Since the 2000 Sydney Olympics, the triathlon has tested athletes with a grueling combination of swimming, cycling and running.

In each Olympic Games since Sydney, there have been both men’s and women’s individual races — and at the Tokyo Games, the mixed team relay event debuted, featuring two men and two women from each competing nation.

As the Paris Olympics approach, here’s how the Olympic triathlon works.

The sequence for the Olympic triathlon is swim, bike, run. This order remains the same at virtually all triathlons worldwide.

The overall Olympic triathlon distance is 51.5km (32 miles). This includes a 1.5km (0.93 mile) swim, 40km (25 mile) cycle, and a 10km (6.2 mile) run.

For the mixed team relay, each athlete traverses a 300m (330 yard) swim, 8km (5 mile) cycle, and a 2km (1.2 mile) run in a relay format.

The all-time record in the men’s event is 1 hour, 45 minutes, 1 second for men, set by Great Britain’s Alistair Brownlee at the Rio Olympics.

Bermuda’s Flora Duffy broke the women’s Olympic record at the Tokyo Games, winning gold in 1:55:36.

The mixed relay record is 1:23:41, set by Great Britain in Tokyo.

As the first leg of the triathlon competition, the swim sets the stage for the entire race and can often make or break a competitor's shot at a medal.

How an athlete approaches the swim leg depends on the competitor's individual strengths and weaknesses. If the swim is a triathlete's strongest event, it is important that they pull ahead of the pack and leave the water as far ahead of the other competitors as possible. Building up a lead going into the bike leg gives the swimmer a buffer zone that the other competitors, who may be stronger cyclists, must overcome.

Meanwhile, positioning is key for the athletes whose strongest event is not the swim. This triathlete needs to stay close to the lead pack and not fall so far behind as to make catching up on dry land impossible. Weaker swimmers often hang back and draft off the lead swimmers, allowing them to conserve energy for the next leg: cycling.

As in the swim leg, a competitor's strengths and weaknesses determine how they will attack the bike course.

The strong bikers will often break away from the pack in order to build a lead over the other athletes who might excel at the run, while the stronger runners will stay in the pack and draft off the lead riders (a legal tactic in Olympic triathlon competition). In an Olympic triathlon, every second counts, so an efficient transition from swim to bike is crucial. A clean swim-to-bike transition typically takes between 20 and 30 seconds.

In the run, the primary tactic for triathletes is simply to cover the 10,000 meters as fast as they can.

The athlete whose strongest event was either the swim or the bike hopes to have built up enough of a lead that he or she can hold off strong runners challenging from behind. The racer whose best event is the run hopes that, over the course of the first two legs, they can remain within striking distance of the leaders with enough energy for a final push at the end. The transition from bike to run tends to be a bit quicker than the swim-to-bike exchange. Competitors must discard their cycling gear and put on their running shoes as efficiently as possible.

What is the best swimming technique for the Olympic triathlon?

Different athletes prefer various strokes, and competitors may use any stroke they prefer. Since any athlete’s goal is to swim as efficiently as possible, freestyle (front crawl) is most recommended and widely used.

Some athletes prefer breaststroke, which is often used when athletes need to recover while still moving forward. Backstroke and butterfly are sparingly, if ever, used in triathlon.

How do athletes pace in the Olympic triathlon?

Each triathlete brings their own strategy, but pacing is crucial for all.

Most athletes will aim to start their triathlon at a slower pace and gradually increase it throughout the race.

Drafting behind other competitors in the swim and cycle portions of the triathlon is a common strategy. This involves swimming or cycling closely behind another athlete to reduce wind resistance and conserve energy, all while maintaining a higher speed.

In all disciplines, adequate fuel and hydration is also paramount.

How do athletes pace the Olympic triathlon run?

Triathletes average between 90% and 98% of their heart-rate threshold while running. This metric serves as a reference point for the maximum sustainable effort an athlete can maintain.

Athletes are often encouraged to track their heart rate in training, track their ideal pace and enter the Olympic triathlon with an iron-clad plan as to how to attack it.