Os teamed up with Ole Einar Bjørndalen, Emil Hegle Svendsen and Tarjei Bø to win top honours in the 4x7.5 kilometres race in Russian town Khanty-Mansiysk, finishing ahead of the hosts and Ukraine in second and third respectively.  

The victory came just days after the 2011 Tōhoku earthquake and tsunami in Japan with the quartet donating their prize money to the relief fund.

Another highlight of Os' career came at the 2009 Biathlon World Championships in Pyeongchang, hosts of the 2018 Winter Olympic Games, where he claimed bronze in the 12.5km pursuit.

Os finished behind team-mate Bjørndalen, winner of the gold medal, and Russian silver medallist Maxim Tchoudov. 

The 36-year-old has been around the World Cup and International Biathlon Union (IBU) Cup circuits since 2003, when he made his debut in the Oslo sprint, with an inauspicious 56th-place finish.

Over the course of his career, he had seven individual World Cup podiums but never a victory.

His final two World Cup appearances came last season at Canmore in Canada and Presque Isle in the United States.

Os was on the podium in the Canmore mixed relay, where he and fellow Norwegians Marte Olsbu, Synnøve Solemdal and Håvard Bogetveit finished third behind winners Germany and runners-up Italy.

He has now undertaken the role of chief executive of Norway’s cross country ski race, Reistadlopet.

"After some back and forth, I have decided to step down my biathlon career," Os said in a Facebook post.

"Biathlon is a lot of fun, but now I have come to a place in my life where it is time to move on.

"In addition to our beautiful daughter Solveig, we are expecting another daughter in July.

"We have bought a house and I got a job. I got a job! Who would have thought that?!

"I am truly grateful for all help and support given by family, friends, fans, coaches, support teams, servicemen, sponsors and other helpers."

Os' retirement comes on the back of two-time Olympic medallist and multiple world champion Ivan Tcherezov of Russia calling time on his career.

Tcherezov, whose career was blighted by a nasty leg break while roller-skiing in 2011, was a seven-time World Cup winner with 19 individual World Cup podiums.

He won silver at the Turin 2006 Olympics in the 4x7.5 kilometres relay, and he added bronze in the same discipline four years later in Vancouver.

Tcherezov also won two World Championship gold medals in the event, in 2007 and 2008, as well as the world mixed relay title in Hochfilzen, Austria in 2005.