel pain in their right side when running for too long? ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [November 7, 2003, 1:32pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/4 "2003-11-07T13:32:19Z")
> [@](#): > > \*Originally posted by Ale \* > \*\*Feeling shy tonight? 🙂 > > About the second part of the question, get ready, it´s gasses building up in a corner of your large intestine, gasses accumulate in that particular bend increasing the pressure there, producing that characterisitc pain. In Spanish is called “flato” (hint: flatulence), I don´t know in English though… \*\* thats weird. Why doesn’t normal flatulence cause that pain and why does the pressure build up in the first place. ---
**Author:** ![Satchmo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/satchmo/32/4223_2.png) [@Satchmo](https://boards.straightdope.com/u/Satchmo)\ **Post date:** [November 7, 2003, 3:40pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/5 "2003-11-07T15:40:31Z")
Yes, really. I was told by my cross country couch, (way back when we had to dodge dinosaurs, you whippersnappers), that the pain in your side came from fatigue of the diaphragm. As you get into better and better shape, it takes longer and farther for this pain to develop, until it’s no longer a problem. I. E. Some other limiting factor kicks in to stop/slow you before your diaphragm starts complaining. Satch ---
**Author:** ![criminalcatalog](https://avatars.discourse-cdn.com/v4/letter/c/e68b1a/32.png) [@criminalcatalog](https://boards.straightdope.com/u/criminalcatalog)\ **Post date:** [November 7, 2003, 4:07pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/6 "2003-11-07T16:07:57Z")
I’m not too sure about that, you might want to check with your gym chair first. Just to be sure there are no discretions. 🙂 ---
**Author:** ![Satchmo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/satchmo/32/4223_2.png) [@Satchmo](https://boards.straightdope.com/u/Satchmo)\ **Post date:** [November 7, 2003, 5:13pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/7 "2003-11-07T17:13:30Z")
Yeah, coach. But he was sitting on the cross country couch. 🙂 Sheesh, I even previewed for once. That’ll learn me. Satch ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [November 7, 2003, 5:43pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/8 "2003-11-07T17:43:43Z")
This is known as a “side stitch.” Dr. Gabe Mirkin states: > [@](#): > > Over the years, I’ve seen a host of explanations for the causes of a side stitch, pain in the right upper part of your belly during running. None were reasonable. Tim Noakes, A medical school professor from South Africa has offered the first reasonable explanation and a successful treatment. > Lack of oxygen to the diaphragm doesn’t cause stitches because blood flow to the diaphragm is not shut off by running. Gas stretching the colon doesn’t cause stitches because the pain does not disappear when you relieve yourself. A swollen liver capsule is not a cause because the liver is not swollen when you have a stitch. > Thick fibrous bands called ligaments extend downward from your diaphragm to hold your liver in place. When you run, your liver drops at the exact time that your diaphragm goes up, stretching the ligaments and causing pain. > Humans have a fixed pattern of breathing when they run. They have a 2 to 1 breathing ratio, they breathe once for each two strides. So, they breathe out when one foot, usually the right, strikes the ground. When you breathe out, your diaphragm goes up, and at the same time, the force of your footstrike causes your liver to go down. This stretches the ligaments that attach the liver to your diaphragm, causing pain. > When you get a stitch, stop running and press your hand deep into your liver to raise it against the diaphragm. BTW, while I’m quoting Mirkin, he also says: > [@](#): > > Research by Dr. Tim Noakes of the University of Cape Town in South Africa, shows that “hitting the wall” is caused by damage to the fibrous connective tissue that surrounds muscles, as a result of the repeated stretching and tearing of the leg muscle fibers each time the feet hit the ground. The muscles affected the most are the quad muscles in the front of the upper legs and the calves in the back of the lower leg. Every time that your feet hit the ground, a shock waves shakes and tears your muscles. Hold your hand on your quad muscles while you are running and you will feel the shock each time your foot hits the ground. > The old explanation is wrong. Muscles store sugar, called glycogen, inside of their cells. During exercise, glycogen is used for energy. "Hitting the wall’ was thought to occur when the leg muscles run out of their stored glycogen. However, after two hours of hard racing, bicycle racers use up their muscle glycogen and they do not “hit the wall” because their muscles are subjected to the smooth rotary motion of pedalling and are not stretched and torn by constant shocks of the foot hitting the ground. > > When you run very fast, you become short of breath and feel like you have to slow down, but if you keep on pushing yourself, you suddenly feel refreshed and can pick up the pace. Do you know what caused your sudden recovery? > It’s called second wind and you don’t even know that your recovery is caused by slowing down when you feel exhausted during exercise. When you exercise intensely, your muscles use large amounts of oxygen. You can run so fast that your muscles require more oxygen than you can breathe in through your lungs and you develop an oxygen debt that causes lactic acid to accumulate in your muscles. This makes your muscles acidic, which causes pain and burning/ and the lactic acid spills over into your bloodstream, causing you to gasp for air. You finally reach a point where you can’t meet your needs for oxygen, which forces you to slow down. You don’t notice that you have slowed down because you are working just as hard as you did when you were running at a faster pace. Not only must you bring in extra oxygen to meet your present needs, you must also use some of the oxygen to make up for the debt that you incurred when you were running at a faster pace. > Eventually, you catch up on your oxygen debt and feel better. So, you pick up the pace and don’t even know that it was the slower running that revived you. You think that there was a change in your metabolism and you call it, second wind. ---
**Author:** ![GilaB](https://avatars.discourse-cdn.com/v4/letter/g/8e7dd6/32.png) [@GilaB](https://boards.straightdope.com/u/GilaB)\ **Post date:** [November 7, 2003, 5:57pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/9 "2003-11-07T17:57:39Z")
If a stitch in my side is the result of stretching of the ligaments holding my liver in place, why do I only get it if I exercise within an hour or so of eating? I don’t think that should change my ratio of breathing:footstrikes as is posited in **barbitu8** ’s cite. ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [November 7, 2003, 6:47pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/10 "2003-11-07T18:47:34Z")
> [@](#): > > \*Originally posted by GilaB \* > \*\*If a stitch in my side is the result of stretching of the ligaments holding my liver in place, why do I only get it if I exercise within an hour or so of eating? I don’t think that should change my ratio of breathing:footstrikes as is posited in **barbitu8** ’s cite. \*\* [http://www.sportsinjurybulletin.com/archive/side-stitches.html?1](http://www.sportsinjurybulletin.com/archive/side-stitches.html?1) (3) If you are stitch-prone, don’t take in any food or water for a couple of hours before you exercise. Eating or drinking shortly before exercising does increase the chances of stitch, possibly because the increased weight of a full stomach creates a stronger downward tug on the diaphragm as the stomach is jolted with each footstrike (cyclists usually don’t have to worry about this rule - unless they are riding on a bumpy road; uneven roads often give their internal organs enough jostling to increase the chances of stitching). Note, though, that if you are going to be exercising continuously for more than an hour, you will want to take in some sports drink 10 minutes before the beginning of your exertion (to begin moving carbohydrate toward your muscles). In this case, you’ll have to rely on tips 1, 2, and 4 to keep you out of stitch trouble. OK, but why do people cough up mucus when running? what causes that is it the lungs stretching, causing mucus production? ---
**Author:** ![The\_Great\_Philosopher](https://avatars.discourse-cdn.com/v4/letter/t/3ec8ea/32.png) [@The\_Great\_Philosopher](https://boards.straightdope.com/u/The_Great_Philosopher)\ **Post date:** [November 7, 2003, 7:10pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/11 "2003-11-07T19:10:47Z")
I was always taught that ‘stitches’ (that pain in your right hand side) is not caused by anything moving or jarring in your body, or pressure building up. I was taught that it’s caused by a simple lack of oxygen. As you run, especially if you are unfit, haven’t warmed up or have just eaten, you respire aerobically (ie. a combination of oxygen and glucose). When you start running, you’re still using the same breathing pattern you were using when you were doing nothing. So after a short while, your body is not taking in enough oxygen to supply all your hard-working cells. So, to replace the rest of the oxygen, you start to respire anaerobically (ie. just using glucose, not oxygen) as well as aerobically. A by-product of anaerobic respiration is lactic acid. When this builds up in your muscles, it causes the pain known as a ‘stitch’. If you keep running with the stitch, eventually you up your breathing pattern to accommodate the more oxygen required, and the stitch goes away. This is the same reason why you have to breathe heavily for a long time even after you’ve finished exercising - you have to replace the oxygen your cells weren’t getting. I can’t explain why the pain is specifically located in the right or left side of the abdomen, but the explanation that ‘the diaphragm is being pulled down’ just doesn’t sound quite right to me. Perhaps I’m wrong - I’m not by any means an expert in biology. About mucus production: again I’m not sure, but my guess would be that because you’re breathing much more frequently, the body increases mucus production to trap the dust and germs that are coming in more quickly. We’re all constantly making mucus, though - it doesn’t suddenly start when you exercise. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [November 7, 2003, 8:54pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/12 "2003-11-07T20:54:12Z")
The lactic acid explanation is BS. Why would you feel it on your right side, just below the diaphragm, which site fits in perfectly with the correct explanation, which, incidentally, was finally scientifically studied after many years of people throwing up their hands, saying, “Gas,” or “Lactic acid,” or “Who knows?” I know many runners who were convinced it was gas, because that’s what they were taught. But did these teachers give a cite or reference to prove their respective teachings? Lactic acid is carried away from the working muscles by the bloodsteam to the liver where it is converted back into glucose. As far as mucous, not all runners have that problem. I’ve never experienced any mucous, but I have developed more spit and phlegm. If my chest is congested, running will clear it out and you will spit out phlegm. Many times after a hard run, I will have saliva around my lips, due to excess saliva production. But no mucous. ---
**Author:** ![The\_Great\_Philosopher](https://avatars.discourse-cdn.com/v4/letter/t/3ec8ea/32.png) [@The\_Great\_Philosopher](https://boards.straightdope.com/u/The_Great_Philosopher)\ **Post date:** [November 7, 2003, 9:07pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/13 "2003-11-07T21:07:38Z")
Indeed - the main problem with the ‘lactic acid’ explanation is that there’s no reason for the pain to be in the right side. You’d think the pain would occur in the leg muscles. After researching it, it appears that no one really knows what causes a stitch (medical science doesn’t seem to know a single thing for sure about our bodies), but most theories agree at least that it has something to do with the diaphragm. Perhaps my teacher was simply trying to prevent confusion. 🙂 ---
**Author:** ![The\_Great\_Philosopher](https://avatars.discourse-cdn.com/v4/letter/t/3ec8ea/32.png) [@The\_Great\_Philosopher](https://boards.straightdope.com/u/The_Great_Philosopher)\ **Post date:** [November 7, 2003, 9:10pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/14 "2003-11-07T21:10:25Z")
Indeed - the main problem with the ‘lactic acid’ explanation is that there’s no reason for the pain to be in the right side. You’d think the pain would occur in the leg muscles. After researching it, it appears that no one really knows what causes a stitch (medical science doesn’t seem to know a single thing for sure about our bodies), but most theories agree at least that it has something to do with the diaphragm. However, lactic acid does cause pain in some muscles, when the liver is overloaded and cannot get rid of all the excess acid. The ‘lactic acid’ idea isn’t simply a hashed-up idea that’s been disproved - you can’t function on anaerobic respiration (that produces lactic acid) alone for more than short periods of time, because the acid causes pain. Otherwise, we’d never need to breathe. 🙂 ---
**Author:** ![The\_Great\_Philosopher](https://avatars.discourse-cdn.com/v4/letter/t/3ec8ea/32.png) [@The\_Great\_Philosopher](https://boards.straightdope.com/u/The_Great_Philosopher)\ **Post date:** [November 7, 2003, 9:11pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/15 "2003-11-07T21:11:53Z")
Oops, my post’s been split in half… ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [November 7, 2003, 9:16pm UTC](https://boards.straightdope.com/t/why-do-you-spit-up-mucus-and-feel-pain-in-your-right-side-when-running/211823/16 "2003-11-07T21:16:13Z")
Noone’s denying that lactic acid is a factor in the pain in the working muscles. However, it is just one factor of a dozen: a whole cascade of events that occurs physiologically during exercise. But it is wrong to attribute that to the infamous stitch or to attribute it to the morning after aches, which is due to DOMS (delayed onset muscle syndrome).