You're sprinting at full speed with a rifle strapped to your back. Your oxygen-starved body is screaming for you to breathe, your heart is pounding, but you have to deprive yourself of air to shoot at - and hit - miniscule targets 50m away. This is biathlon.

What is biathlon?

While technology has moved on and athletes have gotten fitter and quicker, the bare essentials of the sport have changed little since Swedish and Norwegian border guards held the first competition in 1767.

This sport tests both body and mind, combining cross-country skiing which pushes - and sometimes breaches - the limits of athletes' physical powers, before demanding they focus their effort-addled brains on using a rifle to shoot down targets on a range.

While competitors can use the classic style, everyone opts for the more rapid, powerful freestyle form of skiing, with the Norwegians excelling.

The events are tailored for men and women, with female competitors skiing less in terms of distance and uphill climb.

Individual

The longest race competitors face. Starting at 30-second intervals with positions based on a pre-race draw, participants ski five laps of a designated circuit before shooting four times, alternately firing in the lying - or 'prone' - and standing positions twice. Each competitor has five shots to hit the five targets - one missed target means one morale-sapping penalty minute added to their race time.

Sprint

The most explosive of the events, competitors ski off at 30-second intervals - again with start positions based on a draw - shooting once in both positions, but one missed target means having to ski a penalty loop of 150m.

Pursuit

While the Sprint and Individual are races against the clock, the Pursuit is as close as you can get to hand-to-hand combat on skis.

The start order is determined by the finishing positions in either the Individual or Sprint race, with the winner heading out first to be hunted down by the remainder of the field who start in the positions and with the time difference they finished behind the winner in the previous race.

Four visits to the range - though two prone shoots before two standing shoots - with the dreaded penalty loop awaiting those who err.

Relay

A chance for nations to pick their four best biathletes to go head-to-head against the other countries. Biathletes on the first leg start at the same time, and each shoot twice. Three spare rounds - which have to be loaded by hand - are available to make up for any mistakes on the range. If you miss more than three, you're on the loop.

Mass Start

The field is restricted to comply with the number of shooting lanes available, usually 30.

The individual, sprint and pursuit medal winners are all included with the rest of the field being filled out by those in the upper echelons of the World Cup rankings.

Each biathlete shoots four times - two prone, two standing - and if they avoid the penalty loop, will take gold if they are the first over the line.

Home on the range?

The shooting range is where races are won and - more often than not - lost. A missed target can prove fatal and the combination of fatigue and adrenalin-fuelled muscles means holding the 3.5kg rifle steady enough to hit targets some 50m away is a feat only for the brave.

Watch out for the standing shoot! Why? Though the prone targets are only 4.5cm across, biathletes can use the ground to steady themselves, whereas the standing targets - some 11.5cm in diameter - are so much harder to hit late in the races.

Eurosport