Hi Mark, I am no medical expert, nor pretend to know anything about the medical side (I must admit I do not trust the medical profession as a whole, and only trust a few within that profession, alas, why would it have been any different than the rest, right?). My story however may shed some light for you, and hopefully encourage you to "go for it" with a big side of "be extra careful", in my case, I attained both by progressing with a very gradual curve.
I had a very close call to falling through the ceiling of my home while researching in order to run some data wiring for my entertainment system; while I did not fall, avoiding the fall implied overstretching in such a bad position, in a very small space, that I ended with a herniated disk in my lumbar region. Suffice to say that even about three months after the close call, I had a recurrence when trimming my toes that made me fall to the floor incapacitated for about half an hour, without even being able to rotate my body on the floor. Took about one hour before I was able to literally drag myself near a piece of furniture that eventually allowed me to pull myself up minimizing the overwhelming pain on my back, this pain went for weeks where just to sit, I was forced to use the strength of my arms in order to relieve the pain by holding a good portion of my upper body weight, at-all-times.
I discovered pretty quickly that while at the pool, the pain would go away given the body is mostly supported by buoyancy. Owning a monofin at the time seemed like a stupid thing (already owned from years ago, yet had not used it in decades), just undulating with no fins was a terrible ordeal that would bring back the pain. Yet I started by adding a few very soft/slow undulating movements at the end of every swimming (no feet kick, just arms underwater 25 meters in order to feel I would eventually be able to enjoy at least half of what a normal person can enjoy underwater) session, important to do this at the end when you are already warmed up. Pretty soon I found myself asking for at least small body boarding fins, which I bought instead of selling my super stiff monofin. Pretty slowly I eventually started using the fins to undulate slowly, this was "no pain, you gain" situation. Regular small cheap fins were next after a few months, and I eventually bought a medium monofin to create a step before getting back into my hard one.
The disk is not healed, they never heal, yet the strengthening of my back has helped me overcome a seriously handicapping situation to a point where I can now even lift weights of 130 lbs (my wife for a photo session) with very little pain that subsides pretty quickly. I know I will never be back to hundred percent, yet I am already at a good solid 65%, and much like the unattainable monofin seemed before, I may even get back to a hundred eventually.
Perhaps the most important thing you have to keep in mind is to exercise correctly, warm up, push without absolutely no pain, however ridiculously soft it may feel or look, and keep pushing that boundary to your personal limits relentlessly.
Do not jump into a monofin right away, you may hurt yourself, rather build up slowly, and safely without ever straining yourself.
Go for it, become a success story, come back, and tell us about it.
