Twisted rumors.

Add another hazard--albeit minuscule--to running. Timothy L. Pruett of the University of Minnesota in Minneapolis and his colleagues treated two marathoners who developed cecal volvulus, a twisting of the first portion of the large intestine that obstructs the movement of bowel material and causes great pain. It can be fatal if not surgically corrected.

These werent't just any runners. One, a 6-foot-3-1/2-inch, 160-pound man, ran 50 miles a week and his best marathon time was 3 hours, 54 seconds. The second was a 5-foot-8-inch, 128-pound marathoner with a personal best of 2 hours, 30 minutes. Neither had any of the traditional risk factors for cecal volvulus, such as a pelvic mass or pregnancy, the researchers report in the May 9 NEW ENGLAND JOURNAL OF MEDICINE. The tissue that stabilizes the intestines was extra-thin in these very lean men, and the two were probably among the 20 percent of the population whose intestines, from birth, aren't firmly tacked down. The two factors probably allowed the twisting, says Pruett.