I believe I may have hit upon a revolutionary new way to develop significantly stronger nails.

About five months ago my left thumbnail became trapped between the edge of a heavy steel door and the door frame, with the result that a black blood clot developed underneath the nail, just at the cuticle line, and a new nail subsequently started growing underneath causing the old nail to shed itself, (bit like a crab does with its shell)

The interesting thing is that although the new nail directly under the old nail is quite thin, the new growth following on behind appears to be phenomenally thick, at least double the thickness of the old nail.

Obviously it is of no advantage to a right handed guitar player to have an abnormally strong left thumbnail, but just imagine the benefits to be gained if you had every picking finger on your right hand treated in this way, along with the thumb ?

I don't recommend the DIY treatment with the steel door which my thumb underwent, (too inexact), I would get a friend to hit your nail(s) right at the cuticle with the cross pein of a 16 oz hammer, making sure that he (or she) is reasonably skilled in its use. The art is in making sure you get a nice bruise, without drawing any blood.

Or maybe somebody could design a guillotine type implement with a nicely rounded blunt edge to give a more controlled trauma.

No pain, no gain ...