Because I was away from guitar for so long, there is a whole generation of books that I have rarely even looked at. In my journey back to playing again, my ear, heart, and brain were already in great shape because of my training as a theorist and composer. What was, and continues to be, a problem is my hands. My posts over the past 6 years sometimes focus on stretches, exercises, squeezers, and massagers. I made a big jump in progress on that end of things when I started studying the mechanics of muscles and tendons of the hand and forearm. This help me zero in on specific problem areas. Overall, I'd say that this approach paid off big-time for me. Back in my early years, I did a lot of scales, but then supplanted those with patterns, such as: C D E C D E F E E F G E, which is probably the most basic pattern there is. When I do variations of these now, I find some tricky situations from time to time. Here is one: C G D E D A E F, etc. If I am playing these on the first two or three strings around the 12th fret, I find that it is difficult to reliably and cleanly go from my first finger on string 2 to my 3rd finger on string 1, followed by a roll of the 3rd finger to string 2. If I use a pent or minor pent, then the 4th finger would be the one that rolls. This is not a reliable and clean move for me, especially when above the 12th fret using the 4th finger roll from string 1 to 2 (or 2 to 3). I wonder if it would make sense for a guitarist (or book author) to explore other moves that are mechanically more demanding than usual. Maybe the thing to practice would not end with the exercises of the type I mentioned above, but also include exercises that focus specifically on difficult moves. This would give the guitarist a chance to really focus on finger placement, and also develop the kind of strength needed for certain moves like that. Or, instead of strength being the target of an exercise, it could be a stretch. I haven't even mentioned picking and slurs. Two questions: are there books in existence that focus on the kinds of issues I raised? And, would it make sense for a guitarist to have some training in the kinds of specific mechanical moves that I mentioned? To take it to another level, you could write out a sample lick, then identify which muscles and tendons are involved. Then, write out some exercises that focus on those areas of the hand and forearm? And by exercises, here I am thinking of isolated, repetitive moves such as those done in a gym. But wait, there's more. If you are going to do a certain repetitive move, how many reps and sets should you do? How is such information arrived at today? It seems that it is something handed down from teacher to student, or one's own experience. What would a sports medicine specialist and a hand specialist say? Would they make recommendations that are in line with how we arrive at that practicing technique as musicians, or would they say, "oh, no, don't do that x number of time, do this instead, or do this x times, that y time and the set of those two 10 times. What I am getting at, is should there be some medical research applied to improving guitar technique?