Running Abdominal Cramps

Abdominal cramps are one of the most common complaints from runners. It can be quite painful and usually forces runners to rest for a few minutes in an attempt to let the pain subside. Perhaps the most frustrating part of stomach cramps (besides the discomfort) is the seemingly random occurrence of them.

Where the heck do those annoying cramps come from and what can you do about it? This article will answer both of those questions and arm you with enough information to help you mitigate the number of stomach cramps you get in the future.

Diagnosing the cause of abdominal cramps when running

Also known as “side stitches” amongst the running community, stomach cramps are typically the result of two things:

1. A disturbance of the muscles of the abdominal wall
2. A disturbance in the Gastrointestinal system

In the first instance (muscles of the abdominal wall) stomach cramps are likely a result of acute stress placed on your stomach muscles, leading to aggravation that results in muscle cramping. But what do we mean by acute stress? Here are a few examples:

1. Running at a sustained pace above your comfortable running pace. This accelerates your breathing, causing acute stress to be placed on the muscles of the abdomen that help you inhale and exhale.
2. When first starting to run after a long period of inactivity. You’ll be engaging muscles that have not been used in a while so cramping can occur because the abdominal muscles fatigue quickly.
3. Transitioning quickly from one activity to another. This is common in triathletes because the athlete rapidly alters the muscle groups needed for activity such as switching from swimming to the bike stage of the race.

If you think back to the times when you had stomach cramps associated with muscles of the abdominal wall you’ll likely find that they were a result of one of the three items listed above (especially #1 or #2). However, you will probably also notice that the frequency of stomach cramp occurrence falls to nearly zero once you get back in good shape.

The second leading cause of stomach pain in runners comes from Gastrointestinal disturbances. Runners experience multiple types of GI tract issues such as:

1. Farting (not the scientific term but no need to be wordy and formal here)
2. Belching/burping
3. Nausea and vomiting
4. Localized cramping and discomfort
5. Bloating
6. Diarrhea

Perhaps the obvious explanation for some or all of these stomach problems when running comes from the pre-run or pre-race diet. It is never a wise choice to eat something new in the waning hours before a run that you’re not used to consuming either on a regular basis or as part of your typical diet before a run/race. What you eat, when you eat it, and how much you eat all play a major role in the state of your stomach during a run.

Practical Tip: write down what you consume in the 24 – 48 hours before a serious training run or a race. After the run/race take note of how your stomach felt and how you performed. By taking meticulous notes you can usually figure out what settles best and leaves your stomach undisturbed when running. It’s easy to forget the exact items you ate leading up to a run so stay disciplined and detailed by writing that information down for future reference.

The role of hydration in preventing stomach issues

There is plenty of evidence that indicates that proper hydration plays a major role in Gastrointestinal disturbances in runners. As a runner, and especially for those that put in ultra miles, running is an equilibrium challenge. As you sweat you need to replace your fluids. But if you take in too many fluids you can experience bloating and nausea. Take in not enough fluids then you’re body will simply shut down and you can face serious medical risk.

If you look at the below chart you can start to get a sense for the gastric emptying rates of solids versus liquids (i.e. how quickly substances pass through the stomach). While it takes approximately 20 minutes for about 50% of fluids you ingest to pass through the stomach, it takes nearly 90 minutes for about 50% of solids to do the same. Generally speaking if the fluid is not nutrient rich (e.g. water) then it passes through the stomach exponentially fast. However, if the fluid is nutrient rich (e.g. complex carbohydrate solutions) then the rate of gastric emptying is much slower.

The rate of gastric emptying

Because of this sports nutritionists will recommend that endurance athletes consume a nutrient rich fluid while running. This slows the gastric emptying rate of water, helping you to stave off rapid dehydration. If you consume just water and don’t supplement at least some of your fluids with nutrient additives then you’ll have to consume water more frequently and at a higher volume to try and prevent muscle cramping and stomach disturbances associated with low fluid levels in the body.

Interestingly, the presence of fat in the small intestine is known to slow the rate of gastric emptying. If you’re trying to empty the stomach of solids then it is probably a bad idea to have a fatty meal in the hours before a race. Several studies conducted on endurance runners and triathletes have shown that athletes who consume fatty meals within 2 hours of the start time of a race are much more likely to experience nausea and vomiting during the race.

However, some well known ultra marathoners make it a habit to consume an intensely protein and fat filled meal 48 hours before the race. A well known ultra marathon runner habitually eats several double cheeseburgers 2 days before a race and has identified that as his optimal pre-race routine. He contends that it gives him a massive store of fat reserves for him to burn during his 50 and 100 mile races. According to the data above though the fatty meal may play another role. It’s possible that the fat is still present in his small intestine at race time. Because fat in the small intestine slows gastric emptying, the fat he consumes 2 days before a race may be slowing the movement of fluids from his stomach and out of his system, delaying the effects of dehydration. We don’t have the scientific evidence to support this in this article, but it is interesting to note given the preponderance of fatty meals in the diets of ultra runners in the days before a race.

Other recommendations on preventing stomach issues when running

Below is a list of some recommendations that we’ve heard from highly experienced runners when it comes to managing the state of your stomach while running:

1. Research proper nutrition by reading up on exercise diet and physiology pieces published for the running community. The more you learn about your body and how it handles nutrition, the better you’ll be positioned to do #2 below.
2. Experiment with different foods and fluids during your training. Keep a journal of your nutritional tests and hone in on what works for you both in terms of performance enhancement and acceptance by your stomach and GI tract.
3. Try maltodextrin based fluid supplements such as powders you can mix with water
4. Also test out Gu’s, Gel’s and other solids designed for runners that are rich in maltodextrin or other complex carbohydrates
5. Drink a cup of coffee about 2 hours before a long run as it helps you pass your bowel movements much more easily. You don’t want to go into a long run with a backed up digestive tract. It also gives you a dose of caffeine which is a known performance enhancer.
6. Learn to sip your fluids consistently instead of taking in large volumes of it all at once. Aim for one or two mouthfuls every 10-15 minutes when running. This will help you maintain a steady release of fluids throughout the body and not force your stomach to digest a large amount at once (which could aggravate the stomach).
7. Continue to train consistently. Studies show that stomach issues diminish over time as your training continues and your fitness level improves. Run often and your body (including your stomach) will respond positively.
8. Do not try eating anything new on the day of a long race. Introducing foreign meals and supplements can easily upset your stomach.

Despite all of the advice above some runners will still experience chronic stomach issues and abdominal cramping/pain. It is always advised that runners see a doctor about this to pursue a solution. If you’re a runner we would love to hear of your experience dealing with stomach issues on long runs and how you’ve dealt with it.