A triathlon is a multisport race that consists of three different disciplines run consecutively in one sequential event. The three disciplines are swimming, cycling, and running, and they are completed in that order. The distances of each event can vary, but there are four main distances recognized officially: Sprint, Olympic, Half-Iron, and Ironman. The most common distance is the Sprint triathlon, which includes swimming 0.5 miles (750 meters/2,460 feet), cycling 12.4 miles (20 kilometers), and running 3.1 miles (5 kilometers) . The Ironman triathlon is the full distance for the sport and is a 2.4-mile (3.8km) swim, a 112-mile (180k) bike, and then a full marathon of 26.2 miles (42.2km) .

Here are some additional details about each discipline:

• Swimming: The swim is usually done in open water, such as a lake or ocean, and can range from a few hundred meters to several kilometers. Swimmers may wear wetsuits to help with buoyancy and warmth.

• Cycling: The bike segment is usually done on open roads with traffic, but closed circuits are becoming more popular. Triathlon bikes are designed for aerodynamics and have special handlebars called aero-bars or tri-bars, aerodynamic wheels, and other components.

• Running: The run segment is usually done on roads or trails and can range from a few kilometers to a full marathon. Triathletes often cycle with a higher cadence (revolutions per minute) at the end of the bike segment to keep their muscles loose and flexible for running.

In addition to the traditional triathlon, there are various forms of multisport events, such as duathlon, aquathlon, and pentathlon. Winter triathlon, for example, typically includes two events of either cross-country skiing, mountain biking, or outdoor-ice speed skating and finishes with running.

To master triathlon, there is a crucial fourth discipline called transition, where time can be gained or lost. There are two transitions in each race, T1 and T2, where athletes switch from one discipline to another.

Triathlons are becoming increasingly popular, with over 3.5 million participants worldwide. They are more about personal goals than competition, and triathletes of all levels are usually supportive of each other.