I have heard (mainly from the point of view of traditional Chinese medicine) that pelvic floor exercises (Kegel) helps the healing of AF and haemmorhoids. I can’t get my head round this because, AF can be caused by resting anal sphincter pressure being too high. The aim of LIS is to weaken the inner sphincter muscle and hence release anal pressure(?). In contrary, pelvic floor exercise is likely to strengthen the sphincter muscle (makes it less prone to tear? and more elastic?), but wouldn’t it increase the resting pressure or make the anal canal even smaller due to increased muscle mass?

Hi East.
You can't exercise the internal anal sphincter by doing exercises, because the internal anal sphincter is not under voluntary control. It's like the muscles of your intestines and blood vessels. It's controlled by the autonomic nervous system, not by conscious thought.
It's the external anal sphincter that you can consciously squeeze and relax. So when you need to poo, but aren't near a toilet, you squeeze that outer sphincter, and when you are trying to go, you relax it.

My guess is that if you exercise the pelvic floor muscles, you will have stronger control of your external sphincter (also your urethra, which is very good to prevent urinary incontinence), and maybe take some of the strain off the internal sphincter? Just guessing here. Anyway, kegels can't hurt. You can always relax your external sphincter.

I forgot to say - it' the internal sphincter that gets the fissures.

thanks Scientist, but do fissures occur in the internal anal sphincter?
I thought fissures only cut the mucosal layer, a cut in which may expose the internal anal sphincter.
From my understanding, there are 3 main layers:
1). mucosa (incl. squamous epithelium and various mucosal layers) - this is where fissure occurs
2). internal anal sphincter (involuntary smooth muscle cells, as you said is controlled by the automatic nervous system - this is the layer where LIS aims to cut, but not the layer where fissures necessarily occur)
3). external anal sphincter (voluntary skeletal muscle cells that can be controlled)

I guess since the internal anal sphincter is elastic, it doesn't easily get damaged(or so I hope..?), except when there is an abscess or fistula that penetrates into the sphincter muscles.

I did my last postdoc on a gene that is involved in neurite outgrowth but affect body mass, at some point we were going to look at the enteric nervous system, but in the end we gave up because we knew nothing:P and it's too complicated! (so just a descriptive paper in the end..) These days I am a little obsessed with my AF/Hd problem, I think there should be a journal dedicated to this problem since this is so common.. and painful!!

I agree there should be a journal, east!
You are right, fissures are in the epithelium, unless they get really bad and penetrate into the muscular layer (I asked my CRS that very question). I think of it like a superficial cut in the skin which really hurts when you stretch the skin - like a cut in your lip that opens every time you smile.
Similarly the fissure hurts when the sphincter is stretched in a BM, and when the sphincter spasms.
This is just impressions I get when reading around.
The thing I don't understand is why painless BMs cause spasms, and why there is often a period of minutes to hours between a BM and a spasm.
I have a daydream that I go to medical school and qualify as a CRS and make my name studying anal fissures, because the more i read about the sphincter, the more questions I have.

Me too, and I think the best CRS should be a sufferer him/herself! because you would know all the relevant questions to ask and have the resources to research into all those questions!!