Mark Hatmaker has 23 years of experience in the martial arts as well as boxing, wrestling, and Jiujitsu. He has produced several instructional videos, including Escape from Impossible Holds, Brutal Submissions, and Guard Submissions. He lives in Knoxville, Tennessee. Doug Werner is an author of sport and fitness instructional guides, including Boxer's Start-Up and Fighting Fit. He lives in San Diego, California.