Mark Sisson's "Training and Racing Duathlons" ebook. For triathletes, duathletes, runners, cyclists and anyone else serious about fitness. Author Mark Sisson has not only competed at the elite level in distance running and triathlon, he has also coached some of the world's top endurance athletes. This industry standard book (75 pages) "Training and Racing Duathlons" helps you understand the basic concepts of how and why your body responds to training, so you can create the ideal training plan to achieve your fitness goals.