well, the first time i did anything anal a few years ago i absolutely hated it and the days after were filled with horrid constipation and i haven't let anything get near my anus since. . .but i recently gave in and it actually wasn't bad this time, and the days following i have been very regular. so i don't really know if there's much of a correlation. maybe its just that pleasant anal play can help you to relax the muscles and just make it easier?