All About Olympic Triathlon - Triathletes tackle 3 disciplines

The best visuals of the triathlon are in the opening moments. All competitors line up on a floating pontoon and dive en masse into the lake, harbour or river. Their first task is to get in a good position, to avoid getting boxed in or being hit by other competitors' limbs.

After the first frantic 400 metres or so, each competitor tries to stake out a position behind a stronger swimmer, who breaks the water. This helps conserve energy.

Competitive swimming in open water is different than swimming in a pool. Triathletes have to contend with choppy, cold water as well as the elements. They must also orient themselves on non-linear courses through churning water. The course is usually triangular and outlined by buoys.

Because of the cold water, competitors must wear wetsuits if the water temperature is lower than 14C. Athletes can decide whether to wear wetsuits when the temperature is between 14 and 20 degrees. Wetsuits are forbidden at temperatures above 20C. There is some controversy surrounding those wetsuits, too. They're considered an advantage for weaker swimmers, since they add buoyancy.

At the end of the swimming course, competitors emerge from the water, run up a beach or a ramp and rush for their bicycles. The transition from one leg to the next is the triathlon's version of the pit stop and, as in auto racing, these transitions should be smooth and quick - no longer than 30 seconds to get the bike out of the rack, slip on the shoes, run the bike out of the transition zone and get going.

As in car racing, there's a high risk of crashing in the transition zone. Competitors emerge from the water in bunches, all hoping to get a head start on the cycling course, where there's a similar risk of crashing while riding in packs. To bring order to the process, triathletes are required to pick up and drop off their bikes and helmets at designated racks.

The bikes themselves meet the same kind of standards set for bikes in road cycling events. In fact, the cycling leg resembles a road cycling event, with one notable exception: triathletes are allowed to "suck on the wheel" of an opponent. That's a triathlon term that refers to drafting, which is when one cyclist cruises in the slipstream of another to conserve energy.

Occasionally, a weaker cyclist will draft behind a strong cyclist to get through the cycling leg then bound ahead during the running segment. For that reason, some strong cyclists try to break away from the pack.

The running leg is different from the 10,000-metre track event in two respects: it's on a road rather than a track, and it comes after the competitors' strength and energy have been diminished by 90 minutes of swimming and cycling.

In the triathlon, even the best-prepared competitors are susceptible to sunburn, heat exhaustion, dehydration, and cramping.

Triathletes also contend with the same nagging injuries as runners, cyclists, and swimmers - bad knees, Achilles tendons problems and sore backs and shoulders.

But triathletes also suffer bruises, broken noses, and concussions, usually in the first moments of the swimming segment. That's when competitors sometimes grab, punch and kick each other while jostling for position.

During the cycling leg, triathletes career around tight corners in packs, leading to many crashes and spills.

If an athlete jumps the horn at the start, he may be held back for 15 seconds in the first transition. During that time, he can't do anything.

Dangerous behavior at any point in the race might result in a yellow-card warning handed out by a race official. At that point, the triathlete must stop until the official clears him or her to resume the race.

For more dangerous or repeat offences as well as shortcutting the course or accepting outside assistance, triathletes can be disqualified with a red card.