The anus is chiefly supported by muscle, the sphincter being the key one to hold everything in.
The sphincter muscle(s), like every other muscle, can be 'exercised' to a point. Kegel exercises are part of prenatal birth preparation to hopefully prevent prolapse, which happens a lot during the birthing process.
As long as you are not getting gang banged several hours a day (AKA Marathon Sex) and not having large didoes, traffic cones, arms, legs, small children, etc shoved up yonder, the sphincter will not lose its shape.
It has been suggested that an "active" bottom, meaning one who works their butt around the object up yonder, is doing pretty much kegel exercises - in short some resistance training is taking place. If you are 'tightening up' down their for the thrill to your partner, you most likely are going to tighten up your sphincter.
Again as long as you are not getting fisted (or other extremely large objects shoved up there) and not doing marathon sex (sex for several hours day after day) then you most likely will not see any changes to the sphincter.
As for sized objects. Length is important. More important than girth.
![[Image: colon-intestines.png]](http://www.cksinfo.com/clipart/medicine/anatomy/colon-intestines.png)
From these illustration we see that the guts of a human being is composed of three major parts, small intestine, large intestine and rectum.
The rectum is the final area matter passes through on is way out. The rectum is about 12 cm long (4.7 inches) in depth. The remarkable thing here is with slow steady pressures one can 'stretch' it a little and cause the large intestine to move slightly to extend the length of the passage.
This must be done slowly. If done too quickly the inserted object can pierce through the top of the rectum, which is a very bad thing. In cases of rape where objects like broom handles are used, too much handle is shoved in and it rips through the upper corner of the rectum. The patient bleeds - profusely and needs an operation immediately.
This is how your typical size queen can take so much, slow pressures that straighten out the lower intestine (AKA colon) allowing half an arm, a small child, whatever, to be inserted.
Quote:Muscle damage
Fecal incontinence can be caused by injury to one or both of the ring-like muscles at the end of the rectum called the internal and external anal sphincters. During normal function, these sphincters help retain stool. In women, damage can occur during childbirth. The risk of injury is greatest when the birth attendant uses forceps to help the delivery or does an episiotomy.[citation needed] Hemorrhoid surgery can damage the sphincters as well.[citation needed] A pelvic tumor that grows in or becomes attached to the rectum or anus also can cause muscle damage, as can surgery to remove the tumor.[citation needed] Although anal sex resulting in repeated injury to the internal anal sphincter can lead to incontinence, the threat is relatively small.[2] One study among 14 anoreceptive homosexual men and ten non-anoreceptive heterosexual men showed that anoreceptive homosexual men have decreased anal canal resting pressure relative to non-anoreceptive heterosexual men and no associated fecal incontinence.[3] Another study among forty anoreceptive homosexual men and ten non-anoreceptive heterosexual men found a very significant increase in fecal incontinence (fourteen, or 35% amongst the anoreceptive men, and one, or 10% in the non-anoreceptive sample) amongst the anoreceptive sample.[4]
Source:
http://en.wikipedia.org/wiki/Fecal_incontinence
To stress, if one damages the sphincter muscle(s) then there will be problems. As long as initial insertion is done slowly and you slowly graduate to larger girth objects (ergo fingering starts with one finger, a bit of 'finger fucking and massage' then inserting more fingers to slowly open the anus) then there should not be a problem.
I personally do not know about using buttplugs. They are designed to get 'caught' up the anus, having more of a conical shape with a narrower portion near the bottom, this is to keep it inside.
Didoes are typically the same girth along the shaft, a few are made based on penis models thus have a 'head' which can be a bit more tricky since rubber/latex is not as forgiving as the human penis.
I assume you are interested in 'training' for real anal sex with a real penis, then I suggest you keep to sized didoes that are about the size of the average penis which is about 6 inches in length and about 5 inches in circumference.
More data on that is found here:
http://en.wikipedia.org/wiki/Human_penis_size
Considering the depth of the human rectum (almost 5 inches deep) this means that the average size penis is not going to do much to straighten out your colon.
So you most likely will not need to experiment with that.
![[-]](https://gayspeak.com/images/duende_v3_local/collapse.png)
mile: I should have joined this forum a long time back.
