What Causes a Side Stitches When You Run or Exercise?

What Causes a Side Stitches When You Run or Exercise?

image of female runner in pain from side stitches

You’ve probably experienced it before. You’re taking your morning run or you’re smack dab in the middle of a high-intensity interval workout and you suddenly feel a sharp stabbing pain in your side. It’s almost enough to take your breath away! You stop what you’re doing and grip your side in hopes that the stabbing will subside.

Is it appendicitis? Probably not. It’s more likely a stitch in the side, a fairly common affliction among people who exercise, particularly runners. Most people who do any type of endurance exercise have experienced this side stabbing source of discomfort at one time or another and would like to know how to prevent it.

Those Troublesome Side Stitches

So, what causes side stitches? Surprisingly, no one knows for sure – but there are some theories. When you run, especially at a rapid pace, you take deep breaths and suck in lots of air, sometimes in a disorderly fashion. As your lungs fill with air, they push down on your diaphragm, the main muscle involved in respiration and this reduces blood flow to this important respiratory muscle. The diaphragm them feels the pinch and goes into spasms. Those spasms are what causes the sharp pain in your side, at least that’s what some scientists think.

Newbies to the world of running are most likely to be sidelined by a side stitch. When you first start running or doing another form of intense exercise you have yet to master the art of breathing and, therefore, tend to breathe in a disorderly fashion. But, once running becomes routine, your breathing becomes more controlled. This places less pressure on the diaphragm and the spasms become less frequent. So, side stitches are more common in untrained runners than seasoned ones.

Another probable contributor to painful side stitches is eating before a workout. If you chow down on a large meal or a snack high in fat or fiber and then run, your stomach expands and pushes up on your diaphragm. This, too, can trigger spasms of the diaphragm muscle. Why fat and fiber? Both of these dietary components slow stomach emptying and delay movement of food out of the stomach into the lower intestinal tract. Therefore, your stomach stays distended longer after a meal that contains lots of fiber or fat.

But all is not set in stone. Recently, the theory that diaphragmatic spasms cause side stitches is being challenged. A study published in The Journal of Science and Medicine in Sport found that side stitches are more common in people who have poor posture. The theory they developed based on these findings is that bad posture disrupts nerves that run from the neck and back to the abdomen. In this case, you would expect to see more side stitches in runners who have poor posture when running, standing, or sitting and the study found that this is the case. This study also linked with more severe side stitches.

What Should You Do if You Get Side Stitches?

It’s nice to have some idea what causes a side stitch to hit you, but it’s even more important to know how to handle one if it happens. What should you do? Stop running or exercising, of course, and calm your breathing. Instead, take slow deep, controlled breaths. Stretching the side that’s painful is also helpful. Most side stitches are on the right side, so stretch by raising your right hand toward the sky and tilting your body toward the left. Once the discomfort ceases, ease back into what you’re doing by walking for a bit before picking up speed.

How to Prevent Side Stitches

Even better than knowing how to deal with a stitch in the side is preventing one in the first place. First, don’t run or do high-intensity exercise within two hours of a meal. If you know you’ll be exercising, eat a light meal or snack and make sure it’s not high in fat or fiber. Hydration is important, but don’t guzzle large quantities of water just before a workout. Doing so will expand your stomach and it will push up on your diaphragm. This can also worsen acid reflux and cause hiccups as well.

Work on your breathing too. Too often we aren’t aware of how we’re inhaling and exhaling air when we exercise. Focus on inhaling and exhaling through your nose in a steady, controlled manner, keep the same even rhythm as you run or exercise. It takes practice to breathe properly when you run.

Finally, work on your posture. Start by strengthening the muscles in your core and back as these muscles will do the most to improve your alignment. Also, work on releasing tight hip flexors by doing hip flexor stretches. Tight hip flexors from sitting too much throw your body’s alignment off and contribute to poor posture.

The Bottom Line

Side stitches are no fun and, unfortunately, there’s no surefire way to avoid them. The good news is you’re less likely to experience them after you’ve been exercising awhile. To lower your risk, watch how much you eat or drink before a workout. Don’t go into a sweat session with a stomach full of food, particularly fatty foods or snacks high in fiber. Always be aware of your breathing and running form – and don’t forget to warm up before any type of exercise. Ease into it and gradually increase the intensity. This will help moderate your breathing and lead to less air gulping.

Finally, work on your core. A strong, stable core will improve your posture. If side stitches truly are related to poor posture and alignment, you’ll be glad you did! If you have a side stitch that doesn’t go aware after a few minutes, get it checked out as soon as possible. You wouldn’t want to mistake a side stitch for heart-related pain.




The New York Times. “The Claim: Side Stitches? Change Your Posture”
J. Sci. Med. Sport. 2008. Nov 11(6): 569-74.
Med. Sci Sports Exercise. 2000 Feb: 32(2): 432-8.

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