The word "triathlon" is Greek in origin and breaks down to mean "three competitions". A triathlon is a multiple-part race consisting of three tests of endurance. Though there are many types of triathlon races, the traditional version is usually a transition from swimming, to biking, and finally to running. Triathletes compete for the fastest course completion time, including the time it takes to switch between course.
Triathletes train hard and long to get their bodies in prime shape. The sport is largely one of endurance and so the three aspects of training that are focused on are aerobic capacity, lactate threshold, and economy. Many use the sport to keep their bodies healthy and maintain their physical fitness.
In swimming, triathletes tend to use their torso and arms, more so than their legs. In the remaining two stages of the competition, leg muscles are used far more vigorously and so the athletes conserve their strength by using altered swim styles. The swimming portion of the race is done largely in open water, instead of pools.
The cycling portion of the race differs from that of professional bikers and more closely resembles a time trial. The cyclists' bikes are specifically made to be more aerodynamic and streamlined with special handlebars and a steep seat to improve aerodynamics and conserve muscle strength for the running portion of the race.
The running portion of the race is probably the most iconic of the sport. After completing the previous races, muscles are exhausted and the athletes are often surprised at how weak their leg muscles are. In a full Ironman triathlon, the athletes may have to run over 26 miles, after completing a 112 mile bike race, and a 2.6 mile swim race. Depending on skill level, there are different distances for triathlon races. After the triathlon has finished, the athletes take a short rest and are back to training for the next course of grueling races.