Kigen was born in Keiyo District. He graduated in 2005 from the Simotwo High School in Ainabkoi, Keiyo South District where He was represented the school in various competitions. He is based at the PACE Sports Management training camp in Kaptagat.
Kigen's breakthrough year came in 2006 when he represented Kenya internationally at three competitions. He was fifth at the 2006 IAAF World Cross Country Championships – a placing that brought him a gold medal with the Kenyans in the team competition. He set a personal best of 12:58.58 in the 5000 metres at the Bislett Games in Oslo and became the national champion over the distance.[3]
Track running
This earned him selection for the 2006 African Championships in Athletics in Bambous, where he scored a silver medal in his preferred distance before going on to win another silver through a personal best of 28:03.70 in the 10,000 metres event. He was not as successful at the 2006 IAAF World Athletics Final, taking seventh in the 5000 m, but his track form returned at the 2006 IAAF World Cup as he took his second 5000 m silver of the year representing Africa.[3] His career was then disrupted at the end of the season by a severe knee injury in November.[4]
He returned to competition in 2007, but it was in 2008 that he began to regain his form. He won the Great Capital Run in July 2008, recording a course record of 28:42 minutes.[3] At the 2008 IAAF World Athletics Final he ran in the 3000 metres and took fourth place. The following year he attended the 2009 IAAF World Athletics Final (the last edition of the event) and was eleventh over 5000 m.[5]
He was not included in the Kenyan World Cross Country squad and ran his half marathon debut instead at the Lisbon Half Marathon, coming fifth with a time of 1:00:49.[10] Following this he was runner-up to Micah Kogo at the Parelloop in April.[11][12] He competed on the 2011 IAAF Diamond League circuit, but did not finish higher than seventh place. He did, however, set a 10,000 m best of 27:30.53 minutes at the Memorial Van Damme.[13] Kigen dipped under the hour mark for the first time at the Delhi Half Marathon, and his time of 59:58 minutes was just one second behind the winner Lelisa Desisa.[12]