As soon as I pick up the guitar, if I have not warmed up for 15 or so mins, playing extended bar chords causes me a bit of pain in my hand. After warmup this goes away for the most part. Problem is, when heading to practice, I drive, and need to be ready as soon as I get in, as I don’t have 15 mins for warmup.

Anyone got any hand warmup exercises I can do while on the way to practice that will leave me ready for action as soon as I get to the rehersal rooms?

Have you tried one of these hand exercisers?

Still not illegal to use a hand exerciser and drive...yet

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“All music is folk music, I ain't never heard no horse sing a song.” Louis Armstrong

I have the same problem and sort of solved it with the exercises for the carpal tunnel. Given that you are driving do as possible and do some stretches before you drive (hopefully your commute isn't too long).

On the other note I have discovered that I have a less of that barre chord discomfort with the thicker neck profiles. I had for about a month a rented Gibson LP standard with the chunky neck and did not experience the issue as much.

So maybe try that and get yourself in trouble for GAS attack

Read my post in the Arthritis ruled out thread.