If your left arm is getting tired fast (Can't do all the finger taps to eruption without cramping or doggin' out?) then you need to exercise.
#1. Use a raquet ball and squeeze it in the palm of your hand a few minutes a day.
#2. More importantly you need to learn to relax. With accuracy comes speed. Work on accuracy first and speed will come naturally.

Now if it's your RIGHT arm...that's pretty much the same deal. I got tennis elbow when I stayed up all night trying to learn Eugine's Trick Bag. Curls will help that. If you're just trying to break the sound barrier on the metronome the try a different pendulem. Are you using your elbow and moving your whole forearm as fast as you can? If so try just moving your wrist.

Over all the BEST exercise a guitarest can get is PLAYING. Play steele string acoustic when you're in the mood to exercise. It makes electric so much easier.

P.S. FretSlug is correct. Stretch a little before playing/excercising.

[Edited by SwinginDick on 03-24-2002 at 03:25 AM]