Looking to find the answer to that question, I did an internet search for information and found this quote from Violet Blue:

The notion of losing bowel control due to frequent anal penetration is a hurtful myth, perpetuated by our culture’s shame about anal sex. It is usually directed at gay men, though since anal sex has become popular with heterosexual couples, that myth has followed into mainstream culture, no thinks to pundits who confuse opinion for fact, such as Dr. Drew. In fact, playing with anal penetration for pleasure actually tones the muscles, stimulates healthy blood flow to the area, and is a great form of exercise for the sphincter muscles. The more you use the muscles, the better shape they will be in — though because they are smooth muscles, not like the muscles in your biceps, they can’t be “bulked up” so you don’t have to worry about them becoming bigger from “too many” orgasms! Oh, if only there was such a thing as too many orgasms… I digress. But as long as you don’t rush, you stop when you feel pain, and don’t do anything to damage the tissue, you may find that you have even better bootie control than before. -Violet Blue-

So I posted it, adopted that opinion and then received a comment correcting and elaborating on the above assertion from a person I suspect is a health professional. I was not able to verify their credentials. But I assumed that was the case from the physiological specificity of the information. The problem is that no health professional is going to step forward and publicly give their opinion about how safe (or not) pegging is. So I chose not only to believe the information that was offered but to share it as widely as possible – with full disclosure as to the anonymous nature of the submission.

I’m a supporter, and this post will probably get deleted, but…

Talk to a surgeon or spend some time in dissection and you’ll see that it’s not really a myth. Many of the muscles in the anal sphincter are composed of smooth muscle, which are used in your eyelids and a couple other places.

Smooth muscle does not become stronger with use. It cannot withstand significant trauma, but it is fairly elastic and you have to stretch it quite a bit to cause irreversible damage. Depending on your physiology, that limit is probably a one time stress to a diameter 2x as large as your average stool.

If you’re “hammering”, that diameter is probably a lot smaller. But since we don’t have much in the way of before and after clinical exams, nobody knows the safety limits. Because the supplementary muscles are very strong, and we can control them, many people think that it’s simply a question of relaxing. It isn’t.

In truth, by the time you can consciously relax the sphincter to admit large objects, the smooth muscle has probably had a tear or two and isn’t much of a concern anymore. From a practical point of view all it did anyway was keep small amounts of flatulence and liquid waste (mostly water not absorbed in the large bowel) from escaping… not a big problem with most diets.

The ring can tolerate about 2 or 3 significant (painful) tears before it loses enough function to be unimportant in your ability to tolerate “intrusion”. On the bright side: Many overweight or obese people will already have suffered one or more of these tears starting as early as puberty, so it’s not the end of the world. You can get these events from constipation, straining or unusually dry or large bowel movements. This is why so many people think there’s no problem with introducing objects into the rectum.

Can you wreck it from repeated trauma? Certainly. You don’t have to watch much porn to see serious problems in people who have voluntarily subjected themselves to trauma. But thanks to our voluntary control of the other muscles, it doesn’t mean you’ll need diapers.

For the most part, until you’re in your late 70′s, the only person who will suffer from minor anal incontinence will be the person who does your laundry.

Lastly – there’s no science, but the prostate can indeed be bruised with negative effects. Trim those nails, and don’t use hard objects. Good luck!

I replied –

I am always interested in corrections, information and differing viewpoints – so of course I would not delete your comment! I love learning.

First of all – Thank you. This is excellent and very specific physiological information! I am curious to know your qualifications because you sound quite knowledgeable. I’d like to disseminate this information in a more front page way (on all the forums/websites I participate in) to everyone who is looking for it as opposed to hoping they find it hidden in the comments of a blog post. But I’d love to know your qualifications, first – messaged to me in private if you wish.

So tell me if I have this right, please…

1) Muscle tone of the inner sphincter is not built up or improved with more strap-on play. Can it be for the outer sphincter?

2) It is not all about relaxing. Small tears can occur but they are no more serious than tears which can occur normally with constipation, straining or unusually dry or large bowel movements.

3) “But thanks to our voluntary control of the other muscles, it doesn’t mean you’ll need diapers.” I want to understand here – there are 2 sphincters in the rectum, correct? The inner sphincter is involuntary and the outer is voluntary. So does that mean that the damage you describe is only to the inner involuntary? And the outer voluntary overrides the damage in terms of possible incontinence?

4) After all that…As long as you are “reasonable” in your play – not too large, too fast, too hard, sharp objects – you are likely not going to have a problem.

Response:

PS – Please don’t get the idea that I’m bashing your stand. I just spend a lot of time around asses.

Violet Blue’s expertise on that question is a valuable opinion, just like that of some random proctology surgical tech who fancies a good time now and then.

I would submit that asking a jockey what’s good for the horse will get an answer that might not match up with that of the honest race track vet.

Sorry, anon for a reason.

But…

Some doctors smoke cigars even though they know the risks.

But they generally don’t smoke a cigar a day, either. It’s the same with everything else, as well. Humans are pretty creative, and this particular hobby of yours has been around (documented) for at least 5 or 6 thousand years, and has flourished more than once in the last seven centuries.

It’s not unlike drinking diet or regular soft drink every day – it’s slowly stripping away your enamel and etching your teeth with every sip. But it’s not actively killing you.

If you cut down to one or two per week, the effect is still noticeable (to people who pay close attention) but nowhere near as bad as people who drink soft drinks every day. If you drink soft drinks every day, especially if you consume two or more soft drinks (or nurse a large one all day), I guarantee that your teeth will develop hairline cracks, start losing structural integrity and suffer significant loss of enamel. Total elapsed time to seeing the damage: 10 years on average, perhaps 20 if you have amazing genes.

But you won’t see any change from one day to the next, until it’s way too late to realize how far it’s gone. Your hygienist may not even notice any change unless he or she keeps amazingly detailed records.

Luckily, the story for the other end of the alimentary canal is a bit different, at least until you get near the end of your life. Human anatomy is not really standardized. It’s just generally amazingly “similar” in form and function between individuals.

A quick review of any decently illustrated anatomy book will give you a good idea of how the equipment is generally connected, but it won’t tell you much about the actual equipment you’ll be working with.

It won’t tell you how far you can dilate a rectum without causing trauma, or how much [long technical term that translates into how vigorously and with what friction coefficient you can thrust against the mucous membranes ] aka “action” will result in noticeable micro-tears or scarring, and it certainly won’t tell you how much impact the prostate can take without causing significant cell damage.

Why? We have no data… just a few random anecdotes. Try getting a public health grant to study the physio-mechanics of anal sex. It will never happen. The best one could hope for is to persuade someone to wrap the research into a series of rather technical porn films, but no credible doctor would touch it. And even if 50 couples were to agree to submit to a clinical study, there are no protocols. Instant loss of reputation, and with that, loss of income. If you think the syphilis experiments were ethically problematic, you’ll probably have to admit that inducing various failures in the rectum [for science!] might be a bit sketchy.

So we’re not going to accumulate credible scientific evidence, period.

Luckily, we have inference, personal experience and some clinical data from ER trauma cases. It’s not uncommon for patients to be admitted for clinical observation after blunt object trauma, or in cases of rape. It’s not exactly the same, because in many of these cases, the patient was attacked or assaulted. That’s very, very different from willing and consensual activity, but it at least gives us a reference point to calibrate our conclusions with. Most of the trauma occurs from involuntary action, inadequate lubrication and unrealistic expectations. (Really, what kind of fool thinks putting a glass object into a rectum is a good idea?)

But rather than write a treatise, let me just hit the highlights:

penetration through walls

Hemorrhoids

minor and major friction tears

sphincters being torn or split

large muscle tears

prolapse

bruising

Though wall penetration probably won’t happen if you pick your objects correctly. If it’s pointy, it had better be really, really soft. Otherwise, non-rigid objects are unlikely to perforate unless they’re moving really fast or have a significant length of travel relative to diameter, or unless you’re already at the limit of accommodation.

The big H is usually what causes pain and bleeding for most people. If you sit all day, or have children or eat a lousy diet, you’ll eventually suffer from a little red blood, sting and pain and occasionally a thrombosed vein might break and scare you. Eat more fiber and drink less pop. It looks scary and terrible, but hardly anyone ever died from a bleeding bottom.

Friction tears can be avoided with lubrication to a great extent, but it depends on viscosity, heat and displacement. If you’re well coated, and not moving fast enough to displace or dry out the lubricant, you should be OK. If you’re moving quickly, or the lubrication is being absorbed or going away due to other things, or the viscosity is changing from heat, you can start tearing things. You might even trigger a tear in an existing thrombosed vein, and then you’ll be bleeding for a while. It can be scary, but they’ll probably heal up.

If the object is significantly larger than the opening, lubricant can be wiped off enough that dry spots develop, and then bad things happen more often. It’s like the difference between dusting your windows and scrubbing them – even glass can suddenly cause friction if you press hard or fast enough. Minor tears will open the cells on the top layer (and it isn’t very thick – just a few cells) but major tears will shed layers or cause bleeding. They’ll probably heal, but it can take days or weeks.

I’ll leave out the disease vectors, susceptibility to infection and immune response from this, but you should try to keep everything reasonably sterile. I guess flora and fauna are a completely different topic, but let’s just say that interesting things happen with improvised lubes. Saliva is basically worthless.

All Sphincters have four maximums: How far, how fast, how often and rest/recovery time. You cannot judge the limits by anything other than direct visual observation(unlikely) and pain. The problem is that pain usually occurs as the failure limit is breached. A tear or breach will heal, but it will change the equation because it now consists of scar tissue. Elasticity is reduced with each tear, and after around three tears, it is unlikely to close completely ever again. It’s common for this to happen even without objects.

This isn’t the end of the world for your sport, because a lot of people (men and women) manage to tear them via repeated fecal constipation starting at puberty – and even in infants. It hurts. It hurts a lot. But then it stops hurting and life goes on. It isn’t debilitating, but you’ll need to wash more often. It can be worse with loose stools, or fluid leakage, especially if you strain a lot, or have gas. But sharting is now apparently mainstream, so I wouldn’t worry too much.

A major muscle tear is a bigger issue. It’s seen with blunt object trauma and rape. You can have ongoing pain issues from something like this, because the muscles will heal again one way or the other, and it might not be how you want it to heal. You can avoid this by limiting the size and length of your objects. Past this, you’re in fisting territory, and you should ask someone else. Vaginas are way better at size excursions than rectums, largely because the muscles stretch a lot better.

Prolapse is caused by the lining separated from the relatively weak support structure. It happens even without sex, and it’s a well known phenomena with lots of documentation. Limiting speed and size and using proper lubrication will go a long way – apart from muscle decay, you basically have to actively pull or push the rectum out to make that happen. Repeated attempts with inadequate lubrication can cause this to get started.

Bruising is important, but I would suggest that you avoid objects and activities that if imitated in your mouth would damage (hurt or bruise) your soft palate. This immediately rules out the use of captain crunch cereal and milk as a lubricant.

There is some evidence from the prostatic massage crowd that the prostate gland can be harmed(?) by repeated impact from rigid objects, but everything is anecdotal at this point. In general, I’d be more worried about friction and rough impact on the prostate than I would the sphincter. Steer away from glass, hard plastic, wood and the like in favor of softer objects, and make sure things slide over rather than impact. This implies that the shape and materials should be examined closely.

You should be VERY careful about fingernails of even normal length – put a cotton ball or two in the finger tip of your glove if you have even normal length fingernails – and don’t use bare hands.

Finally, stretching will occur, but over time the outer sphincter will almost always recover from anything other than tearing or splitting.

Some people feel that they can go to the bathroom more easily if they periodically do things like this, but some have the opposite experience. Anatomy varies, so there is no one rule fits all recommendation.

It’s more important to watch for edema (puffiness) around the rectum – I suspect that’s how you know when to lay off for a day or two.

On the whole, within limits, this is probably 50x safer than riding a motorcycle. If you’re going to be gentle, it’s probably very low risk. If you’re going to slam it and slam it hard, fast and often you should probably be more concerned about lubrication and trying not to pulverize the prostate with pointy, hard or rigid objects.

Many of the toys being marketed are probably too hard for repeated direct impact on this gland, and there is some evidence that too much pressure may be bad (making infections worse) – it is a gland, after all. They’re not particularly rugged. Go buy a bratwurst, warm it up and put a condom on it. You’ll break it long before you break anything else.

And like I said, some doctors smoke.

OK – here’s the anatomical info.

Look at the two illustrations called “male pelvis” and “female pelvis”. Keep in mind, these are colorized anatomy illustrations, and the actual bodies are from people who donated themselves to science… hence the openings appear larger than they usually are in people who still move.

You can see a couple of interesting things, including the relationship between the inner and outer sphincters. Keep in mind that these are normally closed. In some people the distance through the anal canal is pretty short – an inch or so, and in some people it can be 2x that, or more rarely 3″. Very rarely.

The distance to the posterior lobe of the prostate gland is usually around 1/3 to 1/2 the distance to the sigmoid colon – and the shape and the size of the bowel cavity varies quite a bit based on genetic and environmental factors. It can be as little as 1/4 of the distance depending on age or height.

In the illustration labeled “Rectum and Anal Canal”, you will see why people feel pain under varying conditions. The photographic illustrations don’t show the valves and the relationship and functions of the sphincters very well.

The first place where pain can appear is from forcing the exterior or interior sphincter past the elastic capability limit – especially if you do it quickly or without adequate preparation. Ouch! If the trauma (stretching) occurs very slowly, your body can repair the scar tissue in a way that accommodates displacement and simulates greater elasticity.

The next place is upon contact with and displacement of the rectal valves. You have some ability to move these out of the way or relax them, but in essence you’re trying to convince the rectum that it should open up. Your ability to do this may vary, but few people can pull this trick off on the first few tries.

Millions of women experience this (and I guess many men) from over- enthusiasm from their partners… who get in a little ways and then decide to “seal the deal” before the body has adjusted. Big Mistake, because there’s a good chance that the healing will leave large nodes of scar tissue in places that make future activities painful – apart from the psychological issues.

This is why some people feel pain with small objects that other people can barely notice. The external anal sphincter is quite strong and resilient, and it has three sets of backup muscles that work together. You have to really push it to traumatize all of these to the point that you can’t function anymore, but the interior sphincter isn’t quite so rugged. But again, it can be damaged “naturally” enough that it doesn’t really come into play that much in a large number of adults.

So that’s the deal. We’ve been around for millions of years, and our bodies are designed to try and cope with being torn apart by fangs and claws. Short of perforation or intentionally/accidentally exceeding the “it still feels OK” limit, you’re probably OK to play around like this with a little caution.

But anyone who thinks using objects around three-fingers wide is no big deal probably has already done about as much damage as they can to the interior sphincter. Beyond this, soreness is your best guide, although pain will probably be referred away to your lower abdomen or perineum rather than feeling like your ass hurts.

Note: If it stings or causes sharp pains, you should stop immediately and do something else for a day or two. Ask yourself if you’re hitting rectal valves, or potentially bruising tissue. Repeated and frequent bruising can lead to cancer or other annoying things – once or twice a month is probably the limit for your high speed pile driver imitations. Watch for puffiness in the rectal folds, and be patient if you see swelling that wasn’t there before. Minor swelling is to be expected, but if it looks really puffy, it’s time to back off for a while.

Also, don’t put hydro cortisone or cortisone products in the rectum – they thin out skin layers, which is the last thing you want in an already thin layer of cells.

And btw this is not medical advice. YMMV. I’d just like for people to understand the anatomy before they get crazy – a rectum is a lot of things, but it isn’t a coffee can!

Recap of Important Points:

“…by the time you can consciously relax the sphincter to admit large objects, the smooth muscle has probably had a tear or two and isn’t much of a concern anymore. From a practical point of view all it did anyway was keep small amounts of flatulence and liquid waste…”

“Smooth muscle does not become stronger with use. It cannot withstand significant trauma, but it is fairly elastic and you have to stretch it quite a bit to cause irreversible damage. Depending on your physiology, that limit is probably a one time stress to a diameter 2x as large as your average stool.”

“Finally, stretching will occur, but over time the outer sphincter will almost always recover from anything other than tearing or splitting.”

“The external anal sphincter is quite strong and resilient, and it has three sets of backup muscles that work together. You have to really push it to traumatize all of these to the point that you can’t function anymore, but the interior sphincter isn’t quite so rugged. But again, it can be damaged “naturally” enough that it doesn’t really come into play that much in a large number of adults.”

“If you’re going to slam it and slam it hard, fast and often you should probably be more concerned about lubrication and trying not to pulverize the prostate with pointy, hard or rigid objects.”

My opinion after taking in all this information:Look – anecdotally, even guys who indulge in fisting on a semi-regular basis do not complain of fecal incontinence. Are there studies? No. Will there be? No. As long as you aren’t stupid about it in all the ways we have already discussed (too large, too fast, no lube, hard or sharp objects) especially when you combine more than one of those at a time…AND as long as you pay attention to problem signs like pain or soreness and stop immediately. AND as long as you don’t do the REALLY brainless move of using a desensitizing lubricant…you should be good. But please consider the risks and play with care.

Please feel free, if you are a medical professional – to comment on the accuracy or inaccuracy of the above information – the more anonymous health professionals we have who concur – that lends a tad more credibility to this subject!