Buuxi weedhan soo socota: Niyonkuru ayaa markii ugu horeysay ka qeyb gashay tartan caalami ah wuxuu ahaa 2005 IAAF World Cross Country Championships. Wuxuu ku tartamay tartankii ragga da'da yar wuxuuna dhammeeyay kaalinta 33-aad ee 133 ciyaartooy ah waqtigii ahaa 25 daqiiqo iyo 32 ilbiriqsi. 2005 Jeux de la Francophonie Niyonkuru wuxuu ku tartamay 10,000 mitir. Niyonkuru wuxuu dhammeeyey kaalinta afaraad waqtigii ahaa 29 daqiiqo iyo 18.08 ilbiriqsi, kaliya 0.03 ilbiriqsi ayaa ka dambeeyay billaddii lacagta ahayd, Moroccan Abderrahim Goumri. Niyonkuru ayaa markaa ku tartamay 2006 World Junior Championships. Waxa uu kaalinta shanaad ka galay orodka 10,000 mitir isagoo ku guuleystay 28 daqiiqo iyo 59.92 ilbiriqsi. Wuxuu ahaa 6.63 ilbiriqsi oo ka dambeeya tartanka guuleystaha, Ibrahim Jeilan oo Itoobiyaan ah. Sanadkii 2007, Niyonkuru wuxuu ku tartamay 2007 World Cross Country Championships tartanka ragga da'da yar. Waxa uu dhamaystay kaalinta 13-aad 24 daqiiqo iyo 56 ilbiriqsi. Wuxuu dhammeeyay 49 ilbiriqsi oo ka dambeeya kii bilada dahabka qaatay, Asbel Kiprop oo reer Kenya ah. Sanadkii 2009-kii, Niyonkuru wuxuu ku guuleystay billaddii lacagta ahayd ee orodka 10,000 mitir. Waqtigiisa oo ahaa 29 daqiiqo iyo 37.14 ilbiriqsi wuxuu ahaa 23.67 ilbiriqsi oo ka dambeeya billaddii dahabka ahayd, Essa Ismail Rashed ee Qatar. Niyonkuru wuxuu ahaa 4.97 ilbiriqsi oo ka horreeya billaddii naxaasta ahayd, reer Tunisia El Akhdar Hachani. Niyonkuru wuxuu ku guuleystay 2015 Auray-Vannes Half Marathon waqtigii hal saac, saddex daqiiqo iyo labaatan ilbiriqsi. Ciyaarihii Olombikada ee 2016, Niyonkuru wuxuu ku tartamay
Marathon-ka ragga ee 21 August 2016, laakiin ma uusan dhameysan tartanka. Sanadkii 2017-kii wuxuu ku tartamay tartankii marathon-ka ee ragga ee tartankii ciyaaraha fudud ee adduunka ee 2017, isagoo kaalinta 71aad galay 2:42:27.