Originally posted by thrashmetal78 
I'm having a similar problem, though I'm sure it's because I've only been playing for a few years.  When playing songs that are power chord heavy with alot of sliding, aka Metallica's "The Four Horsemen", my hand doesn't cramp that much, because I try not to push down too hard on the frets.  I have to consciously think, "it's not an acoustic, take it easy", and I usually get through.  It still gets a little stiff, but I usually just work it out afterwards.  However, after I'm done with the song, and it's usually at least a 7 minute one, my left wrist is EXTREMELY stiff and sore.  I bend it back and forth once or twice and I'm good to go, but it still sucks.  I was just wondering if this is a matter of not warming up enough, not playing enough years, or maybe improper technique.  It doesn't hurt when I'm doing other things, so it's not a physical problem.  Any suggestions?