No man, I don't care how well endowed he is, possesses a penis length and/or girth to 'over stretch' the anus/sphincter muscles nor cause permanent change to the anus and lower intestine. Unless you are into fisting and/or, giant toys or are actually dating a horse or donkey, changes in your rectum should not be taking place.
Thus penis to anal intercourse is not going to lead to 'changes' of the physical anus at least none that you will notice.
The sphincter is inherently weak. And yes, as a matter of fact there was research done to 'measure' strength of 'assholes' of humans and several other species, and we humans have the weakest arseholes :biggrin: (Who paid for that? US government)
I read the paper in a medical journal, which one I cannot recall at this moment.
While you may experiences changes in how much pain/discomfort you experience during the act, this is usually more or less mental changes, not changes in the physical structure of the anus.
You might also be strengthening your anal muscles (sphincter and surrounding muscles), however the over all strengthening is a drop in the bucket - barely noticeable, unless you are doing anal exercises (yes there is such.....)
http://www.bwhct.nhs.uk/67_sphincter_exercises_a5-2.pdf
http://www.google.com/webhp?hl=en#sclien...82&bih=661
You may actually be able to relax a lot more than guys who don't have anal sex. THAT relaxing may lead to more relaxation while have a bowel movement.
In reality when having a bowel movement it should be more of a relaxation of the sphincter and related muscles not a 'pushing'. Straining is a sign of constipation, yes most people, most males, are constipated to one degree or another.
I commend you on taking a more proactive stance on your bowel health. High fiber diets have been shown to greatly reduce all manner of bowel disease and have been shown to improve health in various other ways, such as cholesterol, heart, etc.
Few people know since no one teaches the subject, that your typical bowl moment should take place on a regular basis - between 1-2 days. Your stool should be not too soft and not to hard, retaining it shape, but still being malleable when it is 'dumped'.
Urgency in your case is most likely due to your recent change in diet. Your body is not used to the fiber, thus is not aware on how to signal you that a BM is coming. In a month (maybe more, maybe less, depends on your body) you most likely will be more aware that a BM is coming down the pike, your body signally you as it relearns that fecal matter in the lower intestine means you will need to go 'soon' since things are moving a bit better and without strain.
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Leo
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