Oleander, I'm in my 4th year of running. Never happens during speed work, but once happened after a 5K. Now appears to be associated with runs longer than 8-9 miles. If you happen to remember the running forum, PM me?

Cat, yes my uterus is retroverted, so your explanation makes sense: uterus bouncing up and down on lg intestine/rectum causing irritation. (Sheesh!) And I had dropped multivitamin awhile ago while trying to get hypothyroidism straightened out... was taking the Synthroid alone on empty stomach. But need to get back on vit/mineral supplement again... just got out of the habit.