A triathlon is an athletic event made up of three contests (from the Greek). In contemporary usage, the name triathlon is mostly applied to 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.

History
According to some sources, the Triathlon is based on a race in France during the 1920-1930's that was called "Les trois sports", "La Course des Débrouillards" and "La course des Touche à Tout". Nowadays, this race is held every year in France near Joinville le Pont, in Meulan and Poissy. In 1920 the French newspaper "L´Auto" reported on a competition called "Les Trois Sports" with a 3km run, 12km bike and a crossing of the channel Marne. Those three parts were done without any break. There are articles in French newspapers about a race in Marseille in 1927. There is a 1934 article about "Les Trois Sports" (the three sports) at the city of Rochelle about a race with three components: (1) a channel crossing (ca. 200m), (2) a bike competition (10km) around the harbor of Rochelle and the parc Laleu, and (3) a run (1200m) in the stadium André-Barbeau. Since the 1930's, very little was heard about triathlon until its re-invention in 1974 at Mission Bay near San Diego in Southern California where a group of friends began training together. Amongst them were runners, swimmers and cyclists and before long training sessions turned into informal races. Directed and conceived by Jack Johnstone and Don Shanahan, the first Mission Bay Triathlon was held on September 25th 1974 and welcomed 46 athletes. This date is celebrated as the day modern triathlon began.

The first modern long-distance triathlon event ( 3.8 km (2.4 mile) swim / 180 km (112 mile) bike / 42 km (26.2 mile) run) was based on a barroom discussion by soldier John Dunbar, Navy Commander John Collins, and the taxidriver/fitness instructor Gordon Haller (the first winner). The debate was over who was the toughest competitor of 3 different events: The Wakiki Rough Water Swim (2.4 m), the Oahu Bicycle Race (112 m), or the Honolulu Marathon (26.2 m). The race combining all three was organized on February 18,1978 and held on the island of Oahu in Hawai'i. Later, the race was moved to Kona on the Big Island of Hawai'i. Today, a number of Triathlon events over several distances are held around the world, but the Kona still represents the "original Triathlon with the finishers called 'Ironmen'." The Hawaii Ironman Triathlon now serves as the world championship, but the Ironman company hosts other triathlons around the world that are also called Ironmans. In addition long-distance multi-sport events are organized by groups other than the Ironman Company. Sometimes triathlons are described as "Ironman" or "Half-Ironman" refering only to the distances of the respective events.


The International Triathlon Union (ITU), founded in 1989, is an independent triathlon organization and has never officially sanctioned the Ironman Triathlon. Some believe that the Hawaii Ironman should be recognized as the official triathlon world champsionship for the ITU, so This has been the subject of some controversy.

The sport made its debut on the Olympic program at the Sydney Games in 2000 over the Olympic Distance (1500m swim - 40km bike - 10km run, often just "Short Distance") and the Short Distance is organized by several national and international leagues.

Since its founding, triathlon has grown significantly and now includes thousands of races with hundreds of thousands of competitors each year.


Standard race distances
Name Swim Bicycle Run Notes 
sprint 750 m 20 km 5 km A 500 m swim is also common. 
Olympic 1.5 km 40 km 10 km Also known as "international distance", "standard course", or "short course". 
half-Ironman 1.2 mi (1.9 km) 56 mi (90 km) 13.1 mi (21.09 km) This is half the Ironman distance. 
ITU-Long Distance 3.8 to 4.0 km 120 km 30 km The ITU accepts a 5% margin of error in the distance of the cycle and run courses.[1] 
Ironman 2.4 mi (3.8 km) 112 mi (180 km) 26.2 mi (42.195 km) marathon Also known as "iron distance" or "long distance".[2] 

Types of triathlon
There are a number of standard triathlon race distances, including

Sprint Distance Triathlon: 750 meters swim (500m is also very common) / 20 km bike / 5 km run (sometimes called "short course", though that term more frequently refers to Olympic distance races) . The Sprint Distance is the fastest growing triathlon race distance in the United States. 
Olympic Distance Triathlon: 1.5 km (0.9 mile) swim / 40 km (24.9 mile) bike / 10 km (6.2 mile) run (Also called "international distance", "standard course" or "short course") The official triathlon world cup is a series of olympic distance races organized and sanctioned each year by the International Triathlon Union, in 2004 it included thirteen events. These world cup races are conducted in a draft legal format for the bike leg. Many other non-official triathlon races have adopted the olympic distance format. 
Half-Ironman Triathlon: 1.9 km (1.2 mile) swim / 90 km (56 mile) bike / 21 km (13.1 mile) run. Also called a "70.3" or "Tinman." 
ITU-Long Distance Triathlon: 4 km (2.5 mile) swim / 120 km (75 mile) bike / 30 km (18.6 mile) run. This is the race format of the long distance world series of the International Triathlon Union. 
Ironman, Iron Distance and Long Distance Triathlon: 3.8 km (2.4 mile) swim / 180 km (112 mile) bike / 42 km (26.2 mile) run, i.e. a marathon. 
Though there can be some variation in race distances, particularly among short triathlons, most triathlons conform to one of these five standards.

Equilateral Triathlon: A triathlon, proposed by Wainer and De Veaux (1994), in which each leg would take an approximately equal time. For example, their "Olympic" triathlon, run as a relay, should take three world-record holders each about 28 minutes per leg: 2.7 km swim / 22.4 km bike / 10 km run. 
Formula One (F-1) Triathlon: An event that consists of a swim-bike-run combination in multiple groups. For example, a swim to bike to run followed by another swim to bike to run combination done in one event or as a group of events. Another variation example would be a swim-exit-swim followed by a bike to run and another bike to run (looped courses). Typically these events allow bike drafting for age group triathlete entries (note: bike drafting is typically reserved to only pro/elite level triathletes). 
The F-1 frequent transitions between swim, bike and run does not make it a practical format for large groups of bikers to draft as frequently seen in other bike draft legal versions of triathlons where bike drafting is typically limited to pro level triathletes. The F-1 format was created to maintain a reasonably safe format for the development of drafting skills for age groupers. This is specially true for those at the junior level wanting to compete at the draft legal Olympic level in the future. 
Ultraman Triathlon: An event held annually in Hawai'i over a three day period and covering a total distance of 320 miles. 10 km (6.2 mile) ocean swim / 421 km (261.4 mile) cross-country bike / 84 km (52.4 mile) ultramarathon run. Ultraman Canada, held in the Penticton area of British Columbia, is another Ultraman event. 

Nonstandard variations
Winter variants of triathlon, raced in snow-covered conditions, can include (in order):

Cross country skiing, mountain biking and running. 
Cross country skiing, outdoor-ice speed skating and running. 

Another popular variant are so-called off-road triathlons that consist of swimming, mountain biking and trail running. The best-known series of these races is known as XTerra.

Aquathlons are two-stage races consisting of a swimming stage and a running stage. Duathlons comprise a cycling stage and a running stage.

Recent decades have seen the development of a wide variety of so-called "multisport" events, of which triathlon is now considered only one major type.


How a triathlon works
In a typical triathlon, racers arrive at the venue about an hour before the race is to begin, to set up their "transition area". Here they will generally have a rack to hold their bicycle and a small area of ground space for shoes, clothing, etc. In some races, the bicycle stage does not finish in the same place it begins, and athletes will set up two transition areas, one for the swim to bike transition, and one for the bike to run transition.

Racers are generally categorized into separate professional and amateur groups; amateurs are often referred to as "age groupers" who form the great majority of triathletes. One feature that has helped to boost the popularity of such a complex time-intensive sport is the opportunity to compete against others of one's own gender and age group. The age groups are typically set at between 5 and ten year intervals.

In some triathlons, amateur athletes may instead compete against others in heavier-weight divisions. Clydesdale athletes are those men generally over 200 pounds, while Athena athletes are those women generally over 150 pounds. This is not officially sanctioned in any of the professional or Olympic events.

There is usually (as in most marathons) a lower age limit (typically 18) for the longer triathlons (all of the 5 events listed above) but many shorter races have been organised to allow children and teens to compete in triathlon.

After transitions are set up, the athletes don their swim gear and head to the swim area - usually a lake or beach - for the race start. Depending on the type and size of the race, either all the athletes will enter the water at a single signal ("mass start", traditional in Iron-distance races), or in waves spaced every few minutes, usually by age group (wave starts are more common in shorter races where a large number of amateur athletes are competing).

The swim leg usually proceeds around a series of marked buoys and exits the water near the transition area. Racers run out of the water and attempt to change from their swim gear into cycling gear as rapidly as possible. In some of the earliest races, tents were provided for changing clothes. In the modern day, however, competition and pressure for time has led to the development of specialized triathlon clothing that is adequate for both swimming and cycling, meaning many racers' transition consists of little more than removing goggles and pulling on a helmet and cycling shoes. (And in some cases, racers leave shoes attached to their bicycle pedals and put them on while riding.)

The cycling stage proceeds around a marked course and finishes back at the transition area, where racers rack their bicycles and change quickly into running shoes before heading out for the final stage. The run finishes at a finish line usually near the start and transition areas.


Rules of triathlon
Traditionally, triathlon is an individual sport: each athlete is competing against the course and the clock for the best time. As such, athletes are not allowed to receive assistance from anyone else inside or outside the race, with the exception of race-sanctioned aid volunteers who distribute food and water on the course. This also means that team tactics, such as drafting, a cycling tactic in which several riders cluster closely to reduce the air resistance of the group, are not allowed.

This has begun to change with the introduction of triathlon into the Olympic Games. Many Olympic-distance races including the Olympics themselves and ITU World Cup events now allow drafting during the cycling stage. Although this change sparked extensive debate among the triathlon community, it is now gaining acceptance among the community and in any case appears to be here to stay.

Triathlons are timed in sections: 1) from the start of the swim to the beginning of the first transition; 2) from the beginning of the first transition to the end of the second transition; 3) and finally at the end of the run, at which time the triathlon is completed. Results are usually posted on official websites and will show for each triathlete his/her swim time; cycle time (with transitions) included; run time; and total time. Some races also post transition times separately.

Other rules of triathlon vary from race to race and generally involve descriptions of allowable equipment (such as wetsuits, which are allowed in the swimming stage of some races), and prohibitions against interference between athletes.


Professional competitions
The world of professional triathlon is primarily split into three circuits:

The "short course", or Olympic-distance competitive circuit, run by the International Triathlon Union (ITU), which includes the ITU World Cup series and ITU World Championships. In 2004, the ITU World Cup included over 75 different events. 
The "long course", or "Ironman" circuit, run by the World Triathlon Corporation (WTC), which culminates each year with the Hawaii Ironman World Championship. These races are not recognized as "official" by the ITU, but are unquestionably the best-known series of races in the sport. 
The XTerra off-road triathlon championship series. 
In addition, the ITU has a Long Distance Triathlon series, with races slightly shorter (except for the swim) than the Ironman standard. This circuit is a new addition, with four annual events as of 2005. Many of the same athletes compete in Ironman and ITU Long Distance races.

The term Ironman Triathlon is a trademark of the World Triathlon Corporation and refers to the series of races organised by the WTC. Races of this distance which are not organised by the WTC are commonly referred to as Iron Distance Triathlon.


Triathlon and fitness
Triathletes tend to be extraordinarily fit, and many amateur athletes choose triathlon specifically for its fitness benefits. Because all three events are endurance sports, nearly all of triathlon training is cardiovascular exercise. In addition, since triathletes must train for three different disciplines, they tend to have more balanced whole-body muscular development than pure cyclists or runners, whose training emphasizes only a subset of their musculature.


Specialization of swimming, cycling and running in triathlon
Each of the elements of triathlon is a little different from if those sports were encountered alone. While amateur triathletes who also compete in individual swimming, cycling or running races generally apply the same techniques and philosophy to triathlon, seasoned triathletes and professionals have specialized techniques for each discipline that improve their race as a whole.


Swimming
Triathletes will use their legs less vigorously and more carefully than other swimmers, husbanding their energy for the cycle and run to follow. Many triathletes use altered swim strokes to compensate for turbulent, aerated water and to conserve energy for a long swim. "Total Immersion" is one popular swimming style. In addition, the majority of triathlons involve open-water (outdoor) swim stages, rather than pools with lane markers. As a result, triathletes in the swim stage must jockey for position, and can gain some advantage by drafting, following a competitor closely to gain an advantage by swimming in their slipstream. Triathletes will often use "dolphin kicking" and diving to make headway outward against waves and body surfing to use a wave's energy for a bit of speed at the end of the swim stage. Also, open-water swims necessitate "sighting", raising the head to look for landmarks or buoys which mark the course. A modified stroke allows the triathletes to lift the head above water to sight without interrupting the swim or wasting energy.

Because open water swim areas are often cold, specialized triathlon wetsuits have been developed. In addition to warmth, wetsuits add buoyancy and smoothness, both of which increase swimming speed. Wetsuits are only legal in sanctioned events with a water temperature below 78 degrees Fahrenheit (25 degrees Celsius). Some events allow wetsuits regardless of water temperature, and sometimes they are required. Or, in a single event, wetsuits may be allowed for age groupers but not for professionals.


Cycling
Triathlon cycling, with the exception of Olympic triathlon and ITU World Cup races, is very different from most professional bicycle racing because it does not allow drafting, and so racers do not cluster in a peloton. It more closely resembles time trial racing. Triathlon bicycles are generally optimized for aerodynamics, having special handlebars called "aero-bars" or "tri-bars", aerodynamic wheels or other components. Triathlon bikes use a specialized geometry including a steep seat-tube angle both to improve aerodynamics and spare muscle groups needed for running (see also Triathlon equipment). At the end of the bike part, triathletes also often cycle with a higher "cadence" (pedaling speed), which serves in part to keep the muscles loose and flexible for running.


Running
The primary distinguishing feature of running in a triathlon is that it occurs after the athlete has already been exercising in two other disciplines for an extended period of time, so many muscles are already tired. The effect of switching from cycling to running can be very profound; first-time triathletes are often astonished at the bizarre sensation in their thighs a few hundred yards into the run and discover that they run at a much slower pace than they are accustomed to in training. Triathletes train for this phenomenon through transition workouts or "bricks": back-to-back workouts involving two disciplines, most commonly cycling and running. (The term "brick" is derived from a partial anagram of Bike-Run.)


Legendary and well-known events
Hundreds (perhaps thousands) of individual triathlons are held around the world each year. A few of these races are legendary and/or favorites of the triathlon community because they have a long history, or because they have particularly grueling courses and race conditions. A few are listed here.

Hawaii Ironman World Championship, Kona, Hawaii. First held in 1979, only five years after the sport of triathlon was founded. The cycling stage of the race covers more than a hundred miles over lava flats on the big island of Hawaii, where mid-day temperatures often reach over 43 °C (110 °F) and cross-winds sometimes blow at 90 km/h (55 mi/h). The race is often challenging even to competitors with experience in other iron-distance events. 
Escape from Alcatraz, San Francisco, California. This non-standard-length race begins with a 1.5 mile (2.4 km) swim in frigid San Francisco Bay waters around Alcatraz Island, followed by an 18 mile (29 km) bicycle and 8 mile (13 km) run in the extremely hilly terrain of the San Francisco Bay area. The run includes the notorious "Sand Ladder" -- a 400-step staircase climb up a beachside cliff. In recent years, the race has included a fourth event: a one-mile (1.6 km) "warm-up" run between the swim and bike leg to reduce the incidence of hypothermia. 
Wildflower is a Half-Ironman distance race held on or near May 1st at Lake San Antonio in Southern California since 1983. Known for a particularly hilly course, it has expanded now to include three races of different lengths and is one of the largest triathlon events in the world, with over 8,000 athletes attending each year. 
Life Time Fitness Triathlon. Offering the largest professional prize purse in triathlon, this event draws international triathlon talent in large numbers. Pros and amateurs alike are welcome to Minneapolis, MN in late summer to enjoy this exciting race conducted in "equalizer" format. 
HP Norseman Xtreme Triathlon. The race is the world’s toughest iron-distance. It is also the northmost iron-distance, taking place at the same latitude as Anchorage, Alaska. The race travels through some of the most beautiful parts of Norway, and is far from a regular circuit-race. HP Norseman starts in one of the beautiful fjords on the West Coast and finishes inland at 1,850 meters above sea level. Total ascent is 5,000 meters. 

Notable triathletes

Men
Mark Allen 
Hamish Carter 
Bevan Docherty 
Chris McCormack 
Scott Molina 
Dave Scott 
Mike Pigg 
Simon Lessing 
Scott Tinley 
Simon Whitfield 
Peter Reid 
Lothar Leder 
Hunter Kemper 
Peter Robertson 
Dmitriy Gaag 
Faris Al-Sultan 

Women
Kate Allen 
Michellie Jones 
Brigitte McMahon 
Julie Moss 
Paula Newby-Fraser 
Natascha Badmann 
Nicole Hackett 
Pip Taylor 
Vanessa Fernandes 
Emma Snowsill 

Footnotes
^ International Triathlon Union (2003). ITU Competition Rules. (PDF) URL accessed on 2005-12-13. 
^ Because "Ironman Triathlon" is a registered trademark of the World Triathlon Corporation (WTC), only races licensed by the WTC may be called "Ironman." As a result, other races of the same distances are called "iron" or "long" distance.