Whenever you're going to do any form of strenuous exercise, you should always warm up first if you want to avoid possibly hurting yourself. If you were playing baseball you wouldn't just get up there and start hitting balls with all your strength -- you'd swing the bat a few times before you tried to hit a home run. So I believe it's important to warm up before you do pretty much anything on the guitar, be it recording, playing a gig or rehearsing.
Former Megadeth guitarist Marty Friedman has recorded a series of 65 guitar loops that can be used by producers and disc jockeys for various projects. Friedman's loops, which range from high-gain leads and rhythm parts to clean-tone melodies influenced by Japanese and Middle Eastern scales, are available now as a loop library called "Exotic Guitar."
It's been years since Marty Friedman left his high-profile position with Megadeth. Now living in Tokyo, he's become "Mr. Heavy Metal" - a superstar of Japanese TV and the country's multifaceted music scene.