Triathlon

Triathlon is an ancient Greek word that refers to an athletic event made up of three contests. In contemporary usage, the name triathlon is mostly applied to a race consisting of a combination of swimming, cycling and running, in that order. In most modern triathlons, these events are placed back-to-back in immediate sequence and a competitor's official time includes the time required to "transition" between the individual legs of the race, including any time necessary for changing clothes and shoes. As a result, proficiency in swimming, running, and cycling alone is not sufficient to guarantee a triathlete a competitive time: trained triathletes have learned to race each stage in a way that preserves their energy and endurance for subsequent stages.

Duathlon

Duathlon is an athletic event (not to be confused with biathlon) that consists of a running leg, followed by a cycling leg and then another running leg in a format bearing some resemblance to triathlons. In the United States, Duathlon is governed by USA Triathlon; the International Triathlon Union governs the sport internationally.