Cycling, swimming, triathlon, and other endurance sports are close cousins of running. Although there are obvious surface differences (swimming is upper-body dominant, cycling is nonimpact, and so forth), at their core, all endurance disciplines are the same. Success in each of them depends on the ability to sustain aggressive submaximal speeds over long distances. The type of fitness that supports sustained speed in one endurance discipline differs only marginally from the type of fitness that does so in any other discipline.
