Posted: January 8, 2005

Science of Sport: Can The Trots Be Tamed?

The Running Research News Weekly Training Update

In the world of running, the number "65" pops up with surprising frequency.

For example, research reveals that about 65 percent of all runners are injured during an average year (with injury simply defined as a problem significant enough to disrupt usual training). In addition, a recent survey indicates that 65 percent of runners wish that they had more time available for training.

And - up to 65 percent of runners experience assorted difficulties with their gastro-intestinal systems when they run (1). Such "difficulties" include an assortment of different things, but they often revolve around a sudden, urgent, inescapable need to evacuate the large intestine of its contents. Of course, this requirement to clear the colon usually occurs at the worst-possible time, when there is little real "cover" for one's activities and the nearest restroom is miles away.

One study found that 30 percent of the members of a running club were plagued by importunate innard evictions during their morning runs, while 25 percent suffered from diarrhea during or shortly after races (2). Anecdotal reports indicate that some marathoners are forced to make from two to four unscheduled stops inside portable potties during their marathons, lay-overs which significantly reduce their chances of setting PRs. What are the causes of these predicaments? What can you do to prevent intestinal troubles from interfering with your training and racing?

Two theories have been proposed to explain why runners' intestines are problem-prone. The first - the "ischemia theory" - contends that reduced blood flow is the root cause of running-related ailments of the alimentary canal. This theory is appealing, since blood is diverted from your entrails to your muscles and your skin as you scoot along during a workout or race (studies show that intestinal blood flow can drop by 80 percent during exertion). The lack of blood supposedly irritates the intestine, which responds by creating an unusual amount of egesta. The risk of "trotting" consequently increases dramatically, but it is the excited cantering of the chitterlings, not a more-rapid movement of the legs toward the finish line.

Although it is attractive (in a physiological but not aesthetic sense), the ischemia theory does not hold up well under close inspection. For one thing, the frequency of exercise-related diarrhea appears to be higher during training runs, compared with races. If the ischemia theory were correct, one would expect a higher likelihood of colonic looseness during competitions, when exercise is more intense and thus the diversion of blood away from the bowel is greater. In addition, most runners who experience diarrhea while running do not suffer from excessive evacuations when they are intensely engaged in other sports (for example, during cycling, swimming, and rowing). If the ischemia theory were correct, any form of intense exercise should trigger troubles in the internals.

Bear in mind that it's actually not a bad thing that the ischemic theory doesn't fit the data, since there would not be much in the way of corrective actions that you could take if the theory happened to be unassailable. Aside from hydrating yourself very well, it would be difficult to counteract your body's tendency to shut down blood flow to your organs of digestion as you train and race.

A better theory is that the upright posture, the mechanical jarring and jiggling of the contents of the colon associated with each footstrike, and the effect of gravity all aid the movement of fecal material into the rectum during running and thus precipitate a sudden desire for the porcelain throne. Additionally, the increased amount of dietary fiber which often accompanies ample carbohydrate intakes in endurance runners is certain to boost the need for depuration.

Of course, little can be done to eliminate upright running, jarring and jiggling, and the force of gravity, but you can still take some steps to control your bowels during your runs. If you are troubled with diarrhea during your races, for example, a low-fiber diet during the 24 to 36 hours before the race can be helpful. A potential problem is that low-fiber diets are often high in protein and fat and low in carbohydrate, which could interfere with your plans to stock up on leg-muscle glycogen before your race. However, don't forget that you can finish your carbo-loading with one of the commercially available liquid-carb formulas, if you so desire. Remember to try this out before several practice runs which at least mimic important aspects of your race - don't wait for the eve of your big race of the season.

In an investigation carried out with 425 runners (3), athletes reported that their running-related defecation problems were relieved with the use of over-the-counter, anti-diarrheal medications such as Loperamide HCl (a popular brand of this drug is called Imodium), but be cautious if you decide to employ this strategy. Always consult with your doctor before you undertake self-medication, and don't forget that the use of anti-diarrhea meds can produce an unwanted side effect - constipation. It is difficult to imagine setting a PR while your large intestine is bogged down with an excess of excreta.

Finally, take advantage of your natural gastro-colic reflex, a normal, physiological process in which the placement of food in the stomach naturally stimulates the large bowel to empty itself in order to get ready for the next wave of incoming material. Optimal stimuli of the gastro-colic reflex vary among people; for some runners, warm liquids (coffee, tea, or hot cocoa, for example) do a great job of kicking the reflex into high gear, while for others a light meal of easily digestible hot or cold cereal turns the trick. Don't ignore the gastro-colic reflex, but instead establish a routine in which a specific pattern of eating/drinking leads to a near-automatic privy purge. You'll need to use this exact-same beaten path on race morning, and if you have followed a relatively low-fiber diet for the prior 24 to 36 hours there is a good chance that you will complete your race with minimal gut grief.

Very kindest regards,

Owen Anderson

References

(1) "Aetiology of Running-Related Gastrointestinal Dysfunction. How Far Is the Finishing Line?" Sports Medicine, Vol. 26 (6), pp. 365-378, 1998
(2) "The Effect of Running on the Gastrointestinal Tract," Journal of Clinical Gastroenterology, Vol. 6, pp. 461-465, 1984
(3) American Journal of Gastroenterology, Vol. 79, pp. 827-828, 1984

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