That crazy thing that takes all your time to train and then hurts really bad. Kind of.
Triathlon is the ultimate endurance event, focusing on fitness and the highest level of self commitment. Triathlon spans a few different forms, but most consist of a swim, bike and run with terrain depending on the theme of the event.
Triathlon, while incredibly intense, will leave many athletes far surpassing what they thought possible for their level of limitation. While many see this as a grueling sport, with the proper training schedule and motivation, it becomes a favored past time of many. The toughest one is the first.
Triathlon is regarded as beginning in 1920's France called "Les Trois Sports." It has since developed to drop the canoe portion of the race, replacing it with the more traditional swim. It was originally a shorter event, with only a 6 mile bike ride and sub-mile run.
San Diego hosted the first triathlon the sport has now become accustomed to in 1974 and the long-distance high endurance variation -- the Ironman -- was launched in Hawaii in 1977. Since then, the format has grown to develop different lengths and terrain for a unique experience at each event.