For some reason, triathlon attracts many who want to dig into the science of how to train, researching questions like, "Why do I need long runs AND short fast runs?" "Why should I train my core so much if I am not in a sit-up competition?" "Swimming is really the only technique-oriented sport, right?"

It all starts with base training. Marc Evans writes about base training in Triathlete's Edge. The following is an excerpt from his book reprinted here with permission from Human Kinetics.