It is like anything else. It depends on the person and their anatomy. The more friction can be decreased with lube internally and externally and the more time that is taken, the less chance injury will result. Ofcourserubbergloves increasefriction, should be snug fitting and not used with a lubricant that will break them down. Generous cleansing enemas until clear will clear theintestinal tract. The cleansing canbe a clinicalor erotic experience depending on how it is presenter. Body temperature tap water is best as soap is an irritant.some use a certain amout of drinking alchol which should be clear (reds & pinks wil cause unneccesary concern) and non-carbonated and are almost instantly absorbed through the intestinal tract andare best diluted rather than used straight or on the rocks <G>. Insertion and extraction must be done very slowly. Usually the part that is toughest to get past in the internal sphincter. Again depending on a persons anatomy. this may or may not be accomplished. the feeling is INFINITELY MORE INTENSE, than a 1-2 finger prostate massage! Rushing and insufficient lubrication are the most likely cause of injury or prolapse. Nitrate base inhalers such as RUSH OR LOCKER ROOM or many other brands relax msucle and give a sense of Euphoria.WARNING THESE MUST NOT,NOT , NOT BE USED WITH ANY ED PRODUCTS,or Nitrate based meds forangina (Viagra, Levitra or Cialis-see product information) as they will cause a MAJOR and UNSAFE drop in blood pressure that MAY BE FATAL.Expect to be tender at least for a few days following the experience. SEEK MEDICAL ATTENTION FOR ANY BLEEDING