Running Reed wrote:
I...Running, it seems, causes my bowel to cramp, and necessitates the use of a bathroom.
... I wonder if it is just the stress of hard physical effort on my body, but I'm moderalty fit, and have been workingout consistently for a year.
This isn't an uncommon problem, and (happily) there is a solution to it, although it will surprise you, because it has nothing to do with what you eat.
Many people with this problem assume that their "increased digestive activity" is their body's natural reaction to exercise. However, as you mentioned in your post, you (like many people) can do other forms of exercise/working out with no problems, and only experience bowel discomfort when running. Using myself as an example, I come from a cycling background, and could ride a bike for upwards of eight hours with no bowel discomfort, but couldn't last twenty minutes on a run without having problems.
I'll try and explain the reason in the simplest terms possible (I used to teach human physiology at a University):
Your digestive tract is lined by muscles that propel food (and digestive product number 2) along. The activity of the muscles in your digestive tract can be controlled in many ways. Your body can send chemical messages to upregulate or downregulate your digestion (e.g. hormones) and drugs can have an effect too... anybody notice the effect caffeine has your digestion? Eating a huge meal can also stimulate digestion--the presence of a large amount of food in your digestive tract literally stretches the muscles that make up the walls of your intestine. The intestine reacts to this stretching by increasing the activity of the muscles, resulting in what is called "increased intestinal motility", which means everything gets moved along at an increased rate. The intestine senses the stretching by special nerve cells called stretch receptors.
How does this relate to running?
Well, running is a relatively high-impact sport. You subject your body to repeated up-and-down movement, and your body absorbs a small impact every time your foot lands, which sends reverberations throughout your entire body. On 60-minute run, you're basically jiggling all your organs around for an hour. In some people, this running-associated jiggling is sufficient to activate those same stretch receptors in your intestine that are usually only activated when it's full of food. This explains why so many people report these type of bowel problems with running, but not other sports.
Some people find relief by modifying diet/eating patterns/warm-up activities, etc.. As another poster mentioned, some people find the stretching of yoga before a run enough to stimulate their digestion so they get everything out of the way BEFORE their run. I had no luck with any of these things, but found the following two things helped enormously:
1. Monitoring running technique
The more you bounce, the more stress and stretching you place on your intestine. (It's also an inefficient way to run in general). Try to focus on running as smoothly as possible, with minimal up-and-down movement. This is better for your knees as well.
2. Tone your stomach muscles
When I first started running I came from a cycling background and had almost no stomach strength. I could literally feel all my organs jostling up and down as I ran, which was horribly uncomfortable and caused other problems as well. However, as my stomach got stronger, the jostling decreased, and eventually stopped, when combined with improved running technique. Normal stomach exercises like crunches are great, but it's also important to focus on keeping a tight stomach and good posture every time you run, and even while walking.
If you've tried diet and stretching with no relief, please try the two things I've listed above. It worked for me!
