I'm not a physician, but I have figured out a few things by now. For instance, I believe this quote from the first link above is wrong:
As well, although this method may not sound enthralling, if you stick a finger in your rectum and try contracting your PC muscle, you will know that you're doing so because your finger will feel your anus contracting (pressure). Always try to keep your other muscles (thigh, back and abdominal) relaxed.It might well be that potty training tends to make us associate two distinct muscle groups. Kegel exercises are intended for the pubococcygeus (PC) muscles. Near as I can tell from this (pictures here), the anus is operated by the coccygei muscles and the puborectalis. You can figure out the ramifications as an exercise.
I suppose it's possible that the ability to manipulate these distinct groups separately is one of those things like curling your tongue, wiggling your ears, etc, that some people can do and others can't. No doubt the govt is waiting with millions of dollars in grants to fund this research. In the meantime, what you do on your own time is your business.
Now back to the women, doggone it. Here's a Kegel exerciser, which looks like something like a shoe tree or a hand brake. I've heard of others too, which I understand are weighted cones. Apparently they go in big end first, and the stronger the PC muscles are the higher you can hold them in.
Is that enough already?
UPDATE: Not to worry, GH - no empirical research was done wrt the theory in the blockquote above.