A triathlon is a multi-sport endurance event consisting of swimming, cycling, and running in immediate succession over various distances. Triathletes compete for fastest overall course completion time, including timed "transitions" between the individual swim, bike, and run components.
Triathlon races vary in distance. According to the International Triathlon Union, and USA Triathlon, the main international race distances are Sprint distance (750 m swim, 20 km bike, 5 km run), "Olympic distance" (1.5 km swim, 40 km ride, 10 km run), "70.3" (1.9 km swim, 90 km ride, 21.1 km run, such as the Half Ironman), and Ironman )3.8 km swim, 180 km ride, and a marathon: 42.2 km run);
