Stu Mittleman is a much-sought-after fitness educator whose clients include celebrities and business and community leaders as well as thousands of dedicated husbands and wives, mothers and fathers, who aspire to excellence in their health and vitality. Mittleman holds two master's degrees in movement and social science and set a world record by running 1,000 miles in eleven days. Since 1991, he has been a featured guest speaker at Anthony Robbins's Mastery University and runs his own company, WorldUltrafit, based in La Jolla, California. A native New Yorker, he currently lives in Solana Beach, California, with his wife, Mary Beth, and two children, Beau and Mackenzie.

Katherine Callan studied journalism at Boston University and has worked at national consumer magazines, including Success magazine, where she reported on the leading thinkers in self-improvement and human performance. Callan writes and edits for traditional and new-media companies and is launching a specialty publication, For Marathoners Only. She lives and works in New York City and has run thirteen marathons.