Incontinence can be a factor as you run. The urge to urinate or defecate when running does not discriminate by age or gender. Because your body is focused on the muscles and organs being used, any excess in your digestive system will be quickly eliminated so your body can work efficiently as it runs.
One of the most important causes of incontinence when running is the increased level of exercise intensity, as pointed out in a paper on "Nutrition and Exercise Associated Gastrointestinal Problems" by Beate Pfeiffer. During running, up to 80 percent of your blood flow can be redirected from your digestive system to your working muscles. This reduced blood flow to your stomach can reduce the digestive process, and cause you to lose control of your bowels while running. This is not an indicator of an underlying medical condition, but your body's natural reaction to the high level of exertion and stress while running.
Another important consideration regarding the occurrence of incontinence when you run is your nutritional intake. Pfeiffer suggests that new foods should be avoided before running, especially on race day when the physical effort is extremely high. She states that the digestive process can take anywhere from 24 to 72 hours, and that any foods that are high in fiber or fat can increase the need to go to relieve yourself when running. Coffee or caffeine are also known enhancers of increasing the speed of the digestive process, so try to avoid consuming them in excess before a run.
Dr. Tim Noakes notes in "The Lore of Running" that dehydration in combination with higher temperatures can increase the rate of gastric emptying. Pfeiffer states that you can teach your body during your run training to tolerate larger amounts of fluids. However, Pfeiffer states that hypertonic fluids or low-concentrate, diluted electrolyte drinks, increase the likelihood of incontinence while Noakes states that it helps reduce the likelihood. Research from University Medical School in Scotland seems to back Pfeiffer's assertion.
One good reason to not eat too much of or foods that you are not used to before a run is the mechanical effects of the running motion. In other words, the bouncing caused by the impact of running can speed the rate of your stomach emptying, according to Pfeiffer. Because of the increased stress on your gastric system from the bouncing, your stomach needs to get rid or any excess in order to deal with it.
Runners who take pain killers such as aspirin, or ibuprofen, especially in runners who take high doses, are more likely to experience G.I. distress, according to Pfeiffer. A study by Creighton University in Omaha concluded that aspirin and ibuprofen intake when running, cause increased fluid flow to the intestine, and can indeed promote incontinence. Other medications and supplements such as sodium bicarbonate and citrate are likely to to cause incontinence when running.