are strong muscles required?

It's unclear whether you need strong muscles or not, as some users experience results rapidly after getting the Aneros, while for others it takes longer.

It seems likely that the deciding factor isn't muscle strength, but rather mental state and muscle control--being in the right state of mind to have a good prostate-based experience (relaxed and aroused), and the ability of your subconscious to work your muscles around the Aneros in such a way that it stimulates the prostate just right.

At least, that's what I've gathered over my time on this forum.

No, not strong muscles as in trying to clench and pull in with your anus as if to pull the massager back and forth hard against your prostate. But it does take time and patient training, sometimes more for some guys (almost a year for me) to develop the neural feedback loops that allow those involuntary contractions that mysteriously pull the massager inward without you making a conscious effort to do so while at the same time your rectum wants to contract around it kind of like gripping it. That's the motion, and for me it's a very subtle movement of the massager when I've looked with a mirror while this is going on, that drives the orgasm--not big in and out strokes guys tend initially to think that are needed.

I think 'fast twitch' is more important than brute strength. Kegels might help a bit butt regular Aneros use will probably do the job.

-- Isometrics Training Develops Fast Twitch Muscle Fibers --