Are there any weight-bearing  (high resistance, low rep)  exercises that one could do for typing?   Would getting a hand gripper (e.g., Captains of Crush, or HeavyGrips, i.e., of higher quality and resistance levels than the ones in supermarkets) be enough?   I don't quite know the anatomy of the hand to judge what kind of strengthening exercises would be useful specifically for typing stamina.  (I do weighted squats regularly, but they do, er, squat for my hands.)

I am currently at 71wpm on Ryan Heise's test but probably type in the low 60s when not under the gun, so I do have a workable speed.  I am mostly OK, but if I thought I would have less dread of longer typing sessions than with QWERTY, I am not there yet.  I feel moderate finger pains (ring fingers mostly) after only a few paragraphs, and I'd like to have more stamina.  Perhaps it is my general hand strength and health that is the sticking point.   

The strength I seek is not necessarily to increase my typing speed -- I'd like to be able to type longer periods instead of losing my flow because of discomfort.   This would be of great help in rapid speech-writing where I'm trying to flesh out a topic and maybe explore detours if only to delete them later, where any bit of tiredness or ache tends to make me shirk the work, even though I am very interested, thus making for a poor speech.  (I am not a professional speech-writer or speaker, so cannot do whatever full-time practitioners do to alleviate the problem.)  Typing slower (not that 71 is outrageously fast) doesn't seem to help.

Coding, an activity that is relatively more prosaic than prose writing, I find ok, perhaps because of my extensive use of "completions", an option not available to prose, even of the non-creative kind that I deal in.