Is it possible to have a bowel movement during anal penetration? i'd like to try it with my partner but i'm worried something like this can happen. any tips or advice?

Can be involuntary: If there is stool in your rectum, some might be released during anal sex. However, the anus is made more for things to go out than for things to come in -- especially vigorously as with sex. If planning to do this, please be gentle and use lubricant. Your partner wearing a condom might ease your mind about the stool issues.